摘要:

An unhealthy road Focus J. Environ. Monit., 1999, 1 23N With transport now the major source of many air pollutants, scientists need to fill in important gaps in our understanding of associated health risks. Few environmental issues pose such intractable problems as the growth of transport. Across both the developed and the developing worlds, demand for transportation in general, and motor vehicles, in particular, appears insatiable.In many countries, road transport is now the major source of many air pollutants and one of the main contributors of greenhouse gases. In the UK, for example, road traYc is set to increase by up to 50% over the next 20 years.1 Yet in 1995, road transport contributed 22% of national carbon dioxide emissions, up from 17% in 1985. For every 2000 litres of petrol (gasoline) consumed the average car produces: 4720 kg of carbon dioxide (CO2): 188 kg of carbon monoxide (CO); 28 kg of volatile organic compounds (VOCs); and 25.8 kg of nitrogen oxide (NO).2 A 10 mile (16 km) trip in light traYc lasting 11 minutes would produce 2 g of VOCs.2 The same trip in heavy traYc lasting 30 minutes would generate 7 g—a 250% increase in VOC emissions. Of course, we are all to blame.While we notice the deterioration in air quality, especially in cities, and empathise with the need to find more sustainable alternatives, few of us are actually prepared to give up our mobile cocoons. Instead we sit frustrated in traYc queues merrily pumping out pollution. Unpalatable options So what is to be done? Politicians have a variety of instruments at their disposal.Unfortunately, they are mostly expensive, long-term and not voterfriendly. Public transport, such as buses and trams, economic instruments, such as road pricing, and demand management schemes, such as carsharing, are all being muted. While these all have their part to play, experience shows that the incentives (or the sanctions) will have to be extreme to draw most of us away from our beloved cars.In the background, policy-makers always have an eye to the economic importance of the automotive industry. In the short-term, then, (the next 5–10 years at least), internal combustion engines (ICEs), and their associated emissions, will remain a key factor in the environmental equation. As engine technology has advanced, per unit emissions of major pollutants, such as CO2, CO and NO have decreased, mainly due to improvements in combustion eYciency.However, total reductions have been masked by dramatic increases in vehicle numbers and distances travelled. While these ‘traditional’ pollutants will continue to be important (particularly CO2 in the context of global warming), for the most part attention has shifted to other pollutants, such as particulates, VOCs and fuel additives, and their associated health eVects.Problem pollutants Particulates Particulate emissions are now generally measured in terms of PM10. These smaller particle sizes are considered the most representative both of vehicle emissions, and of those particles most likely to cause ill-health. With further advances, it is possible that measures based around even smaller particles (e.g.PM2.5) will become the norm. A high proportion of PM10 comprises fine particles that remain suspended for long periods.3 Concentrations vary seasonally, and are generally highest in the winter months. The variations are less than for other vehicle-related emissions, however, because during the summer months particulate sulfate and nitrate are also produced through photochemical oxidation.In contrast to gaseous pollutants, scientists have not been able to carry out controlled exposures for PM10 as a means of investigating health eVects.3 Thus, risk assessments have had to be based on epidemiological population studies. These pose several problems. Firstly, both particulate concentrations and general health patterns are known to be strongly related to the weather, so it is diYcult to distinguish cause and eVect. Secondly, in urban areas individuals’ exposures to PM10s can vary substantially, whereas air pollution measurements are generally intermittent and highly localised.Thus, the true eVects of low PM concentrations on individuals cannot be determined with confidence from population-based studies.Nevertheless, the evidence of linkages between PMs and human health is mounting. Reviewing the scientific literature, a UK expert panel noted recently that similar results had been found in cities across the world.3 The Panel found increasing evidence of a relationship between the magnitude of the eVect and the concentration of particles to which the population has been exposed.‘Such statistical associations’, they concluded, ‘increase the likelihood that the relationship is causal.’ The Panel also pointed to the lack of reliable evidence on threshold values for health eVects, and called for urgent research. If no threshold level exists then the theoretical basis for PM emission standards is undermined. Volatile organics Road transport is a significant source of VOC’s (also called air toxics), such as benzene, polynuclear aromatic hydrocarbons (PAH’s) and aldehydes.Benzene is a natural constituent of crude oil.2 It acts as an octane enhancer, preventing the fuel from igniting prematurely and causing engine damage. In motor vehicles, benzene arises in exhaust emissions and from evaporation during refuelling. 1,3-butadiene is found in vehicle exhausts.3 Over recent years, the higher olefins, from which it is derived, have been present in petrol in increasing quantities. It is partially removed by catalytic convertors. Many of these species are either suspected or known carcinogens, linked in particular to lymphomas and leukaemias.3 However, much of the24N J.Environ. Monit., 1999, 1 evidence on health eVects is based on a combination of laboratory studies and workplace exposures. Data on ambient exposures and associated health eVects is critically lacking. Fuel additives Following the phasing out of lead, which was used as a fuel additive for over 60 years, the oil industry has developed alternative means of improving fuel quality.2 Oxygenates are oxygen-containing compounds such as alcohols or ethers, which are blended with petrol in small amounts.As well as reducing emissions, some are used as ‘fuel extenders’, allowing other fuels, such as natural gas or biomass, to be added to the crude oil during petrol manufacture. The most common additive today is methyl tertiary butyl ether (MTBE), which is manufactured from a mixture of methanol and isobutylene.In the US, MTBE has been used in petrol since 1979 to reduce emissions of carbon monoxide and hydrocarbons. Despite its clean air benefits, concerns have grown about MTBE’s own environmental impacts, especially in the contamination of surface and groundwater. It is extremely persistent in water and may carry chemicals from petrol along with it into drinking water supplies.In 1998 the US EPA set up a ‘Blue Ribbon Panel’ to address these issues which will report later this year4 [see JEM, 1999, 1 (1) 10N]. EPA has also issued a research strategy, identifying key research and information needs relating to oxygenates in water.5 Topics covered include occurrence, source characterisation, transport, transformation, contaminant removal, exposure, aquatic toxicity and health eVects.To date, MTBE has received little attention in Europe. Denmark, traditionally in the vanguard of European environmental policy, adopted an action plan last year.6 As yet there is little evidence of other European countries following suit, or of action at EU level. Technology options The automotive industry is tackling the emissions issue across a broad front.On the one hand, measures such as engine design, mass reduction and telematics aim towards incremental improvements in fuel eYciency and emission levels. On the other hand, new propulsion systems, such as electric vehicles, fuel cells, LPG and various types of hybrids, aim towards the zeroemission or near-zero emission vehicle.Although steady progress is being made, and many of the advanced propulsion systems are at the demonstration stage, or beyond, future vehicle technology will be evolutionary, rather than revolutionary. Neither manufacturers nor consumers are enthusiastic about change. In any case, experience shows that technological advances are not always beneficial. For example, the widespread switch to diesel, during the early 90’s, is now widely seen as counterproductive.Although using 20–25% less fuel, new diesel vehicles emit 10–15 times more particulates than their petrol equivalents.7 Overall their emissions are estimated to be 3–4 times more carcinogenic. The health consequences of this increasing population of highly polluting diesel vehicles are as yet unknown.Emission benchmarks With limited penetration from other propulsion systems, future emission trends will continue to depend largely on ICE parameters. In particular, fuel eYciency, fuel quality and emission standards will be important benchmarks. Fuel eYciency Improvements in fuel eYciency as a result of technological advances have a knock-on eVect in terms of emissions. As cars burn less fuel, unit emissions of key pollutants also decrease.The European car industry has entered into a voluntary agreement under which CO2 emissions are to be cut by 25% by 2008.8 This will mean producing cars with average emissions of about 140 g km-1. The industry has also committed to commercial production of cars emitting 120 g km-1 during the period 2005–2010. Fuel standards Over recent years fuel has come to be considered with vehicle technology as a potential source of emission reductions.In the US this approach is embodied in the 1990 Clean Air Act, and in the EU in various directives on fuel quality. Under the latest directive, agreed last year, from 2000 sulfur limits in the EU will be set at 350 ppm for diesel and 150 ppm for petrol. Both limits will be tightened to 50 ppm in 2005.The directive also sets allowable levels of aromatics and benzene in 2000 and 2005. As well as fuel quality criteria, the US has promoted the use of reformulated (i.e. oxygenated) petrol and clean vehicle fleets. Starting in 1998, 30% of new vehicles purchased by centrally fuelled fleets in certain cities have been required to use reformulated fuels and to meet emission standards lower than those for other vehicles.The purchase requirement will grow to 70% by 2000. In June last year, more than 30 vehicle manufacturers from Europe, the US and Japan launched the ‘World Fuel Charter’ as the basis for future improvements in fuel quality.9 The Charter sets out fuel specifications and test methods for both petrol and diesel across three market categories.While a watershed in bringing together vehicle manufacturers worldwide, the Charter has not gone down well with the oil industry. It remains to be seen whether, and how soon, the two sides can reach agreement. Emission standards In the US emission standards have been tightened progressively under the so-called tier provisions of the Clean Air Act 1990.New standards for passenger cars and small trucks were fully phased in by 1996. All new vehicles now carry on-board diagnostic systems to alert drivers to malfunctions in emission control equipment. Many cities run mandatory inspection and maintenance programmes to check vehicle emissions on a regular basis. EPA is due to report later this year on whether even tighter standards are needed, technologically feasible and economical.Any further revisions would be introduced from 2004. In the EU, new emission standards were agreed last year that should reduce pollution emissions from new vehicles by up to 70% by 2005. From 2000 new cars will have to comply with their design emission limits for 80 000 km (or five years), rising to FocusJ. Environ.Monit., 1999, 1 25N crowded. As well as environmental regulators and NGOs, industries such as automotive, chemicals, and oil and gas all have an interest. Scientists have a key role to play in bringing together this broad spectrum of opinion, and even in brokering new relationships and partnerships. The breadth of the research issues, and their political and commercial sensitivity, calls for specialised research structures.In the US, the Health EVects Institute, which is funded jointly by government and industry, has contributed important findings on the health eVects of motor vehicle pollution across a variety of areas.10 A similar body is currently being proposed in Europe by ACEA, the European car makers’ association, and others. This, too, would be financed partly by industry and partly by the EU, with a remit to look at vehicle pollution in a European context.The European Commission has recently established its own facility, the Vehicle Emissions Laboratory (VELA), part of its Joint Research Centre, and as yet it is not clear how the two would work together. With research being undertaken worldwide, eVective communication and exchange of information are essential.For particulate research, the US EPA, the European Commission and the UK government have established a Global Information Exchange on Particulate Matter on the Internet.11 This model could be applied eVectively elsewhere. A Mobile Agenda At a technical level, research should focus around the three key pollutants. For particulates, the priorities include:- $ epidemiological and toxicological eVects of ambient particles; $ long-term exposure studies; $ evaluations of particle epidemiology; $ diesel exhaust emissions, including studies of carcinogenicity, eVects of new technologies on size distribution, and quantitative risk assessments.In VOC’s, key concerns include: $ epidemiology of benzene, 1,3-butadiene and aldehydes, to improve extrapolations from high doses to low doses and across species; $ development of biomarkers for use in epidemiological studies; $ extrapolation of health eVects to human populations at ambient exposure levels.Finally, fertile research themes in relation to oxygenates, such as MTBE, include: $ sources and environmental pathways of oxygenates; $ statistically relevant sampling of oxygenate exposures to determine human populations; $ epidemiology and toxicology of oxygenates; $ risk assessments for oxygenates which take account of the above data; $ health eVects of other fuel additives, such as methanol and MMT.Other areas where knowledge is lacking include: $ understanding of the eVects of longterm exposure to ozone; $ combined eVects of exposure to ozone and particles; $ studies of metal-containing additives, such as cerium, to diesel fuel References 1 ENDS Daily, 21/7/98, quoting the UK Sustainable Transport White Paper. 2 Exhaustion: A Guide to T ransportation Emissions, Environment Canada, 1998. Available at www.doe.ca/emission/ toce.html 3 Report of the Expert Panel on Air Quality Standards, The Stationery OYce, London, 1998.Available at www. environment.detr.gov.uk/airq/aqs/ 4 For details of the Panel’s work see www.epa.gov/oms/consumer/fuels/ oxypanel/blueribb.htm 5 Oxygenates in Water: Critical Information and Research Needs, EPA/600/R-98/048, Environmental Protection Agency, Washington D.C., 1998. Available at www.epa.gov/ncea/ oxywtr.htm 6 ENDS Daily, 2/2/98. 7 Based on recent work by the Swedish Environmental Protection Agency. 8 ACEA Press release 29/7/98. For details of the voluntary agreement see ACEA: www.acea.be 9 The Charter, containing detailed fuel specifications, is available at www.acea. be. The oil industry’s views are at www.europia.com 10 For an overview of the Institute’s work and related reports see www.healthe Vects.org 11 For details of the Global Information Exchange Program see www.epa.gov/ oms/interntl/pm/net.htm Mike Sharpe 100 000 km in 2005. On-board diagnostics to monitor emissions will also be mandatory on new petrolengine vehicles from 2000 and on diesel-engine vehicles from 2003.EU countries will be permitted to promote 2005-standard vehicles from 2000 through tax incentives. The legislation is based on the work of the Auto/Oil programme, an extensive technical co-operation between the European Commission and the oil and vehicle manufacturing industries, which is now entering its second phase. The Commission has indicated its intention to incorporate future vehicle emission standards into a unified framework covering all aspects of air quality policy [see p. 26N]. The road for monitoring Clearly, monitoring is central to an informed perspective on transport emissions.The gaps in our knowledge on health eVects are alarmingly large. Standards for fuels and emissions are evolving rapidly, but also diverging. As an increasingly wide range of actors are drawn into the debate, tensions are beginning to grow. All of this calls for a sound underpinning by the analytical sciences. The challenges for the monitoring community are three-fold:- (1) Inform risk assessment and regulation: Governments and industry are eager to apply risk assessment processes to transport emissions, technologies and fuels. Key data is needed to inform these evaluations. In particular, scientists need to address critical gaps in risk assessment for specific pollutants, such as PM10’s and certain VOC’s. (2) Track emerging technologies: With a whole variety of new technologies and fuels being considered, scientists have an important opportunity to lead the debate. Appropriate datasets will be needed to compare the public health risks between new and conventional approaches. For example, as with diesel or MTBE, a new fuel or technology may reduce some pollutants, but increase others or have other unforeseen eVects. Analysts should work with others to identify and assess emerging technologies as early as possible. (3) Build consensus: The vehicle emissions debate is increasingly Focus

ISSN:0960-7919    

DOI:10.1039/a901756i

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

26N J. Environ. Monit. 1999 1 News Legislation Step towards POP treaty The prospect of a global treaty on persistent organic pollutants (POPs) moved closer following an international meeting in Nairobi in January. Organised by the United Nations Environment Programme (UNEP) this was the second round of negotiations aiming towards a global agreement covering 12 of the most harmful POPs including DDT PCBs and dioxins [see JEM 1999 1 (1) 10N]. While steady progress has been made according to UNEP delegates remained divided over whether the treaty should aim towards management or elimination. The EU and Nordic countries argued for an outright ban on production and use across all categories. The US Canada Australia and others say account has to be taken that some chemicals such as dioxins and furans arise as by-products from other activities.A second group of chemicals will be identified at the next round of talks in June. UNEP www.unep.org Nordic Council www.norden.org Pressure grows for phthalate ban Consensus is building in the EU for a ban on the use of phthalate plasticisers in children�s toys. In February Member States rejected a plan by the European Commission to restrict the chemical and argued instead for prohibition. Following advice from a scientific committee last year the Commission had proposed setting limits on the migration from children�s toys of DINP the main phthalate used to soften PVC. Several EU countries have already taken steps to ban the use of phthalates in children�s toys including Austria Denmark Sweden and Greece. The Netherlands is also likely to introduce a national ban if the EU does not act within the next few months.The UK is against a ban arguing that a new migration test developed in Britain would help make migrationbased limits a workable approach. The decision represents a substantial shift in opinion since Member States last year rejected a proposal to ban phthalates under EU product safety law. A revised proposal for an EU-wide ban is likely to be tabled by the Commission�s Consumer AVairs Directorate within the next few months. Denmark tightens chemical controls Wide-ranging revisions to chemicals regulation have been announced by the Danish Environmental Protection Agency. In a strategy covering the next 2�5 years the EPA will expand its list of prohibited substances and strengthen its inspection system.Companies will be given greater responsibility for assessing risks to health and the environment and for making this information publicly available. The initiative will utilise a new computer model developed by the EPA which will be used to generate risk assessment data for around 165 000 chemicals. Alongside the strategy EPA is already developing an action plan on phthalates (see above). Further action plans covering use of pesticides in agriculture and the use of PVC are expected later in the year. Proposals already announced to ban the use of pesticides in private gardens have drawn protests from other EU Member States that the move conflicts with single-market legislation. Danish local and regional authorities have already entered into a voluntary agreement to phase out the use of pesticides by 2003.Danish EPA www.mst.dk Europe moves towards unified air policy In a hectic few months developments in virtually all areas of European air pollution legislation have been proposed that amount to a major overhaul in the EU�s air quality policy. Potentially the most far-reaching measure is the European Commission�s proposal to develop an integrated framework for air quality policy. Clean Air for Europe (CAFE) would provide a strategic framework for emissions and air quality standards replacing the current source- or pollution-specific policies. The Commission argues that since many pollutants such as ozone nitrogen dioxide and particulates come from a variety of sources a more coherent policy is needed. A feasibility study is underway to be followed by a major conference either later this year or early next.The approach has been broadly welcomed by both industry and environmental groups. Other recent developments include $ Final approval by the European Parliament to a new directive on air quality the first �daughter directive� under the 1996 air quality framework law. The directive sets maximum levels in air for sulfur dioxide nitrogen dioxide lead and particulate matter (PM10) and was agreed by the EU Council of Ministers last summer. $ Continuing preparations for revisions to the EU laws on emissions of acid gases and ozone. The proposals are likely to include �national emissions ceilings� for EU Member States that are much tougher than those foreseen in the 1997 EU acidification strategy. A draft ozone strategy and an air quality standard for ozone are also on the cards.$ Continuing debate within the European institutions on proposals to strengthen emission limits for new fossil-fuelled power stations. The Commission�s proposals will halve current limits on sulfur dioxide nitrogen dioxide and dust for new plants licensed from 1st January 2000. The European Parliament and other groups are pushing for even greater cuts. $ Talk of a proposal to unify the waste incineration directives by bringing the emission requirements for municipal and other wastes broadly into line with existing limits for hazardous waste. The legislation is also likely to be extended to emissions to water for the first time. European Commission europa.eu.int/ comm/dg11/ J. Environ. Monit. 1999 1 27N Stalemate on water framework directive The European Parliament and the Council of Ministers are bitterly divided over a proposed framework directive on EU water quality.The Parliament remains at odds with national governments and is continuing to call for much tougher legislation to control water pollution. With the Parliament due to dissolve in May prior to elections in June no agreement is likely before the autumn at the earliest. By this time the Parliament�s powers will have been increased by the entry into force of the EU�s Amsterdam Treaty which gives the Parliament and Council powers of �co-decision� in the environmental area. Among the Parliament�s key demands are a staged phase-out of discharges of hazardous substances by 2020 and an insistence that consumers should always pay the full price of water use. Canada sides with Agency in smog battle The Canadian government has announced its support for the US EPA in the forthcoming law suit over the US smog reduction programme.Due to start in 2003 the Nitrogen Oxide Emissions Reduction Program will apply to 22 mid-west and north-east states and the District of Columbia. EPA is facing a challenge from over 70 entities including Michigan Ohio and other mid-west states who are disputing the programme�s scientific basis regarding the transport and health eVects of NOx and ozone. EPA is supported by 24 parties including environmental and health groups and a coalition of New England states. Canadian Environment Minister Christine Stewart has received the backing of provincial and territorial governments to support the EPA action. Between 30�50% of pollution in Ontario and Quebec and as much as News 90% in New Brunswick and Nova Scotia comes from the US.Environment Canada www.doe.ca Permitting changes will increase environmental benefits Moves to streamline the permitting process one of the most critical elements of the environmental regulatory system have been announced by the US EPA. Under the new plan the Agency will work towards permitting changes that oVer benefits for the environment the regulated facilities and other stakeholders. Performance-based features will be created that specify goals without prescribing how they must be met. Pollution prevention will be encouraged as well as measures to improve public participation in decision-making and reduce administrative burdens. Integrated permitting will also be investigated.Environmental quality Clinton commits to clean air A new initiative to promote the early adoption of innovative air pollution control technologies was among the flagship measures announced by President Clinton in the EPA�s br Partnership Fund will finance partnerships between federal state and local governments and the private sector. Projects financed under the $200 m scheme will be locally managed and self-supporting and should enable communities to achieve their clean air goals sooner. The Fund will stimulate cost-eVective pollution control strategies spur technological innovation and leverage substantial non-federal investment in improved air quality. A further $18 m of new funding has been provided for urban air toxics. EPA says the money will be used to refocus the air toxics programme from a technologybased to a risk-based approach.Other new initiatives in EPA�s $7.2 billion budget include $700 m for �Better America Bonds��tax credits aimed at helping communities address local problems such as traYc congestion water quality and brownfield sites. A major inter-agency initiative on childhood asthma is being launched to fund education outreach and air monitoring. The initiative is part of a $62 m package on childhood health including cancer and developmental diseases. A series of water quality initiatives are also proposed. Implementation of the Clean Water Action Plan will continue with an allocated budget of $651 m. A further $1.625 billion will be available under the Clean Water and Drinking Water State Revolving Fund (SRF) that provides financial assistance for the construction of drinking water and wastewater treatment facilities.For the first time states will have the option to set aside 20% of their SRF budgets for non-point pollution sources such as estuary management and other water quality projects. Other winners in the 2000 budget round include Chemical-Right-to-Know and Environmental Monitoring for Public Access and Community Tracking (EMPACT) which provides real-time environmental quality data. EPA www.epa.gov WHO plans health-environment summit Moves to combat the health and environmental eVects of transport will be top of the agenda at a major international conference in London in June. At the conference organised by the World Health Organisation (WHO) delegates from 51 European countries will sign a charter to reduce the human health costs of transport.Although not legally binding the charter will set quantitative targets for air quality injury and noise. Delegates are also expected to sign up to a second agreement on water and health. Drafted in association with the United Nations Economic Commission for Europe (UNECE) the legally binding protocol covers areas such as adequate drinking water and sanitation water quality and systems for monitoring and measuring health risks. The conference will review progress on national environment and health action plans (NEHAPs) promised at the last ministerial meeting three years ago. The implications for health policy of the pan- European convention on public participation in environmental decisionmaking agreed last June will also be up for discussion.Other sessions will cover industrial pollution climate change local environmental quality and children�s health. NGOs will attend the conference for the first time. WHO Europe www.who.dk/L ondon99 Transport holds back US air quality Continuing growth in transport remains the major barrier to improvements in air 28N J. Environ. Monit. 1999 1 News quality according to the US EPA. In its annual report on air quality trends for 1997 the Agency notes that concentrations of nitrogen dioxide ozone and lead remained unchanged from the previous year and particulate matter decreased by only 1%. Trends in NOx and ozone also show the lowest decreases over the period 1988�97 down 14% and 19% respectively. The 1997 report is the first to include data from EPA�s new monitoring network covering 22 of the US�s smoggiest cities.The monitoring data show that average concentrations of eight air toxics decreased over the previous three years including a significant reduction in benzene. Early analyses indicate these reductions are a result of vehicles switching to reformulated petrol (gasoline). The greatest improvements in ambient concentrations in 1997 were for carbon monoxide (down 7%) and sulfur dioxide (down 4%). Data related to the revised ozone and PM10 standards are also presented. Future reports will include trends related to the new PM2.5 standard for fine particles. EPA OYce of Air Quality Planning and Standards www.epa.gov/oar/aqtrnd97/ Europe unveils benzene baseline New data on atmospheric concentrations of benzene in the European environment have been released by the European Commission�s Joint Research Centre (JRC).The data provides an important baseline for studies of urban air quality and the linkages between benzene and diseases like leukaemia. The JRC�s MACBETH (Monitoring of Atmospheric Concentration of Benzene in European Towns and Homes) project looked at atmospheric benzene levels in six European cities as well as the exposures of key population groups. In both cases date were collected using innovative samplers called �radielli� which are small enough to be worn around the neck. The results will be used to determine the limits set by the 1999 European directive on benzene emissions. Joint Research Centre angela.cardinali@jrc.org UK unveils air quality review The UK will fail to meet its 2005 targets for PM10 a review of national air quality strategy has revealed.Nationwide modelling at urban background sites away from hot spots such as busy roads show widespread exceedance of the existing national objective of 50 mg m-3. Much of the infringement can be associated with imports of pollution from continental Europe. In the light of the report the government has proposed relaxing its immediate objectives for PM10 under the EU air quality directive but will bring forward targets for some other pollutants. For lead the government proposes meeting the directive�s 0.5 mg m-3 standard by 2005 dropping to 0.25 mg m-3 by the end of 2008. Existing objectives for benzene 1,3-butadiene and carbon monoxide have been maintained but their implementation brought forward by two years.Objectives for ozone nitrogen dioxide and sulfur remain unchanged. Monthly updates on UK air quality data from the national network of monitoring stations are available at a new website developed by consultants AEA Technology. DET R www.environment.detr.gov.uk National Air Pollution Index www.aeat.co.uk/netcen/airqual/aqm/ Swedes showcase environmental assessment model A new model for use in local environmental assessments has been developed by the Swedish EPA. The model should make it easier to compare local environmental conditions between diVerent parts of the country and so provide a uniform nation-wide assessment. Environmental quality criteria have been developed for six areas forests agricultural land groundwater lakes and watercourses coasts and seas and contaminated sites.Reports describing the work will be available shortly on the EPA�s website. Swedish EPA www.environ.se France surveys lead risks French local authorities are to identify areas at risk from lead poisoning following new scientific data on the extent of population exposures. The National Institute of Health and Medical Research (INSERM) has reported that over 250 000 children may be aVected by lead from contaminated water and crumbling paint. According to INSERM children living in run-down housing or certain industrial areas show lead levels of 400 mg l-1 per litre of blood compared to the 250 mg l-1 threshold for medical treatment. Proposals from the French Ministry of Health will require doctors to report any cases of children found to have more than 150 mg l-1 of lead in their blood.INSERM www.inserm.fr Chemical hazards EPA extends right-to-know A significant extension of the reporting requirements for releases of toxic chemicals has been announced by EPA under the US right-to-know legislation. The proposed rule would substantially increase public access to information on releases of persistent bioaccumulative toxic chemicals (PBT�s) such as dioxins mercury PCB�s aldrin and heptachlor. These are known to cause a variety of health hazards at low doses including reproductive dicilities are only required to report their PBT releases if they manufacture or process more than 25 000 pounds annually or use more than 10 000 pounds annually. The new ruling would lower the threshold to between 10�100 pounds capturing a lot wider range of users.EPA T oxics Release Inventory www.epa.gov/opptintr/tri/ PVC firms sign environmental charter Nine European manufacturers of emulsion PVC have signed a voluntary agreement to reduce emissions of vinyl chloride monomer (VCM) from their production processes. Signatories who include major companies such as BASF Elf Atochem EVC Norsk Hydro and Solvay commit themselves to achieve a series of VCM targets by 2003. J. Environ. Monit. 1999 1 29N The initiative builds on a 1995 charter covering manufacturers of suspension PVC which accounts for around 85% of European production capacity. Performance under both charters will be subject to independent review the results of which will be published from June this year. Tighter precautions against exposure to VCM are being imposed under EU legislation approved late last year.European Council of V inyl Manufacturers +32 2 676 7211 Ireland�s responsible suppliers The Irish Chemical Marketers� Association (ICMA) has become the tenth distributor organisation to sign up to the international Responsible Care programme. Responsible Care which was launched in 1985 addresses standards of health safety and environmental protection in the chemical industry through a process of continuous improvement. ICMA�s action represents the latest move in the propagation of Responsible Care down the chemical industry supply chain from manufacturers to distributors. ICMA +353 1 605 1564 Testing on health eVects of MMT Additional testing requirements for the manganese-based fuel additive MMT have been announced by the US EPA.MMT is blended with petrol to boast octane rating. EPA says the extension is necessitated by continuing uncertainties regarding MMT�s health eVects and the potential for widespread public exposure to its emission products. The tests are to be implemented under the Alternative Tier 2 provisions of the Clean Air Act. The data generated will allow the Agency to perform a more detailed risk evaluation. EPA OYce of Mobile Sources www.epa.gov/OMS/ Respirable silica exposures Around 100 000 UK employees are still routinely exposed to respirable silica dust despite it being classified as a Group 1 carcinogen according to a report from the UK Health & Safety Executive. The sectors most aVected are quarries heavy clay foundries ceramics construction and mining. Long-term exposure to silica-based dusts can lead to the lung disease silicosis and possibly cancer.The report is part of the HSE�s review of the Maximum Exposure Limit for respirable crystalline silica introduced in 1997 and should provide a useful baseline for future carcinogenicity risk assessments. The MEL in air was set at 0.3 mg m-3. HSE Infoline +44 (0) 541 545500 Women at risk from carcinogens A group of carcinogenic chemicals called aromatic amines (AAs) has been found in human breast milk for the first time. Researchers from the University of Guelph who carried out the study say it could help explain the increased risk of breast cancer for women living in industrial areas. AAs are used in numerous industrial processes including the manufacture of plastics dyes pesticides and pharmaceuticals.News Research news EU finalises research spending; progresses health programme The extent of EU environmental research spending has been clarified following final approval of the Fifth Framework Programme (FP5) covering the period 1998�2002 [see JEM 1999 1(1) 12N and 16N]. Of the total budget of e14.96 billion around e2.5 billion will be devoted to environment-related issues. This includes e160 m for environment and health covering health eVects of air pollution heavy metal and toxic substances noise climate change electromagnetic radiation and the eVects of pollution at the workplace. A further e520 m will go into research on sustainable agriculture fisheries forestry and rural development. The Key Action on �Energy Environment and Sustainable Development� is to receive e2.125 billion over the five-year period split almost equally between environmental projects such as water management and climate change and energy research.While attention was focused on FP5 the Commission was also progressing proposals to renew a little-known programme on research in public health. Following on from a previous action adopted in 1997 the programme aims to improve information on the spread and prevention of diseases linked to environmental pollutants. The action will also contribute to understanding about perception assessment and risk management. As with FP5 before it funding is being hotly disputed between the Parliament and the Council of Ministers. The budget currently proposed covering the period 1999 to 2001 is e3.9 m. MEPs are also pushing to ensure that the programme has a sharper focus.They say it should serve as a launchpad for future legislation to combat health risks. EU R&D Information Service www.cordis.lu CSIRO completes ozone observations Australian and British scientists have spent the southern summer studying the self-cleansing ability of the atmosphere. The Southern Ocean Atmospheric Photochemistry Experiment (SOAPEX) is a major international project to study the chemistry of the lower atmosphere. It brings together scientists from the Australian research body CSIRO the Australian Bureau of Meteorology and three UK universities. UK project leader Professor Stuart Penkett said the experiment had provided �a present-day baseline in the cleanest air present in the atmosphere against which we can check future changes. We will also use our results as a comparison for similar studies in the more polluted northern hemisphere�.Based in north-west Tasmania the project involved measurements from the shore-based research station research aircraft and the CSIRO research vessel Southern Surveyor. Bureau of Meteorology www.bom.gov.au Pilot project on mercury deposition Methods to evaluate the deposition of mercury from air sources to water bodies are being addressed under a 30N J. Environ. Monit. 1999 1 pilot project launched by the US EPA. The $400,000 project is being funded jointly by EPA and the states of Wisconsin and Florida. Field work will be conducted on Devil�s Lake Wisconsin and a portion of the Florida Everglades. Both water courses are on their states� �impaired� lists and have advisories due to the high level of mercury in fish.The project will investigate the relationship between mercury or air emissions and water quality impacts using approaches that take into account air sources when determining total maximum daily loads (TMDL�s). EPA OYce of Wetlands Oceans and Watersheds www.epa.gov/owow/ RSC measures up The Royal Society of Chemistry is leading a �1.15 m research project to develop a new generation of environmental monitoring tools. Measuring up to the Environment is one of 18 projects being funded under the first round of the UK�s Foresight Link News Agriculture and nutrition awards. The scheme encourages links between industry academia and research bodies to address key issues and problems. RSC leads a consortium of 13 organisations including Zeneca Glaxo Wellcome and the universities of Oxford Cambridge UMIST and East Anglia.The sensor technologies developed in the project will be applied in new types of environmental monitoring equipment. RSC www.rsc.org Mobile laboratory takes to the road A new computer program promises to provide rapid on-site evaluations of the health risks faced by people living on or near contaminated sites. Developed by the Van Hall Institute in the Netherlands in conjunction with environmental consultancy Mott MacDonald the enhanced software is part of the Advanced Mobile Analytical Laboratory (AMAL)�a mobile pollution testing laboratory designed and constructed by the Environment Institute of the Joint Research Centre. The AMAL is believed to be the world�s first comprehensive on-site testing facility providing reseawaste soil and water contamination.Vocational training A training and accreditation system for air pollution monitoring in industry is being developed under an EU scheme to promote vocational training. The framework covers all monitoring and measurement methods currently used in Europe. The aim is to establish minimum criteria for environmental training products which will apply across the EU. The resulting training products will be targeted at people involved in air pollution sampling and analysis in industry and regulatory bodies. Delivery will be through a mixture of traditional course materials and new electronic media. CRE Group enquiry@cregroup.com EPA consults on organophosphates Preliminary risk assessments on 12 organophosphate-based pesticides have been released for public comment by EPA�s OYce of Pesticide Programs (OPP).The consultation is part of a wide-ranging review under the Food Quality Protection Act (FQPA). The Clinton administration has said that it is committed to ensuring FQPA is implemented through an open and transparent process and that EPA�s assessments are based on sound science. Organophosphates are widely used on food crops and are also found in home and garden pesticide products. To date health and/or ecological risk assessments have been released for 28 organophosphates and more will be issued during the spring. EPA says that the risk assessments are preliminary and may be revised in future if additional data becomes available. In a related measure EPA has also published a brochure and website informing consumers on practical steps to reduce their exposure to pesticides on food.EPA OYce of Pesticide Programs www.epa.gov/pesticides/opp/ Food link for mystery disease A little understood osteoarticular disorder called Kashin�Beck disease is being linked to contamination of food supplies. Experts discussed the issue in Beijing recently at an international symposium organised by Me�decins Sans Frontie`res. The disabling condition starts in childhood and aVects the growth of joint cartilage in the worst cases leading to dwarfism and painful deformities. The disease occurs mainly in Tibet northern China Mongolia and Siberia. The risk factors seem to include selenium deficiency in the soil fungal contamination of grain and iodine deficiency. These create an environment in which mycotoxins enter the rural food supply.Trials are underway in Tibet involving a variety of measures including selenium and iodine supplements and use of fungicides. British Medical Journal 20th February 1999 Publications Health eVects of PAH�s A new book from WHO evaluates the risks to human health and the environment posed by exposure to 33 non-heterocyclic polycyclic aromatic hydrocarbons (PAH�s). Compounds from this large class were selected for evaluation on the basis of abundant data documenting toxic eVects including carcinogenicity. More than 2000 references to the recent literature are included. Selected Non-heterocyclic Polycyclic Aromatic Hydrocarbons Environmental Health Criteria No.202 World Health Organisation 1998. ISBN 92 4 157202 7. US$156.60. Fate of organics This is a well established reference work for predicting potential exposure routes J.Environ. Monit. 1999 1 31N News for organic chemicals covering air water soil flora and fauna. The third edition includes 22 new mathematical calculations for 73 non-pesticide organic compounds. It covers data for 203 commonly encountered chemical substances and explains hazard prediction based on chemical structure. Fate & T ransport of Organic Chemicals in the Environment A Practical Guide 3rd Edition by Ron E. Ney Jr ISBN 0 86587 626 6 370 pages 1998. �48 Health eVects of toxics This second edition contains a significantly expanded exploration of hazardous chemicals and their eVects on human health and the principles of hazardous materials toxicology and industrial hygiene. Topics covered include industrial hygiene risk assessment epidemiology; medical monitoring treatment and management; industrial toxicology; exposure and entry routes; action of toxic substances; target organ eVects; exposure control methods.Health EVects of T oxic Substances 2nd Edition by M. J. Malachowski ISBN 0 86587 649 5 312 pages 1998 �54 Communicating risk The book presents the discussions and conclusions of a symposium sponsored by the member agencies of the US Department of Health and Human Services Environmental Health Policy Committees Subcommittee on Risk Communication and Education the US Department of Energy and the consortium for Risk Evaluation with Stakeholder Participation. It is the second in the series of �International Reports on Policy and Practice in Occupational and Environmental CD-ROM for the first time.The directory describes the certification procedures of its 9500 clients in 32 countries. Also on the CD-ROM is a new Guide to Certification a manual providing information on the standards and the accreditation requirements. National Quality Assurance +44 0 1582 866766 Newsletters Latest issues of regular newsletters $ DiVusive Monitor. A newsletter on diVusive sampling in the workplace and in the environment. Issue 10 December 1998 includes an article on methods for the determination of hazardous substances. Available from Dr Richard Brown UK Health and Safety Laboratory. E-mail richard.h.iacs.brown@hsl.gov.uk $ Hazardous Substances & Public Health. The Quarterly Newsletter of the Agency for Toxic Substances and Disease Registry (ATSDR).Winter 1998 edition includes articles on children and the environment health eVects of landfills and details of ATSDR publications and events. Available at http://atsdr1.atsdr.cdc.gov/ $ Science and Environment Bulletin. Newsletter of Environment Canada. January/February 1999 issue includes articles on ozone loss in the arctic urban air quality and monitoring of river ecosystems. Available at www.doe.ca/science/ splash.htm $ Update�Winter 1999. The Quarterly Newsletter of the Health EVects Institute. Latest news on health eVects of particulate emissions from motor vehicles and studies of exposure assessments for diesel exhaust. Available from www.healtheVects.org Health of the Ramazzini Institute� published by OEM Press. Communicating Risk in a Changing World Edited by Timothy L.Tinker Maria T. Pavlova Audrey R. Gotsch and Elaine Bratic Arkin with 27 contibuting authors. ISBN 1 883 595207 OEM Health Information Inc. 1998 197 pages �37 Internet guide The book provides a valuable compendium of the most useful environmental resources on the Internet. The Fourth Edition contains 1200 Internet resources and 50% of the previous edition�s listings have been revised. New features include 45 new newsgroups 75 new electronic journals and newsletters 200 new websites. There is a brief description of new HTML tagging. Environment Guide to the Internet 4th Edition by Carol Briggs-Erickson and Toni Murphy ISBN 0 86587 643 6 556 pages 1998 �48 OHS Encyclopedia The latest edition of ILO�s definitive reference guide on occupational health and safety is now available in paper and CD-ROM versions.Encyclopaedia of Occupational Health and Safety 4th Edition International Labour OYce Edited by Jeannie Mager Stellman (Columbia University) 1998. ISBN 9 221 092038 (printed version) ISBN 9 221 098184 (CD-ROM version). Digital QA directory and guide National Quality Assurance the UK�s second largest certification agency has launched its membership directory on Events In vitro toxicology 12�13 April 1999 and Irreversible toxicology. 14 April 1999. Details from Caroline Elliot IBC UK Conferences Gilmoora House 57�61 Mortimer Street London UK W1N 8JX. Occupational Hygiene �99 Promoting a healthy working environment. 13�15 April 1999. Details from British Occupational Hygiene Society Suite 2 Georgian House Great Northern Road Derby UK DE1 1LT. Pesticide Residues in Food and Dietary Risk Assessment.28�29 April 1999 London. Details from Janine Winfield IBC Global Conferences tel +44 0 171 637 4383 IFAT �99�12th International T rade Fair for the Environment and Waste Disposal. 4�8 May 1999 Munich. One of Europe�s largest environmn tel +49 89 94901 Health Comfort and Productivity in Buildings. 6�7 May 1999 London UK. Details from C. Philpott Oscar Faber Marlborough House Upper Marlborough Road St. Albans UK AL1 3UT fax +44 (0) 181 784 5700. 32N J. Environ. Monit. 1999 1 News Air Quality in Europe Challenges for the 2000s. 19�21 May 1999 Venice Italy. Details from Dr Vincenzo Cocheo Padova e-mail fsmpd@tin.it or www.fsm.it or www.ei.jrc.it ET �99. 8�10 June 1999 Birmingham UK. The UK�s largest environmental trade show.Details from Reed Exhibition Companies e-mail et@reedexpo.co.uk 31st Mid-Atlantic Industrial and Hazardous Waste Conference 20�23 June 1999 University of Connecticut Storrs Connecticut. Details from Dr. Barth F. Smets e-mail bsmets@engr.uconn.edu or www.eng2.uconn.edu/environ Health Consequences of Phytoestrogens in Foods. 15 July 1999 London UK. Details from H. Wiseman Society of Chemical Industry tel +44 (0) 181 654 8216 Instrumental Methods of Analysis 19�22 September 1999 Chalkidiki Greece. Details from IMA �99 Secretariat tel +30 1 7723098 or www.chemeng.ntua.gr/IMA99/IMA99.htm 3rd Euroconference on Environmental Analytical Chemistry Environmental Analytical Chemistry for the 21st Century. 9�15 October 1999 Chalkidike Greece. Details from Mrs Zacharerua Loukou fax +30 31 99 77 19; e-mail rloukou@chem.auth.gr; www.chem.auth.gr/euroconf/enviro.html Measurement for Success UK National Measurement Conference �99.2�4 November 1999 Brighton UK. Incorporates BEMC �99�The 9th International Conference on Electromagnetic Measurement. Details from NMP Conference Secretariat National Physical Laboratory e-mail nmp sec@npl.co.uk International Symposium on Occupational Health for Europeans. 3�5 November 1999 Helsinki Finland. Details from Ella Ha�nninen tel +358 9 4747 546; fax +358 9 2413 804; e-mail ella.hanninen@occuphealth.fi or www.occuphealth.fi/eng/project/oh99 30th International Symposium on Environmental Analytical Chemistry. 13�16 June 2000 Espoo Helsinki Finland. Details from International Association of Environmental Analytical Chemistry e-mail iaeacmfrei@access.ch or tiina.harju@vtt.fi Web bytes The European Environment Agency�s Sustainability Targets and Reference (STAR) database is now accessible on the Web.STAR contains inventories of �sustainability reference values� (SRV�s) and �policy target values� (TV�s) for various themes media and economic sectors. SRV�s are commonly agreed standards and TV�s are legally based values. http://star.eea.eu.int/ A new web-gateway oVers access to the services of Dutch research laboratory TNO the Dutch agricultural research group DLO-NL and NIZO Food Research. Aspects covered include toxicology nutrition and food technology www.worldscienceservices.com Checkout advice on career development for scientists at http://uk.nextwave.org The Association for Women in Science and Engineering (AWiSE) has launched its own website oVering mutual support help and advice for women in UK science www.awise.org ERGO the European Research Gateways Online project was launched in December providing convenient access to a wide range of European R&D databases www.cordis.lu/ergo/home.html Info gateways FoE targets carcinogen emitters A website claiming to expose �the top 100 carcinogen-emitting industrial installations� in England and Wales has been set up by environmental pressure group Friends of the Earth.Based on publicly available information on the national chemicals release inventory maintained by the UK Environment Agency the database enables users to identify pollution and polluters in their local areas. The Agency will be launching a similar searchable inventory itself later this year.FoE stresses that both databases only cover about 40% of carcinogen emissions from industrial installations. The remainder are covered by local authorities and not published. It is calling for an 80% reduction in hazardous emissions by 2005 and community right-to-know provisions similar to those in the US. FoE Factory Watch www.foe.co.uk/factorywatch Euro information gateways The European Environment Agency is launching a series of actions to improve public access to environmental information. Together with the European Commission the Agency is to develop an extranet to support the work of EIONET the European Environment Information and Observation Network. EIONET is a collaborative activity involving more than 200 organisations across Europe in the observation and interpretation of environmental data. Under phase two of the project which runs through to 2003 key nodes within the network will be linked electronically and are to act as national clearinghouses for environmental information. A public gateway to EIONET and other environmental databases is also planned. E2RC the European Environmental Reference Centre will be a series of web-based services due for launch this autumn. It will provide structured access to environmental information where p

ISSN:0960-7919    

DOI:10.1039/a901757g

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Detection of petroleum hydrocarbons at low ppb levels using quartz resonator sensors and instrumentation of a smart environmental monitoring system Iwao Sugimoto,* Michiko Seyama and Masayuki Nakamura NTT Lifestyle and Environmental Technology Laboratories, Midori-cho, Musashino-shi, Tokyo 180–8585, Japan Received 27th November 1998, Accepted 8th February 1999 Petroleum hydrocarbon vapors at low ppb levels can be detected using a thickness shear mode resonator (TSMR) coated with a chemical-sensing overlayer, prepared by radiofrequency sputtering of porous sintered-polyethylene (PS-PE).The sensing capabilities of PS-PE sensors were profoundly aVected by the sputtering methods; they were enhanced by the photo-excitation eVect, and were reduced by carbonization and water treatment.The photoassisted PS-PE sensor was extremely sensitive and could detect linear hydrocarbon (>C12) vapors below the ppb level. The time constant of the sorption curve, however, was large, indicating a slow sensing speed. Toward creating instrumentation for a smart environmental monitoring system, the TSMR sensors were arrayed on a circuit board equipped with a serial interface and signal processing chips of the oscillation drive and frequency counter. Co-sorption with water vapor at a relative humidity of about 10% has almost no eVect on the sensing ability of PS-PE sensors for 1,2,4-trimethylbenzene.Conversely, it enhances the sensitivity of the TSMR sensor coated with a D-phenylalanine film. Upward shifts in the baseline are evident with elapsed time.However, a rigorous ten-cycle iteration test for 100 ppm toluene vapor demonstrated good reproducibility of the sensor’s signals. The continuing rise in petroleum hydrocarbon pollution is structural advantages in their chemical-sensing layers. The plasma-produced molecular networks are uniquely charac- driving the development of instrumentation that can rapidly detect spills and contamination in the ground and in water.terized by the radical sites generated by the beam-induced bond cleavage in plasmas.3 Some radicals form cross-linking Some of the largest sources of environmental pollution are the storage, distribution, and transportation facilities of petroleum bonds, yielding high atomic densities.4 Others may remain as trapped radicals, allowing flexible molecular networks. Both fuels such as gasoline, diesel oil, kerosene, and fuel oil.The demand is increasing for field-remote multi-point sensing of these features achieve high dissolution capacities for any type of solute molecules. Of the plasma processing methods, systems that can provide immediate detection of petroleum pollution. sputtering techniques have great potential for preparing highly sensitive layers because this approach is likely to produce high Both in the atmosphere and in water, optical and piezoelectric sensing systems are promising instrumentation for atomic density films with high gas-sorption capacities due to the energetic character of the sputtered species.These sputtered monitoring the level of environmental hydrocarbon pollutants.The optical type has been commercialized by a US company.1 species are likely to enhance the adhesiveness to the transducing film-substrate suitable for chemical-sensing overlayers. The piezoelectric type has been extensively exploited for practical interest due to its capability of measuring extremely small From the chemical sensing aspect, we focused particularly on the fact that PPF networks produced by radiofrequency mass changes below the nanogram level.Among several piezoelectric devices, the thickness shear mode resonator (TSMR) sputtering contain unsaturated carbons (dangling bonds and multiple bonds). These can interact with solute molecules by has been widely used as a mass transducer owing to its high oscillation stability and high signal-to-noise (S/N) ratio.2 specific spin-related interaction5 and p-electron-derived interactions: p–p,6 cation–p,7 CH–p8 and Cl–p9,10 interactions.The The gas-sorption chemistry in chemical-sensing overlayers of TSMRs governs their sensitivities and selectivities. To concentrations of these unsaturated carbons can be increased by photo-assisted sputtering using ultraviolet (UV) light exci- enhance the monitoring ability of the TSMR sensors for petroleum pollution, the overlayers should be interactive with tation.Thus, they play important roles in characterizing the gas-sorption behavior of PPFs.11 hydrocarbons, not with water. In monitoring the gas phase in the field, water vapor is considered the strongest competitor In this paper, we report on PPF-coated TSMR sensors for volatile petroleum hydrocarbons with detection limits at the to the target materials.In the environmental atmosphere, temperature, humidity, and wind are ever-fluctuating and sub-ppb level. The extremely sensitive films can be prepared by a photo-assisted sputtering technique. Our approach uses aVect the concentration of water vapor as well as the target materials.Fortunately, the lipophilic sensing layers are hydro- a porous sintered polyethylene (PE) disk as a sputtering target and UV light irradiation as a supplementary plasma excitation phobic due to their non-polar character. For satisfactory sensing ability, the detection limit for petroleum hydrocarbons source. It has recently been reported that PPFs composed of hydrocarbon networks can be obtained by sputtering a porous in the gas phase must be below the low ppb level.Plasma processing to produce plasma-polymer films (PPFs) sintered PE disk, not the commonly applied low-density PE disk, which is widely manufactured by compression molding.12 is conducted for the most part in a vacuum; this approach is inherently superior to wet processing, because it allows cleanli- We have developed an environmental gas monitoring system using an array of these PPF-coated TSMR sensors.The array ness without the need for organic solvents. In addition, polymeric films produced by plasma processing have salient was installed on a circuit board equipped with a serial interface J. Environ. Monit., 1999, 1, 135–142 135for multi-point sensing and signal processing chips of the compression-molded PE disk.The PE disk coated with the amino acid was then used as a sputtering target after the oscillation drive and frequency counter. Using the dynamic sensor response, the pattern matching technique can classify ethanol had fully evaporated. Helium was introduced into the sputtering chamber at 4 mL min-1, and the rf power was the gases based on a discrimination algorithm.The system can provide on-line monitoring of atmospheric conditions and can applied to the lower target electrode at a density of 0.42 Wcm-2. The detailed procedure of the rf sputtering of classify the gas species via telecommunications networks. amino acids has been described previously.15 Experimental Instrumentation of smart gas-sensing system for identifying environmental vapors Preparation of plasma-polymer-film-coated TSMR sensors We have developed a smart environmental gas-sensing system, The TSMR was fabricated from an AT-cut quartz crystal which can detect and distinguish vapor species.It consists of plate, which was 8.5 mm in diameter and 0.1 mm thick, with a sensor module (Fig. 1), a power supply, and a signal a 5 mm diameter gold electrode.The fundamental resonance processing computer. The sensor module is composed of an frequency of this TSMR was 9 MHz and it was manufactured array of eight PPF-coated TSMR sensors installed on a circuit by Nihon Dempa Kogyo, Tokyo, Japan. board equipped with a custom LSI operating the oscillation PPFs were produced by a diode-type radiofrequency (rf ) and measuring resonance frequency and a multi-port serial sputtering apparatus using the sputter-up configuration.The interface (RS-485) for multi-point sensing. The computer interelectrode space was capable of excitation by irradiation display can show the time-dependent dynamic sensor response of UV light through a CaF2 window using a 300 W low- and gas classification map for discrimination of vapor species. pressure mercury lamp.The detailed structure of the photo- The discrimination algorithm for identifying the vapor species assisted sputtering apparatus has been described previously.13 is based on a pattern matching technique that uses learning Sputtered PPFs were deposited on both sides of the quartz vector quantization (LVQ).16 Two featured parameters were crystal plates, which were placed on the grounded upper extracted: the time constant and the maximum frequency shift electrode.The thickness of the film on each side of the quartz from the dynamic sensor response.17 This procedure based on crystal plate was controlled by the sputtering time to about LVQ is advantageous for fast and accurate discrimination of 0.5 mm.several types of vapor species. For six kinds of vapors, the Polyethylene (PE) films were prepared by using, as a sputter- processing time for determining the winning vector in the LVQ ing target, a porous PE disk (135 mm in diameter) produced map, which can visualize the results of LVQ processing, is less by sintering PE granules (with diameters ranging from 200 to than 1 s.The system can monitor the atmospheric condition, 300 mm). PE disks of two thicknesses (5 and 10 mm) were identify the vapor species, and make this information immediused. We will refer to the films produced by the supplementary ately available for on-line environmental surveillance via telephoto- excitation method as photo films. Those produced using communications networks.We have shown the validity of the a 5 mm thick disk will be termed 5 mm films, to diVerentiate sensing system for discriminating 14 chemical vapors.18 them from the major films obtained from 10 mm thick disks. The PE disk was severely blackened after about 12 sputtering Measurements of sensing capability cycles over about 300 h. The sputtered PE film obtained using this blackish PE target was carbonaceous.We will refer to this Fig. 2 shows schematically the set-up of the gas flow system film as a carbon film. The properties and structures of the for measuring the detection capability of the TSMR sensors. sputtered films are also aVected by the background pressure, The organic vapors were generated by the diVusion tube which can be considered to be a measure of the amounts of method19,20 using a PD-1B standard gas generator from residual gases in the vacuum chamber.These amounts increase Gastec, Kanagawa, Japan. A glass tube preserving the hydrowith background pressure; water is one of the main residual carbon solvent (vapor source) was kept in a temperaturegases attributable to the characteristics of plasma products.In controlled bath using synthetic air (99.9999% pure) as a carrier most cases, the background pressure was 9×10-5 Pa. In some gas and also as a standard or cleaning gas for establishing the cases, however, the atmosphere in the chamber was kept humid initial state of the TSMR sensors. Commercial hydrocarbon with water-saturated cotton and the chamber was evacuated solvents were used without further purification (>98% pure).to be 4×10-3 Pa, which was used as the background level. They are regarded as environmental-residing components of We will refer to the film prepared under humid conditions as gasoline and fuel oil and are classified by the World Health a water film. Organization as very volatile organic compounds (VVOCs), In all cases for PE films, krypton was introduced into the sputtering chamber at 6 mL min-1, and the rf power was applied to the lower electrode at a power density of 0.389 Wcm-2.A fluoropolymer-coated TSMR sensor was also fabricated. The film was produced by rf sputtering of a poly(chlorotrifluoroethylene) (PCTFE) disk, which was manufactured by Daikin Kogyo, Osaka, Japan, using ordinary compression molding.Argon was introduced into the sputtering chamber at 5 mL min-1, and the rf power was applied to the lower target electrode at a density of 1.12 Wcm-2. This fluoropolymer film, which has a solvophobic character14 except for the fluorocarbons, is considered to be a good reference for PE films. For comparison purposes, polar chemical-sensing overlayers of TSMR were also prepared, using a-amino acids.Film synthesis was carried out by rf sputtering of D-phenylalanine and DL-histidine (>98% pure, purchased from Kanto Chemicals, Tokyo, Japan). Each amino acid was suspended Fig. 1 Magnified photograph of sensor module with an embedded array of TSMR sensors. in ethanol and the dispersed solution was spread on the 136 J. Environ. Monit., 1999, 1, 135–142Fig. 2 Schematic diagram of set-up for measuring sorption capacities of TSMR sensors for organic vapors. volatile organic compounds (VOCs), and semi-volatile organic Quadrex MS (50 m x 0.53 mm x 0.25 mm) was used as the capillary column and helium was used as the carrier gas. compounds (SVOCs).21 A naphtha reference standard (Supelco, Bellefonte, PA, USA, Cat. No. 4–7488) was used for the gasoline sample.Also, special-A-grade fuel oil produced Results and discussion commercially in Japan was used for the fuel oil sample without purification. The vapor concentration was controlled by the To determine gas concentrations accurately, a cross-check shape of the diVusion tube and by its temperature, which was between the diVusion tube method and GC analysis was either 30, 40, or 50 °C.The flow rate of the carrier gas was set performed. Based on the diVusion tube method as shown in at 0.2 L min-1, using a mass flow controller. It was possible Fig. 2, the standard gases can be generated, controlling their to install eight TSMR sensors in a 30 mL sensor cell, which concentrations by changing such factors as the shape of the can be used as the sensor module in the smart gas-sensing diVusion tube, the temperature, and the flow rate of the carrier system.The sensor cell was connected to the gas flow line and gas. The gas concentration [C (ppm)] can be estimated as was placed in a temperature-controlled chamber kept at 25 °C. follows: The hydrocarbon stream generated from the gas-generation cell was introduced into the sensor cell after the baseline C= K·Dr·103 F (3) (background) fluctuation had been brought down to below 1 Hz for 10 min.Switching between the baseline and measuring modes was eVected rapidly using a four-way valve, which K= 22.4 M · 273+T 273 · P 760 (4) produced a step response and kept the gas pressure constant before and after switching. The sorption capacities were deter- where Dr (mg min-1) is the diVusion rate, F (mL min-1) the flow rate of the carrier gas, M the molecular weight of the mined by the maximum frequency shifts for 3 h sorption measurements.Sauerbrey’s equation22 was used to relate the generated gas, T (°C) the temperature of the diVusion tube, and P (mmHg) the pressure of the generating gas. frequency shift (Df ) to the change of mass loading (Dm): Table 1 summarizes the vapor concentrations, which were Dm=-[A(rqmq)1/2/2F02]Df (1) calculated using eqn.(3) and measured by GC analysis, under various conditions of diVusion tube shape and temperature. where F0 is the fundamental resonant frequency of the unloaded TSMR (9 MHz), A is the electrode area (0.39 cm2), To calculate the gas concentration precisely, the diVusion rates were determined by the weight loss of a diVusion tube, rq is the density of the quartz (2.65 g cm-3), and mq is the shear modulus of the quartz (2.95×1011 dyn cm-2). With preserving the hydrocarbon solvent at a constant temperature over a period of 1 week.These are some diVerences between these constants, we obtain Cc and Cm. In general, the values for calculated concentrations Dm(ng)=-1.05Df (Hz) (2) (Cc) over 0.1 ppm tend to be lower than the corresponding measured concentrations (Cm).Conversely, values for Cc below A frequency counter (Advantest, R5361A) was used for measuring the resonant frequencies of TSMR sensors to an 0.1 ppm tend to be higher than the corresponding Cm. Under these low-concentration conditions, the contaminants accuracy of 0.1 Hz.It is becoming increasingly important to confirm the accu- in the flow line are clearly detectable by GC analysis. In most cases, the main GC signal of the contaminants can be identified racy of the vapor concentration estimated using the diVusion tube method for low concentrations at the sub-ppm level. The as toluene by its retention time. The other clearly observable contaminants are acetone and n-decane, which are reported as concentrations of hydrocarbon vapors were measured by using gas chromatography (GC).The exhaust gas eluted from a being among the most ubiquitous pollutants in the indoor environment.23 These contaminants are probably generated sensor cell was collected in a gas sorption tube packed with Tenax TA. This sampling tube was set in a thermal desorption from the surface of the inner wall of the gas-lines and the gasgeneration cell, which was coated with fluoropolymer resin injection system (Perkin-Elmer, ATD 400) and the desorbed gas was analyzed by using an HP-5890 II gas chromatograph paint containing typical organic solvents.Even though the gas flow line was cleaned by a flow of pure synthetic air for 4 d equipped with a hydrogen flame ionization detector.A J. Environ. Monit., 1999, 1, 135–142 137Table 1 Gas concentration generated by diVusion tube method Measured vapor DiVusion DiVusion rate Calculated vapor concentration by GC Gas source tubea Temperature/°C (Dr)/mg min-1 concentration (Cc) (ppm) (Cm) (ppm) None D-1 30 — — 0.002b D-5 50 — — 0.0065b 2-Methylpentane D-1 30 17.750 25.210 28.000 2,2,4-Trimethylpentane D-1 30 5.550 5.890 2.100 n-Decane D-1 30 0.121 0.100 0.140 D-1 40 0.233 0.200 0.290 0.007c D-3 30 0.721 0.620 0.850 0.083c n-Dodecane D-2 30 0.040 0.030 0.031 D-3 30 0.114 0.080 0.039 0.005c D-4 30 0.184 0.130 0.092 0.028c n-Tetradecane D-2 50 0.017 0.010 0.005 0.012c D-3 50 0.045 0.030 0.014 0.001c n-Hexadecane D-2 50 0.005 0.003 N.D.d 0.048c D-3 50 0.012 0.007 N.D.d 0.009c D-5 50 0.040 0.022 0.003 0.002c 1,2,4-Trimethylbenzene D-1 30 0.195 0.200 0.210 0.007c D-2 30 0.466 0.470 0.650 3-Ethyltoluene D-2 30 0.729 0.740 0.920 Gasoline D-1 30 — — 1.000b D-2 30 — — 2.900b Fuel oil D-1 30 — — 0.100b D-2 30 — — 0.230b aShape of diVusion tube [cross section (mm2), length (mm)]: D-1 (1.65, 50), D-2 (4.91, 52), D-3 (12.56, 50), D-4 (18.85, 40), D-5 (27.33, 31).bConcentration estimated as n-octane concentration using the total GC signals. cConcentration of toluene, which is detected as the main co-existing compound. dNot detected; lower than the detection limit of 0.0002 ppm. while heating the pipe to 50 °C, the flow line was not completely by a gradual decrease in the frequency shift after taking the maximum positive values, which are as large as a few clean for measuring the sensor ability at the ppb level.In some cases, the concentrations of contaminants were higher than Hertz. Most of the cases marked with an asterisk belong to polar amino acid films. These negative shifts may reflect that of the vapor species to be generated, as shown in Table 1. In particular, for the semi-volatile hydrocarbon n-hexadecane re-vaporization of the sorbed (adsorbed and/or absorbed) gas molecules from the solvent PPF owing to their weak intermol- with a low vapor pressure, it is noteworthy that GC measurements can detect only the contaminants, not the n-hexadecane, ecular interactions.To clarify the background levels of the sensor responses, which was introduced into the gas-generation cell.Table 2 summarizes the downward shifts in the resonant blank tests (as indicated by ‘none’ in Table 2) were performed as follows. The frequency shifts were measured by changing frequencies, over 1 h, of the PPF-coated TSMR sensors exposed to the vapor flow shown in Table 1. In Table 2, the the pure air stream through the cleaning cell to the other pure air stream through the gas-generation cell without introducing asterisks denote negative values of the downward shift caused Table 2 Frequency shifts of PPF-coated TSMR sensors over 1 h.The asterisks denote negative values of the downward shift caused by a gradual decrease in the frequency shift after taking the maximum positive values Condition Sensing film DiVusion PE (water)/ PE (carbon)/ PE/ PE (photo)/ Phe/ His/ PCTFE/ Gas source tube Temperature/°C Hz Hz Hz Hz Hz Hz Hz None D-1 30 2 3 4 5 0 — 0 D-5 50 4 5 10 16 0 — 0 2-Methylpentane D-1 30 7 5 35 39 6 — 2 2,2,4-Trimethylpentane D-1 30 3 2 8 11 * — 1 n-Decane D-1 30 6 4 23 28 6 2 1 D-1 40 35 8 150 186 5 2 0 D-3 30 62 12 235 280 5 1 0 n-Dodecane D-2 30 10 4 22 32 9 6 0 D-3 30 56 13 83 124 7 5 0 D-4 30 84 * 169 229 6 * 0 n-Tetradecane D-2 50 17 12 25 36 9 8 0 D-3 50 18 9 29 39 16 7 0 n-Hexadecane D-2 50 8 7 27 34 5 2 0 D-3 50 5 7 16 23 21 3 0 D-5 50 18 9 31 41 11 4 0 1,2,4-Trimethylbenzene D-2 30 12 7 55 57 1 * 0 3-Ethyltoluene D-2 30 14 7 82 79 * * 0 Gasoline D-1 30 45 17 169 261 1 * 0 D-2 30 29 8 118 135 4 2 0 Fuel oil D-1 30 17 24 38 49 8 * 0 D-2 30 18 8 46 97 10 3 0 138 J.Environ. Monit., 1999, 1, 135–142a gas source. Two ‘none’ conditions correspond to the situations in which contaminant vapors can be generated at maximum (D-5, 50 °C) and minimum (D-1, 30 °C) concentrations. The total amounts of contaminants correspond to noctane concentrations of 6.5 ppb (maximum) and 2 ppb (minimum) (see Table 1). Taking into account this information on the background level of the sensors and the contamination level of the gas flow line, we will now interpret the results of the gas-sorption measurements listed in Tables 1 and 2.Compared with the amino acids and PCTFE films, PE-class films induce larger frequency shifts of the TSMR sensors for all of the hydrocarbon vapors, as shown in Table 2. In particular, PE and PE Fig. 3 Response curves of TSMR sensors for 14 ppb n-tetradecane. (photo) films are extremely sensitive and can detect the linearshaped large hydrocarbons at the sub-ppb level. The hydrocarbon networks of PE-class films are attributable to the lipophilic behavior of the TSMR sensors, applicable to environmental hydrocarbon sensing at the ppb level. The inferior sorption properties of amino acid and PCTFE films are probably due to the low values of the dispersion factor, which is one of the most important molecular descriptors in the well-established linear solvation energy relationship (LSER) equation24–26 quantifying the gas-sorption characteristics of polymeric films. In the LSER equation, the sorption capacity [corresponding to the partition coeYcient (K)] of a solvent polymeric film for the solute vapor can be expressed by a linear combination of the factors of intermolecular interactions: Fig. 4 Response curves of TSMR sensors for 650 ppb log K=C0+r(R2)+s(p2)+a(b2)+b(a2)+l(logL 16) (5) 1,2,4-trimethylbenzene. where C0 is a regression constant; r is the polarizability of the solvent polymer and R2 is that of the solute vapor; s is the 1,2,4-trimethylbenzene, which is representative of the alkylated benzenes. All the sensor response curves can be expressed by polarity of the solvent polymer and p2 is that of the solute vapor; a is the hydrogen-bonding acidity of the solvent polymer a time-dependent equation, based on the sorption/desorption kinetics presented by Langmuir,29 as follows: and b2 is the hydrogen-bonding basicity of the solute vapor; b is the hydrogen-bonding basicity of the solvent polymer and DF(t)=a[1- exp(-t/t)] (6) a2 is the hydrogen-bonding acidity of the solute vapor; and l and logL 16 are the dispersion/cavity factors of the solvent where the gas sorption starts at t=0, DF(t) is the sensor response value (frequency shifts of TSMR) at time t, a is the polymer and solute vapor. The dispersion factor is closely correlated with the lipophilicity evaluated by solubility in n- maximum value of the sensor response at the saturated state equilibrated between sorption and desorption, and t is the hexadecane at 25 °C (known as the Ostwald solubility coeYcient27).time constant. The validity of this kinetic equation has been shown elsewhere.30 In Fig. 3, all the sensors responding to Despite the high vapor concentrations (>1 ppm) of the VVOCs 2-methylpentane and 2,2,4-trimethylpentane, the fre- linear-shaped hydrocarbons have large time constants in their saturation curves, while the time constants in Fig. 4 are smaller. quency shifts of all the TSMR sensors are small for both VVOCs. These low sensitivities are probably caused by their This behavior indicates the slow diVusion of linear-shaped hydrocarbon molecules into the bulk of the film concomitant low dispersion force values, due in turn mainly to their low molecular weight and their branch-shaped molecular struc- with multilayered adsorption at the film surface.Despite the slow responses, the linear-shaped hydrocarbons can eventually tures. The latter structural factor can be explained by the thermodynamic ‘entropy eVects’28 in solvation.In general, the induce large frequency shifts due to their extensive dissolution into the solvent film and self-cohesive accumulation at the film dissolution capabilities of branch-shaped hydrocarbons are inferior to those of linear-shaped hydrocarbons. The linear- surface. The sensitive PE (photo) films are expected to induce detectable response signals for linear-shaped hydrocarbons shaped hydrocarbons are likely to be solvated without disturbing the highly ordered molecular networks of the solvent at the sub-ppb level.Conversely, the alkylated benzene 1,2,4-trimethylbenzene is not likely to diVuse into the bulk of molecules because of their high capability for taking any shape of molecule adaptable for solvent molecular networks.the film and exhibits fast saturation due to self-association occurring in the vicinity of the film surface, because it has a Compared with the background level detected by blank tests, the PE- and PE (photo)-TSMR sensors are suitable for planar and rigid molecular structure. GC analysis reveals that the eluent vapors from gasoline detecting those branch-shaped hydrocarbons classified as VVOCs.and fuel oil have no more than 46 and 39 components, respectively. The vapor concentrations of the sum of all of the The test vapors belonging to the VOCs and SVOCs can be classified as linear-shaped hydrocarbons and alkylated ben- GC signals for gasoline and fuel oil correspond to n-octane concentrations of 1.0 and 0.1 ppm, respectively.As shown in zenes. Compared with the amino acid and PCTFE films, all of the PE films induce satisfactorily large frequency shifts of Table 1, even though the vaporization conditions for both petroleum hydrocarbons are the same, the values for the the TSMR sensors, applicable for environmental monitoring, as shown in Table 2. Fig. 3 and 4 show the TSMR sensor number of components and vapor concentration of gasoline eluents are larger than those of fuel oil, because gasoline is response curves for 14 ppb (Cc) n-tetradecane, which is a typical linear-shaped hydrocarbon, and for 650 ppb (Cc) composed mainly of hydrocarbons (>C10) with higher vapor J.Environ. Monit., 1999, 1, 135–142 139Fig. 7 Response curves of TSMR sensors for 100 ppm toluene vapor Fig. 5 Response curves of TSMR sensors for gasoline vapor (corre- induced by the iterative sorption–desorption cycle. sponding to a 1.0 ppm concentration of n-octane vapor). To evaluate the sensing ability in the presence of humidity, the sensor responses of PPF-coated TSMR sensors exposed to a flow of a binary gaseous mixture of water and a petroleum hydrocarbon, e.g., 1,2,4-trimethylbenzene or n-decane, were measured.Using a humidified vapor measuring apparatus composed of the flow lines of water and petroleum hydrocarbon (as shown in Fig. 8), the background levels at which each TSMR sensor was exposed to a flow of pure synthetic air were first established by setting two sets of four-way valves to feed pure synthetic air. After the sorption equilibrium had been attained, the gas flow into the measuring cell was changed to pure water vapor by turning the four-way valve 2, leaving the four-way Fig. 6 Response curves of TSMR sensors for fuel oil vapor (corre- valve 1 in the pure synthetic air mode. All the response curves sponding to a 230 ppb concentration of n-octane vapor). of the TSMR sensors for sorption of water vapor, in which the relative humidity is at about 10%, are shown in Fig. 9. After the TSMR sensors had been exposed to pure water pressures than those of the components of fuel oil. The sensor response curves for 1.0 ppm gasoline vapor and 0.1 ppm fuel vapor for 3 h, a petroleum hydrocarbon stream was introduced into the humidified sensor cell, replacing the pure synthetic oil vapor are shown in Fig. 5 and 6, respectively. The volatile characteristics of gasoline are attributable to air, by turning the four-way valve 1. The sensor response curves for 1,2,4-trimethylbenzene and n-decane are shown in alkylated benzenes, which are present in gasoline in large amounts but are rare in fuel oil. Therefore, the sensor response Fig. 10 and 11, respectively. Fig. 10 and 11 show the frequency shifts from pure water vapor (background) to a mixture of curve of gasoline vapor (Fig. 5) is similar to that of 1,2,4-trimethylbenzene (Fig. 4).While one of the main compo- water and petroleum hydrocarbon vapors. In all of the water vapor sorption curves (as shown in nents of fuel oil are the linear-shaped hydrocarbons with their high molecular weight, the sensor response curve of fuel oil Fig. 9), the D-phenylalanine film showed a remarkably high sorption capacity for water, reflecting its polar molecular vapor (Fig. 6) resembles that of n-tetradecane (Fig. 3). Hence, the sensor response curve of petroleum products reflects that structure; this was reported previously.15 Conversely, PE-class films with a non-polar character12 had low water sorption of their main components, which can characterize the vaporization behavior of petroleum products.capacities. The PCTFE film in particular shows a negligible aYnity for water vapor, as expected from the hydrophobic To confirm the reproducibility of the sensor’s responses, iterative testing of the sorption/desorption of the typical character of the fluoropolymer. After the water vapor attained suYcient sorption at the hydrocarbon toluene was carried out.Severe conditions were set for the chemical-sensing overlayers of the TSMR sensors, quasi-equilibrium state, petroleum hydrocarbon vapor at a concentration of 200 ppb was introduced into the sensor cell to the extremely high concentration of 100 ppm, to accelerate the solvation damage induced by the restructuring of the to measure the capability for sensing petroleum hydrocarbons in the presence of humidity (Fig. 10 and 11). The responses molecular networks. Ten cycles of the sorption/desorption tests were performed varied widely between the PE-film-coated TSMR sensors. However, regardless of the type of petroleum hydrocarbon, as shown in Fig. 7. The duration of each sorption or desorption period was 30 min.All of the sensor curves responding to the response level was comparable. The frequency shifts of PE-film-coated TSMR sensors are basically the same as the sorption and desorption were then superimposed on their time-dependent drift curves. Good reproducibility was values for pure 1,2,4-trimethylbenzene, as shown in Table 2. Compared with the sensitivity for pure n-decane vapor, the observed for all of the PPF-coated TSMR sensors, taking into account the oVset due to sensor drift.The changes in frequency frequency shifts of these sensors are reduced by the presorption of water vapor. This may be caused by the lipophobic shifts (strength of sensor response) induced by gas-sorption/ desorption had a profound correlation with the degree of character of the water-sorbed PE film, preventing the incorporation of n-decane molecules with their hydrophobic character.oVset induced by individual drift. Toluene vapor induced larger frequency shifts for the TSMR sensors coated with the In all cases, the PE (photo) film shows pronounced sensing ability coincident with its high sensitivity for pure petroleum PE (photo, 5 mm), PE (photo), and PE films, which are composed of lipophilic hydrocarbon networks.12 hydrocarbons. The sensing ability of the D-phenylalanine film for petroleum In practical situations, TSMR sensors are profoundly aVected by the concentration of water vapor, which is usually hydrocarbons was abruptly increased by the co-sorption with water vapor, compared with the negligible sensing ability for higher than that of the petroleum hydrocarbon to be detected. 140 J. Environ. Monit., 1999, 1, 135–142Fig. 8 Schematic diagram of set-up for measuring sorption capacities of TSMR sensors for binary mixtures of water and organic vapors. Fig. 9 Response curves of TSMR sensors for water vapor (RH: Fig. 11 Response curves of TSMR sensors for binary mixture of 8.7% 10.0%). RH water and 200 ppb n-decane.References 1 D. P. Saini, R. Leclerc, S. Coulter and H. Li, SPIE, 1995, 2504, 334. 2 K. Bodenho� fer, A. Hierlemann, G. Noetzel, U. Weimar and W. Go� pel, Anal. Chem., 1996, 68, 2210. 3 Techniques and Applications of Plasma Chemistry, ed. J. R. Hollahan and A. T. Bell, Wiley, New York, USA, 1974. 4 H. B. Olayan, H. S. Hamid and E. D. Owen, J. Macromol. Sci.- Rev.Macromol. Chem. Phys., 1996, C36, 671. 5 J. S. Miller and A. J. Epstein, Angew. Chem. Int. Ed. Engl., 1994, 33, 385. Fig. 10 Response curves of TSMR sensors for binary mixture of 6 C. A. Hunter and J. K. M. Sanders, J. Am. Chem. Soc., 1990, 10.0% RH water and 200 ppb 1,2,4-trimethylbenzene. 112, 5525. 7 J. C. Ma and D. A. Dougherty, Chem. Rev., 1997, 97, 1303. 8 M.-F. Fan, Z.Lin, J. E. McGrey and D. M. P. Mingos, J. Chem. these petroleum hydrocarbons, as shown in Table 2. The Soc., Perkin Trans. 2, 1996, 563. hydrophobic interaction of the water-sorbed film molecules 9 S. W. Benson, J. Am. Chem. Soc., 1993, 115, 6969. and hydrocarbons may play an important role in enhancing 10 I. Sugimoto, M. Nakamura and H. Kuwano, Sens. Actuators, B, 1996, 37, 163. the sensitivity of the sensor. J. Environ. Monit., 1999, 1, 135–142 14111 I. Sugimoto, M. Nakamura, H. Kuwano and R. Shimade, Thin 22 G. Z. Sauerbrey, Z. Phys., 1959, 155, 206. Solid Films, 1997, 310, 303. 23 I. L., Gebeluegi and F. Korte, in Proceedings of the Fifth 12 I. Sugimoto, Analyst, 1998, 123, 1849. International Conference on Indoor Air Quality and Climate, 13 I. Sugimoto and S. Miyake, J. Appl. Phys., 1988, 64, 2700. INDOOR AIR ’90, ISIA@, Toronto, Canada, 1990, vol. 2, 14 Y. Ishikawa, H. Kuwahara and T. Kunitake, J. Am. Chem. Soc., pp. 701–706. 1989, 111, 8530. 24 J. W. Grate and M. H. Abraham, Sens. Actuators, B, 1991, 3, 85. 15 I. Sugimoto, M. Nakamura and H. Kuwano, Anal. Chem., 1994, 25 M. H. Abraham, Pure Appl. Chem., 1993, 65, 2503. 66, 4316. 26 R. A. McGill, M. H. Abraham and J. W. Grate, CHEMTECH, 16 T. Kohonen, Self-Organizing Maps, Springer-Verlag, Berlin, 1994, 27. Germany, 1995. 27 M. H. Abraham, P. L. Grellier and R. A. McGill, J. Chem. Soc., 17 M. Nakamura, I. Sugimoto, H. Kuwano and R. Lemos, Sens. Perkin Trans. 2, 1987, 797. Actuators, B, 1994, 20, 231. 28 J. N. Israelachvili, Intermolecular and Surface Forces, Academic 18 M. Nakamura, I. Sugimoto and H. Kuwano, in Proceedings of the Press, London, UK, 1985. 1997 IEEE International Conference on System, Man, and 29 I. Langmuir, J. Am. Chem. Soc., 1916, 38, 2221. Cybernetics, SMC ’97, IEEE, Orlando, FL, USA, 1997, vol. 4, 30 M. Nakamura, I. Sugimoto and H. Kuwano, J. Intell. Mater. Syst. pp. 3036–3041. Struct., 1994, 5, 315. 19 J. M. H. Fortuin, Anal. Chim. Acta, 1956, 15, 521. 20 G. A. Lugg, Anal. Chem., 1968, 40, 1072. 21 WHO Regional OYce for Europe, Indoor Air Quality: Organic Pollutants, EURO Reports and Studies No. 111, Copenhagen, Paper 8/09298B Denmark, 1989. 142 J. Environ. Monit., 1999, 1, 135&ndash

ISSN:0960-7919    

DOI:10.1039/a809298b

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

The influence of geometry and draught shields on the performance of passive samplers Peter Hofschreuder,* Wobbe van der Meulen, Paul Heeres and Sjaak Slanina Meteorology and Air Quality Group, Agricultural University Wageningen, Duivendaal 2, 6701 AP Wageningen, The Netherlands Received 26th November 1998, Accepted 23rd February 1999 Passive samplers provide an excellent opportunity to perform indicative measurements or establish a dense network of measuring sites. A drawback compared with conventional active measuring methods is the larger spread of results.This variation can, to a large extent, be attributed to the influence of temperature, sampler geometry and wind on sampling results. A proper design of sampler geometry and optimum choice of draught shield can reduce the influence of wind velocity on a badge type sampler to less than 10%.Wire mesh screens prove to be inadequate in damping turbulence. Filters give good results. Attention should be paid to the size and isolation value of the walls of the sampler to prevent thermal updrafts occurring within the sampler. Tube type samplers are less influenced by wind, provided that turbulence is prevented from influencing diVusion within the sampler.where m=mass (mg m-3); f=correction factor for temperature Introduction and pressure; A=surface area of sampler (m2); D=diVusion Passive samplers are attracting increasing attention as a tool coeYcient (m2 s-1); r=concentration of pollutant (mg m-3) in obtaining outdoor air quality data in remote locations far (1=at entrance of the sampler and 2=at the adsorption from electrical connections, and for intensive studies such as surface); t=exposure time (s); and l=diVusion length within epidemiological studies and model validation.The use of sampler (m). passive samplers is strongly supported by the European Union. The correction factor f for temperature and pressure is In Council Directive 96/62/EC of 27 September 1996 on Air proportional to T n, where T=absolute temperature (K), and Quality Assessment and Management, a framework is set for 0.5<n<1.0.6 The correction to STP in the range 263–308 K preliminary assessments of air quality, optimisation of station amounts up to a maximum of 10%.The uncertainty in this siting, supporting generalisation measurements and evalua- correction has a maximum of 6%.tion of existing measurements. In the Guidance Report on The resistance against uptake of the pollutant is defined by Supplementary Assessment under EC Air Quality Directives (1997), it is concluded that the low cost and easy operation Rd= l D of diVusive sampling techniques make them an ideal tool for large scale air pollution surveys with a high spatial resolu- where Rd is resistance (s m-1).This Rd only constitutes the tion. The diVusive sampler is also of particular interest as an resistance within the sampler. Introduction of a draught screen indicative technique. The maximum uncertainty is estimated gives an additional resistance against uptake of pollutant (Rf). in an EC report1 to be about 30%. This uncertainty is mainly At low wind speeds, the possibility exists that there will be a caused by the influence of meteorology on the sampler.This development of a stagnant layer of air in front of the draught paper deals with possibilities of reducing the uncertainty by screen. This layer exhibits another resistance against uptake careful design and reduction of the influence of meteorology (Re).For a badge type sampler (and a tube type sampler with a draught screen) we end up with a total resistance (Rt) against on the sampler. uptake of pollutants of Tube type passive samplers such as the Palmes tube are constructed with a relatively long diVusion distance from the Rt= 1 Rd+Rf+Re entrance of the tube to the sorbent compared with the diameter of the tube. This geometry is chosen to avoid too much The last uncertain factor in the calculation of the sampled influence of external turbulence on the eVective diVusion mass is the equilibrium concentration of the pollutant just length.2 A drawback of this geometry is the low sampling rate above the absorbing material.This may be calculated from of the tube type sampler. To increase the sampling rate of a chemical data.When this concentration plays a role (0), we passive sampler, badge type samplers were developed3 and in obtain a decrease in the concentration gradient during sam- other cases the diVusion length of the tube type sampler was pling and should apply an integrated collection function. In shortened.4 Shortening of the diVusion length increases the practice, using absorbing media with a low equilibrium gas influence of turbulence and wind speed on the sampler and concentration and application of excess absorbing material to makes the entrance geometry more critical.To mitigate probmaintain a low concentration of pollutant in the absorbing lems of this kind, draught shields were introduced.5 material circumvent this situation. The mass of a pollutant that is collected by a passive sampler in a steady state situation during a certain time is derived Aim of the study from Fick’s first law of diVusion and given by the equation14 It can be concluded that the largest source of uncertainty in passive sampling is the uncertainty in the value of Rt. Lowering m= fAD(r1-r2)t l the uncertainty in Rt was the aim of this study.J. Environ. Monit., 1999, 1, 143–147 143When we define the sampling rate to be Theory on the resistance against diVusion The concept of a total resistance (Rt) against uptake of s= A Rt pollutants by diVusion by a passive sampler with a draught shield was presented in the Introduction. To be able to interpret where s=sampling rate (m-3 s-1), it will be clear that we will results, this concept will be extended.obtain a decreasing sampling rate with decreasing wind velocity The resistance of the draught shield can be approximated and that this decrease is more pronounced for badge type by the equation samplers. Rf= e DP Testing passive samplers General requirements for testing passive samplers are described where Rf=resistance of draught shield (s m-1); e=thickness in the draft CEN Standard on Passive Samplers Part 19 and of draught shield (m); and P=porosity.will not be treated here. In the draft CEN Standard on Passive For a filter, the thickness and porosity should be derived Samplers Part 3,10 attention is paid to the influence of environ- from data from the manufacturer. Typical values for Rf for a mental factors on sampler performance and the protection glass fibre filter and a membrane filter are 15–20 s m-1 (e= from adverse environmental conditions. 0.35 mm, P=0.9) and 1–4 s m-1 (e=0.025–0.075 mm, P= In general, samplers are protected against rain by simple 0.85), respectively. When a wire mesh screen is used as a metal profiles, plastic funnels and boxes that are more or less draught shield, the porosity can be calculated by closed but well ventilated by having no bottom or having drilled holes.9 All protective devices should be evaluated with P= L2 (L+d)2 respect to inertia of the material against the gas to be measured and possible interfering emissions from the construction where L=distance between wires (m) and d=diameter of material.wire (m). Shielding against rain almost automatically means protec- Typical values for Rf for commercial wire mesh screens with tion against high wind speeds.Problems may arise at the lower mesh range between 8 and 25 are 35–65 s m-1. end of the wind velocity spectrum. Most draught shields will A value for the external boundary layer resistance (Re) is lower the wind velocity and especially during very stable and diYcult to estimate.This resistance will be very dependent on very unstable atmospheric conditions (at night and on sunny sampler geometry and meteorological conditions. days in summer), this may cause the formation of an external For a flat surface and turbulent conditions, Monteith and boundary layer in front of the sampler entrance and/or even Unsworth7 estimated the average boundary layer thickness a too low refreshment rate in front of the sampler causing independent of wind speed: ‘starvation’ of the sampler.11 Another problem that may arise is the influence of protective devices on the temperature of the d#Z0.8 sampler.Strong insulation during the day or radiative cooling where d=boundary layer thickness (m) and Z=length of during the night may increase respectively decrease the sampler surface (m). Ballesta et al.8 suggested a slight dependence on temperature with respect to the ambient temperature.Hence the wind velocity: the albedo and the isolation of the walls of the protective device should also be considered. The operating temperature d=0.37 An uB0.2 Z0.8 should be known for the conversion of the sampled mass to an average ambient concentration at standard temperature where n=kinematic viscosity of air (1.485×10-5 m2 s-1) and and pressure.6,9 The same considerations as mentioned for u=wind velocity (m s-1).protective devices apply to the passive samplers themselves. When we take Z=0.785z (z=diameter of badge/tube) for Four samplers were used in the experiments. The first the average length of the surface, we can calculate the thickness sampler, which was used to demonstrate the influence of wind of the boundary layer and the corresponding resistance.The speed on the sampling rate, was the original design of the results are presented in Table 1. Willems badge12 (Fig. 1). The total resistance as the sum of diVusional, filter, and The badge is made of polystyrene, being hydrophobic, inert boundary layer resistances for a Willems badge with a glass and having a low permeability for gases.A metal construction fibre draught shield and a modified Palmes tube with a Teflon with high reflectivity could be considered, causing the temperamembrane filter as a draught shield is presented in Table 2. ture of the badge to be as close as possible to ambient A conclusion that can be drawn from these tables is that conditions, but has the disadvantage of a low isolation value.for a tube type sampler the resistance of the draught shield As the badge was primarily used for sampling ammonia, the and the boundary layer resistance are of minor importance drawback of condensation of water vapour on a metal badge and constitute only a few per cent of the total resistance was considered to be more important than a slight diVerence against uptake of the pollutant.For badge type samplers the in temperature. The badges were stuck by means of Velcro to boundary layer resistance can amount up to tens of per cent an angled aluminium plate in an upside down position. The use of a reaction filter (or stainless steel grid) and a spacer of the total resistance.Table 1 Boundary layer thickness (mm) and corresponding resistance according to the equation of Ballesta et al.8 Wind speed/m s-1 Sampler Parameter 0.1 0.2 0.5 1.0 2.0 4.0 10 Willems badge d/mm 3.0 2.6 2.2 1.9 1.7 1.4 1.2 Re/s m-1 131 114 95 83 72 63 52 Palmes tube d/mm 1.5 1.3 1.1 0.96 0.83 0.73 0.60 Re/s m-1 67 58 48 42 37 32 26 144 J.Environ. Monit., 1999, 1, 143–147Table 2 Total resistance (Rt/s m-1) as a function of wind velocity for a Willems badge with a 6 mm diVusion length and a glass fibre filter and a modified Palmes tube with membrane filter as a draught shield Wind speed/m s-1 Sampler 0.1 0.2 0.5 1.0 2.0 4.0 10 Willems badge 411 394 375 363 352 343 332 Palmes tube 1867 1858 1848 1842 1837 1832 1826 sampler allowed eight samples taken from the centre and 12 samples taken from the part of the absorption filter close to the wall of the sampler.For the medium sized sampler one and seven samples were taken, respectively. A fourth sampler was developed, taking the results of the experiments with the Willems badge and the draught shields on the large samplers into account.To avoid the development of an external boundary layer as much as possible, a modifi- cation of the Palmes tube was constructed with a modified draught shield at the entrance (Fig. 3). The materials (polyethylene and FEP-Teflon) are again hydrophobic. No polystyrene is used because of the use of sulfuric acid instead of tartaric acid. Owing to the lower uptake rate, this tube is more appropriate for long measurement periods.13,15 An improvement with respect to the design of the Willems Fig. 1 Diagram of a cylindrical badge (Willems badge). badge is the construction of the draught shield. The Teflon filter is held in place by a tight fitting cap with a centre hole. ring that also keeps the reaction filter in place is obvious. The The distance between the draught shield and the rim of the Teflon membrane is used as a draught shield, and is also tube is no more than the thickness of the cap (0.2 mm).The hydrophobic. It is kept in place by a fixation ring. The sampler external boundary layer is reduced to a minimum in this way. is closed during storage and after exposure by means of a cap. This design can also be used for the badge type samplers.It is important to note that there is a distance between the A drawback of the system is that the transport/closing cap draught shield and the outer rim of the badge of about 7 mm. has to slip over the cap with the centre hole. If this transport The ventilation rate of this external (possible) boundary layer cap fits too tight it will loosen the cap that fixes the entrance is very dependent on meteorological conditions (wind speed filter upon removal.A looser cap is, however, less restrictive and turbulence intensity). It may give rise to an additional in blocking the uptake of ammonia. With this type of cap, the external resistance against uptake of the reacting species. uptake rate of a capped tube was determined to be 0.01% of To study the eVect of draught shields on damping turbulence, the uptake rate of an open tube (with draught shield ).When it was decided to use large samplers in the large wind tunnel the draught shield and cap with centre hole were discarded to have a better view on the influence of turbulence within the and replaced by a cap similar to the cap holding the impregsampler. Two types of large badges were used: a badge of nated stainless steel grids, the uptake rate was only 0.001% of 0.3 m diameter and a variable diVusion length of 0.01–0.23 m that of an open sampler.This is probably mainly due to and a medium sized badge of 0.11 m diameter and a variable diVusion of ammonia through the walls of the sampler. To diVusion length of 0.01–0.1 m. Five types of draught shields avoid passive loading during transport and storage, it was were investigated; a flat PVC plate in front of the large decided to place the closed tubes individually in polyethylene sampler, a flat plate with edges rounded to the inside for the containers with screw caps.medium size sampler (Fig. 2), a coarse wire mesh screen, a fine wire mesh screen and filter-paper. Results and discussion When diVusion of the ammonia within the sampler takes place in still air, the concentration on the adsorption filter The eVect of wind speed on the sampling rate of the original should be uniform.Wall eVects would introduce a systematic Willems badge was studied. Fig. 4 shows the results of theoretidi Verence between the centre and outer edge of the adsorption filter. Turbulence inside the sampler would cause large variations in concentration from place to place on the filter.To be able to study these eVects, circular samples were taken from the adsorption filter in a systematic way. The large Fig. 3 Diagram of a modified Palmes tube. 1=cap for retaining adsorption grids; 2=two stainless steel adsorption grids; 3=FEP Fig. 2 Diagram of large sampler with flat draught shield and medium Teflon tube of 41 mm length; 4=Teflon entrance filter 5 mm pore size; 5=retaining cap with 10 mm diameter centre hole; and 6=transport sized sampler with rounded draught shield in front of the badge opening.guard cap. J. Environ. Monit., 1999, 1, 143–147 145The eYciency of a draught shield Results for the large sampler are given in Table 4 and for the medium sized sampler in Table 5.The results are remarkable when we realise that the standard deviation of the analytical method is only about 0.01 and with calibration samples 0.02–0.04. The tables show that air currents within the samplers lead to no uniform deposition of ammonia on the absorption filter. These currents may result from turbulence entering the sampler or thermal updrafts within the sampler caused by temperature diVerences.The decrease in standard deviation from a situation with a turbulence damping plate and no filter to the situation with a fine wire mesh screen or a glass fibre filter as a draught screen indicates that turbulence may enter the sampler when no proper shielding is used. A second cause of the larger standard deviation compared with that of the analytical method applied is the eVect of the sampler walls on the deposition pattern. Analysis of the results indicates that there is a systematic lower Fig. 4 Theoretical and practical sampling rate for a Willems badge with a diVusion space of 2 mm. absorption next to the walls than in the middle of the sampler. This result can be explained by the non-uniform geometry of the diVusion process next to the wall and probable deposition on the sampler walls.Coating of the walls with acid increased cal calculations and of the experimental determination of the the diVerence in the amount of absorbed ammonia in the sampling rate, s, for the Willems badge (all for STP). middle and next to the walls of the sampler. From Fig. 4 it can be derived that the sampling rate of a The ratio Rt/Rm indicates that air movements within the badge type sampler with a small (2 mm) diVusion space may sampler increase the sampling rate in comparison with the vary by a factor of 2.5 owing to variations in the wind velocity.calculated sampling rate for still air. When maximum pre- The variation in sampling rate will decrease when increasing cautions are applied to prevent turbulence entering the sam- the diVusion length inside the sampler decreases the ratio of pler, the uptake rate is still a factor of 2–3.5 higher than that external resistance to the sum of diVusion and filter resistance.calculated from theory. This factor is less for the large sampler This was the reason for increasing the diVusion length of the having a wall thickness of 5 mm than for the small sampler Willems badge from the original 2 mm to 6 mm.Table 3 gives having a wall thickness of 3 mm. calculated and measured external resistance’s for the original Willems badge with a 2 mm internal diVusion length. Table 4 Ratio of calculated and measured resistance against uptake The external resistance reaches a constant value for wind of ammonia Rt/Rm and standard deviation s of absorption filter velocities larger than 2 m s-1, which is smaller than the samples for a 0.3 m badge type sampler.This ratio and s are presented theoretical value. The high rim (11 mm) of the sampler may as a function of l, S and Rf a introduce enhanced turbulence above the filter, decreasing the boundary layer thickness. In a low wind velocity situation a l S Rf Rt/Rm s thicker boundary layer may develop because of the rim, giving 0.01 — 40 3.9 6.0 rise to a higher boundary layer thickness than derived from 0.01 — 50 2.6 4.4 theory. 0.18 — 40 15.2 2.4 The 6 mm version of the Willems badge has a rim of 7 mm 0.18 — 50 6.9 1.5 instead of 11 mm and a resistance due to the diVusion length 0.18 0.015 50 3.6 0.8 and filter of 280 s m-1 instead of 105 s m-1.This will reduce 0.23 — 40 24.6 3.8 0.23 — 40 2.2 0.4 the variation in sampling rate from a factor of 2.5 to a factor 0.23 — 50 4.1 0.7 of 1.5, assuming the same boundary layer resistance. In reality, 0.23 — 50 2.6 0.5 this factor may even be lower than 1.5 when we take into 0.23 0.01 40 — 0.6 account that the maximum boundary layer thickness due to 0.23 0.015 40 2.2 0.4 the rim at low wind velocity will be less. 0.23 0.01 50 2.6 0.5 Assuming a linear relationship between rim height and 0.23 0.015 17 2.6 0.5 boundary layer thickness at u=0.2 m s-1, the variation in al=diVusion distance inside sampler (m); S=distance between draught sampling rate is estimated to be about 1.3.plate and sampler entrance (m); Rf=resistance of draught shield It will be obvious that a construction of the draught shield (s m-1) [40=coarse wire mesh (mesh size 17), 50=fine wire mesh (mesh size 50) and 17=glass fibre filter]; Rt/Rm=ratio of calculated for the Willems badge similar to that of the modified Palmes total resistance and measured total resistance; and s=standard devi- tube will largely avoid problems with a variable sampling rate ation of amount of ammonia on filter samples.and reduce the variation close to the theoretical value of 1.1. Table 5 Ratio of calculated and measured resistance against uptake Table 3 Theoretical and measured external resistances for a 2 mm of ammonia Rt/Rm and standard deviation s of absorption filter samples for a 0.11 m badge type sampler.This ratio and s are Willems badge as a function of wind velocity presented as a function of diVusion distance l, distance between turbulence damping plate and sampler base S and type of draught Wind speed/m s-1 screen, indicated by its resistance Rf Parameter 0.1 0.2 0.5 1.0 2.0 4.0 10 l S Rf Rt/Rm s Theoretical 131 114 95 83 72 63 52 Re/s m-1 0.08 0.01 — 17.0 7.0 0.08 0.01 40 3.5 3.5 Experimental — 232 137 76 38 38 — Re/s m-1 0.08 — 40 3.5 3.5 146 J.Environ. Monit., 1999, 1, 143–147The results of the experiments were used in the design of the modified Palmes tube. This tube should experience a minimum influence of ambient conditions on the sampling rate. Fig. 5 shows the results with the modified Palmes tube compared with the ECN wet rotating denuder (AMOR) as a reference sampler in a field experiment in Bavaria, Germany.15 In this case the calculated concentrations match the reference concentration very well.There is no indication of internal circulation of air within the sampler or influence of a boundary layer resistance. Conclusions Wind velocity influences the uptake rate of passive samplers. The influence is less for tube samplers than for badge type samplers. With a proper design of badge type samplers, the influence of wind velocity on the uptake rate can be diminished to 10% at a wind velocity of 0.2 m s-1.Draught shields are vital for proper functioning of badge Fig. 5 Linear relationship between passive sampler data and reference type samplers. The draught shield can be made of fine wire concentration for ammonia based on 2 week averages for six parallel mesh screen or a filter.samplers. Turbulence damping plates in front of a proper draught shield are not needed. 7 J. L. Monteith and M. H. Unsworth, Principles of Environmental Physics, Edward Arnold, London, 1990. A large air space within a passive sampler may give rise to 8 P.Pe� rez Ballesta, E. G. Ferradas and A.M. Aznar, Environ. Sci. thermal circulation, enhancing the sampling rate of the instru- Technol., 1993, 27, 2031. ment in an unpredictable way. 9 Ambient Air Quality; DiVusive Samplers for the Determination of Gases and Vapours—Requirements and Test Methods, Part 1. General Requirements, Draft Report, CEN/TC 264/WG11, 1998. References 10 Ambient Air Quality; DiVusive Samplers for the Determination of Gases and Vapours—Requirements and Test Methods.Part 3. Guide 1 R. van Aalst, L. Edwards, T. Pulles, E. de Saeger, M. Tombrou for Selection, Use and Maintenance, Draft Report, CEN/TC and D. Tonnesen, Guidance Report on Supplementary Assessment 264/WG11, 1998. Under EC Air Quality Directives. Second Draft, European 11 R. H. Brown, Pure Appl. Chem., 1993, 65, 1859. Commission, Brussels, 1997. 12 J. J. H. Willems and P. Hofschreuder, in A Passive Monitor for 2 E. D. Palmes, A. F. Gunnison, J. Di Matteo and C. Tomczyk, Am. Measuring Ammonia, ed. I. Allegrini, A. Febo and C. Perrino. Air Ind. Hyg. Assoc. J., 1976, 37, 570. Pollution Research Report 37, 1991, CEC, Brussels, pp. 113–121. 3 R. G. Lewis, J. D. Mulik, R. W. Coutant, G. W. Wooten and 13 G. P. Wyers, A. Wayers, J. J. Moels, Th. R. Thysse, J. H. Puyzer, C. R. McMillin, Anal. Chem., 1985, 57, 214. H. L. M. Verhagen and J. W. Erioman, Karakterisering van de 4 K. J. Hargreaves and D. H. F. Atkins, The Measurement of Regionale Concentratieveldevan Ammoniak: Monstername en Ammonia in the Outdoor Environment Using Passive DiVusion Tube Meetstrategie, ECN Report C-95-109, 1995. Samplers, Report AERE R 12568, Harwell Laboratory, Culham, 14 J. D. Posner and G. Moore, Am. Ind. Hyg. Assoc. J., 1985, 46, 277. 15 M. Kirchner, S. Braeutigam, M. Ferm, M. Haas, M. Hangartner, 1987. P. Hofschreuder, A. Kasper-Giebel, H. Roemmelt, J. Striedner, L. 5 D. B. Orr, J. C. Hipfner, W. H. Chan, M. A. Lusis and J. E. Hunt, de Temmerman, W. Terzer, L. Thoeni, H. Werner and R. Atmos. Environ., 1987, 21, 1473. Zimmerling, to be published. 6 T. Hafkenscheid, Comments on Document CEN/TC 264/11 n 50, 1998, (Concerning Correction for Pressure and Temperature for Passive Samplers), CEN/TC 264/WG11 N69, 1998. Paper 8/09269I J. Environ. Monit., 1999, 1, 143–147 147

ISSN:0960-7919    

DOI:10.1039/a809269i

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Workplace monitoring of hydrogen peroxide using titanyl-coated sorbents G. Hecht,* S. Aubert, F. Gerardin and M. Hery Institut National de Recherche et de Se�curite�, Avenue de Bourgogne, BP 27, F-54501 Vandoeuvre les Nancy, France. E-mail: hechtg@inrs.fr; Fax: +33 3 8350 2060; Tel:+33 3 8350 2000 Received 6th November 1998, Accepted 4th January 1999 The current methods of sampling hydrogen peroxide, based on bubbling in acid solutions (titanium tetrachloride or titanium oxysulfate), are unsuitable for personal sampling.An alternative medium has been developed: silica gel coated with titanium oxysulfate. Sample tubes of this new sampling medium are suitable for personal sampling. The sampling performance is the same as that of the methods based on bubbling, but the tubes must be desorbed as soon as possible, even if the spectrophotometric analysis can be postponed.Special emphasis has been placed on the possible interference by peracetic acid, which is currently used in conjunction with hydrogen peroxide in the food industry. (ii) Sulfuric acid (Merck, Merck Cle�venot, Nogent-sur-Marne, Introduction France, ref. 731.1000). Hydrogen peroxide is widely used for disinfection, particularly (iii) Aqueous solution of hydrogen peroxide (30%) (Prolabo, in the medical field and in the food industry.It is an irritant of Fontenay-sous-Bois, France, 23.615.245). the eyes, mucous membranes and skin. In humans, the inhalation (iv) Silica gel (0.2–0.5 mm) for column chromatography of high concentrations of hydrogen peroxide vapour or the mist (Merck, ref. 7733.1000). may cause irritation and inflammation of the nose and throat. Coating solution: 250 mL of H2SO4 are added to 21 g of Severe systemic poisoning may also cause headache, dizziness, TiOSO4. The solution is then heated, stirring continuously vomiting, diarrhoea, pulmonary oedema and unconsciousness.1 until it becomes clear. After cooling, this solution is added to TheAmericanConference ofGovernmental IndustrialHygienists 250 mL of deionised water and made up to 500 mL.This (ACGIH) recommends a TLV-TWA2 (threshold limit value-time solution is about 0.2 M. weighted average) of 1.4 mg m-3, very close to the corresponding Coating of silica gel: 100 g of silica gel and 25 mL of coating French limit value3 of 1.5 mg m-3. solution are mixed thoroughly.A method of sampling and analysing hydrogen peroxide Absorbing solution (for midget fritted-glass impingers): the was described by Pilz and Johann4 based on the formation of coating solution is diluted with deionised water to a concena coloured complex with titanium tetrachloride. Samples were tration of about 5 mM. collected by drawing known volumes of air through midget fritted-glass impingers containing an absorbing solution.After Materials sampling, the concentration of the complex formed was meas- (i) 4 mL capacity reservoirs (Bond Elut, Varian, Les Ullis, ured by spectrophotometry at 415 nm. The Occupational France, 1213–1008). Safety and Health Administration (OSHA) proposed replacing (ii) Porous polyethylene (20 mm pore size) frits (Bond Elut, titanium tetrachloride by titanium oxysulfate,5 and then substi- Varian 1213–1020).tuted a polarographic determination for the spectrophoto- Packing of sampling tubes: the reservoirs are packed with metric method,6 to obtain a better analytical detection limit about 0.8 g of coated silica gel placed between two polyethyland to minimise interferences. ene frits.The main advantage of the OSHA method, apart from its enhanced detection limit, is the better stability of the absorbing Analytical methods solution, which remains stable for several weeks without Midget fritted-glass impingers: 15 mL of the absorbing solution change, in contrast with the complex formed by the reaction are placed into the midget fritted-glass impinger. After sam- with titanium tetrachloride which can only be kept for one or pling, the absorbing solution is transferred to a vial.The two days. Both methods use midget fritted-glass impingers bubbler is rinsed with deionised water and transferred to the which make it diYcult to take personal samples. The aim of vial. The solution is made up to 25 mL. our study was to replace these sampling solutions by a medium Sampling tubes: after sampling, 8 mL of sulfuric acid (1 M) suitable for the requirements of occupational hygiene.Tubes are percolated through the coated silica gel. In our tests, the containing silica gel coated with titanium oxysulfate were used. desorption solution is then made up to 25 mL (for comparison The performance levels of this new medium and of the bubbling with samples taken by bubbling) or to 10 mL (for comparison in oxysulfate solution were then compared.of tubes with others). In both cases, the quantity of hydrogen peroxide sampled is determined by comparison with a calibration curve made Materials and methods up of standards prepared in the same way as the samples (midget fritted-glass impingers or tubes). The solutions are Reagents analysed by spectrophotometry at 410 nm.The response is linear for solutions of up to 30 mg L-1. Spectrophotometric (i) Titanium oxysulfate (Riedel de Hae�n, Hoechst, Paris La De�fense, France, ref. 14023). determination was chosen on account of both its shorter J. Environ. Monit., 1999, 1, 149–152 149analysis time and wider availability in laboratories, despite having a poorer detection limit and being more prone to interference than polarography. Tests in the laboratory Generation of controlled test atmospheres The controlled test atmospheres used in this evaluation were generated by volatilising and diluting hydrogen peroxide with air.A motorised syringe (KD Scientific, Bioblock, Illkirch, France) delivered a constant flow of an aqueous solution of hydrogen peroxide (about 0.2M).This solution was volatilised in a heated manifold and then mixed with air. The flow was again diluted with air to obtain the desired concentration. Eight samples could be taken simultaneously in the final chamber at flow rates of up to 0.8 L min-1. A diagram of the device is provided in Fig. 1. EYciency of the sampling method on tubes Six series of samples were taken, each consisting of four Fig. 2 Specific device for hydrogen peroxide vaporisation. samples obtained in midget fritted-glass impingers and four on tubes. The sampling rate was 0.8 L min-1 for both. The and at the analytical limit of the spectrophotometric method. results (arithmetic mean and standard deviation) of this test In the same way and on day D, the same quantities of are summarised in Table 1.There is a close agreement between hydrogen peroxide (34 mg and 272 mg) were injected directly the two types of sample. in 10 mL of absorbing solution contained in vials. The tubes and absorbing solutions were then analysed in Stability of samples batches of 6 or 12, on diVerent days from D+1 to D+61. It was not possible to use the above mentioned device to The results of these tests are given in Table 2.The reference generate samples on which a stability study could be performed 100 corresponds to fresh samples prepared on each day of as the quantity of hydrogen peroxide generated varies with analysis from hydrogen peroxide solution whose concentration time. A specific device, details of which are given in Fig. 2, had been checked just before preparation. For tubes analysed therefore had to be designed. A known volume of a known after D+4, the recovery percentage is under 90%, whereas for solution of hydrogen peroxide (about 0.1 M, titrated by the the absorbing solutions the recovery percentage is close to potassium iodide/sodium thiosulfate method6) was volatilised 100% for all the analyses performed from D+1 to D+61.As on sampling tubes. Two series of 30 samples were prepared the solutions were not stored in the dark, it is unlikely that on day D: one with 10 mL of the hydrogen peroxide solution the poor recovery of the hydrogen peroxide sampled on tubes (34 mg of hydrogen peroxide) and the other with 80 mL after several days is due to the destruction of the ‘peroxytitanyl (272 mg).The first value corresponds to a four-hour sample cation‘ by light.orbing solutions are in fact equivalat 10% of the limit value, whereas the second corresponds to ent to tubes which have been desorbed immediately after a sample of identical duration at a concentration of 1.1 mg m-3 sampling. Consequently, the tubes sampled must be desorbed as soon as possible, even if the analysis can be postponed.The poor recovery of the hydrogen peroxide after a few days is due to the migration of the complex sampled. This migration can be seen in Fig. 3. Only one direction is visible, but it seems reasonable to suppose that the migration develops in both directions. Interferences All compounds likely to interfere with the determination of hydrogen peroxide were not investigated in this study, which limited itself in scope to those liable to be used in conjunction with hydrogen peroxide in industry.OSHA reports permanganate and iodide ions as compounds which make the spectro- Fig. 1 Generation system for hydrogen peroxide production. photometric determination of hydrogen peroxide impossible, but they are rarely used jointly.On the other hand, peracetic Table 1 EYciency of the sampling method on tubes in the laboratory acid is often used as a sterilisation agent at ambient temperature, especially for fruit juice packaging, and peracetic acid Conc./mg m-3 (RSD) solutions contain hydrogen peroxide. To study how this substance interferes with the determination of hydrogen peroxide, Series N Sampling time/min Impingers Tubes the previously described method (see Analytical methods sec- 1 4 140 1.21 (±5.7) 1.22 (±3.9) tion) and a peracetic acid determination method by Pinkernell 2 4 130 1.43 (±4.2) 1.45 (±2.9) et al.7 were used.Peracetic acid (PAA) oxidises rapidly methyl- 3 4 80 1.54 (±6.0) 1.52 (±1.6) p-tolylsulfide (MTS) leading to methyl-p-tolylsulfoxide 4 4 100 1.90 (±2.1) 1.85 (±3.1) (MTSO): 5 4 135 2.84 (±2.9) 2.85 (±3.7) 6 4 60 2.74 (±2.8) 2.72 (±4.1) CH3C(O)OOH+CH3C6H4SCH3�CH3C6H4S(O)CH3 RSD, relative standard deviation.+CH3COOH 150 J. Environ. Monit., 1999, 1, 149–152Table 2 Storage data for the samples and the absorbing solutions Desorption Analysis N Reference % (RSD) N Sample % (RSD) Low level D+1 D+1 6 97 (±1.2) 6 103 (±1.5) D+8 D+8 6 89 (±5.2) D+20 D+20 6 107 (±0.8) 6 86 (±4.1) D+61 D+61 12 104 (±0.9) 12 71 (±6.1) D+8 D+20 6 104 (±3.3) 6 88 (±4.7) D+8 D+61 6 101 (±3.1) 6 89 (±6.5) High level D+1 D+1 6 98 (±0.7) 6 100 (±0.4) D+4 D+4 6 96 (±1.7) D+16 D+16 6 104 (±1.0) 6 90 (±1.4) D+57 D+57 12 101 (±0.8) 12 77 (±1.2) D+1 D+16 6 102 (±1.1) 6 99 (±1.2) D+4 D+57 6 100 (±1.2) 6 95 (±2.8) RSD, relative standard deviation.Fig. 3 D, Tube prepared on day D; D+6, same tube on day D+6. The reaction kinetics are very fast with peracetic acid, but very slow with hydrogen peroxide. The tests performed in our laboratory show that, after two days of reaction between MTS and hydrogen peroxide, the quantity of MTSO formed is 16 times lower than that observed using a solution of peracetic acid at the same concentration as the hydrogen peroxide Fig. 4 Comparison of tube and impinger sampling in workplace solution. The quantity of MTSO generated does not increase atmospheres. further later. A study was conducted to assess the interference due to peracetic acid in the determination of hydrogen peroxide. (i) Standards containing from 0.5 to 5 mM per sample in the absorbing solution were prepared from a 0.1M hydrogen peroxide solution.(ii) A 4% aqueous solution was prepared from a peracetic acid solution (CH3C(O)OOH#6 M, H2O22 M). (iii) Test A: 5 mL of MTS (Aldrich, Sigma Aldrich, Saint Quentin-Fallavier, France, ref. 623–13–2) (4 mM) were placed into three vials. Five mL of the 4% PAA solution were added to the first, 10 mL to the second and 20 mL to the third.After 5 min of reaction, the volume of the three vials was made up to 10 mL with the absorbing solution. The three solutions were analysed by spectrophotometry, using the calibration curve of (i) as reference. This test gave the quantity of hydrogen peroxide in the peracetic acid solution. (iv) Test B: the same experiment as in A, but with the Table 3 Interference of peracetic acid (PAA) in the determination of hydrogen peroxide Fig. 5 Comparison of successive samples versus single sample. ‘Real’ conc. of ‘Real’ conc. of ‘Apparent’ conc. PAA solution H2O2/mM PAA/mM ofH2 O2/mM added/mL (Test A) (Test B) (Test C) absorbing solution being replaced by a methanol–water 5 0.29 1.14 0.82 (75+25) mixture. The analysis of MTSO (Fluka, Sigma 10 0.60 2.23 1.67 Aldrich, Saint Quentin-Fallavier, France, ref. 69422) was 20 1.23 4.36 3.35 carried out by high performance liquid chromatography J. Environ. Monit., 1999, 1, 149–152 151is shown in Fig. 4. Like the laboratory test the results are satisfactory, with an underestimate of about 5% for the sampling on the tube compared with the sampling on the impinger. Considering this small diVerence, it does not seem necessary to use a correction factor.Comparison of single sample and successive samples The aim of this test was to check the ability of a tube to be sampled over an entire working shift. The result given by a sample taken for the whole working shift was compared with that given by several samples taken successively over the same duration. The correlation between the elements of the pairs of the results is shown in Fig. 5 and, as can be seen, is excellent, with a slight overestimate for the successive samplings. Fig. 6 Influence of the sampling rate. Influence of the sampling rate This test was performed in order to check if sampling could (HPLC). From these values of MTSO the concentration of be carried out at a low flow rate. Low flow pumps are useful: PAA in the peracetic acid solution could be determined.their weight and dimensions are smaller and they are better (v) Test C: 5 mL of the 4% PAA solution were placed into tolerated by the workers. Ten pairs of samples were taken for the first vial, 10 mL in the second and 20 mL in the third. The one to two hours: one sampled at 0.25 l min-1 and the other three vials were made up to 10 mL with the absorbing solution.at 1 L min-1. The correlation between the elements of the The three solutions were analysed by spectrophotometry, pairs is shown in Fig. 6. Although the correlation is good, for using the calibration curve of (i) as reference. This test low atmospheric concentrations (around one-tenth of the limit highlighted the influence of the presence of peracetic acid on value), the low flow samples are about 30% below the high the determination of hydrogen peroxide. flow samples.No comparison tests were made during a whole The results of these tests are summarised in Table 3 and working shift. show that peracetic acid interferes in the determination of hydrogen peroxide. From this series of tests, it would appear that 1 mM of peracetic acid corresponds to an apparent Conclusion 0.5 mM of hydrogen peroxide.The sampling medium developed in this study is a good This finding is not really surprising. Purnell et al.8 have alternative to sampling by bubbling in an impinger. It allows described a method of sampling and analysing methyl ketone industrial hygienists to take personal samples easily.If they peroxide in air which is based on the same principle as the are desorbed rapidly after sampling, the samples can be kept method by Pilz and Johann.4 It is therefore likely that all without loss for a long time (up to two months). This medium organic peroxides will lead to an overestimate of the quantity is suitable for the measurement of monopollution by hydrogen of hydrogen peroxide.peroxide, but it does not provide industrial hygienists with the The validation was not performed completely in accordance means of avoiding interferences inherent in spectrophotometric with the requirements of a test method such as, for example, techniques. From a practical point of view, the interference the EN 76 standard:9 generating a controlled hydrogen due to peracetic acid seems the most likely, because of its peroxide atmosphere is diYcult; we do not know of any direct widespread use in conjunction with hydrogen peroxide in the reading analyser for hydrogen peroxide food industry.Tests in workplace atmospheres References The method was tested in two factories, one packaging milk 1 American Conference of Governmental Industrial Hygienists and the other fruit juice.Both factories use the TetrapakA (ACGIH), Documentation of the Threshold Limit Values and packaging process. Three types of validation were performed. Biological Exposure Indices, ACGIH, Cincinnati, 6th edn., 1991. (i) Comparison of the concentrations measured by sampling 2 American Conference of Governmental Industrial Hygienists (ACGIH), Threshold Limit Values for Chemical Substances and on tubes containing coated silica gel and on midget fritted- Physical Agents, ACGIH, Cincinnati, 1998.glass impingers. 3 Ministe`re du Travail, Valeurs Limites D’exposition Professionnelle (ii) For the sampling on tubes, comparison of a sample aux Agents Chimiques en France, INRS, Paris, ND 1945, 1996. taken for 5 to 8 h with a series of samples taken at the 4 W.Pilz and I. Johann, Int. J. Environ. Anal. Chem., 1974, 3, 257. same time and place during successive periods of an hour. 5 Occupational Safety and Health Administration (OSHA), (iii) The influence of the sampling rate was investigated for Analytical Methods Manual, OSHA, Salt Lake City, 2nd edn., 1990, method VI-6. samples taken on tubes. Two samples, one at a rate of 6 Occupational Safety and Health Administration (OSHA), 1 Lmin-1 and the other at 0.25 L min-1 were taken simul- Analytical Methods Manual, OSHA, Salt Lake City, 2nd edn., 1990, taneously at the same place. method ID-126-SG. For the first two tests, the sampling pumps were calibrated 7 U. Pinkernell, U. Karst and K. Camann, Anal. Chem., 1994, 66, at very similar flows (about 1 L min-1) and the inlets of the 2599. impinger and of the tubes were sampling through the same 8 C. J. Purnell, G. L. Martin and H. Wolfson, Ann. Occup. Hyg., 1979, 22, 383. T-shaped aperture. 9 European Committee for Standardization, Workplace Atmospheres—Pumped Sorbent Tubes for the Determination of Comparison of tubes and impingers Gases and Vapours.—Requirements and Test Methods, EN 1076, CEN, Brussels, 1997. Fifty seven pairs of samples, one on a tube and the other on an impinger were taken in the two factories with atmospheric Paper 8/08686I concentrations of hydrogen peroxide ranging from 0.5 to 4 mgm-3. The correlation between the elements of the pairs 152 J. Environ. Monit., 1999, 1, 149–152

ISSN:0960-7919    

DOI:10.1039/a808686i

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Urinary nickel concentrations and selected pregnancy outcomes in delivering women and their newborns among arctic populations of Norway and Russia Jon Øyvind Odland,*a Evert Nieboer,ac Natalya Romanova,b Yngvar Thomassen,b Tor Norsethb and Eiliv Lunda aInstitute of Community Medicine, University of Tromsø, N-9037 Tromsø, Norway bNational Institute of Occupational Health, P.O. Box 8149 Dep, N-0033 Oslo, Norway cDepartment of Biochemistry, McMaster University, Hamilton, Ontario, Canada L8N 32S Received 8th December 1998, Accepted 4th February 1999 The two objectives of this study were to compare urinary nickel excretion in pregnant women and their newborns living in the Murmansk and Arkhangelsk Counties of Russia with that in comparable Norwegian populations living in Finnmark and the city of Bergen and to assess the influence on pregnancy outcome of diVerent risk variables, specifically urinary nickel concentrations and questionnaire-based anamnestic information.Life-style information and urine samples were collected from 50 consecutive mother–infant pairs from hospital delivery departments in three Russian and three Norwegian communities.Pregnancy outcomes were verified from medical records. Urinary nickel excretion was significantly higher in the Russian communities, independent of the presence of a nickel refinery as a local environmental source. The birth weight and mean body mass index of the newborn children (BMIC) were significantly lower ( p<0.001) in the Russian groups, with or without adjustment for gestational age.A multivariate linear regression analysis indicated that maternal urinary nickel concentration had no impact on birth weight. The maternal body mass index (BMI) and maternal height were positive explanatory variables; maternal urinary creatinine is suggested as a weak negative factor. Smoking was shown to be a strong negative predictor only in the Norwegian group among whom there was a significantly higher smoking frequency ( p= 0.005).The significant contribution of a country factor in the predictive model is interpreted to indicate that a number of important risk factors for low birth weight were not identified. in a Russian nickel refinery.4,5 The evidence of teratogenic Introduction and developmental eVects of nickel in animal studies is diYcult Considerable attention is being paid to industrial pollution in to interpret with confidence.6–8 Compared with cadmium,9 the regions adjoining the Norwegian–Russian border, especially lead10 and mercury,11 there is clearly a paucity of data in relation to the substantial emissions of sulfur dioxide and concerning nickel exposure in relation to reproduction and metals by the nickel industry in the Kola Peninsula of Russia.pregnancy outcome. Further, the literature on nickel concen- Nearly half of the tonnage of metals released is nickel, with trations in body fluids during pregnancy is very scarce, and iron and copper other major contributors.1 Extensive environ- the suggested nickel urine reference values12,13 or the results mental damage has resulted from these pollutants and has reported in surveys14–16 do not include pregnant women or generated considerable concern about public health in Russia, newborn children.Norway and Finland. A Joint Norwegian–Russian Commission The present study had the following two specific objectives: on Environmental Cooperation was established in 1988 and (i) to compare urinary nickel excretion in pregnant women encouraged extensive investigation of the pollution of air, water, and their newborns living in the Murmansk and Arkhangelsk soil and biota.2,3 By contrast, very little has been done on the Counties of Russia with that in comparable Norwegian popuinvestigation of human health, even though there has been lations living in eastern Finnmark and the city of Bergen; (ii) considerable focus by the media on reproductive and develop- to assess the influence on pregnancy outcome of diVerent risk mental issues related to nickel exposure.Our interest in the variables, specifically urinary nickel concentrations and quespresent project derived from this public interest and had as its tionnaire-based anamnestic information. objective the determination of whether there is a scientific basis This study was approved by The Regional Ethical for this concern.We used a two-pronged approach: (i) an Committee, University of Tromsø, Norway, the Norwegian assessment of the exposure to nickel of pregnant women selected Data Inspectorate and the Regional Health Administrations from the general public and its relation, together with other of Murmansk and Arkhangelsk Counties.factors, to pregnancy outcome; (ii) an investigation of the reproductive health of female nickel workers. The results of the Materials and methods first component are reported in this study. The reproductive/developmental eVects of nickel have not Study population and procedures been firmly established in humans, although some concern exists about apparent increases in spontaneous abortions and Personal contacts with colleagues in the diVerent hospital structural malformations (especially cardiovascular and mus- delivery departments were established, and all procedures and protocols were provided in Norwegian, English and Russian.culoskeletal ) in newborn babies whose mothers were employed J. Environ. Monit., 1999, 1, 153–161 153The Russian geographic sites in our study were Nikel and in Nikel, 1 in Monchegorsk, 19 in Bergen and 4 in Kirkenes.Even though anamnestic information and maternal samples Monchegorsk in Murmansk County and Arkhangelsk in were collected, the mother and child were excluded from the Arkhangelsk County. Nikel (23 000 inhabitants) and study’s statistical analyses (see below). Monchegorsk (65 000 inhabitants) are communities with nickel In an interview, local midwives or gynaecologists adminis- refining operations.Arkhangelsk is the biggest city on the tered a questionnaire that addressed the following particulars: White Sea, with almost 450 000 inhabitants and five big pulp age, parity, height and weight of mother, ethnic background, and paper plants in the surrounding area, but no metal places of residence exceeding 6 months, schooling, occupation, producing industry.The Norwegian reference cities were smoking habits, alcohol consumption, medication, serious Kirkenes, Hammerfest and Bergen (Fig. 1). Kirkenes (approxidiseases and dietary habits related to local food intake. The mately 4500 inhabitants) is located near the Russian– following information was collected from the delivery depart- Norwegian border, 50 km from Nikel.The delivery department ment medical records about the mothers and births: maternal there receives women from the eastern part of Finnmark (total age, weight and height, Naegele term, date of birth, length population, 28 000), the area geographically adjacent to the and weight of baby, weight of placenta, Apgar score (clinical Russian border.Hammerfest (12 000 inhabitants) is a coastal estimate of the conditions of an infant 1–5 min after birth), city of Finnmark; the hospital delivery department there congenital malformations, gestational age and individual com- receives women from the western part of Finnmark (a total ments by the doctor or midwife.The informed consent form of 45 000 residents), including the main native Saami centres and collection of anamnestic information were completed in Finnmark County. Bergen is the second biggest city of before the delivery process started in order to minimize stress. Norway in the southwest part of the country (total population, Collection of the neonatal urine specimens was performed in 220 000), with no major metal producing industry.It was a manner that avoided interruption of the delivery situation. included because it represents a non-Arctic urban community. Information by questionnaire and urine samples were col- Sample collection and analysis lected from at least 50 consecutive women presenting themselves to the hospital delivery departments in each location; The urine of mothers was sampled at two stages: the first time the first-voided urine from their newborn babies was also at week 20 of pregnancy (only in Kirkenes and Nikel ) and obtained. The registration and sampling were performed in the second time together with blood sampling at 1–2 days the following time periods: Arkhangelsk in April–May 1993; postpartum.Maternal urine was collected directly into a Kirkenes in November 1993–January 1994; Hammerfest in disposable plastic cup for transfer to containers (NØD-0438 December 1993–January 1994; Bergen in June 1994; and Nikel CERBO Norge A/S, Oslo, Norway; volume, 20 mL); both the and Monchegorsk in March–June 1994. Urines were collected cup and the container were tested and found not to contamifrom a total of 265 children; of these 137 were Russian (Nikel, nate the urine samples with detectable amounts of nickel N=42; Monchegorsk, N=49; and Arkhangelsk, N=46) and (<10 nmol L-1).For sampling from the neonate immediately 128 were Norwegian (Kirkenes, N=46, Hammerfest, N=51; postpartum, a uridome (126–0004, Hollister Norge, Oslo, and Bergen, N=31). The women were asked to join the study Norway) was attached by plasters to the child’s genitalia until by means of completing a consent form.the first void was produced. For ethical reasons, we had to Very few cases interrupted the consecutive enrolment. stop the sampling if the uridome irritated the very sensitive Pregnant women in Kirkenes with prepartum complications skin of the newborns. The urine samples were immediately or suspected delivery problems are sent to the Regional frozen at -20 °C.Within 3 months, all the materials collected Hospital in Tromsø. In the sampling period, two transfers were transported frozen to the city of Bodø in Norway for were registered. Hammerfest hospital has a neonatal intensive storage in a -70 °C freezer. care department and no cases were sent to Tromsø before After thawing, the urine samples were heated for 1 h at delivery during the sampling period.None of the delivering 95 °C in an oven to redissolve the urine precipitates and to women refused to join the study. However, the complicated ensure sterility. Urine was analysed without further preurine sampling procedure for neonates sometimes resulted in treatment. Nickel in urine was measured by electrothermal skin irritation, especially if the period before the first voiding atomic absorption spectrometry employing Zeeman-based was long.Consequently, neonatal urine samples could not be Perkin-Elmer Model 5100 PC/HGA-600 and Perkin-Elmer obtained from some of the infants: 4 cases in Arkhangelsk, 8 SIMAA 6000/THGA graphite atomizer systems (Bodenseewerk Perkin-Elmer GmbH, U� berlingen, Germany) calibrated with urine matched standard solutions.17 The accuracy and precision of the measurements were assessed routinely by using human urine quality materials obtained from NycoMed Ltd., Oslo, Norway (Seronorm STE 101021 and 403125).The day-to-day variation of the nickel measurements in these reference materials was typically 10%.The average nickel concentrations of STE 101021 and 403125 human urine measured during the analysis period were 41±5 nmol L-1 and 661±56 nmol L-1 respectively. This is in good agreement with the manufacturer’s recommended values of 43 and 681 nmol L-1. The detection limit of the method used was 10 nmol L-1 of nickel. The creatinine content was measured by a Beckman Creatinine Analyser (Beckman Instruments, Brea, CA, USA) based on JaVe’s reaction.Only in Nikel and Monchegorsk did the study group include women who worked in departments of the local refinery with potential exposure to nickel. It should be noted that, today, maternity leave starts 70 days before the anticipated date of delivery, while it was 56 days during the study period.Fig. 1 Schematic map of the Russian Barents region. Bergen is located Consequently, since urine samples in Monchegorsk were col- in the southwest of Norway, and is not shown on the map. (Courtesy of Elin Hanssen, NILU, Tromsø, Norway.) lected shortly after birth, the employees included were not 154 J. Environ. Monit., 1999, 1, 153–161recently occupationally exposed.In Nikel, a comparison is 0.07). Mean maternal weights at term were not diVerent ( p= possible between samples collected while still at work (week 0.11), while mothers’ mean height was significantly lower in 20) and postpartum. the Russian group ( p<0.001). However, this did not result in Tap water samples (10 or 12) were collected in the following diVerent maternal body mass index (BMI) values (p=0.87).Russian communities: Nikel, Zapolyarniy, Monchegorsk, Pregnancy outcomes Arkhangelsk and Umba (the latter is located in the Kola Peninsula, south of Apatity on the White Sea). Homes were Compared to the Norwegian results, the mean birth weight selected at random, the taps were flushed for a few minutes and body mass index of the newborn child (BMIC) were and the samples were collected directly into the same containers significantly lower in the Russian group (p<0.001, Table 2), as used for the urine samples.The shipping, storage and a diVerence that was retained after adjustment for gestational analysis of the tap water were carried out in the same manner age or gender. Babies were somewhat longer in the Russian as for the urine specimens.In some cases, the water samples group (p<0.001), while the diVerences in mean placenta were not frozen and were analysed soon after their arrival at weight and head circumference were not statistically significant. the laboratory in Oslo. Twenty-four hours before measure- The children in Arkhangelsk had the lowest mean birth weight, ment, 0.5 mL 65% ultrapure nitric acid was added to each with the highest values being reported in Kirkenes. The mean 20 mL sample in order to recover any surface-adsorbed nickel.gestational age was significantly lower in Russia (p<0.001), Nickel measurements were performed in the same way as for being the lowest in Arkhangelsk. These findings are consistent urine, but calibration was against aqueous standard solutions. with a prevalence of 15% of children with birth weights of less Surface water CSPS-SW1 (Spectrapure Standards Ltd., Oslo, than 2500 g in Arkhangelsk, compared to 3.5% in the two Norway) trace-metal quality-control materials were used other Russian groups.Importantly, the diVerence between the routinely. The day-to-day variation of the nickel measuremean birth weights for Russia and Norway remained signifi- ments in these reference materials was typically 5%.The mean cant (p<0.001) when omitting the Arkhangelsk group in the nickel concentration measured in CSPS-SW1, batch 102, comparison. As might be expected from the small number of was 164±5 nmolL-1 (certified value 170±9 nmolL-1 of nickel ). subjects in our study,18 only four children were born with registered malformations, two in Norway and two in Russia.Statistical analysis One perinatal death (a child with hydrocephalus in In the statistical assessment univariate analysis, analysis of Arkhangelsk) was identified. variance and multiple linear regression analyses were In the Russian group, a total of 15 women were employed employed. An association was accepted when the 95% confi- in the nickel industry, six in Nikel, who apparently worked dence interval (CI) of the regression coeYcient did not include in departments with little nickel exposure, and nine in zero.The Bartlett’s test for homogeneity of variance and the Monchegorsk, who were potentially exposed in the electrore- Mantel–Haenszel and Fischer exact tests for comparison of fining department.However, as already indicated, due to proportions were used. In all groups, the urinary nickel results their maternity leave none of these women were recently were highly skewed, and the non-parametric Wilcoxon rank occupationally exposed. The nine women working in the sum test or the Kruskal–Wallis test for two groups were Monchegorsk electrorefinery had babies with an average birth selected.Concentrations below the detection limit (DL) were weht of 3342 g (2540–4200), which is higher than the mean arbitrarily assigned the value of 1/2DL. Information on the birth weight in the total Russian study population; one baby years of education, defined as years at school, was missing in had a registered malformation (a minor limb defect).Seven the Russian questionnaire responses and could therefore not of these nine nickel workers were daily smokers (77.8%), be included in the regression analysis. Neither could the which exceeds the mean smoking frequency reported in Table 1; answers about alcohol consumption be used, since 49 of the the delivery frequency was identical to that for the total Russian respondents were reluctant to answer this section of Russian group (mean of 1.2).the questionnaire. Since only one child was lighter than 2500 g among the Norwegian subjects, it was decided to use the birth Urinary nickel concentrations weight outcome as a continuous variable instead of categorical The urinary nickel levels for the children and their mothers (i.e. by defining low birth weight as <2500 g).Birth weights are provided in Table 3. Both the neonatal and maternal corresponding to gestational ages of 30–38 weeks were adjusted medians of the unadjusted urinary nickel concentrations were using the observed rate of increase of 166 g per week. considerably higher among the Russian subjects compared to the Norwegians ( p<0.001). Values reported for the Norwegian Results group fall within the baseline reference interval of 9–100 Population characteristics nmol L-1;12,13,19 while the Russian concentrations are mostly outside of it (maternal range at term, 5–2108 nmol L-1).The mean age of the mothers was significantly higher in Creatinine adjustment did not aVect these comparisons. Norway than in Russia (27.7, range 17–40; 25.1, range 14–44; Focusing on the towns of Nikel and Monchegorsk and the respectively; p<0.001; Table 1).The percentage of the city of Arkhangelsk, we found that, for all three Russian Norwegian mothers who were registered as smokers was centres, the median nickel concentrations were higher than for 35.9%, of whom 13.3% might be regarded as heavy smokers the Norwegian populations studied.Intercommunity compari- (>10 cigarettes per day). By comparison, the Russian group sons for the three Russian populations revealed that, relative had a smoking prevalence of 17.4%, none of them in the heavy to Arkhangelsk, the median creatinine-adjusted nickel concen- smokers’ category (Table 1). Complications related to pretrations for Nikel and Monchegorsk were significantly higher eclamptic conditions, specifically hypertension, oedema, pro- ( p<0.001).This diVerence was not apparent for the unad- teinuria or anaemia, were significantly higher in the Russian justed nickel concentrations. In the Nikel and Kirkenes groups, group (p=0.03). Local food consumption was categorized on additional urines were also collected in the 20th week of the basis of whether the consumption of locally produced fish, pregnancy and at term.Neither the Nikel or the Kirkenes meat, vegetables, mushrooms and berries occurred daily or group demonstrated diVerences between the two stages of not. The Monchegorsk group was not adequately examined pregnancy (p>0.5, N=42 and p>0.5, N=41 respectively). in this component of the questionnaire to be considered in the Occupationally exposed women in Monchegorsk (N=9, who interpretation of the data.The number of previous deliveries had worked in the electrolysis tank house, but with no recent was significantly lower for the Russian subjects compared to the Norwegian group (means of 1.2 and 1.4 respectively; p= industrial exposure) had a median urinary nickel concentration J.Environ. Monit., 1999, 1, 153–161 155Table 1. Population characteristics Russia Norway Characteristic (N=137) (N=128) p Values Mean maternal agea/years 25.1 27.7 <0.001e (s, range) (5.9, 14–44) (5.3, 17–40) Mean number of deliveriesa 1.2 1.4 0.07e (range) (0–4) (0–5) Mean maternal weighta/kg 70.9 73.5 0.11e (range) (41–101) (46–123) Mean maternal heighta/cm 163 166 <0.001e (range) (150–174) (155–182) Mean body mass index (BMI)/kg m-2 26.7 26.6 0.87e (range) (17.3–39.6) (18.4–38.0) Pre-eclamptic conditionac 26 12 0.03f (19.0%) (9.4%) Smoking habitsb (%) Non-smokers 82.6 64.1 0.005f 1–10 cigarettes per day 17.4 22.7 >10 cigarettes per day 0 13.3 Smoking frequency 17.4 35.9 Local food intake (%)bd 86.1 61.0 <0.001f aBased on medical records; for maternal height only, N=121 (Russia) and N=93 (Norway).bBased on questionnaire. cAt least two of the parameters: hypertension, oedema, proteinuria. dRegular use of locally produced vegetables, potatoes, berries and/or locally produced fish or meat; the Monchegorsk group is not included (see text). et-test. fChi-squared test. Table 2 Comparison between selected pregnancy outcomes in Russia and Norway Russia Norway Outcomea (N=137) (N=128) p Values Mean birth weight/g 3195 3590 <0.001b (s, range) (579, 1400–5100) (502, 2200–4960) Mean length of baby/cm 51.8 50.7 <0.001b (range) (41–58) (45–58) BMIC/kg m-2 11.9 13.9 <0.001b (s, range) (1.7, 7.5–18.2) (1.4, 10.1–19.4) Mean placenta weight/g 582 621 0.06b (range) (300–900) (350–1050) Mean gestational age/weeks 38.7 39.8 <0.001b (range) (31–42) (36–42) Mean head 35.0 35.0 0.92b circumference/cm (range) (32–38) (30–39) aAll information is derived from medical records.bComparison of country means by t-test. Table 3 Median nickel urine concentrations of delivering women and their babies in Arctic areas of Russia and Norway (nmol L-1)a Group studied Russia Nikel Monchegorsk Arkhangelsk Norway Kirkenes Hammerfest Bergen (N=137) (N=42) (N=49) (N=46) (N=128) (N=46) (N=51) (N=31) p Valueb Maternal urine nickel 85 90 83 85 5 5 14 15 <0.001 at term/nmol l-1 5–2108 5–694 5–2108 19–1258 5–85 5–26 5–82 5–85 Maternal urine nickel 9 13 10 6 1 1 3 2 <0.001 at term, adjusted for 1–285 1–139 3–285 1–49 0.2–41 0.2–8 0.2–41 0.3–36 creatinine/nmol Ni per mmol creat Nickel in baby’s first-voided 34 41 37 24 5 5 5 5 <0.001 urine/nmol L-1 5–561 5–561 5–374 5–260 5–48 5–20 5–48 5–24 Baby’s urine nickel, 11 31 12 5 2 3 2 2 <0.001 adjusted for 1–510 3–510 2–45 1–325 0.4–187 0.4–34 0.5–187 0.5–13 creatinine/nmol Ni per mmol creat aMedian value and range are given. For statistical purposes, values below the DL of 10 nmol L-1 were set at cDL. bFor the comparison of the total Norwegian and Russian data sets, non-parametric statistics were used (see text).of 66 nmol L-1, somewhat less than that in the total Russian variable. The regression coeYcient corresponding to the change in the baby’s weight in grams per unit of the explanatory group (median value, 85 nmol L-1). variable was first examined. For both the Russian and Norwegian subjects, maternal urinary creatinine is suggested Univariate linear regression as a weak negative predictor (not significant).For the total The results of the univariate analysis are provided in Table 4. Russian group, there were no other variables significantly associated or even nearly so with the two outcomes. For the The birth weight or the BMIC was selected as the dependent 156 J.Environ. Monit., 1999, 1, 153–161Table 4 Linear regression analysis of birth weight Russia/Norway Russia Norway (adjusted for country) Weight Weight Weight Variable change (CI)a p Valueb change (CI)a p Valueb change (CI )a p Valueb Maternal Age (years) 8.5 (-8, 25) >0.05 10 (-7, 27) >0.05 9 (-3, 21) >0.05 Smoking (categorical, 116 (-86, 318) >0.05 -193 (-312, -73) <0.005 -91 (-200, 18) >0.05 amount smoked)c Local food consumption -82 (-366, 202) >0.05 -181 (-359, -3) <0.05 -146 (-302, 10) >0.05 (categorical, yes/no)c Pre-eclamptic conditions 1.8 (-249, 252) >0.05 -5 (-307, 297) >0.05 0 (-190, 189) >0.05 (categorical, yes/no)c Number of deliveries 58 (-45, 161) >0.05 23 (55, 101) >0.05 38 (-25, 100) >0.05 Gender of baby, M/F 64(- 136, 263) >0.05 -126 (-316, 65) >0.05 -19 (-158, 120) >0.05 Maternal weight/kg 6 (-3, 15) >0.05 12 (5, 19) <0.001 9 (3–15) <0.005 Maternal height/cm -2 (-22, 18) >0.05 21 (6, 36) <0.005 10 (-3, 22) >0.05 BMI/kg m-2 16 (-7, 39) >0.05 31 (11, 52) <0.005 22 (6, 38) <0.01 Maternal urine -0.1 (-0.5, 0.3) >0.05 1 (-4, 6) >0.05 -0.1 (-0.5, 0.3) >0.05 nickel/nmol L-1 Maternal urine -8 (-23, 6) >0.05 -13 (-32, 7) >0.05 -10 (-21, 2) >0.05 creatinine/mmol L-1 Child’s urine -0.6 (-2.0, 0.8) >0.05 -3 (-14, 8) >0.05 -0.6 (-1.9, 0.7) >0.05 nickel/nmol L-1 Child’s urine creatinine/mmol L-1 12 (-15, 39) >0.05 10 (-13, 33) >0.05 11 (-6, 29) >0.05 Maternal adjusted urine -0.9 (-4, 2) >0.05 9 (-8, 27) >0.05 -3 (-6, 0.1) >0.05 nickel/nmol Ni per mmol creat Child’s adjusted urine -0.6 (-2, 0.6) >0.05 1 (-4, 6) >0.05 -0.6 (-1.7, 0.6) >0.05 nickel/nmol Ni per mmol creat aWeight change in grams per unit of explanatory variable; CI, 95% confidence interval.bBased on the partial F-statistic. cSee Table 1 for classification.Table 5 Multivariate linear regression analysis model to predict birth combined Norwegian subjects, the following associations weight for the combined Russian/Norwegian populationab reached significance: maternal weight ( p<0.001), maternal height ( p<0.005), BMI (p<0.005), smoking ( p<0.005) and Change in birth local food consumption ( p<0.05). On combining the Russian weight/g and Norwegian study groups and adjusting for country, the Variable (95% CI) p Value associations with maternal weight ( p<0.005) and BMI Maternal urinary -1 (-6, 5) >0.05 ( p<0.01) remained significant, as did the near significance of nickel/nmol L-1 maternal urinary creatinine.Adjustment of birth weight for BMI/kg m-2 25 (8, 42) <0.005 gestational age strengthened the maternal weight and BMI Maternal height/cm 14 (0, 27) <0.05 dependences (both p<0.001), but did not alter the remaining Maternal urinary -10 (-22, 3) >0.05 associations substantially.creatinine/mmol L-1 Smoking (0, 1–10 -25 (-148, 99) >0.05 For BMIC, there were no significant associations for the or >10 cigarettes) Russian subjects; among the Norwegian group, smoking was Country (Russia/Norway) 315 (143, 487) <0.001 negatively correlated (p<0.025), while maternal weight ( p<0.025) and BMI (p<0.025) were positively so.Only the aSince 52 maternal heights were not reported and the data sets for the other variables had some omissions, N=200 (see Table 1); all values maternal weight (p<0.025) and BMI (p<0.01) retained sigare mutually adjusted.bThe F-statistic for the model is 7.3, with d.f. nificance for the combined countries. As with birth weight, 6 and 194; p<0.001. adjustment for gestational age strengthened the relationship with maternal weight and BMI (both p<0.001). Log transformation or square transformation of the nickel concentrations added no additional information; neither did urinary creatinine is negative (nearly significant); a very strong the grouping of birth weight by 500 g increments.unspecified country factor is evident ( p<0.001). The model was optimized20 by removal of local food consumption and Multivariate linear regression neonatal urinary creatinine. Judging by the partial F-statistic, the explanatory contributions of both of these variables were The variables for which significant or near-significant associations with birth weight were observed in either of the two low and not statistically significant; that of maternal urinary nickel was zero.Introducing gestational age-adjusted birth countries (see Table 4) were tested in a multivariate model. Because a major focus of this study was a comparison of weight as the dependent variable strengthened the positive predictive value of BMI (p<0.001) and maternal height urinary nickel excretion, maternal urinary nickel was also carried forward.Maternal body weight was not included since (p<0.025) and weakened the country factor slightly (p<0.01), leaving the other predictors unchanged. In the corresponding it is related to BMI.By contrast, the exclusion of maternal height as an independent explanatory variable resulted in a multivariate model with BMIC as the dependent variable (Table 6), BMI (p<0.01 or 0.001) and the country factor significant loss of information. The model summarized in Table 5 shows BMI (p<0.005) and maternal height (p<0.05) ( p<0.001) were the only notable variables (with or without adjustment for gestational age).as positive predictors, while the contribution of maternal J. Environ. Monit., 1999, 1, 153–161 157Table 6 Multivariate linear regression analysis model to predict child’s body mass index for the combined Russian/Norwegian populationab Change in birth weight/g Variable (95% CI) p Value Maternal urinary nickel/nmol L-1 0 (-0.03, 0.004) >0.05 BMI/kg m-2 0.07 (0.02, 0.12) <0.01 Maternal height/cm 0.01 (-0.03, 0.05) >0.05 Maternal urinary creatinine/mmol L-1 0.002 (-0.03, 0.04) >0.05 Smoking (0, 1–10 or >10 cigarettes per day) -0.06 (-0.42, 0.31) >0.05 Country (Russia/Norway) 1.9 (1.4, 2.4) <0.001 aSince 52 maternal heights were not reported and the data sets for the other variables had some omissions, N=199 (see Table 1); all values are mutually adjusted.bThe F-statistic for the model is 15.8, with d.f. 6 and 193; p<0.001. Birth weight in relation to neonatal urinary nickel concentrations Group analysis of neonatal urinary nickel concentrations (group 1, <15 nmol L-1; group 2, 15–170 nmol L-1; group 3, >170 nmol L-1) demonstrated no evidence for a dependence of birth weight (or BMIC; data not reported) on neonatal urinary nickel concentrations (Norwegian group, p= 0.5; Russian group, p=0.3 or 0.2; all relative to group 1 by ttest).Neither was a risk for reduced birth weight apparent when the weights were compared for urinary nickel levels below and above 34 nmol L-1, corresponding to the mean reference background concentration reported for nonpregnant adults.19 Nickel in tap water Russian communities with local nickel refineries, namely Nikel Fig. 2 A comparison of the frequency distribution of the logand Zapolyarniy (see Fig. 1), had significantly higher nickel transformed urinary nickel data for the Russian groups surveyed in levels in the drinking water (median values of 1224 and the present study (N=179; includes the results from week 20 of 578 nmol L-1, respectively) compared to the four other pregnancy in Nikel ) with that (N=52) reported for female workers employed in the Electrorefinery Department of the Severonickel Russian and two Norwegian locations (medians in the range operation in Monchegorsk.8 The sample collection and analytical 9–85 nmol l-1, p<0.001). In the Russian communities with procedures were identical to those described in the text; urine samples no local point sources of nickel, specifically Kirovsk, Apatity were collected in May 1996 and correspond to the first morning void and Umba, values were closer to the Norwegian levels (median collected at home to minimize inadvertent contamination.The median values of 9, 85 and 14 nmol L-1 respectively).Ten out of 12 and range of the nickel concentrations for the nickel workers were tap water samples from Arkhangelsk were at the DL or below 1496 (289–14 620) nmol L-1, compared to 99 (5–2108) nmol L-1 in the total Russian population in the current study. Ambient air nickel (all from private kitchens); the two detectable values were 12 levels in the Monchegorsk Electrorefinery Department8 were in the and 20 nmol L-1 (collected at the Institute of Physiology, range 60–1200 mg m-3, which appear to be higher by about a factor Ural Branch of Russian Academy of Science, Arkhangelsk, of 1000 to 10 000 or more than reported air levels for the town of and a private kitchen of a colleague).Nikel and the surrounding area, including the Norwegian–Russian border area.14,15 Discussion during parturition and postpartum suVered from severe analyt- Urinary nickel concentrations ical deficiencies and therefore can only be interpreted with considerable caution.6 Birth-associated trauma may have con- The comparison of the urinary nickel concentrations reported in the present study with published background reference tributed to the slightly higher urinary nickel concentrations in the present pregnant females, when compared to other adults.intervals12,13,19 (<100 nmol L-1) is beneficial. Clearly, the results for the Russian study groups exceed this reference Making comparisons for Nikel, the median urinary nickel value for the pregnant women of the present study was 90 upper limit, while the values for the Norwegian communities are well below it.The slightly higher creatinine-adjusted con- nmol L-1, compared to 58 nmol L-1 for other residents (N= 371, 70% female).15 centrations observed for the Nikel and Monchegorsk populations relative to Arkhangelsk (p<0.001) suggest some The higher urinary nickel excretion among the Russian groups does not have an obvious explanation.Nickel in tap environmental contribution due to the presence of the local nickel smelters. Such an impact of nickel refining on non- water, perhaps in combination with enhanced air levels, probably accounts for the higher creatinine-adjusted urinary nickel occupationally exposed community members has been reported previously for the city of Sudbury, Ontario.21,22 It is levels observed for Nikel and Monchegorsk, compared to Arkhangelsk.Since there are no nickel refineries or any other interesting to compare the Russian data for the pregnant women surveyed with recently obtained results for Russian obvious nickel point source in Arkhangelsk, other explanations are required to account for the major portion of the Russian/ females working in a Kola Peninsula nickel electrorefinery.This is done in Fig. 2. It is evident from this figure that the Norwegian urinary nickel anomaly. It is known that certain foodstuVs are relatively enriched in nickel, such as cocoa, nuts, two groups compared have separate frequency distribution patterns. The overlap between them is minimal. dried legumes and certain grains.7,24 Special dietary sources in the Russian community might therefore be suspect.Leaching There has been some suggestion that nickel excretion is increased during pregnancy, parturition and postpartum.23 into drinking water from nickel-plated pipes or from cooking utensils constitutes another explanation. Oral prostheses are Earlier reports of drastic increases in serum or urinary nickel 158 J. Environ. Monit., 1999, 1, 153–161in use in Russia that apparently have significant nickel con- of the explanatory variables should be consulted before acceptance of the suggested associations.tents, and this may well be an unexpected source of nickel.8 To our knowledge, nickel in first-voided urines of neonates The univariate linear regression data and the multivariate model reinforce that smoking is a predictor of low birth has not been reported previously. Because so many urinary nickel concentrations in both Norwegian mothers and neonates weight.The data presented suggest it reaches significance only if the smoking rate is moderately high, such as seen among were below or at the DL, it is diYcult to compare their relative magnitudes. This is not the case for the Russian population the Norwegian subjects.The retention of BMI ( p<0.005) and maternal height (p<0.05) in the multivariate model conforms studied. A comparison of maternal and neonatal creatininewith the general acceptance of maternal weight and height as adjusted nickel levels shows the latter to be lower (p<0.001). positive determinants. Similarly, urinary creatinine as a near From the perspective of the glomerular filtration rate (GFR), significant variable in the linear and multiple regressions this is not unexpected.At birth, the neonatal GFR appears to suggests that this parameter might be more sensitive in be about 20% of adult values.25 explaining birth weight than clinical diagnosis of the preeclamptic condition as a categorical variable.It is obvious from the magnitude of the ‘country’ slope factor in Table 5 Birth weight as a pregnancy outcome that we have failed to identify important predictors of birth Birth weight is recognized as an important indicator of the weight. The replacement of birth weight by BMIC did not health status of neonates.26 Temporal changes in this parameter improve the model, although adjusting for gestational age may serve as an index to socioeconomic conditions that impact strengthened the BMI influence and left the unspecified country on reproductive and developmental health.It is also known factor unchanged. Presumably, these results reflect unidentified to be sensitive to adverse environmental conditions, as illus- diVerences in economic conditions, cultural practices or trated by cigarette smoking.As a pregnancy outcome, birth nutritional factors. weight permits an outcome comparison unaVected by cultural diVerences and medical uncertainties such as outcome defi- Limitations of the study nitions. Congenital malformations and perinatal morbidity are examples. However, birth weight has some disadvantages as a A number of information biases can be identified.Answers dependent variable for pregnancy outcome, due to genetic concerning the consumption of local food were not provided diVerences.27,28 On the other hand, the BMIC has been in the Russian community of Monchegorsk. The reason for suggested to have some advantages as an index to the this may reflect the decision by the local interviewer not to nutritional status of newborn children.29–31 It would appear emphasize this component.The refusal by 36% of the Russian that the BMIC is somewhat less sensitive to the explanatory respondents to provide information about alcohol consumpvariables examined in our study. tion suggests that this topic is culturally sensitive. Even fewer Among the statistically significant associations reported in individuals responded to educational background questions Table 4 for the linear regression between birth weight and a there.Inconsistency between interviewers is also of concern. number of explanatory variables are those recognized for However, this was unavoidable since so many diVerent comhaving a known positive impact on birth weight (i.e. maternal munities were involved.Further, the questionnaire was transweight, maternal height, BMI, number of deliveries)32 or a lated from Norwegian into Russian and this may have had a negative eVect (i.e. smoking, hypertensive pregnancy compli- steering eVect on some of the questions. Of course, inherent cations).32–34 BMI is considered a measure of body fatness. It ambiguities in the questions may have influenced the consistis strongly influenced by age and sex, but not by ethnicity.35 ency of the answers.In our estimation, the discrepancies Since we are dealing with females of comparable age, BMI between Norwegian and Russian physicians in classifying may thus be taken as a suitable index of adipose tissue mass. pregnancy complications and outcomes were minimal. An Although not included in the analysis, alcohol consumption example is the diagnosis of the pre-eclamptic condition.during pregnancy is also well known to reduce birth weight. Selection bias might have occurred for two reasons, namely It is of interest that the 35.9% smoking frequency found transfer of cases with complications to regional hospitals and among the Norwegian group concurs almost exactly with the the exclusion from the statistical treatment of mothers and proportion of subjects identified as daily smokers prior to their neonates because of the unavailability of neonatal urine pregnancy in a recent survey of 4766 pregnant Norwegian samples.Patient transfers were few and were registered. women.36 Inclusion of the neonatal weights for those without urinary It is tempting to interpret the apparent but weak negative nickel samples only reduces the diVerence between the Russian impact of maternal urinary creatinine as indicative of subclin- and Norwegian birth weight means by 4 g, which does not ical pre-eclamptic manifestations.In support, it is noted that aVect the significance test (p<0.001). Clearly, the significant pre-eclampsia was found to be more prevalent in the Russian Russian/Norwegian dissimilarity in birth weights is not communities (p=0.03).Interestingly, past pre-eclampsia explained by gestational age diVerences. appears to increase the risk of microalbuminuria,37 and Although many explanatory variables were examined, it is increased urinary creatinine levels have been noted as early as likely that others exist, as well as unidentified confounders.week 19 of gestation in patients who subsequently developed However, there is evidence that this may not be too critical. pregnancy-induced hypertension.38 The positive association In two overview reports on our work, one on essential trace suggested for neonatal urinary creatinine and birth weight elements (copper, zinc, iron and selenium)40 and the other on (not significant) also seems inherently reasonable.One might metal pollutants (cadmium, lead and mercury)1 in the periexpect, by analogy to adults, that body mass or surface area pheral blood compartment of many of the individuals in the determines the rate of urinary creatinine excretion. The latter present study, no obvious concentration diVerences that might has indeed been correlated with birth weight.39 Local food be expected to influence birth weight appeared to exist between intake may constitute a nutritional factor or environmental the Norwegian and Russian groups.For example, the iron contaminant issue. However, caution must be practised in status of pregnant women was somewhat better in Russia than interpreting at face value the associations suggested by single in Norway, and serum zinc levels were low in both countries regressions, even when statistically significant, because of inter- relative to established reference intervals.40 Whole blood cadpredictor influences and possible correlations among variables.mium and mercury concentrations were higher in the Norwegian communities than in Russia, while it was the Consequently, the outcome of a multiple regression analysis J.Environ. Monit., 1999, 1, 153–161 159reverse order for lead. The mean Russian lead level of extended to Knut Dalaker, Ka°re Augensen, Babill Stray- 0.18 mmol L-1 in whole blood was within the international Pedersen, Alexander Duriagin, Elvira Khotova, Leonid background reference interval of <0.20 mmol L-1.Zhivakov, Irina Perminova, Jevgenij Bojko, Anatoli Tkatchev, Due to logistical and technical limitations, as well as econ- Tone Smith-Sivertsen, Gunhild Sand, Per Einar Fiskebeck omic restrictions, the sample size for each country was too and, especially, midwife Marie Hallonen for their kind support small to detect diVerences in the incidence of congenital in diVerent phases of the project.defects. Much larger populations need to be examined to identify such outcomes with adequate statistical power, as they are relatively rare.18 The small number of cases identified in References the present study is consistent with this. 1 J. Ø. Odland, N. Romanova, G. Sand, Y. Thomassen, B. Salbu, Although we made every eVort to minimize inadvertent E.Lund and E. Nieboer, in Environmental Biomonitoring, contamination of the samples, the lack of opportunity to be Exposure Assessment and Specimen Banking, ACS Symposium personally involved in the early stages of the sample history Series No. 654, ed. K. S. Subramanian and G. V. Iyengar, (i.e. collection, handling, storage and transport to the labora- American Chemical Society, Washington, 1997, pp. 135–150. tory) limited our ability to control the contamination risk. 2 B. Sivertsen, T. Makarova, L. O. Hagen and A. A. Baklanov, Air Pollution in the Border Areas of Norway and Russia, Summary This may account for some of the outliers corresponding to Report 1990–91, Report no NILU OR 8/92, Norwegian Institute the highest urinary nickel concentrations. for Air Research, Lillestrøm, Norway, 1992. 3 L. O. Hagen and B. Sivertsen, Overva°king av Luft- og Concluding remarks Nedbørkvalitet i Grenseomra° dene i Norge og Russland, Oktober 1991-Mars 1992, Report no 505/92, TA 897/1992, NILU OR It is interesting that two physical parameters (BMI and height), 82/92, Norwegian Institute for Air Research, Lillestrøm, Norway, a metabolic measure (maternal urinary creatinine excretion) 1992.and a life-style factor (smoking) were the strongest predictors 4 T. Norseth, Sci. Total Environ., 1994, 148, 103. 5 V. P. Chashschin, G. P. Artunina and T. Norseth, Sci. Total of neonatal birth weight in this combined Russian/Norwegian Environ., 1994, 148, 287. study population. The unimportance of urinary nickel 6 E. Nieboer, F. E. Rossetto and R.Menon, in Metal Ions in excretion, and thus nickel exposure, as an explanatory variable Biological Systems, Nickel and its Role in Biology, ed. H. Sigel and for birth weight is consistent with the recent conclusion of the A. Sigel, Marcel Dekker, New York, 1988, pp. 359–402. Norwegian–Russian Health Study that no major health eVects 7 International Programme on Chemical Safety, Environmental can be assigned to nickel as an air pollutant in the vicinity of Health Criteria 108, Nickel, World Health Organization, Geneva, 1991.the nickel refining operations in Nikel and Zapolyarniy.16 This 8 E. Nieboer, V. P. Tchachtchine, J. Ø. Odland and Y. Thomassen, is not surprising. The local ambient air nickel concentrations Reproductive and Developmental Health in Relation to there are low, although above background (54 ng m-3 com- Occupational Exposure to Nickel in the Kola Peninsula of Russia: a pared to 23 ng m-3 respectively; measured as the respirable Feasibility Study, McMaster University, Hamilton, ON, Canada, fraction, which seems to be comparable to the inhalable July 24, 1997.fraction in this instance15,16). It may be concluded from the 9 L. Jarup, M.Berglund, C. G. Elinder, G. Nordberg and M. Nikel and Monchegorsk urinary nickel data that the nickel Vahter, Scand. J. Work Environ. Health, 1998, 24, 1. 10 K. W. Andrews, D. A. Savitz and I. Hertz-Picciotto, Am. J. Ind. refineries as local point sources only minimally aVect the body Med. 1994, 26, 13. burden of nickel. 11 J. C. Hansen, U. Tarp and J.Bohm, Arch. Environ. Health, 1990, The above conclusion should not be extended to females 45, 355. occupationally exposed to nickel for the following reasons. 12 C. Minoia, E. Sabbioni, P. Apostoli, R. Pietra, L. Pozzoli, First, nickel is known to be transferred readily across the M. Gallorini, G. Nicolaou, L. Alesio and E. Capodaglio, Sci. placenta.41,42 Since nickel in urine is proportional to nickel in Total Environ., 1990, 95, 89. 13 D. M. Templeton, F. W. Sunderman Jr and R. F. M Herber, Sci. the blood plasma compartment,22 it may be inferred that Total Environ., 1994, 148, 243. serum nickel also constitutes an index to embryonic or foetal 14 T. Smith-Sivertsen, E. Lund, Y. Thomassen and T. Norseth, Arch. exposure. Because of the high occupational nickel exposures Environ.Health, 1997, 52, 464. experienced by these workers (see Fig. 28,43,44), in utero expo- 15 T. Smith-Sivertsen, V. P. Tchachtchine, E. Lund, V. Bykov, sure cannot be dismissed. Second, concern has been expressed Y. Thomassen and T. Norseth, Environ. Health Perspect., 1998, about increases in spontaneous abortions among females who 106, 503. 16 T. Smith-Sivertsen, V.P. Tchachtchine, E. Lund, T. Norseth and work in the nickel electrorefinery at Monchegorsk.5 An appar- V. Bykov, The Norwegian–Russian Health Study 1994/95. A Cross- ent increase in selected congenital malformations was also sectional Study of Pollution and Health in the Border Area, ISM noted. Third, mechanistically speaking,26 nickel compounds Skriftserie Nr. 42, University of Tromsø, Tromsø, Norway, 1997.are potentially teratogenic and embryotoxic because they are 17 B. Welz, G. Schlemmer and J. R. Mudakav, J. Anal. At. genotoxic. Respiratory tract cancers have been associated with Spectrom., 1992, 7, 1257. occupational exposures to water-soluble and particulate 18 Medical Birth Registry of Norway, Annual Report 1995, (mostly oxides and sulfides) forms.43,45,46 Clearly, follow-up University of Bergen, Bergen, Norway, 1996. 19 F. W. Sunderman Jr, Scand. J. Work Environ. Health, 1993, 19 studies are needed. We have recently illustrated that a compre- (Suppl. 1), 34. hensive epidemiological assessment of reproductive and devel- 20 D. G. Altman, Practical Statistics for Medical Research, Chapman opmental health among female nickel refinery workers in the & Hall, London, 1991, pp. 336–351. Kola Peninsula is technically feasible.8 21 S. M. Hopfer, W. P. Fay and F. W. Sunderman Jr., Ann. Clin. Lab. Sci., 1989, 19, 161. 22 E. Nieboer, W. E. Sanford and B. C. Stace, in Nickel and Human Acknowledgements Health: Current Perspectives (Advances in Environmental Science This work was supported by the University of Tromsø, Steering and Technology, Vol. 25), ed. E. Nieboer and J. O. Nriagu, John Wiley, New York, 1992, pp. 49–68. Group of Medical Research in Finnmark and Nordland, and 23 S. Nomoto, T. Hirabayashi and T. Fukuda, in Chemical the Royal Norwegian Department of Foreign AVairs, East- Toxicology and Clinical Chemistry of Metals, ed. S. S. Brown and European Secretariat. The authors wish to thank the staV at J. Savory, Academic Press, New York, 1983, pp. 351–352. the obstetric departments of hospitals in Bergen, Kirkenes, 24 G. D. Nielsen, in Nickel and Human Health: Current Perspectives Hammerfest, Nikel, Monchegorsk and Arkhangelsk for their (Advances in Environmental Science and Technology, Vol. 25), ed. excellent cooperation in the administration of the question- E. Nieboer and J. O. Nriagu, John Wiley, New York, 1992, pp. 201–210. naires and collection of specimens. Acknowledgement is 160 J. Environ. Monit., 1999, 1, 153–16125 I. Ichikawa, Pediatric Textbook of Fluids and Electrolytes, 37 R. A. North, D. Simmons, D. Barnfather and M. Upjohn, Aust. NZ J. Obstet. Gynaecol., 1996, 36, 233. Williams & Wilkins, Baltimore, 1990, pp. 494–495. 38 P. N. Baker and G. A. Hackett, Obstet. Gynecol., 1994, 83, 745. 26 H. Taskinen, Scand. J. Work Environ. Health, 1990, 16, 297. 39 J. L. Sutphen, Pediatrics, 1982, 69, 719. 27 T. J. Cole, J. V. Freeman and M. A. Preece, Stat. Med., 1998, 40 J. Ø. Odland, N. Romanova, G. Sand, Y. Thomassen, J. Brox, 17, 407. E. Khotova, A. Duriagin, E. Lund and E. Nieboer, Arct. Med. 28 T. Chard, A. Soe and K. Costeloe, J. Perinat. Med., 1997, 25, 111. Res., 1996, 55 (Suppl 1), 38. 29 K. Wandja, P. J. Hooft and H. P. van de Voorde, J. Gynecol. 41 F. W. Sunderman Jr., Ann. Clin. Lab. Sci., 1977, 7, 377. Obstet. Biol. Reprod. (Paris), 1995, 24, 444. 42 T. W. Clarkson, G. F. Nordberg and P. R. Sager, Scand. J. Work 30 T. J. Cole, G. L. Henson, J. M. Tremble and N. V. Colley, Ann. Environ. Health, 1985, 11, 145. Hum. Biol., 1997, 24, 289. 43 Y. Thomassen, E. Nieboer, D. Ellingsen, S. Hetland, T. Norseth, 31 L. Raman, G. Vasanthi, K. V. Rao, C. Parvathi, N. Balakrishna, J. Ø. Odland, N. Romanova, S. Chernova and V. P. Tchachtchine, N. Vasumathi, A. Raval and K. Adinarayana, Indian Pediatr., J. Environ. Monit., 1999, 1, 15. 1989, 26, 630. 44 E. Nieboer, in Nickel and Human Health: Current Perspectives 32 M. A. Wilcox and I. R. Johnson, Curr. Obstet. Gynaecol., 1990, (Advances in Environmental Sciences and Technology, Vol 25), ed. 2, 100. E. Nieboer and J. O. Nriagu, John Wiley, New York, 1992, 33 B. Backe, Acta Obstet. Gynecol. Scand., 1993, 72, 172. pp. 37–47. 34 P. Oian and J. M. Maltau, Tidsskr. Nor Laegeforen, 1995, 115, 45 R. Doll (ed.-in-chief ), Scand. J.Work Environ. Health, 1990, 16, 1. 698. 46 International Agency for Research on Cancer, Evaluation of 35 D. Gallagher M. Visser, D. Sepulveda, R. N. Pierson, T. Harris Carcinogenic Risks to Humans, Vol. 49, Chromium, Nickel and and S. B. Heymsfield, Am. J. Epidemiol., 1996, 143, 228. Welding, World Health Organization, Geneva, 1990. 36 K. Eriksson, K. Haug, K. A° . Salvesen, B-E Nesheim, G. Nylander, S. Rasmussen, K. Andersen, J. O. Nakling and S. H. Eik-Nes, Acta Obstet. Gynecol. Scand., 1998, 77, 159. Paper 8/09577I J. Environ. Monit., 1999, 1, 153–161 161

ISSN:0960-7919    

DOI:10.1039/a809577i

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Use of quadrupole GC-MS and ion trap GC-MS-MS for determining 3-hydroxy fatty acids in settled house dust: relation to endotoxin activity Anita Saraf,a Ju-Hyeong Park,b Donald K. Miltonb and Lennart Larsson*a aDepartment of Infectious Diseases and Medical Microbiology, Section of Bacteriology, University of Lund, S-223 62 Lund, Sweden. E-mail: Lennart.Larsson@mmb.lu.se bDepartment of Environmental Health, Harvard School of Public Health, Boston, MA 02115, USA Received 18th November 1998, Accepted 8th February 1999 Gas chromatography-mass spectrometry (GC-MS) using a quadrupole instrument and GC-tandem MS (GC-MSMS) using an ion trap instrument were applied to determine 3-hydroxy fatty acids (3-OH FAs) with 10–18 carbon chain lengths, specific components of the endotoxin ( lipopolysaccharide, LPS) of Gram-negative bacteria, in 30 house dust samples. The two methods provided similar detection sensitivity for methyl ester/trimethylsilyl derivatives of the 3-OH FAs and allowed these acids to be distinguished from co-eluting 2-OH FA derivatives.The correlation coeYcients between endotoxin activity (Limulus test) and the combined amounts of 3-OH C10, 3-OH C12, and 3-OH C14 were 0.60 and 0.61 when using GC-MS and GC-MS-MS, respectively. The superior selectivity of GC-MS-MS was illustrated in analyses of sub-milligram amounts of dust, where the chromatograms achieved by GC-MS were diYcult to interpret due to a high background and several closely eluting compounds. GC-MS-MS is therefore preferable to GC-MS for determining 3-OH FAs in minute (sub-milligram) amounts of dust.degrees of correlation have been found between the results of Introduction 3-OH FA determinations and Limulus assays.18–21 One finding Endotoxin is the name given to a class of biological molecules has been that LPS associated with 3-OH C16 and 3-OH C18 that have certain characteristic toxic eVects. Endotoxins are has lower potency than when associated with 3-OH C10, 3- lipopolysaccharides (LPS) present in the outer membrane of OH C12, and 3-OH C14.18,22 Gram-negative bacteria, occurring abundantly in domestic Gas chromatography-mass spectrometry (GC-MS) is the house dust and in several agricultural and occupational preferred analytical technique for determining 3-OH FAs in environments.Exposure to high concentrations of airborne chemically complex environments.The GC-MS method preendotoxin is associated with bronchial inflammation, acute dominantly used includes analysis of these acids as methyl airflow obstruction and inhalation fever.1–7 Endotoxin has ester (Me)/trimethylsilyl (TMS) derivatives by using a quadrualso been associated with work-related illness in non- pole type of instrument.Selected ion monitoring (SIM) is agricultural environments.8–10 Endotoxin in house dust has used in order to achieve high detection sensitivity; it is inevibeen associated with increased asthma severity.11 Inhaled table, however, that by applying SIM the detection specificity endotoxin is a potent proinflammatory substance that triggers will be lowered in comparison with full scan analysis.We have a cascade of cellular inflammatory responses primarily through previously shown that Me/TMS derivatives of 3-OH FAs can activating pulmonary macrophages.12 be distinguished from the corresponding 2-OH FA derivatives Environmental endotoxin is usually measured by diVerent by focusing at a fragment specific for the former (m/z 175).23 versions of the Limulus amebocyte lysate (LAL) assay.However, whether this fragment is specific enough to dis- Measurement of clotting enzyme activity by means of a tinguish 3-OH FAs also from other co-eluting compounds that synthetic chromogenic substrate and the formation of a gel may be present in dust samples is not known. clot forms the basis of the chromogenic and gel clot LAL Tandem MS (GC-MS-MS), using ion-trap technology, has assay.13,14 However, the toxicity of endotoxin from diVerent been applied to achieve improved detection selectivity.In this Gram-negative bacteria can vary substantially both quantitat- technique, the ions formed initially are subjected to further ively and qualitatively,15,16 and the LAL gel assay may not fragmentations, and the fragment (daughter) ions are monireflect all these diVerences.tored. However, a disadvantage of this approach may be the Determination of 3-hydroxylated fatty acids (3-OH FAs), unwanted side-reactions and other events that may occur in of 10–18 carbon chain lengths, has been applied to measure an ion trap upon introduction of samples containing relatively LPS in environmental samples. This method is reproducible large amounts of compounds that co-elute with the analytes.and excludes the risk of interference from other biologically In the present study, results from analyses of Me/TMS active components, such as b-1–3 glucan, that can be encoun- derivatives of 3-OH FAs in settled house dust samples by tered in the LAL assays. The analysis also provides some using quadrupole GC-MS were compared with those obtained information about the origin of the endotoxin, because the using ion trap GC-MS-MS.The aims were (1) to evaluate the relative distribution of the individual 3-OH FAs varies between specificity of the m/z 175 fragment for determining LPS in diVerent species of Gram-negative bacteria.17 However, this such samples, (2) to assess the performance of ion trap GCmethod measures the total mass of LPS, irrespective of the MS-MS for measuring 3-OH FAs in samples containing coeluting compounds, including 2-OH FAs, and (3) to correlate bioactivity, and sensitivity is lower than in LAL assays.Various J. Environ. Monit., 1999, 1, 163–168 163the results of the GC-MS and GC-MS-MS analyses of 3-OH endotoxin units with reference to EC5 reference standard endotoxin (US Pharmacopeia, 1 ng EC5=10 endotoxin FAs with Limulus activity.units, EU). Experimental Preparation of samples for GC-MS and GC-MS-MS Chemicals and glassware Dust samples were heated in 2 ml of 4 M methanolic HCl Pentafluoropropionic anhydride (PFPA) and pyridine were (10 ml of acetyl chloride added to 22 ml of methanol ) for 18 h purchased from Fluka Chemie (Buchs, Switzerland), triethyl- at 100 °C and cooled to room temperature, after which amine was obtained from Sigma (St.Louis, MO, USA), and deuterated 3-OH C14 methyl ester was added as an internal N,O-bis-(trimethylsilyl ) trifluoroacetamide (BSTFA) was from standard. A volume of 1 ml of water was added, and the Acros (Geel, Belgium). The 2- and 3-OH FA methyl esters with preparations were extracted with 2×1.5 ml of heptane, dried chains of 10, 12, 14, 16, and 18 carbons were purchased from using a stream of nitrogen, dissolved in 1 ml of dichloro- Larodan Lipids (Malmo� , Sweden), and deuterated 3-OH-C14 methane–heptane (1+1, v/v), and applied to a silica gel was a gift from Dr.David White. Solvents were of analytical- column (1 ml, 100 mg Si; Varian, Harbor City, CA, USA) reagent grade and used without further purification.Glass that had been preconditioned with 1 ml of diethyl ether and test-tubes were equipped with PTFE-lined screw caps. 1 ml of dichloromethane–heptane (1+1, v/v). The column was washed twice with 1 ml of dichloromethane–heptane (1+1, Dust samples v/v), whereafter hydroxylated fatty acid methyl esters were eluted with two 1 ml portions of diethyl ether.The eluates House dust samples were collected with a Eureka Mightywere then dried under a stream of nitrogen, dissolved in 1 ml Mite vacuum cleaner modified to collect dust in cellulose of pentane–dichloromethane (1+1, v/v), and divided into two extraction thimbles (19×90 mm; Whatman, Maidstone, Kent, portions.The hydroxy acid esters in one portion were subjected UK) for an ongoing study of home endotoxin exposure and to TMS derivatization (using BSTFA) as previously childhood asthma. Separate clean rigid tubes were used described,23 and those in the other portion were subjected to between the sampling surface and the thimble for each sample pentafluoropropionyl (PFP) derivatization as follows.Extracts to prevent cross-contamination. Thimbles were placed iairwere evaporated using a stream of nitrogen and dissolved in tight plastic bags immediately after collection. No later than 30 ml of triethylamine-containing (1% v/v) acetonitrile. the day after collection the recovered dust was weighed, sifted Thereafter, 20 ml of PFPA were added, and the mixture was through a 500 mm mesh sieve, and the fine dust reweighed and heated at 37 °C for 15 min.After cooling to room temperature, aliquoted for various analyses. Of a total of 143 dust samples 750 ml of hexane and 1 ml of 0.1 M phosphate buVer (pH 7.0) that were subjected to GC-MS analysis for 3-OH FAs, a subwere added, and the mixture was vortexed and centrifuged set of 30 samples was taken for the comparison with GC-MS- (approximately 1000g).The hexane phase was then applied to MS in this study. The sub-set was taken by randomly choosing a disposable silica gel column that had previously been rinsed 15 samples from the lowest quintile and another 15 samples with 3×1 ml of dichloromethane, and the Me/PFP derivatives from the highest quintile of house dust endotoxin activity (EU were eluted using 3×1 ml of the same solvent.After evapor- per mg dust). ation, the product was redissolved in heptane and used for Endotoxin assays analysis. Furthermore, five aliquots ranging from 0.15 to 1.0 mg of The endotoxic biological activity of the dust samples was one of the 30 dust samples were prepared for 3-OH FA measured by the kinetic Limulus assay with the resistantanalysis.parallel-line estimation (KLARE) method, described pre- Apart from the TMS and PFP derivatives, several other viously.24,25 Limulus amebocyte lysate (LAL) was obtained derivatives of 2- and 3-OH fatty acid methyl ester (FAME) from BioWhittaker (Walkersville, MD, USA), reference stan- standards, prepared essentially according to previously dard endotoxin from the US Pharmacopeia (Rockville, MD, described methods, were analyzed.These included methoxy,26 USA), and control standard endotoxin from Associates of pentafluorobenzoyl,27 tert-butyldimethylsilyl,28 heptafluoro- Cape Cod (Woods Hole, MA, USA). All glassware was heated butyryl (prepared in the same way as the PFP derivatives in to 270 °C for 30 min prior to use. Control and reference the present study), acetate, propionate and butyrate derivastandards and field samples were serially diluted for endotoxin tives.29 FAMEs with underivatized hydroxy groups were also analysis in a standard buVer (of 0.01% triethylamine – 0.05 M studied.potassium phosphate). A 25 mg portion of sifted dust was placed in glass tubes with 5 ml of buVer and bath-sonicated GC-MS and GC-MS-MS for 1 h with vortexing at 15 min intervals.An initial 1+24 dilution of dust extracts with suspended particulate was made A VG Trio-1 S quadrupole mass spectrometer (VG, Manchester, UK) connected to a Hewlett-Packard Model before the start of the serial dilutions used in the assay. Duplicate 50 ml aliquots of five serial dilutions of dust extracts 5890 gas chromatograph was used.The fused-silica capillary column (CP-Sil 5CB-MS, 0.25 mm film thickness, and a control standard endotoxin were placed in an endotoxinfree 96-well, flat-bottomed polystyrene microplate (Associates 30 m×0.25 mm id; Chrompack, Middelburg, The Netherlands) was temperature programmed, at 20 °Cmin-1, of Cape Cod); 50 ml of LAL were added and the microplate was agitated.The absorbance of each well was recorded at from 90 to 280 °C. The injector was kept at 280 °C, the interface at 290 °C, and the ion source at 200 °C. Injections 405 nm every 30 s for 120 min during incubation at 37 °C. The response parameter for the LAL reaction was the maximum were made in the splitless mode using a Hewlett-Packard Model 7673 autosampler; helium, at a flow rate of 1 ml min-1, rate of absorbance change (Vmax).The log potency and its variance were computed using resistant regression and Tukey’s was used as a carrier gas. This instrument was used to analyze TMS-derivatized samples only, operating in SIM mode with jackknife. Interference was detected by analysis of covariance and a standard algorithm was used to eliminate such eVects electron impact (EI ) ionization; the ionization energy was 70 eV.during an iterative data analysis. Results were considered valid if the final data analysis found no statistically significant An ion trap GC-MS-MS instrument, Model Saturn 2000 (Varian, Palo Alto, CA, USA), equipped with the same type diVerence between the dose-response slopes for the control standard and environmental sample.Results are reported in of fused-silica capillary column as in the quadrupole instru- 164 J. Environ. Monit., 1999, 1, 163–168ment (see above), was used. Samples were injected in the splitless mode using a Varian Model 8200 CX autosampler. Column temperature was programmed from 90 to 280 °C at a rate of 20 °Cmin-1; the temperature of the injector was 280 °C and that of the transfer line (between GC and MS) 280 °C.The ion trap was held at 180 °C for the TMS derivatives and at 200 °C for all other derivatives studied. The derivatized acid standards were all analyzed by GC-MS on this instrument; in addition, TMS- and PFP-derivatized standards and dust samples were also subjected to GC-MS-MS analysis. Conditions for formation of daughter ions from suitable parent ions selected from the mass spectra of TMS- and PFPderivatized 3-OH FAMEs were optimized by repeatedly injecting 1000–5000 pg of each marker derivative and studying the influence of diVerent fragmentation conditions [voltage, time, resonance/non-resonance mode, digital/analogue conversion values (DAC), and excitation storage level ].PFP derivatives were analyzed in selected ejection chemical ionization (SECI) mode, using isobutane as the reagent gas; the selected parent ions were fragmented in resonance mode.TMS derivatives were analyzed by using EI; the parent ion m/z 175 was fragmented (non-resonance mode). A 1ml aliquot (total volume 100 ml ) of a prepared dust sample was injected for each analysis. The results of the analyses of the TMS-derivatized dust samples by GC-MS-MS were compared with the results obtained when the same preparations were analyzed by quadrupole GC-MS.Statistical analyses Because the samples analyzed were taken from the lowest and highest quintiles, the distribution of endotoxin and concentrations were not Gaussian, even after log transformation. Therefore, the Spearman rank correlations were computed to examine associations between endotoxin level and LPS content of dust samples. Results Standard solutions PFP derivatives of the 2- and 3-OH FAMEs were well separated chromatographically.The EI spectra of the 3-OH FA derivatives showed excessive fragmentation. The SECI spectra were dominated by ions of m/z [M-163] ( loss of CF3–CF2–COO) which were therefore used for fragmentation in the MS-MS analyses, resulting in fragments of m/z [M-163-32] (further loss of CH3OH; Fig. 1). Fragmentation Fig. 1 Mass spectra of the methyl ester/PFP derivative of 3-OH C16 was achieved by using the resonance mode at an excitation obtained in the EI (upper) and in the SECI (middle) mode, and a storage level of 48 m/z for 20 ms and voltages of 0.24 V (3- SECI-MS-MS spectrum of the same compound after fragmentation of m/z 269 (lower).OH C10), 0.25 V (3-OH C12), 0.26 V (3-OH C14), 0.22 V (3-OH C16) and 0.23 V (3-OH C18). The heptafluorobutyryl derivatives also separated chromatographically and the SECI spectra were identical with those of the PFP derivatives. The FAMEs. However, a considerable peak tailing was observed, leading to poor sensitivity.The tert-butyldimethylsilyl deriva- detection sensitivity for both derivatives was comparable; however, the PFP derivatives had shorter retention times, thus tives of the corresponding 2- and 3-OH FAMEs showed a partial chromatographic separation that decreased with they were used in subsequent studies. Mass spectra of the 3-OH FAME TMS derivatives were increasing carbon chain length.The spectra of the 2- and 3- OH FA derivatives were virtually identical and dominated by dominated by ions of m/z 175 (cleavage of the C3–C4 linkage) and m/z [M-15] ions ( loss of CH3). The 2-OH FA derivatives m/z [M-57] {loss of –C(CH3)3}. The 3-OH FAME/methoxy derivatives produced dominant m/z [M-15] ions ( loss of also produced m/z [M-15] ions, but not m/z 175; as reported earlier,23 there was no chromatographic separation of the CH3), whereas the 2-OH FA derivatives gave [M-59] ions (cleavage of C1–C2 linkage); however, the yields were low corresponding 2- and 3-OH FAs.Fragmentation of m/z 175 ions for 50 ms at 18 V and an excitation storage level of 48 which resulted in poor detection sensitivity. None of the other derivatives of the 2- and 3-OH FAs of m/z (non-resonance mode) resulted in two distinctive fragment ions, m/z 131 and m/z 73.30 identical chain lengths was separated chromatographically.The Me/pentafluorobenzoyl derivatives of both 2- and 3-OH Methyl esters of the 2- and 3-OH FAs (with non-derivatized hydroxy groups) were well separated chromatographically; FAs gave identical spectra, dominated by ions of m/z 195 (pentafluorobenzoyl group).The spectra of 2- and 3-OH ions of m/z 103 (fragmentation between C3 and C4) were found for all of the 3-OH FAMEs but not for the 2-OH FAME acetate, propionate and butyrate derivatives were J. Environ. Monit., 1999, 1, 163–168 165dominated by m/z [M-59] ( loss of CH3COO), [M-73] ( loss instrument. After the preparations had been diluted 10-fold with heptane and re-analyzed using the same GC-MS-MS of CH3CH2COO), and [M-87] ( loss of CH3CH2CH2COO), respectively.conditions, a marked increase in the relative amounts of 3- OH C16 and 3-OH C18 was noticed (Fig. 3). The fragment ion spectra of the 3-OH FA derivatives were dominated by m/z Dust samples 131. However, when the amounts injected were small ( less PFP derivatives.All dust samples studied contained detect- than approximately 50 pg) the spectra were dominated by m/z able amounts of both 2- and 3-OH FAs of 10, 12, 14, 16, and 175 provided that background subtraction was not applied 18 carbon chain lengths. As mentioned, chromatographic (Fig. 4). These results demonstrate that only part of the m/z separation was achieved for all of the acids when analyzed as 175 ions originate from 3-OH FAs, and that SIM may not be Me/PFP derivatives (Fig. 2). Preparations were analyzed both specific enough for determining 3-OH FAs, e.g., in small in the SECI-MS mode and by using SECI-MS-MS; as expected, amounts of dust. SECI-MS-MS gave lower background noise than SECI-MS (data not shown). In the MS-MS experiments, ions of m/z Detection sensitivity.Both quadrupole GC-MS and ion trap [M-195] were used for quantification. The amounts of the 3- GC-MS-MS revealed the presence of all of the studied 3-OH OH FAs compared with the corresponding 2-OH FAs were FAs (from C10 to C18) in the five (0.15–1.0 mg) aliquots of lower for C16 and C18 than for C10, C12 or C14. Thus, the relative amounts (mean values) of 3-OH FAs to the sum of 2- and 3-OH FAs were 0.86, 0.95, 0.75, 0.24, and 0.44 for C10, C12, C14, C16, and C18, respectively (Table 1A).TMS derivatives. Ions of m/z 175, m/z 178 (internal standard) and m/z [M-15] were monitored in the quadrupole GC-MS analysis. The 3-OH FAs were quantified by dividing the area of the m/z 175 ions by the area of the m/z 178 ions for each sample (m/z 175 is considered to be specific for 3-OH FAs, whereas m/z [M-15] is assumed to represent the sum of 2-OH and 3-OH FAs).The relative amounts (mean values) of the area of the m/z 175 ion to that of the [M-15] ion were 0.73, 1.0, 0.8, 0.23, and 0.56 for C10, C12, C14, C16, and C18, respectively (Table 1B). The same preparations were also run on the ion trap instrument in the EI-MS-MS mode, fragmenting the m/z 175 ion; m/z 131 was used for quantification.Relatively small amounts of both 3-OH C16 and 3-OH C18 were detected as compared with the results obtained with the quadrupole Fig. 2 SECI-MS-MS analysis of methyl ester/PFP-derivatized 2- and 3-OH FAs, with chains of 10–18 carbon atoms (blackened), present in a house dust sample. The amount injected corresponded to 100 mg of dust and 2.4 ng of internal standard (I.S).Table 1 Ratios (mean) of 3-OH FAs to sum of 2- and 3-OH FAs (methyl ester/PFP derivatives) (A) and ratios (mean) of the intensity of the m/z 175 to the m/z [M-15] ions (methyl ester/TMS derivatives of hydroxy acids) (B) determined for the set of 30 dust samples Fig. 3 Methyl ester/TMS-derivatized hydroxy FAs of 10–18 carbon atom chain lengths in a house dust sample analyzed by quadrupole A: B: GC-MS in the EI-SIM mode, monitoring m/z 175, m/z 178 (internal Acid Mean±s Mean±s standard), and m/z [M-15].The amount injected corresponded to 50 mg of dust and 1.2 ng of internal standard (upper three tracings). C10 0.86±0.10 0.73±0.15 Results are also shown for the same preparation before (middle two C12 0.95±0.03 1.00±0.05 tracings) and after a 10-fold dilution ( lower two tracings), analyzed C14 0.75±0.17 0.80±0.26 by ion-trap EI-MS-MS, with fragmentation of m/z 175 monitoring C16 0.24±0.11 0.23±0.09 m/z 131; fragment m/z 134 was monitored for the internal standard C18 0.44±0.24 0.56±0.21 (I.S ). 166 J. Environ. Monit., 1999, 1, 163–168Fig. 5 Methyl ester/TMS-derivatized 3-OH FAs of 10–18 carbon atom chain lengths in a house dust sample analyzed by ion-trap EI-MS-MS Fig. 4 Fragment ion spectrum (using m/z 175) of the methyl ester/ (fragmentation of m/z 175, monitoring m/z 131; upper) and by TMS derivative of 3-OH C16 in a standard solution (upper) and in a quadrupole GC-MS in the EI-SIM mode (lower). The amount injected dust sample ( lower); background subtraction was not applied.corresponded to 1.35 mg of dust. the dust samples that were analyzed separately as Me/TMS derivatives. However, the superior selectivity of MS-MS specificity be achieved. In the first studies published on this resulted in chromatograms that were easier to interpret than subject,19,20 where GC-MS of Me/pentafluorobenzoyl derivathose obtained by quadrupole analysis (Fig. 5). The sensitivit- tives was used in the CI-negative ion mode, the presence of ies for the Me/PFP derivatives were considerably lower (data substantial amounts of 2-OH FAs of 10–18 carbon chain not shown). lengths in organic dust samples was overlooked; thus, the reported amounts of 3-OH FAs were overestimated since Correlation between GC-MS/GC-MS-MS and Limulus results chromatographic separation was not achieved.In later investigations, Me/TMS-derivatized samples were used and analyzed Endotoxin levels observed in the 30 dust samples ranged from in the EI mode, and it was found that 2- and 3-OH FAs could 24 to 516 EU mg-1 house dust and generally no evidence of be distinguished even though they co-eluted from the GC interference was shown during Vmax data analysis to estimate column; only the latter produced m/z 175 ions, whereas both log potency of endotoxin.The correlation between results of 2- and 3-OH FA derivatives produced m/z [M-15].23 In the the Limulus assays and the 3-OH FA analyses (using Me/TMS present study, we showed that Me/PFP derivatives of 2-and derivatives) depended upon the individual acid or the combi- 3-OH FAs separate chromatographically and that 2-OH FAs, nations of acids chosen to calculate the number of moles of mainly those with 16 and 18 carbon chain lengths, are ubiqui- LPS (moles of acids divided by four). Correlation was best tous in house dust.We also found that the discrepancies when 3-OH FAs of 10, 12 or 14 carbon chain lengths were between the intensities of the m/z 175 and m/z [M-15] ions considered, either individually or in diVerent combinations.In seen when analyzing Me/TMS derivatives were primarily due the quadrupole GC-MS analyses, correlation coeYcients of to co-elution of the 2- and 3-OH FA derivatives, since the 0.59, 0.57, and 0.61 were obtained for 3-OH C10, 3-OH C12, ratios of the intensities of these ions and the ratios of the 3- and 3-OH C14, respectively.A correlation coeYcient of 0.60 OH FAs to the sum of 2- and 3-OH FAs were in general ( p=0.0006) was obtained when all three of these acids were agreement (Table 1). taken into consideration. With 3-OH C16 and C18 the corre- Compared with GC-MS analysis in the SIM mode, GC- lation coeYcients were 0.22 and 0.38, respectively. In the ion MS-MS provides superior analytical specificity, and ion trap trap GC-MS-MS analyses of the 10-fold diluted samples use instruments are particularly suitable for the latter type of of 3-OH C10 gave a correlation coeYcient of 0.65, with 3-OH analysis.We have previously reported details concerning detec- C12 it was 0.56 and with 3-OH C14 it was 0.65.The correlation tion limit,30 reproducibility,18 and quantification18 of the 3- coeYcient was 0.61 (p=0.0004) when a combination of these OH FAME/TMS derivatives.However, it is also generally three acids was used. With 3-OH C16 and C18 the correlation accepted that the sample capacity of ion traps is limited. coeYcients were 0.27 and 0.44, respectively. Introduction of a large amount of a component into a trap results in a shorter ionization time (which is regulated auto- Discussion matically).In our analyses of undiluted dust preparations, the ionization time was approximately 2000–3000 ms for the For a successful application of 3-OH FA analysis to determine LPS in environmental samples, it is essential that high detection C10–C14 3-OH FAs but only about one-third as long for the J. Environ. Monit., 1999, 1, 163–168 1675 R.Rylander, P. Haglind andM. Lundholm, Am. Rev. Respir. Dis., C16 and C18 3-OH FAs, probably due to the simultaneous 1985, 131, 209. elution of appreciable amounts of C16 and C18 2-OH FA 6 D. A. Schwartz, P. S. Thorne, S. J. Yagla, L. F. Burmeister, S. A. derivatives. The results of these analyses showed that the Olenchock, J. L. Watt and T. J. Quinn, Am.J. Respir. Crit. Care relative amounts of the C16 and C18 3-OH FAs compared with Med., 1995, 152, 603. the C10–C14 3-OH FAs were considerably smaller than the 7 A. Thelin, O� . Tegler and R. Rylander, Eur. J. Respir. Dis., 1984, 65, 266. results obtained with the quadrupole instrument. However, 8 D. K. Flaherty, F. H. Deck, J. Cooper, K. Bishop, P. A. after a 10-fold dilution and re-analysis, ionization times were Winzenburger, L.R. Smith, L. Bynum and W. B. Witmer, Infect. substantially longer, and these diVerences in the relative peak Immun., 1984, 43, 206. areas were not observed (Fig. 3). 9 D. K. Milton, J. Amsel, C. E. Reed, P. L. Enright, L. R. Brown, The fragmentation conditions used in GC-MS-MS were G. L. Aughenbaugh and P.R. Morey, Am. J.Ind. Med., 1995, adjusted so that most of the m/z 175 fragment formed ions of 28, 469. 10 D. K. Milton, D. Wypij, D. Kriebel, M.Walters, S. K. Hammond m/z 131 (used for quantification) and m/z 73. However, when and J. Evans, Am. J. Ind. Med., 1996, 29, 3. analyzing small amounts of dust samples, ions of m/z 175 11 O. Michel, J. Kips, J. Duchateau, F. Vertongen, L. Robert, H. dominated over m/z 131 provided that background subtraction Collet, R.Pauwels and R. Sergysels, Am. J. Respir. Crit. Care was not applied (Fig. 4), indicating that an appreciable pro- Med., 1996, 154, 1641. portion of the former ion represents compound(s) other than 12 R. Rylander and L. Beijer, Am. Rev. Respir. Dis., 1987, 135, 83. 3-OH FAs. The diVerence in specificity between quadrupole 13 S.Iwanaga, T. Morita, T. Harada, S. Nakamura, M. Niwa, K. Takada, T. Kimura and S. Sakakibara, Haemostasis, 1978, 7, 183. GC-MS and ion trap GC-MS-MS was illustrated by the 14 J. Levin and F. B. Bang, Thromb. Diath. Haemorrh., 1968, 19, analysis of a 0.15 mg dust sample; the identities of the 186. extraneous peaks seen in the quadrupole GC-MS trace are not 15 I. Helander, M.Salkinoja-Salonen and R. Rylander, Infect. known (Fig. 5). Immun., 1980, 29, 859. The correlation between 3-OH FA composition and endo- 16 M. W. Baseler, B. Fogelmark and R. Burrell, Infect. Immun.,1983, toxin activity (Limulus test) was similar regardless of whether 40, 133. 17 S. G. Wilkinson, in Microbial Lipids, ed. C. Ratledge and S. G. GC-MS-MS or GC-MS was applied; however, several milli- Wilkinson, Academic Press, London, 1988, vol. 1, pp. 299–488. grams of dust samples were used in this comparison. Our 18 A. Saraf, L. Larsson, H. Burge and D. Milton, Appl. Environ. results show that GC-MS-MS is the preferred method when Microbiol., 1997, 63, 2554. only sub-milligram amounts of dust are available for analysis, 19 A. Sonesson, L. Larsson, A. Fox, G.Westerdahl and G. Odham, which may be the case, e.g., when studying airborne particles J. Chromatogr. B, 1988, 431, 1. in various indoor environments. 20 A. Sonesson, L. Larsson, A. Schu� tz, L. Hagmar and T. Hallberg, Appl. Environ. Microbiol., 1990, 56, 1271. 21 M. Walters, D. Milton, L. Larsson and T. Ford, Appl. Environ. Acknowledgements Microbiol., 1994, 60, 996. 22 L. Ma°rtensson, W. Gradowska and L. Larsson, Aerobiologia, Financial support from the Swedish Council for Building 1997, 13, 99. Research, Swedish Society for Medical Research, The Royal 23 Z. Mielniczuk, E. Mielniczuk and L. Larsson, J. Microbiol. Physiographic Society in Lund, Medical Faculty at the Methods, 1993, 17, 91. 24 D. K. Milton, H. A. Feldman, D. S. Neuberg, R. J. Bruckner and University of Lund, The Crafoord Foundation and the US I. A. Greaves, Environ. Res., 1992, 57, 212. National Institute of Environmental Health Sciences grant 25 D. K. Milton, D. K. Johnson and J. H. Park, Am. Ind. Hyg. Assoc. number ES07036 is greatly acknowledged. J., 1997, 58, 861. 26 W. Gradowska and L. Larsson, J. Microbiol. Methods, 1994, 20, 55. References 27 Z. Mielniczuk, S. Alugupalli, E. Mielniczuk and L. Larsson, J. Chromatogr., 1992, 623, 115. 1 R. M. Castellan, S. A. Olenchock, K. B. Kinsley and J. L. 28 B. O. Axelsson, A. Saraf and L. Larsson, J. Chromatogr. B, 1995, Hankinson, N. Engl. J. Med., 1987, 317, 605. 666, 77. 2 K. J. Donham, D. C. Zavala and J. A. Merchant, Arch. Environ. 29 K. Blau, in Handbook of Derivatives for Chromatography, ed. K. Health, 1984, 39, 96. Blau and J. Halket, Wiley, Chichester, 2nd edn., 1995, pp. 31–47. 3 G. doPico, D. Flaherty, P. Bhansali and N. Chavaje, J. Allergy 30 A. Saraf and L. Larsson, J. Mass Spectrom., 1996, 31, 389. Clin. Immunol., 1982, 69, 435. 4 P. J. Jagielo, P. S. Thorne, J. L.Watt, K. L. Frees, T. J. Quinn and D. A. Schwartz, Chest, 1996, 110, 263. Paper 8/09019J 168 J. Environ. Monit., 1999, 1, 163&ndash

ISSN:0960-7919    

DOI:10.1039/a809019j

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Distributions of lead and cadmium in dust in the vicinity of a sewage sludge incinerator Yaping Feng and Rod Barratt* Department of Environmental and Mechanical Engineering, Faculty of Technology, The Open University, Walton Hall, Milton Keynes, UK MK76AA. E-mail: r.s.barratt@open.ac.uk Received 26th October 1998, Accepted 18th January 1999 The content of lead and cadmium in surface dust within a 4 km radius of a sewage sludge incinerator has been investigated.Particular attention was given to Pb and Cd in diVerent size fractions of dust, an aspect not explored in previous studies, and the diVerences between expressions of contamination as concentration or loading were examined. Despite suggestions from reports that sludge incinerators may have diYculty in complying with emission standards, the present investigation found little evidence for a major contribution to local pollution by the incinerator.Certainly, the highest Cd level was found some 2.2 km downwind of the prevailing wind direction from the incinerator, suggesting some resultant contamination, although the levels do not appear to be excessive. Similar observations apply to Pb contamination of the area.While data of the type produced in this study contribute to an understanding of environmental quality, both loadings and levels need to be considered, as the implications of only consideration one of these may be limited and even misleading. similar conclusion for the USA, by suggesting that, as cadmium Introduction is preferentially associated with the fine particles, it is therefore Incineration has many attractions as a waste disposal option, not easily trapped.More recent statistics support the view from in particular the volume reduction and sterile residue that the UK and indicate that 10 tonnes of cadmium were emitted result from the process. The option to recycle the energy from UK incinerators in 1991, representing 32% of total content of waste is an added attraction.However, the public emissions to air. By comparison, lead emissions from incineroften does not see incineration in the same favourable light as ation amounted to 161 tonnes, but this was a very much smaller a safe environmental option, and this may be due to reports proportion ( less than 2%) of the total emissions, with smelting of contamination around incineration plants.Incineration of and petrol being more significant. Surprisingly, however, the domestic refuse and its potential contamination by trace metals suggestions of the significant potential pollution were not borne have been studied relatively extensively. Cadmium in domestic out by environmental measurements. Hutton et al.8 did not find refuse may be present principally as cadmium-stabilised plas- a marked environmental impact around a major incinerator in tics, cadmium pigments, plated scrap, batteries, cadmium- London following their study on deposited dust.A similar soldered articles and in alloys. Measurements of the amount observation was reported by Barratt,9 who used data from of cadmium in domestic waste have placed the range from 9 suspended particulate monitoring to show that industrial and to 140 ppm.Using a typical cadmium content of 12 ppm1 in other local activities had a greater impact on the local environthe estimated 20 million tonnes of household waste generated ment than refuse incineration. This limited impact should not annually,2 the cadmium content of domestic waste generated be surprising if the conclusions of Vogg et al.10 are considered.in the UK is estimated at 240 tonnes per year. If commercial These workers gave a scheme for the distribution of cadmium waste is included, the total rises to 420 tonnes. Sludge pro- (Fig. 1). According to this scheme, 70% of the cadmium enters duction in the European Union (EU) is expected to increase the flue gas, but most is removed by the gas cleaning device by 50% to the year 2005, yet forthcoming landfill directives before final release to the atmosphere.may further restrict sludge disposal options,3 making alterna- Considering sewage sludge in particular, annual arisings tive disposal routes essential. Nationally, about 4% of con- were estimated to be between 30 and 40 million tonnes (wet trolled waste is incinerated,2 and so up to 9.6 tonnes of weight) in the UK, equivalent to about 1 million tonnes dry cadmium may enter the incineration stream from domestic weight.2 Sewage sludge production in the Severn–Trent region waste.It has been shown by one study4 that the element then amounted to about 159 thousand tonnes yearly between 1992 distributes itself through fine bottom ash (41 ppm), fly ash (64 ppm), atmospheric particulate matter (1100 ppm), quench water (0.04 pm) and fly ash scrubber water (1.7 ppm).This distribution suggests that a substantial proportion of cadmium is volatilised and emitted as aerosol. For the UK, the corollary is that over 8.5 tonnes of cadmium would be emitted from incineration each year. This is of a similar magnitude to the estimate of 6 tonnes per year made by Wadge and Hutton on the basis of their measured emission data.5 Based on these measurements and their previously reported emissions inventory data,6 Hutton and Symon concluded that incineration was the single largest source of atmos- Fig. 1 Distribution of cadmium from incineration. pheric cadmium release in the UK. Greenberg et al.7 draw a J.Environ. Monit., 1999, 1, 169–176 169Table 1 Sewage sludge incinerator characteristics and 1995.11 The cadmium and lead content of sludge has declined over the years, largely due to more demanding Furnace type Multiple hearth controls and better treatment of industrial eZuents and encour- EZuents in addition Metals, engineering, food, agement from water companies.2 However, increases in the to domestic chemicals, car manufacturing amount of sewage sludge have been predicted in the future,12 Sludge type Primary sludge and activated sludge, with and without as population growth and more stringent eZuent standards digestion create their impact.The phase out of disposal of sewage sludge No. of furnaces 2 operational, 1 standby to sea by the end of 1998 raised the level of interest in sewage Furnace temperature/°C 900 burning, 400–450 outlet sludge incineration, and several reappraisals of the disposal Furnace retention/min 60 option have been published.13,14 In 1980, only 4% of sewage Gas cleaning Water spray+electrostatic sludge went to incinerators, but with the opening of new plant, precipitator; 99.7% eYciency this proportion had risen to 7% of arisings in 1990.A sixfold Discharge height/m 92 (above ground) increase or greater was predicted as a result of the ban on Discharge temperature/°C 310 disposal to sea, and this would take the proportion incinerated Distance from residences/m 1500 to 30% of all sludge.12 However, there is also interest in recycling of sludge for agriculture, land restoration and landscaping. This destination accounted for about 56% of sludge Meteorological data from the nearby airport, reflected in in the Severn–Trent region, while only 9% of the sludge went Fig. 2, indicate that winds blow predominantly from the 191– to incineration at the time of this investigation. 250° sector (south westerlies for typically 28% of the time). In Estimates of cadmium emissions vary according to the addition, Pasquill stability category D is most common with assumptions made.One attempt suggested that 48 424 tonnes wind speeds of 4–7 m s-1. On this basis, it was possible to of dry solids were incinerated annually in the West Midlands, circumscribe the incinerator with arcs of potential impact and this could allow 2.8 tonnes of cadmium to be volatilised.15 using standard atmospheric dispersion modelling methods.17 The decline in metal content of sludge since that time will These arcs were drawn at radial distances of approximately obviously reduce the potential release to atmosphere of toxic 0.4, 0.7, 1.2, 2.6 and 5.5 km, corresponding to stability categor- metals, such as lead and cadmium, but one report cited ies A to D respectively, as indicated in Fig. 3, which shows evidence that sewage sludge incinerators cannot easily meet the sampling locations. Similar distances resulted from applistandards of emission for cadmium.12 cation of the SCREEN computer model for atmospheric The present study is related to an investigation of lead and dispersion.18 In practice, the actual sampling sites were located cadmium contamination around one of the oldest sewage as close as possible to these arcs in an attempt to identify the sludge incinerators in the UK.Particular attention is drawn most likely areas of pollution, while allowing for accessibility to the studies on diVerent particle sizes, an aspect largely and the availability of samples. Sites upwind and downwind ignored in earlier studies on municipal waste incinerators, and of the source along the prevailing wind direction were investia factor which may help in the diVerentiation of potential gated for comparison.sources. DiVerences in expressing environmental quality in terms of contaminant loading (as mg m-2) and contaminant Methods level (as mg g-1) were also examined. This distinction between the concepts of level (in mg g-1) and loading (in mg m-2) is Sampling sites were located at 1–4 km around the incinerator.important in this discussion. Such diVerent representations of Descriptions of the 23 sites represented in Fig. 3 are given in data make comparisons diYcult and may lead to diVerent Table 2. conclusions. This problem is best illustrated by an example involving two hypothetical samples.If sample 1 were collected from an area of 1 m2, while sample 2 were collected from 10 m2, the dust loading for both may be 1000 mg m-2 and both levels of lead 1000 mg g-1. However, the loading of lead, for sample 1, is 1000 mg m-2, while that for sample 2 is 100 mg m-2. Depending on which method is used for the presentation of the results, it may be concluded that the quality of dust expressed by the level of lead is the same, but it may be argued that in terms of the quality of the environment, area 2 is better than area 1.This study has explored the potential impact of sludge incineration on the local environment, and addressed the contradictions mentioned above on the potential impact of incineration on cadmium contamination in the local environment.Sampling area and methodology The investigation was carried out in an area centred on the sewage sludge incinerator at Coleshill near Birmingham. The incinerator was commissioned in 1976, is of multiple hearth design, and burns about 14 000 tonnes of sludge a year.11 Heavy contamination of sewage by metals from a significant contribution of industrial flows was one justification for the choice of incinerator.High-pressure water sprays before electrostatic precipitation treat the eZuent gases from the furnace. A summary of the incinerator characteristics is given in Fig. 2 Wind rose for the area under investigation. Table 1.16 170 J. Environ. Monit., 1999, 1, 169–176This method was used for digesting dust samples. The high pressure achieved in sealed vessels undoubtedly accounts for the eVective digestion. The programme used in the microwave oven method brought the samples to 175–180 °C at a peak pressure of around 6 atm for most samples.When HF is used in the digestion procedure, it is essential to remove HF from the residue, otherwise it will etch glassware and electrodes used in diVerential pulse anodic stripping voltammetry (DPASV).A suitable removal procedure involves reaction of HF with boric acid. Metal determination The literature on the use of diVerential pulse anodic stripping voltammetry (DPASV) for the determination of Pb and Cd in dust is limited; the method has been used primarily for the determination of metals in airborne particles and in soil. However, DPASV oVers rapid and simultaneous determination Fig. 3 Sampling locations. of Pb and Cd, as well as Zn and Cu, if desired. A simpler treatment of dust samples and less expensive equipment are further advantages. The optimal conditions for dust analyses Sampling sites were selected as far as possible from roads, are summarised in Table 3. Three standard reference materials with the exception of site 1, which served as a comparison.were used to validate the analytical methods (Table 4), and Dust samples were collected by brushing, using a new brush show that negligible losses occurred during the analyses and, with synthetic bristles for each sample to avoid risk of contami- in particular, that no cadmium was lost during the drying step. nation. Samples were stored in self-sealing plastic bags. Further details of the digestion and analysis procedures have been described elsewhere.20–22 Sample treatment Results and discussion The whole of each site dust was sieved through three diVerent Particle size distribution sized brass sieves.Stones, paper, glass fragments and anything larger than 1 mm were removed. The dusts were separated Surface ground dust is usually not as uniform in size as dust into three sizes: <75 mm, 75–500 mm and 500–1000 mm.The deposited from the atmosphere, and the sizes of particles fall samples were dried in an electric oven at 105 °C until a constant weight was achieved (more than 3 h). Table 3 Typical measuring parameters for Pb and Cd determination by DPASV Microwave oven techniques have been used to digest various kinds of samples for many years,19 and are many times more Hg drop size Medium eYcient than classical heating techniques.The technique used Degassing 5–10 min here involved microwave heating of the sample with acid Deposition potential -0.8 V contained in a closed vessel comprising a body, cap and Deposition time 2 min for 0.1–0.01 ppm pressure release valve.The whole of the vessel was constructed 5 min for 0.01–0.001 ppm 10 min for <0.001 ppm of TeflonA, which is relatively transparent to microwaves. A Delay 10–30 s carousel within the oven holds several sample vessels. Heating Sweep rate 10 mV s-1 causes a build up of pressure within the closed vessel, and this Sweep range -0.8 V to -0.3 V facilitates breakdown of the sample owing to the higher boiling Pulse amplitude 50 mV point of the reagents.Table 2 Sampling site details Site Location Area sampled/m2 1 On a bridge, no vehicular access 1 2 Corrage on side road, no traYc 1 3 Side road by a public house, coarse surface 3 4 On the road between front garden and house 3 5 Rear yard of stable, ground 1 6 Side road, near railway 1 7 Front of house, no parking 1 8 Lake water purification site 1 9 Between power station gate and church 1 10 Power station 400 kV substation 2 11 Farm, no hard surface, so no definable sampling area n/a 12 Side road, on pavement 1 13 Outside ground of hotel reception 1 14 Front grounds of the pricate house 2 15 Outside gate of sludge treatment works 1 16 Footpath 5 17 Rear yard of church 5 18 Residential footpath 1 19 Disused hospital, front yard 0.25 20 School, forecourt 1 21 Car park 1 22 Outside front gate 1 23 Children’s centre, footpath 1 J. Environ.Monit., 1999, 1, 169–176 171Table 4 Recovery tests Certificated value Determined value Recovery (%) Sample code Pb/mg g-1 Cd/mg g-1 Pb/mg g-1 Cd/mg g-1 Pb Cd B1-76 10.87±0.17 470±9 10.74±0.86 440.34±26.90 98.8 93.7 (urban waste incineration ash) N16-48 6.55±0.08 75±7 6.48±1.35 69.61±7.59 98.9 92.8 (urban particulate matter) C83-01 0.079±0.012 2.45±0.3 0.073±0.01 2.25±0.20 92.4 91.8 (river sediment, n=3–6) within a wide range.According to a definition in the UK Clean Air Acts, dust as particulate matter smaller than 76 mm but with a lower limit of 1 mm. In this work, dust was separated into three size ranges, <75 mm, 75–500 mm and 500–1000 mm, in order to determine the metal content in the fine particulate matter which is most likely to escape the gas cleaning plant.This approach may help to diVerentiate metals resulting from incineration and other sources. Dust particles bigger than 1000 mm were discarded as extraneous matter according to normal practice in dust sampling.Such larger particles are regarded as having less relevance to adverse health eVects. The average weight percentage of each size fraction of dust is shown in Table 5. From Table 5, it can be seen that fine dust (<75 mm) constitutes only about 10% of dust by mass. More than 70% of particles fall into the size range of 75–500 mm, while particles in the range 500–1000 mm make up, on average, less than 20% of dust by mass.Since the collection eYciency of any air pollution control device diminishes as the particle size decreases, it can be expected that particulate matter released from the incinerator will be in the smaller size fractions. Dispersion over distance will also tend to separate particles over 30 mm, while particles below 10 mm will tend to behave more like gaseous pollutants.Thus dust fraction will be more readily transported through the atmosphere, but will be diluted during transport and on the ground by dust from other sources. The extent of this will depend on natural and human activity, and local circumstances. Pb and Cd levels in dust The levels of Pb and Cd in diVerent sized dusts were determined and gave the results presented in Figs. 4(a) and 4(b) respect- Fig. 4 (a) Lead levels (mg g-1) in deposited dust. (b) Cadmium levels ively, with summary statistics in Table 6. The results indicate (mg g-1) in deposited dust. Table 5 Dust particle size distribution (%) that Cd levels in fine dust exceed those in coarse dust. Pb Size range levels change more widely as the particle size increases. <75 mm 75–500 mm 500–1000 mm Figs. 5(a) and 5(b) present lead and cadmium levels in fine dust as contours or isopleths with the incinerator location at Median 9.5 73.4 16.2 the centre.While statistically insignificant on the basis of mean Mean 10.9 70.4 18.4 upwind and downwind results, it may be seen that the highest Range 0.37–48.22 40.71–86.14 5.15–47.83 Cd level is in the downwind direction from the incinerator, at Table 6 Lead and cadmium levels (mg g-1) in deposited dust <75 mm 75–500 mm 500–1000 mm Pb Cd Pb Cd Pb Cd Median 230 2.2 96.2 0.86 71.5 0.99 Mean 278 2.6 154 1.0 856 1.3 Range 24.3–565.6 0.46–8.81 10.28–613.5 0.04–3.21 8.4–8340 0.28–6.03 Downwind meana 232.4 2.64 124.4 0.88 734.5 1.32 s=113.5 s=2.13 s=115.6 s=0.76 s=219.0 s=1.45 Upwind mean 346.6 2.52 197.7 1.18 1043 1.25 s=203.7 s=1.39 s=181.7 s=0.97 s=1875 s=1.18 aDenotes site downwind of the incinerator on prevailing wind basis of Fig. 2. 172 J. Environ. Monit., 1999, 1, 169–176site 8, about 2.25–2.5 km distant. This is the region where the although data from the mid-range size indicate the greatest concentration elsewhere (site 19). greatest contribution by airborne dispersion from the incinerator to ground level concentrations was predicted under the Levels of Pb show no obvious relationship to the presence of the incinerator.Areas with the highest levels are in opposite most common stability category in the UK, namely class D. It is noteworthy that the same conclusion would be drawn directions; both upwind and downwind of the incinerator.Of special note is the observation that the highest levels occur in from an analysis of the levels in the largest sized particles, Fig. 5 (a) Lead levels (mg g-1) with the incinerator location at the centre. (b) Cadmium levels (mg g-1) with the incinerator location at the centre. J. Environ. Monit., 1999, 1, 169–176 173Fig. 6 Dust loading (mg m-2) around the incinerator (at centre).coarse dust fractions, suggesting that the incinerator is not the matches the locations for the highest loading of dust. By comparison, the highest lead loading is found at only one of source of the metal in these samples, which were collected at greater distances from the stack. These results suggest that, these locations. The highest Cd levels were found to the northeast of the incinerator in the line of the prevailing wind based on contaminant concentrations, particulate matter released from the stack of the incinerator contributes to direction, as discussed above.However, the site showing the highest Cd loading was located to the southwest of the cadmium contamination of dust on the ground, although the contribution appears to be minimal, with other pollution incinerator, where large amounts of dust are deposited on the ground in the area of a disused hospital.The highest Pb sources predominating. No impact on lead levels is indicated. loading was northwest of the incinerator in a car park and near a motorway (M42) junction, and present in a large Pb and Cd loading in dust as a measure of environmental quality amount of fine deposited dust.While some high concentrations To evaluate the quality of the environment, it is necessary to of Pb were found elsewhere, the Pb loading was low because consider the quantities of both metals and dust. A parallel for the amount of deposited dust was relatively low. The signifi- this is in relation to emissions to atmosphere, for which an cance of these observations is that they demonstrate the care assessment of mass emission may be more meaningful than that is necessary in representing and interpreting data on using concentrations alone.Dust is only one environmental environmental quality. medium in which metals may be found, but in many respects it is unique. It is neither like air, which disperses widely in Comparison with guidelines on pollution space, nor like water in which dispersion within rivers, lakes and seas is possible.Since dust does not disperse uniformly, We have noted previously the lack of nationally agreed reference levels for judging the acceptability of trace metal concen- metals contained within the dust matrix cannot be expected to spread uniformly, even in the absence of a local source of trations in dust.23 Standards on pollution by trace metals in dust do not exist, although in their absence, tentative guidelines pollution.A representation of the dust loading is given in Fig. 6 with the respective metal loading in Figs. 7(a) and 7(b). have been used by organisations such as the former Greater London Council. A guideline concentration for lead was The loading of a metal pollutant is a parameter to describe the quality of the environment concerned with dust spread.It adopted at 500 mg g-1 to indicate the need for further investigation, while a level of 5000 mg g-1 indicated the need for is expressed as: control action. In common with many of the diYculties Loading (mg m-2)=[ level (mg g-1)×weight (g)]/area (m2) associated with dust data, the implications of particle size are not stated.Nevertheless, it will be noticed from Fig. 4(a) that and Table 7 summarises the loading in the area under investigation. While generally in agreement with the picture from the the investigation level is exceeded at seven sites, while the action limit is also exceeded for coarse dust from sites 5 and levels of the metals, loading can suggest diVerent conclusions at certain sites.For example, site 21 appears to have the 15. Other possible criteria for comparison are the guidelines on contaminated land.24 The guidelines give threshold ‘trigger greatest contamination in fine and medium dusts, but not of the largest dusts. concentrations’ from spot samples of air-dried soil as 3 mg kg-1 for Cd and 500 mg kg-1 for Pb in domestic gardens, By comparing the spatial distributions represented as isopleths in Fig. 8, it is evident that the cadmium loading closely while for parks and public open spaces, the limits are 15 and 174 J. Environ. Monit., 1999, 1, 169–176Table 7 Pb and Cd loadings (mg g-2) in deposited dust. Loading (mg m-2)=[ level (mg g-1)×weight (g)]/area (m2) <75 mm 75–500 mm 500–1000 mm Pb Cd Pb Cd Pb Cd Median 539 3.6 2130 16.8 501 6.06 Mean 1645 32.2 3440 62.5 7620 12.95 Range 11.29–16822 0.17–379.2 191.4–10 235 0.31–739.6 33.25–85 530 0.31–123.5 Downwind meana 1940 21.7 2773 29.81 7188 9.74 (s=4447) (s=57.46) (s=3107) (s=47.13) (s=21 920) (s=13.7) Upwind mean 1108 48.46 4004 110.56 7642 13.33 (s=1118) (s=124.3) (s=3702) (s=255.1) (s=17 311) (s=39.68) aDenotes site downwind of the incinerator on prevailing wind basis of Fig. 2. 2000 mg kg-1 respectively. Fine dust is often regarded as of representation of environmental quality than concentration alone. A further proposal for guidelines for both soils and greatest significance as a potential risk to health in view of the dusts starts from the assumption that a single value is inappro- greater likelihood of inhalation or ingestion. On the basis of priate.25 Thus, a guideline deemed acceptable in an industrial the more stringent criteria applied to the finest dust fraction, area would be unacceptable in a school playground.This the lead values fail at the same sites, whereas cadmium levels guideline for a location is derived from a mathematical model fail at one-quarter of the sites sampled, and most severely at using blood lead as the measure of tolerability.Background site 8. Nowhere is the limit for public open spaces breached or baseline blood lead concentrations in the population are for cadmium. It is notable that dust from site 8 exhibits included in the model and, in the absence of such data, this relatively high Cd levels in all particle sizes.In addition, the guideline is not used here. Both the numerical values and the second highest Cd level in the sub-75 mm fraction occurs at maps indicate that, in terms of the levels of trace metals, the site 4, which is similarly located in the direction of the incinerator appears to have little impact on lead levels. prevailing wind. No guidelines are available for loading of the However, the highest cadmium level is located near to the site pollutants, although by combining the level with the amount at which dispersion modelling predicts an impact from small of dust, it may be argued that this oVers a more meaningful particles.In view of the variability in the data, a critical view must always be taken of all measurements on dusts, although the relative values from many samples do allow a broad picture to be drawn.On this basis, from the limited study reported here, it is possible to conclude that the level of contamination does not appear to give cause for concern. Conclusions In this investigation, we have demonstrated further applications of the assessment of environmental quality by analyses of surface dusts. Incineration is recognised as having the potential to cause local contamination, although the literature includes conflicting views of the extent to which this occurs in practice.This study has shown that there is contamination by cadmium near a sewage sludge incinerator. However, on the basis of the limited guidelines available, the environmental impact of the incinerator is relatively small compared with that of other human activities in the area.Special attention has been drawn to the implications of the particle size of the dust in relation to the metal content found, and the manner in which the results are presented. The size fraction analysed has a significant eVect on the conclusions drawn, but guidelines oVer little help in such interpretation.Only by carrying out studies such as this, in which all particle size ranges are considered, can greater confidence be placed in the conclusions on metal content and the likely contamination sources. References 1 Cadmium in the Environmental and its Significance to Man, Pollution Paper No 17, HMSO, London, 1980. 2 The UK Environment, HMSO, London, 1992. 3 A. Malik and N. Crowe, Energy World, 1998, 264, 14. 4 S. L. Law and G. E. Gordon, Environ. Sci. Technol., 1979, 13, 432. 5 A. Wadge and M. Hutton, Sci. Total Environ., 1987, 67, 91. 6 M. Hutton and C. Symon, Sci. Total Environ., 1986, 57, 129. 7 R. R. Greenberg, W. H. Zoller and G. E. Gordon, Environ. Sci. Technol., 1978, 12, 566. 8 M. Hutton, A Wadge and P. J. Milligan, Atmos. Environ., 1988, Fig. 7 (a) Pb loadings (mg m-2) in deposited dust.(b) Cd loadings 22, 411. 9 R. S. Barratt, Sci. Total Environ., 1988, 72, 211. (mg m-2) in deposited dust. J. Environ. Monit., 1999, 1, 169–176 175Fig. 8 (a) Lead loading (mg m-2) around the incinerator (at centre). (b) Cadmium loading (mg m-2) around the incinerator (at centre). 10 H. Vogg, H. Braun, M. Metzer and J. Schneider, Waste Manag. Triangle Park, NC, 1970. 18 Breeze Version of EPA SCREEN Model, Trinity Consultants Inc, Res., 1986, 4, 65. 11 Stewardship, Severn–Trent Environmental Report 1995, Severn– Dallas, Texas. 19 G. M. Kimber and S. Kokot, Trends Anal Chem., 1990, 9(6), 203. Trent plc, Birmingham, 1995. 12 Royal Commission on Environmental Pollution, 17th Report, 20 Y. Feng and R. S. Barratt, Sci. Total Environ., 1994, 143, 157. 21 Y. Feng and R. S. Barratt, Bull. Electrochem., 1993, 9, 589. Incineration of Waste, HMSO, London, May, 1993. 13 P. Lowe, J. Inst. Water Environ. Manag., 1988, 2, 416. 22 Y. Feng and R. S. Barratt, Analyst, 1994, 119, 2805. 23 R. S. Barratt, Int. J. Environ. Anal. Chem., 1990, 40, 77. 14 R. C. Frost, J. Inst.Water Environ. Manag., 1988, 2, 465. 15 C. J. Tennant, Multimedia Levels and Sources of Cadmium in a UK 24 Department of the Environment, Tentative Trigger Concentrations for Selected Inorganic Contaminants, ICRCL 59/83, London, Industrial Conurbation, Research Note 18, JURUE, Aston University, 1982. 1983. 25 B. G. Wixson and B. E. Davies, Environ. Sci. Technol., 1994, 16 Department of the Environment, Report of the Sub-Committee on the Disposal of Sewage Sludge by Incineration, Standing Technical 28, 26A. Committee Report No. 14, DoE, London, 1978. 17 D. B. Turner, Workbook of Atmospheric Dispersion Estimates, Paper 8/08286C Environmental Protection Agency, Publication AP-26, Research 176 J. Environ. Monit., 1999, 1, 169–176

ISSN:0960-7919    

DOI:10.1039/a808286c

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Carbonate induced dissolution of uranium containing precipitates under cement leachate conditions M. Sutton,a P. Warwick,*a A. Halla and C. Jonesb aDepartment of Chemistry, Loughborough University, Leicestershire, UK LE11 3TU bBritish Nuclear Fuels plc, Springfields, Salwick, Preston, Lancashire, UK PR4 0XJ Received 26th November 1998, Accepted 6th January 1999 The eVects of carbonate on uranium (VI) solubility under aerobic and cementitious conditions have been investigated.The information is of relevance to low level nuclear waste disposal. Aqueous NaOH, KOH, Ca(OH)2 and a cement leachate solution were added to uranyl nitrate solution. Afterwards, increasing amounts of ammonium carbonate were added to re-dissolve the precipitates. The precipitates were characterised by means of X-ray powder diVraction (XRPD) measurements and modelling studies. The model calculations were performed using the MINTEQA2 speciation code, with an expanded database incorporating uranium stability constants taken from the HATCHES database.The measured and predicted amounts of CO32- needed to dissolve the precipitates were compared. The knowledge gained from the ‘pure’ systems was used to rationalise the precipitation and re-dissolution behaviour observed in the leachate system.The lack of uranium solubility at low carbonate levels brought into question literature formation constants for UO2(OH)3- and UO2(OH)42-. An approximate log K value of 26.8 for K2U2O7 formation was estimated from the KOH results at pH 12. Generally, uranium solubilities are expected to be insignificant at low level nuclear waste sites because anaerobic conditions should persist.However, this study has demonstrated that solubility in leachate could rise at high pH and high carbonate levels, if aerobic conditions were to develop. Soluble U(VI) species would be formed. The novel part of the study has been to reproduce the eVects and to correlate enhanced solubilities with model predictions.Consequently, the study has re-emphasised the need for appropriate environmental monitoring of such sites. technique and, in the second, the dissolution eVects of carbonate 1 Introduction were compared with predicted eVects. The predictionswere made Conditions such as pH and Eh in low level nuclear waste using the MINTEQA2 speciation model,3 augmented with stabrepositories will evolve.Steel will corrode, organic waste will ility constants taken from the HATCHES4 database. The comdegrade and cementitious materials, if present, will partially plete uranium database used is given in Table 1. dissolve.1 The eVects of such changes on radionuclide solubilit- The final aim of the study was to use the knowledge gained ies in ground and surface waters must be predicted.from the ‘pure’ systems to rationalise and model the dissolution Microbial degradation of organic waste produces CO2 and behaviour observed in the grout leachate system. CH4. However, cementitious materials, if present, will undergo Of course, the hydrolytic behaviour of uranium and its partial dissolution creating alkaline conditions; CO2 will then complexation reactions with carbonate have received a great dissolve.The resulting carbonate/bicarbonate systems will deal of attention over the years. However, investigations have encourage dissolution of actinides. Complex carbonato species generally been confined to low carbonate concentrations, at could form. low CO2 partial pressures (PCO2) and low pH values.For Accordingly, the first aim of this study was to measure the example, Ciavatta et al.14 experimented at pH=2.95–4.88, levels of carbonate needed to re-solubilise uranium(VI) solids, whilst Maya15 operated at pH=4.87–8.41 and a PCO2 value precipitated under conditions relevant to waste disposal in between 10-2 and 10-3.6 atm. Kramer-Schnabel et al.16 cementitious environments.Aerobic studies were undertaken employed pH=3.63–5.71 and a PCO2 range of 10-6–10-11 because such conditions could arguably arise at the outset or atm. Meinrath et al.17 used pH=4–7.5 and PCO2=10-6.5 to later in a repository, after the organic waste has degraded and 10-13. The topic has been reviewed by Grenthe et al.7 aerated water has re-infiltrated the site.2 Under anaerobic Of more direct relevance to this study, the work of conditions, highly insoluble uranium(IV) dioxide would be Brownsword et al.18 may be cited.These workers conducted formed so re-solubilisation would be minimal. a uranium solubility study, using water equilibrated with an Uranium(VI) precipitates were produced in NaOH, KOH, ordinary Portland cement (OPC) and pulverised fly ash (PFA) Ca(OH)2 and cementitious grout leachate solutions, then mixture, at pH=11–12, but they purposely used nitrogen treated with increasing amounts of ammonium carbonate to glove boxes to exclude CO2 to avoid uranium carbonate eVect re-dissolution.The grout leachate was used to approxi- complexation. In the pH range 9–10, the uranium solubility mate real conditions. The cementitious grout is used as a was found to be between ~10-5 and ~10-6M when sodium backfill for low level radioactive waste.The experiments were uranate was the solubility limiting phase, and ~10-6M when carried out at selected pH values in the range 9–12. calcium uranate was the solid phase. Similarly, Baston et al.,19 The second major aim of the study was to identify the who studied uranium solubility over the range pH=4–13 in a precipitates formed in the ‘pure’ NaOH, KOH and Ca(OH)2 cement leachate system, noted uranium solubilities of systems.Two approaches were used. In the first, the precipitates ~8×10-6 M for pH 9 and ~7×10-7M for pH=10–11, but again the carbonate concentration was only 2.2×10-5 M. were investigated using the X-ray powder diVraction (XRPD) J.Environ. Monit., 1999, 1, 177–182 177Table 1 Formation constants for aqueous species and minerals used in MINTEQA2 modelling of uranium solubility and speciation ID number Formula Reactants Formation constant, log Kf Reference Aqueous species 893 UO22+ U4+ +2H2O -4H+ -2e- -9.04 4,5 3301400 HCO3- CO32- +H+ 10.33 4,6 8931402 UO2(CO3)34- UO22+ +3CO32- 21.64 4,5 8933300 UO2OH+ UO22+ +H2O -H+ -5.20 4,7 8930020 UO2(OH)2(aq) UO22+ +2H2O -2H+ -10.30 4,7 8933301 (UO2)2(OH)22+ 2UO22+ +2H2O -2H+ -5.62 4,5 8930022 (UO2)2OH3+ 2UO22+ +H2O -H+ -2.72 4,5 8930023 (UO2)3(OH)42+ 3UO22+ +4H2O -4H+ 11.85 4,5 8931404 (UO2)2CO3(OH)3- 2UO22+ +CO32- +3H2O -3H+ -0.87 4,5 8931403 (UO2)3(CO3)66- 3UO22+ +6CO32- 54.02 4,5 8933302 (UO2)3(OH)5+ 3UO22+ +5H2O -5H+ -15.58 4,5 8930024 (UO2)3(OH)7- 3UO22+ +7H2O -7H+ -31.00 4,7 8930027 UO2(OH)3- UO22+ +3H2O -3H+ -19.20a 4,7 8930028 UO2(OH)42- UO22+ +4H2O -4H+ -33.0a 4,7 8931400 UO2CO3(aq) UO22+ +CO32- 9.67 4,8 8931401 UO2(CO3)22- UO22+ +2CO32- 16.94 4,7 Minerals 9989301 Na2U2O7 2UO22+ +2Na+ +3H2O -6H+ 22.60 4,7 2089302 b-UO2(OH)2 UO22+ +2H2O -2H+ 4.94 4,5 2089303 Schoepite UO22+ +3H2O -2H+ 5.16 4,5 5089300 Rutherfordine UO22+ +CO32- -14.49 4,8 2089301 Gummite UO22+ +H2O -2H+ 10.41 4,5 9989304 Na2UO4 UO22+ +2Na+ +2H2O -4H+ 30.03 7 2089300 UO3 (c) UO22+ +H2O -2H+ 7.70 4,9 9989303 K2UO4 UO22+ +2K+ +2H2O -4H+ 30.46 4,7 9989305 K2U2O7 2UO22+ +2K+ +3H2O -6H+ 26.80b — 9989306 CaU2O7 UO22+ +2Ca2+ +3H2O -6H+ 42.00 4 9989302 CaUO4 UO22+ +Ca2+ +2H2O -4H+ 15.90 4,7 5015001 Calcite Ca2+ +CO32- 8.47 4,10 5015000 Aragonite Ca2+ +CO32- 8.34 4,11 2015000 Lime Ca2+ +2H2O -2H+ 22.81 4,12 2015001 Portlandite Ca2+ +H2O -2H+ 32.63 4,13 aRemoved from model.bEstimated to model KOH pH 12 system. Finally, Heath et al.,20 using an OPC/BFS (blast furnace slag) IR-120 cation exchange resin (BDH/Merck, Lutterworth, Leics., UK) was prepared (length=30 cm, internal diameter= mixture, reported a uranium concentration of ~1×10-6 M at pH=10, but again under negligible PCO2 conditions.Clearly, 2 cm) and washed with 200 cm3 of 5 M hydrochloric acid followed by 1000 cm3 of deionised water. Uranyl nitrate further solubility studies at higher carbonate concentrations were warranted. solution (250 cm3 of a 0.02 M solution) was added and Pa was removed by elution with 100 cm3 of HCl acid (0.5 M).The uranium was then eluted with 100 cm3 of hydrochloric 2 Experimental acid (4 M). The thorium remained on the column. The resulting uranium solution was reduced in volume using a 2.1 Equipment rotary evaporator and allowed to crystallise. The resulting pH values were determined using a ROSS combination elec- crystals were re-dissolved in 4 M nitric acid, and the crystallistrode (Orion Research, Quadrachem, Forest Row, East Sussex, ation was repeated once in 4 M nitric acid and twice in UK) and a digital pH meter (model 720A, Orion Research).deionised water. The purified uranyl nitrate was dissolved in The pH meter was calibrated with commercial buVers at pH deionised water and used as required. values of 4.0, 7.0 and 10.0.The accuracy at high pH was confirmed by measuring the pH of a mixture comprising 6 cm3 of 0.2M NaOH and 25 cm3 of 0.2M KCl known to possess 2.3 Determination of uranium(VI ) using arsenazo-III colorimetric reagent a pH of 12.0.21 X-Ray powder diVraction (XRPD) measurements were The method of uranium determination was based on the performed using a Philips Scientific (Cambridge, UK) X-ray arsenazo-III (AAIII) method described by Savvin.22 Stock generator (Cu Ka,1=1.541 A° , 40 kV, 20 mA).Data were AAIII solution (2.5 mM) was prepared by dissolving the solid collected and interpreted using a Siemens Sietronics (205 mg, Fluka, Gillingham, Dorset, UK) in deionised water DiVractometer Automation SIE122D (supplied by (100 cm3), containing a few drops of 0.2 M nitric acid and Hiltonbrooks X-ray Sales and Services, Grange Holmes 0.5 g sodium acetate at pH 2.5.The stock was stored in amber Chapel, Cheshire, UK). coloured glass bottles. For each determination, the sample Spectrophotometric absorbance measurements were made solution was filtered through 0.2 mm Acrodisc syringe filters using a Philips Scientific model PU8730 spectrophotometer.(Gelman Sciences, Northampton, UK). Then AAIII solution (0.35 cm3) was added to the filtrate before adjusting the 2.2 Preparation of radiochemically purified uranium solutions volume to 10 cm3 using deionised water. After standing for ten minutes, the absorbances of the U–AAIII complexes were Uranium was purified radiochemically by removing thorium and protactinium decay products from uranyl nitrate hexahy- measured at 655 nm.Calibration plots were produced using standard uranium solutions and subjecting them to the same drate using ion exchange. A column packed with Amberlite 178 J. Environ. Monit., 1999, 1, 177–182procedures as the samples. The plots were used to determine 3 Results and discussion the uranium concentrations in the dissolved samples. 3.1 Identification of the precipitates formed in the ‘pure’ NaOH, KOH and Ca(OH)2 systems using X-ray powder 2.4 Preparation of the cementitious grout leachate solution diVraction (XRPD) A cementitious grout, kindly supplied by BNFL plc (Seascale, The XRPD patterns of the precipitates formed at pH values Cumbria, UK), was leached with water. A suitable amount of 9 and 10 in the NaOH system showed broad peaks at 7.4 A° .of grout (25 g) was contacted with deionised water (250 cm3) However, both uranyl hydroxide (b-UO2(OH)2) and schoepite in a sealed glass flask for 4 d until the pH became constant at (UO3.2H2O) give peaks in this region and no distinction 11.8. Then, the resulting suspension was filtered (0.45 mm between the two solid phases was possible.At pH 11 and 12, membrane, Gelman Sciences), and analysed for major cations a peak at ca. 6.0 A° indicated the presence of sodium diuranate and anions. The concentrations of the major cations were (Na2U2O7). However, the possibility of the precipitate being determined by ICP-MS [ VG-Elemental (Winsford, Cheshire, a mixture of UO3.2H2O/b-UO2(OH)2 and Na2U2O7 could UK) PlasmaQuad 2+, 1000 °C] and major anions by ion not be dismissed.All the X-ray diVraction patterns were ‘noisy’ exchange chromatography (Dionex, Sunnyvale, CA, USA). due to the amorphous nature of the precipitates. The results are given in Table 2. The XRPD patterns of the precipitates formed in KOH at pH values of 9 and 10 were identical to those in NaOH but, at higher pH values of 11 and 12, a peak was observed at 2.5 X-Ray powder diVraction (XRPD) measurements 6.6 A° indicating the presence of another species, probably Uranium containing precipitates were prepared by adding either K2UO4 or K2U2O7.NaOH and KOH solutions in turn to aliquots of uranyl nitrate The precipitate formed at pH 9 using Ca(OH)2 showed the solution, at pH values of 9, 10, 11 and 12. After three days usual peak at 7.4 A° but, at pH values of 10–12, the peak aging, the precipitates were filtered oV, using 0.2 mm mem- moved to 7.7 A° indicating CaUO4 or CaU2O7 formation.The branes, washed with deionised water, stored in a desiccator precipitate produced at pH 5.5 gave a similar pattern. for 2 weeks, then powdered and analysed by XRPD.23 However, Linklater et al.24 state that high temperatures are Precipitates were formed in Ca(OH)2 solution at the same pH needed to produce the high crystallinity of calcium uranate values but, for reference purposes, because mixed precipitates and Berner25 states that calcium uranate would not be stable were always formed, a solid was prepared by mixing the uranyl in hyperalkaline cement pore waters.nitrate solution with calcium nitrate solution at pH 5.5.The XRPD patterns of the precipitates formed in the cement leachate system could not be resolved. An aging test was carried out on the precipitate produced 2.6 Dissolution tests at pH 9.0 in the NaOH system. Over 8 weeks, the peaks The initial series of tests was performed in aqueous NaOH. narrowed, but their positions did not alter. The observations The alkali was added to uranyl nitrate solution (5 cm3 aliquots indicated that the precipitate was becoming more crystalline, of 1×10-2M UO22+ ions).Precipitates were produced at pH but not changing chemically. values of 9.0, 10.0, 11.0 and 12.0, in four series of duplicated glass vials. The vials were sealed to prevent ingress of atmos- 3.2 Measurement of the levels of carbonate needed to pheric carbon dioxide and the precipitates were allowed to age re-solubilise uranium(VI ) precipitates for 3 days.Increasing aliquots of ammonium carbonate solution, in air-free deionised water, were subsequently added to The dissolution behaviour of each precipitate, as a function of added CO32- concentration, is presented graphically in each series of vials to give carbonate concentrations ranging from 1×10-4 to 0.1 M.The pH values were maintained by the addition of fresh aqueous NaOH and the final volumes were brought to 10 cm3 by adding deionised, degassed water. Immediately after treatment, each vial was resealed and the contents left for a further 24 h. The resulting mixtures were filtered using 0.2 mm Acrodisc syringe filters and the filtrates were analysed for uranium using the AAIII method described earlier.Subsequently, the same tests were performed using aqueous KOH, Ca(OH)2 and the cement leachate solution. The pH adjustments that were needed, following the addition of carbonate, were made using the appropriate alkali for each ‘pure’ system and the leachate solution for the cement system. Table 2 Analytical data obtained for the cementitious grout leachate solution Component Concentration/mM Na+ 41.13 K+ 91.28 Ca2+ 19.25 Cl- 0.01 Fig. 1 The eVect of added carbonate on the dissolution of uranium NO3- 0.00 precipitates formed at pH values of (a) 9, (b) 10, (c) 11 and (d) 12 in SO42- 0.31 NaOH solution. Solid diamonds represent experimental results. The CO32- 0.13 curves are MINTEQA2 predictions in which model b-UO2(OH)2, UO3.2H2O, Na2UO4 and Na2U2O7 were simultaneously considered pH 11.77 as possible solid phases.J. Environ. Monit., 1999, 1, 177–182 179Fig. 4 The eVect of added carbonate on the dissolution of uranium Fig. 2 The eVect of added carbonate on the dissolution of uranium containing precipitates formed at pH values of (a) 9, (b) 10, (c) 11 precipitates formed at pH values of (a) 9, (b) 10, (c) 11 and (d) 12 in and (d) 11.8 in cement leachate solution.Solid diamonds represent KOH solution. Solid diamonds represent experimental results. The experimental results. The curves are fitted. Important solid phases curves at pH 9 and 10 are composite predictions; the curves at pH 11 were UO3.2H2O and CaUO4 at pH values of 9, 10 and 11, and and 12 are fitted. Important solid phases within the MINTEQA2 UO3.2H2O, Na2U2O7, K2U2O7 and CaUO4 at pH 11.8.model were b-UO2(OH)2, UO3.2H2O, K2UO4 and K2U2O7. In the NaOH system, the amount of added CO32- needed to eVect complete dissolution increased significantly at pH 11, suggesting a change in the solid phase. In the KOH system, no significant change was noted up to and including pH 11.In the Ca(OH)2 system, steps were observed in the dissolution profiles (Fig. 3), which clearly indicated that the precipitates were mixtures of two components with considerably diVerent solubilities. The amount of CO32- required for complete dissolution at pH 10 exceeded that required at pH 9. The grout system showed stepped dissolution profiles, similar to the Ca(OH)2 system, but the steps were not so well defined. 3.3 Identification of the precipitates formed in the ‘pure’ NaOH, KOH and Ca(OH)2 systems from the MINTEQA2 model predictions Speciation models assume the attainment of equilibrium, whereas rapid precipitation reactions often give amorphous precipitates. Also kinetics may influence solid phase composition with eVects which may not be nullified even by aging.Fig. 3 The eVect of added carbonate on the dissolution of uranium However, following a choice regarding the important aqueous containing precipitates formed at pH values of (a) 9, (b) 10, (c) 11 and (d) 12 in Ca(OH)2 solution. Solid diamonds represent experimen- species, only one discrepancy between the initially predicted tal results. The curves are MINTEQA2 predictions in which model and observed precipitation/re-dissolution patterns was noted b-UO2(OH)2, UO3.2H2O and CaUO4 were simultaneously considered (see below).as possible solid phases. The correlation between predictions in the NaOH system and experimental observations can be seen in Fig. 1. All relevant solid phases were included as ‘possible’ solids, but Figs. 1–4. From the plots, the minimum amounts of added CO32- needed to dissolve the precipitates completely were only UO3.2H2O and Na2U2O7 were found to be important. At pH values of 9.0 and 10, the solid modelled as 100% estimated. These ‘experimental’ values are presented alongside the predicted values (see below) in Table 3. UO3.2H2O but, at pH 12, as 100% Na2U2O7. At pH 11, the proportions were 53% UO3.2H2O and 47% Na2U2O7.It may It may be noted that complete dissolution was not achieved in any system at pH 12 nor in the Ca(OH)2 system at pH 11. be noted that Na2UO4 modelled as undersaturated even in the absence of carbonate. The predicted changes reflected the In these cases, the MINTEQA2 predicted values are presented alone. The higher pH values could not be maintained with XRPD evidence.The solid phase composition is summarised in Table 4. increasing amounts of added ammonium carbonate. The weakly basic NH4+ ions aVected the hydroxide concentration. The KOH system (Fig. 2), at pH values of 9 and 10, also provided experimental results which correlated with predic- The higher pH values could have been reached using NaOH or KOH, but common ion eVects would have been introduced, tions.The solid phase was UO3.2H2O. However, at pH values of 11 and 12, the XRPD data suggested an additional solid aVecting the speciation. 180 J. Environ. Monit., 1999, 1, 177–182Table 3 Experimental and modelled concentration of added carbonate required to re-dissolve a 5 mM uranium precipitate at pH 9, 10, 11 and 12 in NaOH, KOH, Ca(OH)2 and grout leachate (pH 11.8) Carbonate concentration (mM) required for 100% re-dissolution pH 9.0 pH 10.0 pH 11.0 pH 12.0 Expt Model Expt Model Expt Model Expt Model NaOH 10 14 15 14 25 30 n/a 110 KOH 15 14 15 14 15 20 n/a 95 Ca(OH)2 54 40 89 90 n/a 302 n/a 1900 Grout leachate 48 45 66 60 n/a 210 n/a 1120 Table 4 Percentage modelled composition of uranium precipitates at carbonate concentrations of 1.4×10-3 M, 1.2×10-3M and pH 9, 10, 11 and 12 in NaOH, KOH, Ca(OH)2 and grout leachate 2.2×10-3 M, respectively.It should be emphasised that the UO2(OH)3- and pH 9 pH 10 pH 11 pH 12a UO2(OH)42- species were not included in the quoted MINTEQA2 results. Their inclusion destroyed all correlation NaOH Schoepite 10 100 53 0 between experimental observations and model predictions. Na2U2O7 0 0 47 100 Significant uranium dissolution was predicted in all systems if these species were included in the modelling, even in the KOH Schoepite 100 100 22 2 absence of CO32-, thus contradicting the observations.It was K2U2O7 0 0 78 98 concluded that either the literature formation constants for these species were too large or kinetic eVects were hindering Ca(OH)2 Schoepite 38 34 30 0 their formation.Certainly Grenthe7 states that, at high uran- CaUO4 62 66 70 100 ium concentrations, polymeric species such as (UO2)3(OH)7- are more likely to form than monomeric species such as Grout leachate Schoepite 30 37.5 0 0 UO2(OH)3-. K2U2O7 0 0 38 56 Na2U2O7 0 0 12 14 3.4 Rationalising the dissolution behaviour of the precipitates CaUO4 70 62.5 50 30 formed in the grout leachate system apH=11.8 for grout leachate.The dissolution of uranium containing precipitates in the cement leachate system at pH values of 9, 10, 11 and 11.8 is shown graphically in Fig. 4. b-UO2(OH)2, UO3 .2H2O, phase not predicted by the initial model calculations. Also the UO2CO3, NaUO4, Na2U2O7, K2U2O7, CaU2O7, CaUO4 and pH 12 results did not correspond to K2UO4 dissolution. Since CaCO3 were all included in the model calculations as possible the XRPD evidence had suggested K2UO4 or K2U2O7, the solids (see Table 1).As can be seen, the pH 9, 10 and 11 pH 12 data were fitted and a log K value of 26.8 was derived results with Ca(OH)2 showed similarities to the leachate for K2U2O7 formation. No previous estimate of this constant results.The two steps, characteristic of UO3.2H2O and could be found in the literature. Subsequent modelling at CaUO4, are present. However, the first step is less well defined pH 11 indicated that mixed solid phases containing up to 78% in the leachate system than in the pure system. Furthermore, K2U2O7 gave virtually the same dissolution profiles as pure the second step at each pH indicates that only a portion of UO3.2H2O.Consequently, this solid phase composition was the Ca in the leachate has reacted. In the Ca(OH)2 system, used to provide the modelled curve shown in Fig. 2, at pH 11. all the Ca present appeared in the precipitates. At pH 11, the The compositions of the precipitates in the KOH system are step in the modelling curve is an arbitrary choice; it represents included in Table 4. a level of CaUO4 intermediate between the pH 10 and 11.8 In the Ca(OH)2 system, correlation between experimental values.The amount of CaUO4 in the precipitates could not and predicted results was again observed. At each pH, be predicted so the MINTEQA2 model was not used in UO3.2H2O and CaUO4 mixtures were formed (see Table 4).predictive mode. The assumed total amounts of Ca2+ present The dissolution patterns (Fig. 3) provided two steps. The first were adjusted to reflect the heights of the second steps. step corresponded to the dissolution of UO3.2H2O and the To fit the pH 11.8 data, a mixed precipitate containing second step to CaUO4 dissolution. The concentration of Ca UO3.2H2O, Na2U2O7, K2U2O7 and CaUO4 was imposed on involved in the second step corresponded to the amount of the model by adjusting the total Na+ and K+ concentrations Ca(OH)2 originally present in solution.At pH 12, in addition to the Ca2+ concentration. re-dissolution was minimal, indicating that the solid phase was composed entirely of CaUO4. The model calculations showed that the dominant aqueous 4 Conclusions species were similar in each system.In the absence of carbonate, the major dissolved species was (UO2)3(OH)7-. At low This study has contributed to the knowledge base needed for nuclear waste risk assessment. The processes involved in the carbonate concentrations, the majority of the dissolved uranium was present as the mixed hydroxycarbonate species, aerobic dissolution of uranium(VI) have been highlighted.With the exception of the KOH system at pH 11, the precipi- (UO2)2CO3(OH)3-. However, the tricarbonato ion, UO2(CO3)34-, dominated at higher concentrations. For tates in the ‘pure’ systems and their dissolution patterns were predicted using solubility product principles alone. In the example, in the NaOH system at pH=9.0, the major aqueous species was the mixed hydroxycarbonate up to an added cementitious grout leachate system, kinetics appeared to influence the results.CaUO4 formation was not quantitative. CO32- concentration of 3.8×10-3 M. The tricarbonato ion then became dominant. At pH values of 10, 11 and 12, the Problems associated with CaUO4 formation cited earlier may have been involved in the leachate system.24,25 Of course, in tricarbonato ion was the only significant species above added J.Environ. Monit., 1999, 1, 177–182 18111 L. N. Plummer and E. Busenberg, Geochim. Cosmochim. Acta, waste repositories fully equilibrated outcomes are likely since 1982, 46, 1011. the changes will be slow. 12 R. M. Smith and A. E. Martell, Critical Stability Constants, Volume 4: Inorganic Complexes, Plenum Press, New York, 1976.The authors would like to thank BNFL plc for financial 13 B. W. Goodwin and M. Munday, A Reference Guide to SOLMNQ—An Interactive Solution—Mineral Equilibrium support. Program, AECL-7800, Atomic Energy of Canada Ltd., Mississauga, Ontario, Canada, 1983. 14 L. Ciavatta, D. Ferri, M. Grimaldi, R. Palombari and References F. Salvatore, J.Inorg. Nucl. Chem., 1979, 41, 1175. 1 P. N. Humphreys, R. McGarry, S. M. A. HoVmann and P. Binks, 15 L. Maya, Inorg. Chem., 1982, 21, 2895. Microbiol. Rev., 1997, 20, 557. 16 U. Kramer-Schnabel, H. BischoV, R. H. Xi and G. Marx, 2 T. Johnstone, P. N. Humphreys, D. Trivedi and A. HoVmann, Radiochim. Acta, 1992, 56, 183. ASME, 1995, 2, 1521. 17 G. Meinrath, Y. Kato, T. Kimura and Z.Yoshida, Radiochim. 3 J. D. Allison, K. J. Novo-Gradac and D. S. Brown, MINTEQA2 Acta, 1996, 75, 159. v3, Environmental Research Laboratory, OYce of Research & 18 M. Brownsword, A. B. Buchan, F. T. Ewart, R. McCrohon, Development, United States Environmental Protection Agency, G. J. Ormerod, J. L. Smith-Briggs and H. P. Thomason, in Athens, Georgia, 1991. Scientific Basis for Nuclear Waste Management, XIII International Symposium, ed.V. M. Oversby and P. W. Brown, Materials 4 J. E. Cross and F. T. Ewart, HATCHES—A Thermodynamic Research Society, Virginia, USA, 1990, vol. 176, p. 557. Database and Management System, Nirex Report NSS/R212, 19 G. M. N. Baston, M. Brownsword, J. E. Cross, J. Hobley, A. D. Nirex, Didcot, Oxfordshire, UK, 1990. Moreton, J.L. Smith-Briggs and H. P. Thomason, The Solubility 5 I. Grenthe, J. Fuger, R. J. Lemire, A. B. Muller, C. Nyugen-Trung of Uranium in Cementitious Near-Field Conditions, Nirex Report and H. Wanner, Chemical Thermodynamics of Uranium, Final NSS/R222, Nirex, Didcot, Oxfordshire, UK, 1993. Draft for Peer Review, OECD NEA, Paris, 1990. 20 B. F. Greenfield, D. J. Ilett, M. Ito, R. McCrohon, T. G. Heath, 6 R. M. Smith and A. E. Martell, Critical Stability Constants. First C. J. Tweed, S. J. Williams and M. Yui, Radiochim. Acta, 1998, Supplement, Plenum Press, New York, 1982, p. 5. 82, 27. 7 I. Grenthe, J. Fuger, R. J. M. Konings, R. J. Lemire, A. B. Muller, 21 Handbook of Chemistry and Physics, ed. R. C. Weast, CRC, Boca C. Nyugen-Trung and H.Wanner, The Chemical Thermodynamics Raton, FL, 1969, vol. 49, p. D79. of Uranium, Elsevier, Amsterdam, 1992, vol. 1. 22 S. B. Savvin, Talanta, 1961, 8, 673. 8 H. Wanner and I. Forest, Chemical Thermodynamics of 23 JCPDS, Joint Committee for Powder DiVraction Standards, Americium, OECD NEA, Amsterdam, 1995, p. 2. Hanwalt Search Encyclopaedia, ed. W. F. McClune, International 9 R. J. Lemire and P. R. Tremaine, J. Chem. Eng. Data, 1980, Centre for DiVraction Data, Swarthmore, PA, USA, 1978. 25, 361. 24 C. M. Linklater, Y. Albisson, W. R. Alexander, I. Casas, I. G. 10 D. L. Parkhurst, D. C. Thorstenson and N. Plummer, McKinley and P. Sellin, J. Contam. Hydrol., 1996, 21, 59. PHREEQE—A Computer Program for Geochemical Calculations, 25 H. R. Berner, Cement and Concrete Res., 1992, 22, 465. Report USGS/WRI-80-96, NTIS Tech. Rep. PB81-167801, United States Geological Survey, Reston, VA, USA, 1980, revised 1985. Paper 8/09262A 182 J. Environ. Monit., 1999, 1, 177–182

ISSN:0960-7919    

DOI:10.1039/a809262a

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Optimizing the removal of carbon phases in soils and sediments for sequential chemical extractions by coulometry† Michael K. Schultz,*a Steven R. Biegalski,b Kenneth G. W. Inna, Lee Yu,b William C. Burnett,c Joylene L. W. Thomasa and Gregory E. Smithc aNational Institute of Standards and Technology, Ionizing Radiation Division, Mail Stop 8462, 100 Bureau Drive, Gaithersburg, MD 20899-8462, USA bNational Institute of Standards and Technology, Analytical Chemistry Division, Building 222/Room A125, Gaithersburg, MD 20899, USA cDepartment of Oceanography, Florida State University, Tallahassee, FL 32306-3048, USA.E-mail: burnett@ocean.fsu.edu Received 19th January 1999, Accepted 3rd March 1999 We have developed a coulometric technique to optimize the removal of the carbonate and organic fractions for sequential chemical extractions of soils and sediments. The coulometric system facilitates optimizing these two fractions by direct real-time measurement of carbon dioxide (CO2) evolved during the removal of these two fractions.Further analyses by ICP-MS and alpha-spectrometry aided in interpreting the results of coulometry experiments. The eVects of time, temperature, ionic strength and pH were investigated.The sensitivity of the coulometric reaction vessel/detection system was suYcient even at very low total carbon content (<0.1 mol kg-1). The eYciency of the system is estimated to be 96% with a standard deviation of 8%. Experiments were carried out using NIST Standard Reference Materials 4357 Ocean Sediment (OS), 2704 BuValo River Sediment (BRS), and pure calcium carbonate.Carbonate minerals were dissolved selectively using an ammonium acetate–acetic acid buVer. Organic matter was then oxidized to CO2 using hydrogen peroxide (H2O2) in nitric acid. The carbonate fraction was completely dissolved within 120 min under all conditions examined ( literature suggests up to 8 h). For the OS standard, the oxidation of organic matter self-perpetuates between 45 and 50 °C, a factor of two less than commonly suggested, while organic carbon in the BRS standard required 80 °C for the reaction to proceed to completion.For complete oxidation of organic matter, we find that at least three additions of H2O2 are required (popular methods suggest one or two). Perhaps the most confounding challenge to developing Introduction reliable sequential extraction methods is optimizing the selec- Sequential chemical extractions are used often to partition soil tivity of the extractions. The ideal sequential extraction protoand sediment samples into operationally defined fractions.The col maximizes the selective destruction of each target phase in techniques are designed to obtain indirect evidence of the primary geochemical host phases of metals, radionuclides, and other parameters. The sequential extraction approach is applied not only to study stable and radioactive-metal contaminants in the environment,1–5 but also to investigate natural cycling of metals6–9 and the geochemical partitioning of phosphate. 10 Variations in the experimental conditions for sequential extraction techniques are numerous: choice of reagents, reagent concentrations, reaction temperatures and reaction times vary widely.However, certain fundamental procedures are employed consistently to apply such methods. In general, a soil or sediment is subjected to a series of chemical treatments, each designed to attach a unique geochemical phase of the sample.In each step, the sample and reagent are shaken or agitated in some way (at a specified temperature) for some period of time. Following this reaction period, the solid and aqueous phases are separated by centrifugation and/or filtration. The residual solid material is reserved for the next reaction step in the sequence and the fluid phase is analyzed for the analyte(s) of interest (Fig. 1). †Present address: General Engineering Laboratories, Radiochemistry Division, 2040 Savage Road, Charleston, SC, USA. Fig. 1 Illustration of a single sequential extraction step. E-mail: mks@mail.gel.com. J. Environ. Monit., 1999, 1, 183–190 183the sequence and minimizes the attack on remaining soil or Carbon fractions sediment components; the selectivity of the reaction conditions Carbonate fraction is critical.We make a critical distinction here between the terms ‘fractionation’ and ‘speciation’. Speciation refers to spec- ‘Carbonate’ phases represent an important sink for radioific physico-chemical forms. For example, one could refer nuclides and trace metals in the environment. Trace and to a polymeric aqueous Pu oxyhydroxyl complex radioactive metals may absorb and/or co-precipitate with (PuO2)2(OH)22+ or a crystalline Am(OH)3 solid.Frac- carbonates inorganically and biogenically.7 For example, U is tionation in sequential extractions, on the other hand, refers known to coprecipitate biogeochemically (with calcium Ca) to the process of operationally defined selective dissolution of from sea-water in the formation of calcium carbonate shell ‘macro-scale’ geochemical components of solid-phase natural- material.14 Similarly, Am adsorbs strongly to the surface of matrix materials, e.g., carbonate minerals or oxides of Fe and calcite.15 Carbonates may be present in soils and sediments in Mn, combined with radiometric measurements of radioactive variable chemical composition, degree of crystallinity and analyte nuclides released during the dissolution reaction.particle size. The forms commonly found in soils and sediments Although complete phase-specificity of the reaction steps is include aragonite, calcite, dolomite, magnesite, and siderite. unlikely, the results of these experiments represent indirect A number of similar methods are recommended for the evidence of possible and/or probable geochemical associations selective dissolution of carbonate minerals in soils and sediof the radioactive element in question with these macro-scale ments.1–10,16 Most recently, many of these approaches are soil or sediment components and thus provide valuable infor- based on a protocol presented by Tessier et al.,6 who used a mation concerning the conditions under which the element 1 mol L-1 sodium acetate CH3COONa (NaAc) extraction of may be released to the environment.carbonates for 5 h, adjusted to pH 5 with acetic acid We are developing a standard sequential extraction protocol CH3COOH (HAc). Ideally, the acetate buVer reacts with solid for determining the fractionation of radionuclides in soils and calcite (and other carbonate forms) in the sample to produce sediments.The method is being developed using NIST free-aqueous Ca2+, gaseous CO2, and liquid water H2O by Standard Reference Materials SRMs. The proposed protocol the reaction: is to consist of six operationally defined fractions (Table 1). As part of the method development, we are optimizing the CaCO3(s)+2H+(aq)�Ca2+(aq)+CO2(g)+H2O(l ) (1) extraction of U and Pu in a marine sediment standard (NIST In the Tessier et al.study,6 the authors assessed the complete- Standard Reference Material 4357 Ocean Sediment—OS). In ness of the reaction by monitoring the dissolution of stable this context, optimum conditions are defined as those which Ca. Although the reaction is designed to selectively dissolve allow for maximum extraction of the intended geochemical carbonates, the dissolution of amorphous and easily dissolved phase with minimum attack on non-targeted fractions.The (poorly crystalline) metal oxides/oxyhydroxides may also occur phase specificity of the extractions is monitored generally by during this reaction (specifically adsorbed metals may also be measuring the extraction of stable metals associated with the extracted during this reaction step).For example, Miller et al.16 ‘macro-scale’ fraction in question. For example, the dissolution suggested a 0.44 mol L-1 HAc (calculated pH 2.5) extraction of reducible Fe and Mn oxides can be monitored by extraction for 8 h and refined their interpretation of the target ‘phase’ to of Fe and Mn into the fluid phase. Elements such as Al, Ti, &lsq;some poorly crystalline hydroxy- and carbonate-metal phases’.and Si, on the other hand, would indicate the dissolution of Salbu et al.4 modified the Tessier procedure for selective more refractory phases. The experimental variables being dissolution of carbonates by reducing the time of the reaction tested are time, temperature and reagent concentration. The to 2 h.Our approach was to monitor the dissolution reaction, choice of reagents, reaction temperatures, and reagent concennot only indirectly (by measuring stable metals in the extract- tration ranges, as well as the development of our experimental ant solutions), but also directly via evolved CO2. design, are described elsewhere.11–13 In this paper, we present a novel coulometric approach to optimizing the dissolution of carbonates and the oxidation of organic matter (of soils and Organic matter fraction sediments) for sequential extractions by using real-time measurements of evolved carbon dioxide (CO2).In addition Organic matter is also recognized as an eYcient sink for radionuclides and metals in the soils and sediments.17,18 (for the carbonate fraction), we provide stable-element data (by ICP-MS) and alpha-spectrometry results to assist in Examples of organic compounds found in the environment include humic and fulvic acids.Organic-metal binding is often understanding the coulometry experiments. Our results provide valuable information for optimizing these two important frac- described by specific functional group substructures in humic and fulvic substances (such as citrates, carboxylates, tions of typical sequential extraction protocols.Table 1 Test fractions for developing the NIST standard sequential extraction protocol. Further details concerning the development of this standard protocol may be found in Schultz et al.11,12 Test settings Reagent Target phase Temperature/°C Time/h Concentration/M MgCl2 Exchangeable ions 25/50/90 1/2/4 0.1/0.4/1.0 NH4Ac–HAc Carbonates 25/50/90 1/4/16 0.5/1/2 (pH 5) NH2OH·HCl Reducible oxides 25/50/90 1/4/16 0.01/0.04/0.1 (pH 2) H2O2–HNO3 Organic matter 25/50/90 1/4/16 30% H2O2 a (pH 2) HNO3 Resistant oxides and sulfides 25/50/90 1/4/16 4/8/16 Fusionb Residual Total dissolution aParameter tested was the number of additions of 30% H2O2 needed to oxidize all organic matter.bResidual fraction is total dissolution of most refractory fraction of material by fusion. 184 J. Environ. Monit., 1999, 1, 183–190phthalates, and phenols) that form moderately to highly stable Experimental metal complexes.19 Reagents and dilutions Three common methods have been suggested for the oxidation or extraction of organic matter in soils and sediments: All reagents used for these experiments were ACS Reagent (1) oxidation by sodium hypochlorite NaOCl; (2) extraction Grade.Extractant solutions were prepared by volumetric by alkali [sodium (Na) or potassium (K) pyrophosphate dilutions (uncertainty of ±4%, 95% confidence level ). Mass (Na4P2O7 or K4P2O7)]; and (3) oxidation by hydrogen per- measurements of sediment samples were made to 10 mg. oxide H2O2.Dilutions for stable element analyses (where necessary) were prepared either by volumetric dilution using 100 mL or 50 mL volumetric flasks with a stated measurement uncertainty of Sodium hypochlorite. NaOCl was first used by Anderson20 ±2% (95% confidence level ) or gravimetrically using a Mettler to oxidize organic matter in order to pre-treat soil for mineral- PE 360 digital balance to 1 mg.We estimate the uncertainty ogical characterization. The reaction, carried out at pH 9.5, for mass measurements to be ±0.2% (mechanical ) and ±1% destroys soil organic matter with little non-targeted dissolution (digital ) (95% confidence level ). of oxides/oxyhydroxides of Mn and Fe.21 However, the tech- Extractions nique is designed for extraction of soils of negligible carbonate content.22 In addition, the high pH of this reaction may cause Sediment standards used for this study were oven-dried at analyte–metal hydrolysis and readsorption to remaining solid- 50 °C (for at least 12 h) and stored in a desiccator until use.phase surfaces prior to separation of solid and aqueous All carbonate extractions (unless otherwise stated) used a 1551 phases.11 reagent (mL) to sample (g) ratio (150 mL reagent: 10 g sediment).For the stable-element analysis experiments, NH4Ac solutions were adjusted to pH 5 by dropwise addition of 25% Alkali pyrophosphates. Organic matter in soils and sediments acetic acid. For the coulometry experiments, the pH of the is charge stabilized by calcium, iron, aluminium and other solutions was varied by adjusting the concentration of the metal cations.Solutions containing anions that can remove NH4Ac in a 25% HAc solution until the desired pH was these stabilizing metals, by precipitation, the formation of achieved. For all carbonate experiments, sediments were prechelates or coordination complexes, are very eVective in the extracted with 150 mL 0.5 mol L-1 magnesium chloride extraction of humic materials.Extraction using alkali pyro- (MgCl2) (15 mL reagent: 1 g sample, 1 h, 25 °C). For the phosphates at pH 10 has been used in a number of studies to organic matter coulometry experiments, 10 g samples were identify organically bound metals in soils and sediments.5,16,23 pre-extracted with 150 mL 0.1 mol L-1 NH4Ac in 25% HAc Unfortunately, alkali pyrophosphates have been shown to for 120 min.All pre-extractions were followed by two rinses dissolve oxides of Fe and Mn22 and the high pH leads to the with 50 mL deionized distilled water (DDW). The sediment same problems as mentioned for the NaOCl extractions. aliquots were separated from the solution phase by centrifugation (2500 rpm for 30 min) and the supernatant solution was either discarded or reserved for stable element analysis.For the organic fraction, the residues from these pre- Hydrogen peroxide. An alternative to the high pH NaOCl extractions were then transferred to the reaction vessel using and pyrophosphate methods was advanced by Tessier et al.6 0.1–0.001 mol L-1 HNO3. Organic matter was oxidized by The strategy introduced by these authors was to oxidize soil the addition of 30% hydrogen peroxide (H2O2), in 20 mL or sediment organic matter following the dissolution of carbonaliquots (2 mL 30% H2O2: 1 g sample), using a graduated ates and the reductive dissolution of the oxide phase.This glass syringe. At least three additions of H2O2 were required strategy is advantageous (over the hypohalous reagents and for complete oxidation of organic matter.No eVect on evolved alkali pyrophosphates) for determining organically bound CO2 of solution pH (from pH 1 to pH 3) was observed for metals and radionuclides. Most importantly, a lower pH (2) these experiments. In separate experiments, the evolution of reduces the hydrolysis and readsorption of metallic elements CO2 was monitored for the ‘exchangeable’ MgCl2 extraction to remaining solid surfaces. This point is critical for the and the ‘reducible’ NH2OH·HCl fractions: no evolution of optimization of our sequential extraction protocol; for CO2 was observed for either of these reaction steps.example, Pu4+ hydrolysis and adsorption to solid surfaces begins at just above pH 2.24 In addition, the specificity of this Carbon measurements by coulometry approach appears to be superior to NaOCl and pyrophosphate techniques.First, incorrect identification of inorganically A variety of thermal and wet-chemical procedures has been sorbed analytes is minimized by a change in extraction order: developed for the measurement of total carbon (TC), organic the ‘carbonate’ and ‘reducible oxide’ fractions are extracted carbon (OC) and inorganic carbon (IC).Total carbon determiprior to the oxidation of organic material. Second, the non- nations are commonly made via coulometry, manometry, targeted dissolution of carbonates by NaOCl is eliminated. infrared gas analysis, and gas chromatography. For this work, Third, our coulometry experiments indicate that dissolution a coulometer was chosen to make CO2 measurements.25 of reducible oxides by NH2OH·HCl (pH 2, HNO3) proceeds Coulometric techniques have been used in a number of studies with no apparent oxidation of organic matter.concerning both the TC content and the partitioning of IC The approach to optimizing the selectivity of the organic and OC in sediments and sea-water.26–28 For our purposes, matter fraction (for sequential extractions) has been, in general, the method provided the necessary sensitivity, the ability for to monitor the dissolution of non-targeted phases (i.e., stable real-time CO2 measurements, and the flexibility to be incorporelement analyses of extracts).However, no stable metal exists ated in-line with a reaction vessel. Reactions were carried out that can be used to indicate unambiguously the oxidation of in a 250 mL glass reaction flask, equipped with a temperature organic matter for this application.In the present study, we monitor/control unit (Fig. 2). A Teflon-coated thermometer oVer a novel approach to optimizing the carbonate and organic was inserted into port one and sealed with a Teflon stopper.matter fractions by monitoring evolved CO2 produced by these To begin an analysis, samples were transferred to the reaction reactions. This approach provides a clear picture of the rates vessel via port 3 with a minimum amount of distilled deionized and completeness of the reactions for these two important water. The port was then sealed and a high-purity gaseous oxygen (O2) carrier stream was introduced.Airtight seals were fractions in a sequential extraction sequence. J. Environ. Monit., 1999, 1, 183–190 185results of these experiments describe unambiguously the dissolution of carbonates and the oxidation of organic matter for optimizing the conditions for the sequential extraction of these two fractions. Stable metal analyses by ICP-MS In addition to CO2 measurements, stable element analyses by ICP-MS were conducted for a separate set of carbonate extractions in this study.The intention of these experiments was to use Ca dissolution (as well as stable Al, Fe, K, Mn, Sr, and Ti) to assess the selectivity of the carbonate reaction with changes in the reaction conditions. The reaction variables tested were: (1) time of extraction; (2) temperature of extraction; and (3) reagent concentration (ionic strength).These Fig. 2 Experimental setup for coulometry experiments: (a) temperature experiments were conducted according to a full-factorial exper- controller/monitor; (b) magnetic stirring plate, with heating mantle; imental design, based upon the principles presented in Box (c) reaction vessel with three ports and magnetic stirbar, Teflon coated et al.29 The full-factorial experimental design assesses the main thermometer inserted through a Teflon stopper in port 1, samples and reagents introduced through port 3; (d) water cooled condenser; (e) eVects of each of these three variables (and interactions Drierite water vapor scrubber; (f ) in-line furnace; (g) magnesium between variables) in a minimum number of experimental runs perchlorate water vapor scrubber; (h) acid dichromate NOx scrubber; (at predetermined variable settings).We illustrate the technique (i) MnO2 NOx scrubber; ( j) coulometry cell; (k) CO2 inlet port; ( l ) using a three-dimensional figure (Fig. 3), with the axes rep- electrode; (m) silver electrode; (n) salt bridge; (o) light source; (p) resenting independent variables time (xtm), temperature (xtp), photo-detector.and concentration (xc). The origin represents experiments conducted at the ‘low’ setting (coded ‘-’) for each variable maintained by the use of Teflon sleeves at each port/fitting (1 h, 25 °C, 0.1 M NH4Ac). The opposite end of each axis interface and spring-held glass flanges at each portal. The O2 thus represents the high setting (coded ‘+’) of each variable flow rate to the coulometer was maintained at a constant (4 h, 90 °C, and 1 M NH4Ac, Fig. 3). A midpoint experiment 100 cm3 min-1. The system was allowed to purge until a was included to account for curvature in the relationship constant minimum background level was achieved (1 mg between response y (% metal extracted) and changes in xi. C min-1 to 5 mg Cmin-1).Background minima were reached The experimental uncertainty can be estimated by conducting within about 15 min. Reagents were added through a septum duplicate extractions at tetrahedral positions on the cube. By mounted at the top of port 3 using a 20 mL glass syringe. conducting experiments at each of the indicated points on the Once the reaction began, evolved CO2 was carried through a cube, a mathematical relationship is established which series of purification scrubbers prior to entering the coulodescribes a possible model for the response y with changes in meter.The gas stream passed first through a water-cooled xi. If all variables and interactions are important, the equation condenser followed by a Drierite tower to remove water and that describes this model is acid vapor.This was followed by thermal treatment of the gas stream in an in-line combustion furnace at 950 °C to assure y= 1 2 Cm+btmxtm+btpxtp+bcxc+btm·tpxtmxtp+btm·cxtmxc +btp·cxtpxc+btm·tp·cxtmxtpxc D complete oxidation of C to CO2 [possible trace quantities of carbon monoxide (CO) are oxidized at this step]. Following (2) combustion, final purification was achieved via a magnesium where y is equal to the response of the dependant variable (% perchlorate (MgClO4) tower (designed to remove remaining extracted) and m represents the grand mean of all responses.water vapor) and an acid dichromate–MnO2 NOx scrubber to The bis are empirically obtained relational constants which remove acid impurities. Once purified, the gas stream enters describe the change in y (eVect) as we move from the (-) to the coulometer cell and is measured. the (+) setting for each variable individually.Interactions The coulometer cell is filled with a partially aqueous medium between independent variables xtm, xtp, and xc are described containing monoethanolamine (HOCH2CH2NH2, MEA) and by terms 5, 6, 7, and 8 in eqn.(2). The main eVect, i.e., bi, of a colorimetric indicator. A platinum cathode and a silver each individual independent variable is determined by the electrode are positioned in the cell and the assembly is posdi Verence between the average of the response y for experi- itioned between a light source and a photodetector. When a gas stream passes through the solution, CO2 is quantitatively absorbed, reacting with the MEA to form a titratable acid (hydroxyethylcarbamic acid, HOCH2CH2NHCOOH).This acid causes the indicator color to fade. Photodetection monitors the change in the color of the solution as a per cent. transmittance (%T ). As the %T increases, the titration current is automatically activated to electrochemically generate base at a rate proportional to the %T.When the solution returns to its original color, the current stops. CO2 introduced to the cell is thus determined as a proportion to the titration current. The eYciency of the system was determined by: (1) reacting pure calcite with the acetic acid buVer (pH 4); and (2) by measuring evolved CO2 from the carbonate and organic matter fractions of the NIST SRM 2704 BuValo River Sediment BRS (certified for total C).Based on these experiments, the Fig. 3 Cubic representation of the full-factorial experimental design. eYciency of the system is 96% with a standard deviation of Main eVects of each variable (time, temperature, and concentration) 8%. A literal interpretation of the reaction rates is not sug- are determined by the diVerence between the average response of gested here (the rate of CO2 introduced to the coulometer cell analytes (% extracted) at the high setting (4 experiments) and the low setting (4 experiments).is partly a function of the in-line O2 flow rate). However, the 186 J. Environ. Monit., 1999, 1, 183–190ments conducted at the (-) level and experiments conducted for Ca, Mn, Sr and U. Our coulometry results clearly show that the reaction of the acetate buVer with carbonate in the at the (+) level., i.e., bi=y: +-y: -.We monitored the response of stable elements Al, Ba, Ca, OS standard proceeds to completion (independent of acidity from pH 3 to pH 5) within 2 h (Fig. 4 A,B). ‘Completion’ is Fe, K, Mn, Pb, Sr, and Ti at two pre-specified levels for each variable and a midpoint experiment was included to account defined here as the point where the reaction rate slows to less than one per cent.of the total-integrated evolved C. For pure for curvature in response (Table 1). Concentrations of stable nuclides were measured with an ELAN 5000 inductively calcite, the reaction is complete within about 1 h and is complete in less than 90 min for the BRS (Fig. 5). As men- coupled plasma mass spectrometer (ICP-MS) from PE-Sciex ( Thornhill, Ontario, Canada). The TotalQuant mode, which tioned earlier, the TC content of the OS standard is very low. Estimates by thermal techniques suggest a TC content of quantifies the spectral information for elements of the entire periodic table, was used for all measurements. The instrument approximately 3.5 mg g-1 or 0.35%. The total Ca concentration in the OS (CaT) is about 6.3 mg g-1.31 If evolved CO2 was calibrated using a solution containing 20 ng g-1 for each of 25 elements (Be, Mg, Al, Sc, V, Cr, Mn, Co, Ni, Cu, Zn, represents dissolution of CaCO3, one can calculate (stoichio- As, Se, Sr, Mo, Ag, Cd, Sb, Ba, La, Eu, Yb, Tl, Pb, Th).This solution was prepared by diluting (with 1.5% high purity HNO3) a multi-element standard purchased from High Purity Standards (Charleston, SC).NIST SRMs 1640 ‘Trace Elements in Natural Water’ and 1643d ‘Trace Elements in Water’ were used as quality controls for instrument calibration and sample analysis. Five replicate measurements were made for each sample (with a dwell time of 0.5 s at each nuclide mass). Alpha-spectrometry Uranium and Pu isotopic analyses were performed by methods similar to those presented by Burnett et al.30 Radiochemical separations were performed using a tandem column arrangement, with extraction chromatography resins UTEVA and TRU (manufactured by EiChrom Industries, Darien, IL, USA).Counting sources were prepared by cerium fluoride microprecipitation/filtration and counted in vacuumcontrolled alpha-spectrometry chambers using solid-state silicon semiconductor detectors.Results and discussion Carbonate fraction Fig. 4 Real-time measurement of evolved CO2 (as mg C) for the carbonate fraction of the OS standard at pH 3 (A) and pH 5 (B). Based on our results (from coulometry and ICP-MS analyses Right axis shows the reaction rate (mg min-1 of C). Left axis shows of the extracts from the full-factorial experiment), reaction the total integrated CO2 (as mg C) over time. Duplicate runs (solid temperature and time of extraction are important variables and broken lines) are shown in this figure to highlight reproducibility. for determining optimum conditions for the carbonate fraction.In both A and B, the reaction rate slows to background in less than 2 h.We observed little eVect on the extraction of stable elements Al, Ca, Fe, K, Mn, Sr, or U and Pu isotopes resulting from changes in ionic strength (from 0.5 mol L-1 NH4Ac to 2 mol L-1 NH4Ac, at pH 5, Table 2). The eVects of reaction temperature and time of extraction were observed most clearly Table 2 Main eVects of changes in temperature, concentration, and time for extraction of select elements for the carbonate fraction of the OS standard Total extracted (%)a EVectb Average Temp. Conc.Time Element (m)c Range (xtm) (xc) (xtm) Al 0.0 0.0–0.01 <0 <0 <0 K 2.4 1.0–4.8 1.7 0.4 0.5 Ca 33 10–50 17 <0 10 Mn 6.9 1.3–15 7.6 0.06 3.8 Fe 0.3 0.0–0.1 <0 0.18 <0 Sr 8.5 3.4–15 3.4 <0 2.6 U 6.6 1.8–14 5.2 <0 2.2 Pu 0.3 0.0–0.1 <0 0 <0 aTotal concentrations of elements in the OS are based on estimates (given for information purposes) provided in the NIST certificate for SRM.bThe main eVects are calculated as the diVerence between the Fig. 5 Experimental results for (A) pure calcite and (B) the carbonate average per cent. extracted at the high and low settings for each fraction of the BRS standard at pH 5.The reaction rate slows to variable. cThe average corresponds to m in eqn. 2. background in less than 2 h for both experiments. J. Environ. Monit., 1999, 1, 183–190 187metrically) an expected value for extracted Ca (under the same the amount suggested by Tessier et al. (20 mL of 30% H2O2 per addition for a 10 g sample size). In every case, at least conditions) of about 36 mg.We ran separate carbonate extractions (n=4 replicates, 1.0 mol L-1 NH4Ac, 2 h, 25 °C, pre- three additions of H2O2 were necessary for complete oxidation of OC (Figs. 6–8). In each of the figures, Xs mark the addition extracted with MgCl2) to compare the extracted Ca value with the value obtained from coulometry measurements. The value of H2O2. For the BRS standard, sediment organic matter appears to be partitioned further into temperature dependent was somewhat low (33 mg Ca, standard deviation of 3 mg Ca), but within one standard deviation of the value for Ca reaction phases.In the case of BRS standard, the highest temperature required for the reaction to self-perpetuate was calculated by the IC measured by coulometry. 80 °C. The 80 °C temperature is consistent with that suggested A substantial portion of a Mn-bearing phase is dissolved by a number of authors, including Tessier et al.6 and Salbu when the extractions are carried out at 90 °C, the eVect is et al.4 However, at least three additions of H2O2 were required enhanced for extractions carried out at 90 °C for 16 h.Uranium for the complete oxidation of OC for both the OS and the BRS.exhibits similar behavior: as much as 14% is extracted at 90 °C, For the OS at 90 °C, the reaction rate increased rapidly to 16 h, indicating that a correlation may exist between dissolua maximum for carbon of approximately 1500 mg min-1, tion of Mn and U under these conditions. Further evidence that the lower temperature is more selective (in terms of carbonate dissolution) is found in U5Ca ratios of extraction solutions.If one assumes that the mass ratio of U5Ca in seawater (Rsw) is preserved in the formation of pure calcium carbonate shells, then this value can be compared to our extractions as a measure of specificity. For the carbonate extractions carried out at 25 °C, the U5Ca ratio (Rex) agrees remarkably well with that of average Rsw (Rex/Rsw=1.13). On the other hand, for extractions carried out at 90 °C, the U5Ca ratio R90 is roughly two and one half times that of Rsw (R90/Rsw=2.6).The U5Ca ratio for the midpoint experiment Rmid (50 °C, 4 h, 1 mol L-1 NH4Ac, pH 5) was elevated from the low settings extractions (Rmid/Rsw=1.6). These results (when combined with the direct measurement of evolved CO2) suggest that extraction at 25 °C, for about 2 h, is most selective (in terms of carbonate dissolution) at pH 5 using the acetate buVer.Organic fraction The important factors in optimizing the extraction of organic matter are the reaction temperature and the timing of the additions of H2O2. In optimizing the conditions for this reaction (as well as the other extractions in our sequence), the Fig. 6 Real-time measurement of the oxidation of organic carbon in goal is to determine the least harsh conditions under which the OS standard by evolved CO2 (as mg C) at (A) 90°C and (B) the reaction proceeds to completion. The protocol suggested 70 °C. Xs mark the addition of 30% H2O2. by Tessier et al.6 calls for a temperature of 85 °C and a series of four steps.The sample is first suspended in a 0.01 mol L-1 HNO3 solution. At time t=0 an aliquot of 30% H2O2 (2 mL H2O2 per g of sample) is added and the reaction is allowed to proceed for 3 h. At this point, a second aliquot of H2O2 is added and the reaction is allowed to proceed for an additional 2 h. Following this second reaction period, an aliquot of 3.2 mol L-1 NH4Ac is added and the sample agitated for an additional 30 min.The addition of the salt solution is intended to prevent the readsorption of released metals to remaining solid phase particles. Salbu et al.4 modified this overall procedure to a single addition of H2O2 for 5.5 h at a temperature of 80 °C, followed by the addition of the NH4Ac salt solution. Our results, for the extraction of sediment organic matter from the OS standard, indicate that the temperature of the H2O2 reaction with organic matter may be reduced by as much as a factor of two.In our experiments, the Tessier method was simulated and the evolved CO2 monitored via coulometry. Reactions were begun (by adding H2O2) with the HNO3 solution at temperatures of 90, 70 and 50 °C. In a fourth experiment, the reaction temperature was ramped slowly from room temperature until the reaction self-perpetuated.Duplicate experiments were carried out at each temperature. Results of single experiments are shown here for simplicity. The oxidation reactions were observed to be somewhat exothermic—the reaction vessel temperature self-elevated by Fig. 7 Experimental results for the oxidation of organic carbon in the as much as 20% from the set temperature while the reaction OS standard by evolved CO2 (as mg C), at (A) 50 °C and (B) by slowly elevating the set temperature from 35 to 45 °C.X as Fig. 6. was in progress. H2O2 was added in aliquots proportional to 188 J. Environ. Monit., 1999, 1, 183–190of H2O2 produced no further reaction at 60 °C. The set temperature was increased a third time (to 80 °C) and the reaction began to proceed, with a fourth addition of H2O2 required for completeness.The data show clearly that the organic matter reaction is highly temperature dependant and that at least three additions of H2O2 are required to oxidize OC in these two samples (BRS and OS). Conclusions For the OS standard, BRS standard, and pure calcite, the carbonate extraction can be accomplished (using the NH4Ac–HAc buVer, pH 3 to pH 5) in less than 120 min.This contrasts previously suggested reaction times for this fraction of between 5 and 8 h. For the OS standard, our results indicate that increased time and temperature result in dissolution of non-targeted phases (perhaps Mn oxide/oxyhydroxide). Thus, a shorter reaction time at a lower temperature is more selective in terms of carbonate dissolution.The oxidation of organic matter was highly temperature dependent for the two sediment standards studied. For the OS, the oxidation reaction of organic matter with H2O2 selfperpetuates between 45 and 50 °C, and is complete in about Fig. 8 Experimental results for the oxidation of organic carbon in the 6 h with three additions of 30% H2O2 (in 2 h intervals).On BRS standard by evolved CO2 (as mg C) for an initial experiment (A) the other hand, the reaction can be completed in about 1 h and an ‘optimized’ extraction (B). Organic C in this sediment is (with three additions of H2O2) when conducted at 90 °C. In partitioned into temperature dependent fractions. Four additions of contrast, the organic carbon in the BRS can be partitioned by H2O2 were required to reach a reaction rate of <1% of the total the reaction temperature.This sediment consists of an easily integrated C. X as Fig. 6. oxidized component (50 °C) and two more refractory organic carbon phases, requiring temperatures of 60 and 70 °C for the reaction to proceed. In each case, the temperature required 300 mg min-1, and 20 mg min-1 following each of three additions of 20 mL 30% H2O2 (Fig. 6A). The reactant was for the reaction to proceed was lower than that commonly suggested for this application. quickly used up with each addition as the reaction rate approached zero mg min-1 of carbon within about 15 min of The timing of the additions of H2O2 is also critical for optimizing the selectivity of the organic extraction. At least each addition of H2O2.Our goal in these experiments was to understand the oxidation reaction (over time) as a function of three additions of H2O2 were required for the complete oxidation of organic matter in this study. We suggest that for temperature. Clearly, at 90 °C, the organic matter extraction could be completed within about 1 h, with three additions of optimum selectivity the H2O2 should be added intermittently as the reaction slows to near zero. H2O2 at 20 min intervals.Similar results were obtained when the reaction was carried out at 70 °C (Fig. 6B). The reaction Real-time measurement of evolved CO2 (by coulometry) is a useful tool for identifying the appropriate number and timing rate slowed substantially when the set temperature was lowered to 50 °C (Fig. 7A). In this case, the rate maximum reached of H2O2 additions required for this reaction step. For selective sequential extractions, the lower temperature may be preferred about 600 mg min-1 rapidly and fell to near zero within about 45 min. The total time needed for complete oxidation of to reduce the attack of the HNO3 medium on non-targeted geochemical phases.Because of diVerences in type and quantity organic matter was approximately 180 min. The ascertain a possible temperature dependent reaction barrier, a fourth of carbon-bearing species in natural soils and sediments, the use of coulometry reduces the uncertainty in setting the experiment was conducted in which H2O2 was added initially at room temperature and the temperature was ramped slowly ‘optimum’ conditions for selective chemical extractions.until the reaction began to self-perpetuate. When approached in this way the reaction proceeded slowly, beginning at about 35 °C, and increased rapidly to a rate maximum of about Acknowledgements 175 mg min-1 of carbon when the solution temperature reached about 45 °C (set temperature of 50 °C).The reaction Laboratory space and instrumentation for coulometry work for this study were provided by Dr. Lloyd Currie and staV was slightly exothermic and reached a maximum of 53 °C with each addition of H2O2 (Fig. 7B). The reaction went to members Donna Klinedinst and Julie Van Vulkenburg of the Analytical Chemistry Division (NIST). The authors gratefully completeness in about 6 h when carried out in this way.In contrast to the OS standard, OC in the BRS standard acknowledge Dr. Currie and his staV for thoughtful conversations and cheerful cooperation throughout this project. appears to be partitioned into temperature dependent fractions. A reaction maximum (~250 mg min-1) was reached rapidly at 45 °C (Fig. 8A) and increased to over 400 mg min-1 when the reaction was begun with a set temperature of 50 °C Disclaimer (Fig. 8B). The reaction was then allowed to proceed until oxidation appeared to be at a constant minimum, at which Certain commercial equipment, instruments, or materials are identified in this paper to foster understanding. Such identifi- point an aliquot of H2O2 was added. When no further reaction was observed (with a system purge period of about 10 min), cation does not imply recommendation by the National Institute of Standards and Technology, nor does it imply that the set temperature was increased to 60 °C.The reaction began to proceed once again at this set temperature. However, again the materials or equipment are necessarily the best available for the purpose. a constant minimum was observed after about 1 h and addition J.Environ. Monit., 1999, 1, 183–190 18917 E. R. Sholkovitz, Geochim. Cosmochim. Acta, 1976, 40, 831. References 18 G. R. Choppin and B. E. Stout, Chem. Brit., 1991, 27, 1126. 19 J. A. Leenheer, G. K. Brown, P. MacCarthy and S. E. Cabaniss, 1 E. I. Hamilton and R. J. Clifton, Mar. Ecol. Prog. Ser., 1980, Environ. Sci. Technol., 1998, 32, 2410. 3, 267. 20 J. U. Anderson, Clays Clay Miner., 1963, 10, 380. 2 S. R. Aston, D. J. Assinder, D. A. Stanners and J. E. Rae, Mar. 21 L. M. Lavkulich and J. H. Wiens, Soil Sci. Soc. Am. Proc., 1970, Pollut. Bull., 1981, 12, 308. 34, 755. 3 D. H. Oughton, B. Salbu, T. L. Brand, J. P. Day and A. Aarkrog, 22 L. M. Shuman, Soil Sci. Soc. Am., 1983, 47, 656. Analyst, 1993, 118, 1101. 23 R. G. McLaren and D. V. Crawford, J. Soil Sci., 1973, 24, 172. 4 B. Salbu, T. Krekling, D. H. Oughton, G. Østby, V. A. 24 A. L. Sanchez, J. W. Murray and T. H. Sibley, Geochim. Kashparov, T. L. Brand and J. P. Day, Analyst, 1994, 119, 125. Cosmochim. Acta, 1985, 49, 2297. 5 S. B. Clark, W. H. Johnson, M. A. Malek, S. M. Serkiz and T. G. 25 E. W. D. HuVman, Microchem. J., 1977, 2, 567. Hinton, Radiochim. Acta, 1996, 74, 173. 26 C. R. Glenn, M. A. Arthur, H. W. Yeh and W. C. Burnett, Mar. 6 A. Tessier, P. Campbell and M. Bisson, Anal. Chem., 1979, 51, 844. Geol., 1988, 80, 287. 7 T. T. Chao, J. Geochem. Explor., 1984, 20, 101. 27 C. Robinson and P. J. Williams, Mar. Chem., 1991, 34, 157. 8 B. Collier, J. Dymonds, R. Conard and H. D. Holland, Geophys. 28 K. M. Johnson, K., D. Wills, D. B. Butler, W. K. Johnson and Monogr., 1991, 63, 235. C. S. Wong, Mar. Chem., 1993, 44, 167. 9 W.M. Landing and B. L. Lewis, Geophys. Monogr., 1991, 63, 251. 29 G. E. P. Box, W. G. Hunter and J. S. Hunter, Statistics for 10 K. C. Ruttenburg, Limnol. Oceanogr., 1992, 37, 1460. Experimenters: An Introduction to Design Analysis and Model 11 M. K. Schultz, W. C. Burnett, K. G. W. Inn, J. W. L. Thomas and Building, John Wiley and Sons, New York, NY, USA, 1978, Z. Lin, J. Res. Natl. Inst. Stand. Technol., 1996, 101, 707. pp. 534–582. 12 M. K. Schultz, K. G. W. Inn, Z. C. Lin, W. C. Burnett, G. E. 30 W. C. Burnett, D. R. Corbett and M. K. Schultz, 12th Waste Smith, S. R. Biegalski and J. Filliben, Appl. Radiat. Isot., 1998, Testing and Quality Assurance Symposium, Environmental 49, 1289. Protection Agency/American Chemical Society, July 23–26, 1996, 13 M. K. Schultz, W. C. Burnett and K. G. W. Inn, J. Environ. Washington, DC, USA, pp. 77–86. Radioact., 1998, 40, 155. 31 K. G. W. Inn, Z. Lin and J. M. R. Hutchinson, Certificate, 14 J. H. Schroeder, D. S. Miller and G. M. Friedman, J. Sediment Standard Reference Material 4357—NIST Ocean Sediment, Petrol., 1970, 40, 672. National Institute of Standards and Technology, Gaithersburg, 15 P. M. Shanbag and J. W. Morse, Geochim. Cosmochim. Acta, MD, USA, 1996. 1982, 46, 241. 16 W. P. Miller, D. C. Martens and L. W. Zelazny, Soil Sci. Soc. Am., 1986, 50, 598. Paper 9/00534J 190 J. Environ. Monit., 1999, 1, 183–190

ISSN:0960-7919    

DOI:10.1039/a900534j

出版商:RSC    

年代:1999

数据来源: RSC