摘要:

IntroductionCarbon monoxide (CO) is formed from incomplete fuel oxidation during both biomass burning and anthropogenic combustion processes; these two sources are estimated to contribute roughly equally to the CO budget on the global scale.1-3In the United States, transportation sources account for about 80%, industrial sources for 7%, and electrical utilities for only 0.5% of the total tabulated anthropogenic CO emissions.4Electric utility power plant operating conditions are carefully monitored to optimize combustion efficiency, and typically operate at efficiencies exceeding 99.9% based on tabulated emissions of CO and CO2.5,6Power plants are not expected to be significant sources of CO; however, as they are large sources of CO2, small changes in fuel combustion efficiency could result in large percentage increases in CO emissions. Carbon monoxide emissions are monitored periodically by direct measurement of flue gases, but more typically are calculated using emissions factors appropriate to the burner technology and type and amount of fuel consumed.7-9We present the results of airborne measurements in plumes downwind of seven different power plants in eastern and central Texas. Substantial enhancements in CO mixing ratios were observed in plumes from three of four lignite coal-fired power plants. Multiple transects at different distances downwind and on different days suggest the elevated CO emissions were reasonably constant over time scales of hours to days. Another power plant with both sub-bituminous coal and natural gas-fired units was also found to be emitting substantial amounts of CO, but these emissions were highly variable over time. Carbon monoxide emissions from other coal- and gas-fired power plants were found to be in good agreement with tabulated emissions inventories.We analyze data from near-field (2–50 km) transects downwind of each source and establish that the power plants are the sources of the observed elevated CO. We then calculate annual power plant CO emission rates from the slopes of bivariate linear least-squares regression fits10to correlated plume NOyand CO2data.11Finally, we compare CO emission rates derived from the measured plume data to those tabulated in State and Federal emissions inventories for these power plant sources.

ISSN:1464-0325    

DOI:10.1039/b201486f

出版商:RSC    

年代:2002

数据来源: RSC

摘要:

Lead, arguably one of the first metals recognized as poisonous, has been the focus of increasing public health regulation in the 20th century.1Much of this regulation is addressed to the protection of children and reflects burgeoning knowledge of the developing nervous system's special vulnerability to lead's neurotoxic influences. Public health legislation in this area has been shaped by the weight of research findings and has shown a slow evolution toward more strict guidelines. The last major change in lead regulation stems from recommendations made by the CDC in 1991 (see below). However, research into the physiological effects of this metal in the last decade has been particularly fruitful in providing new information on the manifold influences of this ancient poison. The present review concerns some of these more recent developments in the study of childhood lead poisoning and proposes that recently published findings may mandate the need for changes in the regulation of lead exposure, federal housing and health policies.Public health legislation in the US regarding lead encompasses screening of children, methods of hazard identification and control, training requirements for lead abatement workers, permissible uses of lead, industrial lead emissions, occupational exposure, environmental intervention and medical treatment.2However, all of the lead regulations are based on a consensus, now more than a decade old, by regulatory agencies as to what constitutes safe and unsafe levels of lead in the human body.Lead is primarily absorbedviarespiration and ingestion and carried throughout the body by the blood and thereby enters all tissues of the body. For this reason, measurement of blood lead levels is the most common method for establishing degree of exposure in humans and is usually reported in μg of lead per deciliter of blood (i.e.μg dl−1). Increasing scientific information about lead's effects in children has resulted in a progressive decrease in the blood lead level that is generally recognized as the threshold for poisoning. In the 1950's “normal”, or medically non-significant blood lead levels were thought to be from 60–80 μg dl−1; this level was progressively dropped – to 50 μg dl−1, then 40 μg dl−1in the 1960's, to 30 μg dl−1in 1975, to 25 μg dl−1in 1985 and finally, in 1991, to 10 μg dl−1.3This most recent decrease was based on a CDC expert panel's review of research published through 1991. They concluded that “...the scientific evidence showing that some adverse effects occur at blood lead levels at least as low as 10 μg dl−1in children has become so overwhelming and compelling that it must be a major force in determining how we approach childhood lead exposure.” The CDC panel also posited; “Some studies have suggested harmful effects at even lower levels, but the body of information accumulated so far is not adequate for effects below about 10 μg dl−1to be evaluated definitively. As yet, no threshold has been identified for the harmful effects of lead.”4In the years intervening since the CDC's 1991 published statement, there has been a spate of studies investigating the physiological effects of low concentrations of lead in experimental systems and the neurobehavioral effects of low-level lead exposure in children. Some of these studies are discussed below.

ISSN:1464-0325    

DOI:10.1039/b403259b

出版商:RSC    

年代:2004

数据来源: RSC

摘要:

IntroductionAnalysis of ammonium present in estuarine, coastal and open-ocean waters is fundamental to understanding biogeochemical cycling of nitrogen and its influence upon marine ecosystems. Ammonium is involved in many biogeochemical processes. It fuels ‘regenerated’ production by marine phytoplankton,1is produced by heterotrophic bacteria, and is involved in other microbial processes such as nitrification and denitrification.2The net result of these processes is that ammonium is frequently present at concentrations lower than 1 μmol L−1. Such low concentrations are difficult to analyse as they are close to or below the detection limit for many methods and the risk of contamination is high.1Many of the analytical methods currently used are modifications of the indophenol blue (or Berthelot) reaction, using spectrophotometry to measure the products.3–7These techniques generally use phenol, which can be difficult to work with in confined areas such as shipboard laboratories. Several of these methods are time consuming and sensitive to changes in reaction conditions and contamination.8,9Ortho-phthaldialdehyde (OPA) is used routinely to determine a range of amino acids by HPLC with fluorescence detection.10–13The derivatisation reaction uses a thiol, usually 2-mercaptoethanol, as a mild reductant.14The resulting 1-alkylthio-2-alkyl-substituted isoindoles are intensely fluorescent. Several authors have used the 2-mercaptoethanol-OPA reagent in flow-injection analysis (FIA) for ammonia determination.15–17In 1991, Jones18also described a method that incorporated the 2-mercaptoethanol-OPA reaction into a gas-diffusion FIA system for analysis of marine waters. He included procedures for purifying and removing interference in reagents by ammonia or volatile amines.OPA has been used in the analysis of various thiols by HPLC.19Sulfite was also detectable by this method. Genfa and Dasgupta20used sulfite in their FIA method for analysing ammonium in fresh water. Sulfite was more stable and acceptable to work with than 2-mercaptoethanol but was less reactive. Kérouel and Aminot21developed this method further for use with brackish and saline water samples, as did Holmeset al.22who developed a highly sensitive manual method. Aminotet al.23also developed a method suitable forin situanalyses. The method described here combines the advantages of the gas-diffusion method of Jones18with the sulfite-OPA reaction. It optimises the method for ultra-trace level measurement, avoids the use of phenol, and guards against common sources of interference and contamination in shore-based and shipboard laboratories.

ISSN:1464-0325    

DOI:10.1039/b405924g

出版商:RSC    

年代:2004

数据来源: RSC

摘要:

IntroductionContamination of the environment with arsenic from both anthropogenic and natural sources has occurred in many parts of the world and is a global problem. Elevated levels of arsenic from natural and industrial sources have been reported in several countries of America, such as Chile, Argentina, Mexico, Canada and the United States of America.1Elevated antimony concentrations are generally associated with high arsenic concentrations in sulfide ores. The most important anthropogenic emission sources to the environment for metalloids are the non-ferrous mining and smelting industries and the burning of coal and petroleum. Gross contamination of surface soils and plants by dust and smelter fumes from copper and lead smelters have been reported; the nearest samples to mine industries present the highest concentrations but the levels decrease with increasing distance.2–7Slight contamination by these metalloids may also arise from the application of sewage sludge and fertiliser to soil. While a world-wide community of researchers work on arsenic speciation, transformation, transport, seasonal cycling, accumulation, geochemistry and toxicology, scarce information is available about the mobilisation and transformation of antimony in the different compartments of the environment. Many arsenic compounds are toxic and potentially carcinogenic, which raises much concern from the environmental, occupational and nutritional points of view according to ATSDR (Agency for Toxic Substances and Disease Registry).8Because of the toxicity of its compounds, antimony is listed as a priority pollutant by the United States Environmental Protection Agency and by the Council of the European Communities.9,10It is on the list of hazardous substances under the Basel Convention concerning the restriction of transfer of hazardous waste across borders.11In agricultural soils, toxic elements have received a great deal of attention because of their long term effects on crop yields, soil quality, accumulation in crop tissue and potential source of risk to animals, farmer and consumer. But the mobility of trace elements, their bioavailability and related eco-toxicity to plants depend strongly on their specific chemical forms or types of binding rather than the total element contents. However, the determination of specific chemical species is difficult and often hardly possible. Therefore, in practice determinations of phases defined by their functione.g.“bioavailable forms” or “carbonate bound forms”, are usually carried out by single or sequential extraction with reagents having different chemical properties.12The function relating soil parameters to element availability seems to be complex, and several models have been used to approach this problem.13–15The physico-chemical characteristics of soils result in important control of the adsorptive capacities and therefore will affect the availability of elements to plants.16But these interactions vary with the element, soil type and the form in which the metal or metalloid itself is present or enters the soil.17–20Relative to antimony, Hammelet al.have described that in polluted soils it is mostly immobile.21In contrast, in soils with high mobile antimony content, an accumulation of this element was observed in leaves of spinach grown under controlled conditions; the correlation between the mobile fraction and antimony in leaves was found.22In general, there is scarce evidence of accumulation of antimony in food chains represented by soil–vegetation–invertebrate–insectivore pathways in grasslands.4,23In Chile, copper mining is by far the major economic activity, but in spite of the economical importance, mining has contributed to the propagations of heavy metals in the environment. In a previous paper we reported the total concentrations of copper, arsenic and antimony in affected and unaffected agricultural soils, from the north and central region in Chile.24High concentrations of these elements in soils collected near the smelters and mining industries, clearly showed the impact produced by these activities. Following our research on these elements in Chilean ecosystems, and taking into account that total elemental concentrations are not reliable indicators of environmental risk, a further study to obtain information on their mobility and transfer into plants was performed. In this paper, which follows on from the previous work, the fraction of these elements extracted by 0.05 M EDTA pH 7 from 20 different agricultural soils was determined. Their uptake by forage alfalfa plants (Medicago sativa) collected from the same sites where soils were sampled (total concentrations in the edible tissues) is discussed. The relationships between the total concentrations and extractable fractions of these elements in soils and their total contents in alfalfa plants were examined. The effect of some physico-chemical parameters on the extractable fraction were also considered.

ISSN:1464-0325    

DOI:10.1039/b304840c

出版商:RSC    

年代:2003

数据来源: RSC

摘要:

Home lifeNot a city dweller by origins or inclination, Harrison lives some 20 miles out of Birmingham on the edge of a small town called Stourport-on-Severn where with his wife Susan he manages a “garden” of some four and a half acres which includes a small flock of sheep, some hens, geese and ducks. They are accompanied by their son Edmund, aged 10, and intermittently by son Tom (24 years), daughter Polly (22) and stepsons Andrew (24) and Alistair (22). Domestic life is never dull!

ISSN:1464-0325    

DOI:10.1039/b305100p

出版商:RSC    

年代:2003

数据来源: RSC

摘要:

IntroductionThe impact of ground level pollution on the environment and human health is of concern to the local and national governments of Canada and the United States, as well as many other countries worldwide.1High concentrations of ozone in the lower troposphere are considered an important issue of air quality and tropospheric chemistry.2Surface ozone concentrations during summertime in many regions of north-eastern Canada and the United States have been measured to exceed standard levels.3Usually it is difficult to quantify the direct contribution of precursor species to the pollutant concentrations. Chemical species, after being directly emitted into the atmosphere from anthropogenic and natural sources, undergo complex non-linear physical-chemical transformations, in which new species can be formed from their precursors.4Moreover, meteorology can also play important roles in the pollution formation processes. Biswas and Rao5and Hogrefeet al.6pointed out that photochemical models can be very sensitive to meteorological inputs after they examined the variability in the predictions of the Urban Airshed Model (UAM-V) when the meteorological input was derived from two different meteorological models, namely, RAMS (or RAMS3b) and MM5. Hogrefeet al.6found that such a variability can be decomposed into intra-day, diurnal, synoptic and long-term meteorological effects. The observed concentrations at a given site are therefore the comprehensive result of emissions, chemical transformations, microphysical processes and meteorological actions.Many regional air quality models have been developed so far to study ozone, and more recently particulate matter (PM). Jacobsonet al.7developed the model GATOR for modelling ozone and PM in the Los Angeles metropolitan area.8–10Other air quality models include CIT,11URM12UAM-V,13CAMx,14SAQM,15MAQSIP,16,17SMRAQ18and Models-3.19Comparison studies for many air quality models can be found in Russell and Dennis.20In Canada, two air quality models have been developed: ADOM (Acid Deposition and Oxidant Model)21and CHRONOS (Canadian Hemispheric and Regional Ozone and NOxsystem).22Until now, pre-calculated meteorological fields were used to drive the transport of chemical species in most of the regional air quality models mentioned above. Such “off-line” models often include differences between the vertical and horizontal grids and sub-grid scale parameterizations can be inconsistent for temporal resolution.23An online chemistry modeling system, in which the meteorological fields are computed concurrently with the chemistry, will have significant advantages. In this paper, we present comparisons of results obtained from the online regional air quality modeling system MC2AQ to observation data from the routine ground-based monitoring network in Canada and the United States.

ISSN:1464-0325    

DOI:10.1039/b204784p

出版商:RSC    

年代:2002

数据来源: RSC

摘要:

IntroductionRice is the only staple crop grown under flooded soil conditions. Under anaerobic conditions, arsenic in soil is converted readily to arsenite which is mobile, leading to arsenic in rice grain being around 10-fold higher than for other crops.1This occurs in soils which have no or limited anthropogenic contamination. Rice grain arsenic levels are elevated further when grown in soils subject to anthropogenic contamination such as: arsenical pesticide use, base and precious mining and smelting impacted soils, and contaminated water irrigated soils.2–8Inorganic arsenic, a class 1 non-threshold carcinogen,9,10and dimethyl arsinic acid (DMA) constitute the dominant arsenic species present in rice while traces of monomethyl arsonic acid (MMA) are sometimes reported,11as well as a residual fraction that is either not extractable or does not elute from the chromatographic column. Inorganic arsenic can constitute up to 90% of total arsenic present in grain, but on average accounts for around 50% of total grain arsenic.11A number of previous studies had suggested that rice cooking was important to the arsenic content of the cooked grain.12–18Some of these studies focus on how cooking techniques may reduce rice arsenic content,12,13while others focus on how arsenic in cooking water affects arsenic content of cooked rice.14–18Rinsing rice before washing and then cooking the rice in a high water : rice ratio (6 : 1) and not allowing the water to evaporate to dryness significantly reduced the arsenic burden of the rice,12,13with one study suggesting that the arsenic was primarily lost as inorganic arsenic, specifically arsenite.12Previous studies on rice cooking12–18had not systematically looked at: (a) differences between wholegrain (brown) or polished (white) rice or (b) commonly used cooking techniques such as low and high water : rice volume and steaming. Similarly, systematic speciation and/or mass balances are inconsistent or absent between previous studies.13–8Par-boiled rice also needs to be considered due to its widespread utilization. This current study sets out the systematic determination of the effect of cooking on the concentrations of arsenic species in rice.

ISSN:1464-0325    

DOI:10.1039/b816906c

出版商:RSC    

年代:2008

数据来源: RSC

摘要:

Over the last thirty years, the study of chemical pollution has focused primarily on a relatively small set of “priority” pollutants, especially those pesticides and industrial intermediates thought to be acutely toxic or carcinogenic and environmentally persistent.1Whilst emissions from manufacturing and other intensive users of chemicals such as agriculture are now well controlled, they form only one piece of a much larger puzzle. In particular, it is increasingly apparent that many of the chemicals we find around us in our everyday lives, in pharmaceuticals and personal care products (PPCPs), also have an environmental impact.We have known for 20 years or more that certain pharmaceutically active compounds, such as caffeine, nicotine and aspirin, can enter the environment, especially in highly populated areas.2,3The main pathways areviatreated and untreated sewage effluent. More recently, evidence has begun to show that numerous personal care products, such as fragrances and sunscreens, as well as a wide range of therapeutic drugs are occurring in the environment and drinking water, especially in natural waters receiving sewage. While the concentrations of these substances are very low, their long-term impact on the environment and human health is unknown.

ISSN:1464-0325    

DOI:10.1039/b304973f

出版商:RSC    

年代:2003

数据来源: RSC

摘要:

Peter Görner was born in Czechoslovakia in 1950. He studied Chemical Engineering at Technical University of Bratislava and received his PhD in Physical Chemistry from Charles University of Prague. Since then, he has been involved in aerosol research. Previously at the French National Coal Board Research Center in Paris and from 1987 at the National Research Institute on Occupational Safety and Health in Nancy, Laboratory of Aerosol Metrology. His current research interest is aerosol sampling, measurement and analysis in the workplace.

ISSN:1464-0325    

DOI:10.1039/b508671j

出版商:RSC    

年代:2005

数据来源: RSC

摘要:

IntroductionThe use of the naturally bioluminescent marine bacteriumVibrio fischerito assess toxicity was developed in the 1970s and made commercially available as the Microtox® assay.1However, there have been concerns about the applicability of this bioassay to terrestrial environmental samples as assays making use ofVibriobased bioluminescence sensors require that the test be performed under saline conditions. This may alter the bioavailability of pollutants when compared with field conditions. This problem may be overcome by the use of ecologically relevant bacteria that have been genetically modified to include bioluminescent properties.Since their initial conception, these tests have been widely used in determining the toxicity of inorganic, polar organic and hydrophobic organic chemicals in waters, soils and sediments. In general, the test is a low cost, high throughput technique for environmental sample analysis.2Many authors have reported that the bacterial bioassay can be interpreted as an indication of the bioavailable fraction of a given contaminant in a selected matrix. Ecotoxicological research has been conducted on other organisms such as nematodes, earthworms and fish.3–5However, the crucial factor is whether or not there is relationship between these bioassays and their environmental relevance.Cronin and Schultz proposed the use of QSARs for ecotoxicity tests on a range of organic compounds.6Compounds with the same mode of action create a biological response related to physico-chemical differences of the molecules. This strategy is widely adopted to develop and validate new assays and to compare between assays and across trophic levels. While QSARs may be applicable in aqueous systems, this may not be the case with other environmental matrices.Many different extraction techniques have been developed as researchers attempt to obtain samples that are chemically and environmentally relevant. For unsaturated soils, two water-based techniques are commonly used, centrifugation and porous membrane extraction.Pore water can be removed quickly and easily from most soils by centrifugation, although some soil types can be more problematical and the method may not be suitable forin situextractions.7–11Porous membrane techniques can remove water from large volumes of soil where centrifugation is unsuitable.10,11Filamentous porous membrane samplers (Rhizons) have also been used to extract samples under a given matric suction from re-packed soils in pots.12Tiensinget al.compared centrifugation and Rhizon sampler approaches and acknowledged that both were suitable for metal application.13Water is often an ineffective extraction solvent for organic compounds. To this end co-solvency with either an alcohol or dimethylsulfoxide (DMSO) has been proposed, as this increases the pollutant recovery, yet is miscible in water and compatible with luminescence based bacterial bioassays.14,15This approach has been shown to work for a wide range of contaminants including chlorophenols, herbicides, organotins, naphthalene and pesticides.16–21Non-exhaustive extraction techniques (NEETs) have been used to extract PAHs from soil with mixed success.19,21The aim of this paper was to compare the response of bioluminescent bacterial assays to those of higher organisms in order to evaluate their relative merits in terrestrial ecotoxicity testing.

ISSN:1464-0325    

DOI:10.1039/b613734b

出版商:RSC    

年代:2006

数据来源: RSC