摘要:

Pentachlorophenol in indoor environments. Does a single measurement of air and dust concentrations represent the contamination?† Ju�rgen Schnelle-Kreis,*ab Hagen Scherb,c Istvan Gebefu�gia and Antonius Kettrupab aGSF–National Research Center for Environment and Health, Institute of Ecological Chemistry, Ingolsta�dter Landstrasse 1, D-85758 Neuherberg, Germany. E-mail: jurgen.schnelle@gsf.de bDepartment of Ecological Chemistry and Environmental Analytical Chemistry, Technical University Munich, D-85358 Freising, Germany.cGSF–National Research Center for Environment and Health, Institute of Biomathematics and Biometry, Ingolsta�dter Landstrasse 1, D-85758 Neuherberg, Germany Received 30th March 1999, Accepted 12th May 1999 In order to be able to make a decision, as to whether a room or building has a health-endangering pentachlorophenol (PCP) concentration, usually the PCP concentrations in air and settled dust are measured. The variability of the PCP concentration in indoor air and dust was studied. Air and dust samples were taken from 75 rooms in 30 buildings with suspicion of application of PCP-containing wood preservatives.Sampling was repeated four times within 18 months.Thirty-six rooms were reconstructed within the study; 39 rooms had unchanged contamination status during the study. The four times repeated measurements of PCP concentrations in air and dust in these rooms showed large variations of the measured values. The variability of the results is to a large extent in the same range as the measured values.The observed relative standard deviation of the PCP concentrations in air and dust does not depend on the average PCP concentration detected in the individual rooms. population of the USA. Today, as a result of the decrease in Introduction PCP concentrations in blood and urine and the long persistence Until the 1980s, pentachlorophenol (PCP) was one of the of PCP in treated wood, indoor air can be assumed to be a most heavily used pesticides worldwide.It has been registered more important source of PCP exposure for people living in for use as an insecticide, herbicide, algicide, fungicide, wood houses with PCP-treated wood. preservative, germicide, and molluscicide.1 Since 1987, wood PCP in indoor environments is measured mainly by air or preservatives and other pesticides containing PCP have no dust analysis.Air analysis has many restrictions. It is known longer been available for home and garden use in the USA. that PCP concentrations in indoor air are variable to a high Nowadays, in the USA only certified applicators can purchase degree, depending on room ventilation, humidity, and temperaand use PCP. It is still used as a wood preservative for power ture.17,18 Moreover, air analyses can only measure the momenline poles, railroad ties, cross arms, and fence posts.In many tary concentration of PCP. Therefore, valid air analysis is time other countries the production and use of PCP are prohibited, consuming and expensive. On the other hand, the investigation e.g. in Germany since 1989.2 of settled dust is a proven and simple screening analysis for PCP is eYciently absorbed by the lungs, skin,3,4 and gastroindoor contamination with semi-volatile compounds.Krause intestinal lining.5 The main exposure to PCP is by dermal and Englert19 found a high correlation (r=0.8) between PCP contact, by inhalation of PCP from oV-gassing of treated concentrations in dust from vacuum cleaner bags and PCP wood products and ingestion of contaminated food and water.concentrations in urine. Meissner and Schweinsberg20 reported Moreover, PCP is a metabolite of the endogenous conversion a correlation of PCP concentrations in passively deposited sus- of hexachlorobenzene,6,7 pentachlorobenzene,8 pentachloroanpended particulate matter of houses with PCP-treated wood isole,9,10 and possibly hexachlorocyclohexane ( lindane) and and the concentration of PCP in the urine of exposed persons.pentachloronitrobenzene.11 In our study we found a significant correlation of PCP The health eVects of exposure to PCP were summarized by concentrations in air and freshly settled dust21 and significant the Agency for Toxic Substances and Disease Registry.1 Longcorrelations of PCP concentration in air with PCP concen- term exposure to low levels can harm the liver, kidneys, blood, trations in blood and urine.22 lungs, nervous system, immune system, and gastrointestinal In the German ‘‘PCP Guideline’’ of 1997, PCP concen- tract.The International Agency for Research on Cancer’s trations in air higher than 0.1 mg m-3 and concentrations in classification of PCP is possibly carcinogenic to humans dust higher than 1 mg kg-1 indicate the need for further (Group 2B).12 Recently, the hormonal action of PCP has been measurements (human monitoring).23 under discussion.13–15 The aim of this investigation was to determine the variability In the late 1980s, Hattemeyer-Frey and Travis16 concluded of PCP concentration in the indoor air and in (freshly) settled that food had major importance for human intake of PCP. dust samples.Our goal was to answer the question of whether Especially fruits, grains, and vegetables were assumed to there is a way to discover the ‘‘real contamination’’ of a room account for 99.9% of human exposure to PCP in the general or building and, if possible, how many measurements are necessary to reach this target.†Presented at AIRMON ’99, Geilo, Norway, February 10–14, 1999. J. Environ. Monit., 1999, 1, 353–356 353Experimental The concentrations of PCP in air and settled dust in houses with the use of wood preservatives containing PCP and the PCP blood and urine levels of the occupants of the houses were investigated. Forty-six occupants in 30 buildings were involved in this study.Houses with supposed use of wood preservatives based on earlier results were chosen. In each house samples from 1–3 rooms were investigated. The selection of the rooms depended on the time period used by the occupants (bedroom, living room, oYce, etc.). However, some of the rooms did not contain treated wood parts. A total of 75 rooms were involved in this study.Beginning in May 1996, sampling of air dust was repeated four times in each house within 18 months. Prior to each sampling the occupants were asked to stop active ventilation of the rooms at least 12 h before sampling, and not to clean the floor 2 d before sampling. The rooms were used in the usual way during sampling, except for keeping the windows closed. Two parallel air samples were taken in each room.Sampling took place in two impingers in series with 75 ml of 0.1M K2CO3 solution each. The air flow rate was 2 1 min-1. The sampling duration was 5 h, so a total volume of 600 1 was sampled. Temperature, relative humidity, and atmospheric pressure were measured and recorded in each room during sampling. Dust samples were taken instantly after air sampling by vacuuming 1–2 m2 of flooring. The filters used (70 mm round Fig. 1 PCP concentrations in air. Results of the four times repeated paper filters, Schleicher & Schu� ll ) were positioned in a special measurements. filter holder (Alk, Denmark) direct at the opening of the vacuum cleaner tube to avoid contamination. In dust sampling, special care was taken to sample only fresh dust.‘‘Old dust’’ normally exhibits higher loads of PCP, so sampling old dust could cause unusually high values in the samples. Special care was paid to avoid dust sampling from PCP-treated materials. Nevertheless, in one case a PCP-treated carpet was vacuumed, leading to extremely high PCP values in the dust. The data for this sample were excluded from further consideration.Air and dust samples were analysed with dual column GC-ECD after acetylation with acetic anhydride.18 Results and discussion Thirty-six of the 75 rooms investigated were reconstructed within the period of our study. Therefore, we had 39 rooms with an unchanged contamination status during the measurement campaign. The following discussion of the variability of the PCP concentrations isthe measurements in these unchanged rooms.The PCP concentrations in air in these rooms were in the range from <0.3 to 236.9 ng m-3 (mean 11.8 ng m-3) and those in dust from 83 mg kg-1 to 12.5 mg kg-1 (mean 1.4 mg kg-1). In order to establish whether the variance of the four repeated measurements exceeds the variance of the parallel samples in the first step, the pooled standard deviation was calculated from the results for the duplicate samples and the method repeatability was estimated.A relative standard deviation (RSD) of 25% was calculated for the air analysis method. The four times repeated measurements of PCP concentrations Fig. 2 PCP concentrations in dust. Results of the four times repeated in air and dust showed a high variation of the measured values measurements.(Fig. 1 and 2). The variation of the results is to a large extent in the same range as the average concentrations determined. In the air analysis we found RSDs of the four times repeated exhibited reproducible results only in some rooms with very low PCP concentrations in air, where no PCP source could be measurements in the range 12.7–164% (mean 65.4%).In order to check the repeatability of the air measurements a variance identified. In 30 cases the variance of the repeated measurements exceeded the variance of the parallel measurements. ratio test (F-test) was performed. In this test the RSDs of the four times repeated measurements were compared with those This result reflects the high variability of indoor air concentrations of PCP.It is known that PCP concentrations in calculated from the parallel samples. The F-test ( p = 95%) 354 J. Environ. Monit., 1999, 1, 353–356indoor air depend on room ventilation, humidity, and tempera- ments only together with information on the situation in the building. When there is any doubt about the contamination ture (source strength). Therefore, air analyses can only measure the momentary concentration.status, determination of the PCP concentration in air is indicated. In the German ‘‘PCP Guideline’’ these measure- The repeated measurements of the PCP concentration in dust showed similar results for the variability. The RSD ranged ments are the next step in the investigation of possible danger to the inhabitants or users of a building. Exceeding the limit between 8.4 and 127.5% (mean 41.7%).As only a single sample was taken from each sampling, no formal test for the repeat- of 100 ng m-3 indicates the need for further measurements (human monitoring). ability could be performed. The high variability of the dust data reflects the high heterogeneity of the matrix dust. The Regarding the variation of the PCP concentration in air, care is reasonable.An underestimation of the contamination degree of adsorption of PCP on dust depends on the composition, shape, and size of the particles. It also depends on the status is possible. The investigation of our results from four times repeated parallel sampling unequivocally shows this time for which the particles are exposed to the PCP in the air.Older dust samples normally exhibit higher PCP loads than possibility. From the examples in Fig. 5 it can be seen that in some cases a single measurement of the PCP concentration in fresh dust. At present, unfortunately, there is no suitable method to determine the age of the dust sampled. air is not valid for a decision as to whether to undertake an investigation of the blood of the inhabitants or not. For this Our suspicion that the value of the RSD of the results of the repeated measurements is correlated inversely with the decision data from dust measurements and from the possibly treated wood are also necessary.If in doubt, human monitoring average concentrations was refuted by the data. The dependences of the RSDs from the measured PCP concentrations is indicated.Air sampling is also used for monitoring the success of the are plotted in Fig. 3 and 4. The relative variance of the PCP concentrations in air and dust found in the four times repeated reconstruction of a contaminated building. The data from the 36 rooms which were reconstructed within our study again measurements in the diVerent rooms does not depend on the value of the average concentration in the individual room.exhibit a scattered picture (Fig. 6). In some cases a reduction of the PCP concentrations in air is observed and in some cases The question of whether there is a way to discover the ‘‘real contamination’’ of a room will be discussed on the basis of not. In all cases where the reduction is not very distinct, a thorough examination of the executed reconstruction is neces- the German ‘‘PCP Guideline’’.In this guideline the measurement of PCP concentrations of freshly settled dust is prescribed sary. Special attention should be paid to contaminated objects as secondary sources. as a first step in measuring the contamination of a room or building. If a PCP concentration in dust of 1 mg kg-1 is The results of our study clearly show that single data on PCP concentrations in air or dust should be handled very exceeded, the measurement of the PCP concentration in air is indicated.Our study had shown that the measurement of PCP carefully. In many cases the decision for room or building reconstruction can only be made by taking a set of data concentrations in dust can lead to a false estimation of the room contamination status.The high variability of the matrix including human monitoring into account. of the settled dust and the diYculties in taking representative samples led to results which are useful for screening analyses, but not for a decision about the extent of contamination. Therefore, we recommend the use of results from dust measure- Fig. 5 PCP concentrations in air.Examples of parallel samples in the four times repeated measurements. Rooms with unchanged contamination status during the study. Fig. 3 RSD of the PCP concentration in air versus the average PCP concentration in the four times repeated measurements. Fig. 6 PCP concentrations in air. Examples of parallel samples in the Fig. 4 RSD of the PCP concentration in dust versus the average PCP four times repeated measurements.Rooms with reconstruction during the study. concentration in the four times repeated measurements. J. Environ. Monit., 1999, 1, 353–356 35512 International Agency for Research on Cancer, IARC Monographs References on the Evaluation of the Carcinogenic Risk of Chemicals to Humans, Vol. 53: Occupational Exposures in Insecticide Application, and 1 ATSDR, Agency for Toxic Substances and Disease Registry Some Pesticides, IARC, Lyon, 1991.Toxicological Profile for Pentachlorophenol, US Department of 13 B. J. Danzo, Environ. Health Perspect., 1997, 105, 294. Health and Human Services, Atlanta, GA, 1994. 14 G. Flouriot, F. Pakdel and Y. Valotaire, J. Mol. Endocrinol., 1995, 2 Pentachlorphenol-Verbotsverordnung (PCP-V), Bundesgesetzblatt, 15, 143.Bundesdruckerei, Bonn, 1/1989, 2235. 15 F. W. Jekat, M. L. Meisel and H. WinterhoV, Toxicol. Lett., 1994, 3 G. L. Quiao, J. D. Brooks and J. E. Riviere, Toxicol. Appl. Chem., 71, 9. 1997, 147(2), 234. 16 H. A. Hattemeyer-Frey and C. C. Travis, Environ. Contam. 4 S. W. Horstmann, A. Rossner, D. A. Kalman and M. S. Morgan, Toxicol., 1989, 18, 482.J. Environ. Sci. Health, Part A, 1990, 24, 229. 17 F. Schweinsberg, D. Zo� ltzer and G. Volland, in VDI-Berichte 5 W. H. Braun and M. W. SauerhoV, Toxicol. Appl. Pharmacol., 1060, VDI-Verlag, Du� sseldorf, 1993, pp. 215–228. 1976, 38, 525. 18 I. Gebefu� gi, H. Parlar and F. Korte, Ecotoxical Environ. Saf., 6 J. To-Figueras, M. Sala, R. Otero, C. Barrot, M. Santiago-Silva, 1979, 3, 269.M. Rodamilans, C. Herrero, J. Grimalt and J. Sunyer, Environ. 19 Krause and N. Englert, Holz Roh-Werkst. 1980, 38, 429. Health Perspect., 1997, 105, 78. 20 T. Meissner and F. Schweinsberg, Toxicol. Lett. 1996, 88, 237. 7 C. den Besten, M. M. Bennik, M. van Iersel, M. A. Peters, 21 J. Schnelle-Kreis, H. Scherb, I. Gebefu� gi, A. Kettrup and C. Teunis and P. J. van Bladeren, Chem. Biol. Interact., 1994, E. Weigelt, Indoor Air, submitted for pub. 90, 121. 22 J. Schnelle-Kreis, H. Scherb, I. Gebefu� gi, A. Kettrup and 8 K. Umegaki, S. Ikegami and T. Ichikawa, J. Nutr., 1995, 125, 147. E. Weigelt, in preparation. 9 J. H. Yuan, T. J. Goehl, E. Murrill, R. Moore, J. Clark, L. Hongm 23 Deutsches Institut fu� r Bautechnik (DIBt), Richtlinie fu�r die and R. Irwin, Xenobiotika, 1993, 23, 427. Bewertung und Sanierung Pentachlorphenol (PCP)-belasteter 10 G. J. Ikeda, P. P. Sapienza and P. I. Warr, Food Chem. Toxicol., BaustoVe und Bauteile in Geba�uden (PCP-Richtlinie) [PCPGuidelines], Mitteilungen DIBt, 1997, 28, 6–17. 1994, 32, 1137. 11 G. Koss and W. Koransky, UBA-Berichte 3/1987, Erich Schmidt Verlag, Berlin, 1987. Paper 9/02563D 356 J. Environ. Monit., 1999, 1, 353&n

ISSN:1464-0325    

DOI:10.1039/a902563d

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

The eVect of wind direction on the observed size distribution of particle adsorbed polycyclic aromatic hydrocarbons on an inner city sampling site† Ju�rgen Schnelle-Kreis,*ab Thomas Ja�nsch,b Kathrin Wolf,a Istvan Gebefu�gia and Antonius Kettrupab aGSF—National Research Center for Environment and Health, Institute of Ecological Chemistry, Ingolsta�dter Landstrasse 1, D-85758 Neuherberg, Germany.E-mail: jurgen.schnelle@gsf.de bDepartment of Ecological Chemistry and Environmental Analytical Chemistry, Technical University Munich, D-85358 Freising, Germany Received 23rd February 1999, Accepted 13th May 1999 An investigation of the variability in the size distribution of particle adsorbed polycyclic aromatic hydrocarbons (PAHs) on an inner city sampling site showed diVerences depending on the wind direction.Particle size distributions of PAHs from outdoor air sampling were measured in Munich from 1994 to 1997. The sampling site is located northeast of a crossing with heavy traYc and southwest of a large inner city park. Depending on the wind direction, three diVerent size distributions of particle adsorbed PAHs were observed. The maximum PAH concentration on very small particles (geometric mean diameter 75 nm) was observed with wind from west to southwest coming directly from the crossing area or the roads with heavy traYc.The maximum PAH concentration on particles with geometric mean diameter of 260 nm was found on days with wind from the built-up area north of the sampling site. On particles with geometric mean diameter of 920 nm the maximum PAH concentration was found on days with main wind directions from northeast to east.On these days the wind is blowing from the direction of the city park nearby. The distribution of particle adsorbed PAHs within diVerent particle size classes is substantially influenced by the distance of the sampling site from strong sources of PAH loaded particulate matter.break between mechanically generated particles and combus- Introduction tion particles is at a point smaller than 2.5 mm. A particle size Recent epidemiological studies have convincingly of about 1 mm is stated to represent the break in particles demonstrated associations between ambient mass concen- from diVerent sources.10 Tuch et al. investigated the variation trations of small particles and a range of indices of health.1–4 in particle number and mass concentrations in the size range The results of these studies and animal toxicology and in vitro 0.01–2.5 mm on an inner city sampling site.They suggest that experiments support the hypothesis that both physical (particle ‘particles larger than 2.5 mm (or even larger than 0.5 mm) are size, shape, surface) and chemical (dissolved and leached rare in the European urban environment’.11 As PAHs are the chemicals, surface catalytic reactions) properties of the par- result of incomplete combustion, they are a potential marker ticles are involved in toxic, genotoxic and carcinogenic health for particles from combustion sources.12 eVect mechanisms of inhaled particulates.As particles with diameters <0.1 mm (termed ultrafine Pagano et al.investigated the mutagenicity of total (PM-10) particles) coagulate relatively fast ( lifetimes <1 h),13 diVerand particle size fractions of urban particulates.5 They found ences in particle size distributions with the distance of the no correlation between total or coarse particle concentrations sampling site from major sources such as busy roads are in air and the mutagenic activity but did find correlations with expected, especially for particles <1 mm.These changes in size smaller particle size; moreover, the finer the particles, the distributions are expected to be accompanied by changes in greater is the mutagenicity. Particle toxicity and carcinogenicity concentration of chemical compounds in the size classes.are enhanced by numerous organic constituents, e.g. PAHs Obviously, changes in observed particle size distributions are and oxy- and nitro-PAHs. In the urban atmosphere PAHs are influenced by meteorological conditions (e.g., wind direction strongly associated with fine particles.6,7 The emissions of and speed, relative humidity, temperature and ground level automobiles, especially of diesel engines, are a major source thermal inversions).14 The aim of this study was to investigate of fine and ultrafine particles in urban environments.The mass the variability in the observed size distribution of particle distributions of particulate emissions from modern diesel adsorbed PAHs on an inner city sampling site depending on engines usually exhibit three log-normal modes that are centred diVerent wind directions and on the distance from a crossing at aerodynamic particle diameters of 0.09, 0.2 and 0.7–1 mm,8 with heavy traYc.whereas spark ignition vehicles exhibit bimodal distributions with maximum particle numbers at 0.04–0.06 and 0.9–1.4 mm.9 Experimental Research by Noble and Prather indicates that a connection may exist between particle size, composition and source.The Sampling was performed in Munich in 1994 and 1996–97. The sampling site is located northeast of a crossing of roads with heavy traYc. North of the sampling site there is a railway and †Presented at AIRMON ’99, Geilo, Norway, February 10–14, 1999. J. Environ. Monit., 1999, 1, 357–360 357northeast of the site is a large inner city park.The environs are strongly correlated with each other (Person correlation coeYcient r0.84, p=0.0001). There are no statistically sig- of the sampling site are shown in Fig. 1. The oYcial data of the daily traYc census from the city administration at the nificant outliers detectable except pyrene in sampling period 2 (sample ID Pa2). In this summer period the pyrene concen- crossing are 36 000 cars plus 2400 trucks on one road and 13 000 cars plus 1000 trucks on the other.trations in the samples were significantly lower than those of the other PAHs than in the other samples. We assume that Samples were taken at two diVerent distances from the crossing, 10 m (site A) and approximately 80 m (site B). Six- photochemical reactions of pyrene and not evaporation losses during sampling are responsible for the relatively lower concen- stage Berner low-pressure cascade impactors at a flow rate of 79.8 l min-1 were used for sampling.Uncoated aluminum foils trations detected. This assumption is supported by the fluoranthene (b.p. lower than that of pyrene) concentrations, which were employed as the sampling substrate.The particles were separated into the size ranges 0.04–0.14, 0.14–0.49, 0.49–1.72, do not exhibit this reduction. The PAH concentrations are strongly correlated with the daily average concentrations of 1.72–6.0 and 6.0–21.0 mm with geometric mean diameters of 0.075, 0.26, 0.92, 3.2 and 11.2 mm, respectively. Owing to the NO (r=0.88, p=0.0001) and CO (r=0.82, p=0.0001). The constant PAH pattern we found for all our samples is an low PAH concentrations on coarse particles, the fractions >1.72 mm were combined for each sample.Parallel to sampling indicator that the same sources predominate in all the sampling periods. Although no significant diVerences in the PAH pattern the meteorological conditions of wind direction, wind speed, relative humidity and temperature and the concentrations of were observed even in the single size ranges of the sampled particulates, diVerent distributions of the PAHs within the size CO, O3, NO and NO2 (30 min averages) were measured.Table 1 lists the sampling periods and the average values of classes were obvious. the above parameters for each sampling period. Samples were extracted with dichloromethane in an Size distributions of the particle associated PAHs ultrasonic bath, fractionated by column chromatography and analyzed by HPLC according to a previously published In 1994 we took samples at site A at a 10 m distance from the crossing.In each sample from these sampling periods we found method.15 For this study quantitative data were measured for fluoranthene, pyrene, chrysene, benzo[b]fluoranthene, benzo[-e distribution of the particle associated PAHs in the particle size classes; 45–55% of the total amount of PAHs was k]fluoranthene, benzo[a]pyrene and benzo[ ghi ]perylene. found on the first impactor stage (0.04–0.14 mm, geometric mean diameter 0.075 mm).Hence we assumed that this distri- Results and discussion bution is typical of an inner city situation with freshly generated aerosol from motor vehicles.Concentrations of the PAHs In 1996 and 1997 we repeated the measurements at this The concentrations of the PAHs in the investigated samples sampling location. Unfortunately, we were not able to take are given in Table 2. The total concentration of the quantified the samples at exactly the same place until the end of 1997.PAHs ranged from 1.7 to 15.2 ng m-3. In order to identify The new sampling site was about 80 m from the crossing (site diVerences in the PAH patterns, we added the PAH concen- B). Surprisingly, in our sampling period in December 1996 we trations from the single impactor stages to the total concen- measured PAH distributions in the particle size classes similar trations of the individual PAHs.These total concentrations to those that we found to be more representative of sampling sites at the outskirts of cities.15,16 In these samples the maximum amount of PAHs was found in the size range 0.14–1.72 mm. The greater distance from the crossing area, which is a strong local source of PAHs and fine aerosol, could be a possible reason for these diVerences in the observed PAH distributions.In order to investigate the influence of the distance we ran another sampling period and took parallel samples at 10 m (site A) and 80 m (site B) from the crossing. The evaluation of the data we obtained from these samples led to no distinct result. The total concentrations of the PAHs were equal at both sites except on the last day (Pa4/8).On this day, with wind from the crossing the PAH concentrations are signifi- cantly lower at the sampling site further from the crossing. The diVerences in the size distributions of the PAHs in these parallel samples are very small and in most cases not crucial. Even on the only day with wind from the crossing area no significant diVerences in the size distribution were observed (Fig. 2b). Analyzing the data from all sampling periods, we found a strong connection between the observed PAH distribution in the particle size ranges and the wind direction. Depending on the wind direction, three diVerent distributions with maximum PAH concentration in a single size range were observed. The maximum PAH concentration on very small particles was observed with wind from west to southwest (Fig. 3). On these days the wind was blowing directly from the crossing area or the roads with heavy traYc; 45–55% of the total amount of PAHs was found on the first impactor stage with a geometric mean diameter of 75 nm. On days with changing wind directions from northeast to southeast we found the maximum Fig. 1 Environs of the sampling site. PAH concentrations on particles with a geometric mean diam- 358 J.Environ. Monit., 1999, 1, 357–360Table 1 Sampling periods, average values of temperature (T), relative humidity (RH), windspeed (WS) and concentrations of ozone, nitrogen oxides and carbon monoxide during the sampling Sample Sampling RH WS/ O3/ NO/ NO2/ CO/ ID period T/°C (%) ms-1 mg m-3 mg m-3 mg m-3 mg m-3 Pa1/1 02.03.94–03.03.94 6.8 72 2.1 31 53 33 1.5 Pa1/2 03.03.94–04.03.94 8.4 63 2.1 27 60 36 1.7 Pa2/1 16.08.94–17.08.94 20.8 46 0.9 63 41 47 1.4 Pa2/2 17.08.94–18.08.94 17.7 72 1.0 40 69 64 1.4 Pa2/3 18.08.94–19.08.94 17.0 54 1.0 26 76 48 1.5 Pa3/1 09.12.96–10.12.96 -1.9 87 1.4 4 67 46 1.2 Pa3/2 10.12.96–11.12.96 0.1 82 0.7 4 162 59 2.2 Pa3/3 11.12.96–12.12.96 -1.5 87 0.6 4 182 65 2.1 Pa3/4 12.12.96–13.12.96 0.5 79 0.5 4 381 89 3.7 Pa3/5 13.12.96–14.12.96 4.4 85 1.1 5 191 69 3.0 Pa3/6 16.12.96–17.12.96 1.1 78 1.0 5 160 61 2.1 Pa3/7 17.12.96–18.12.96 5.1 78 0.6 7 233 76 3.1 Pa4/1 28.10.97–29.10.97 -0.6 57 4.7 38 8 17 0.9 Pa4/2 29.10.97–30.10.97 0.6 54 4.0 31 8 24 1.0 Pa4/3 30.10.97–31.10.97 3.4 48 1.9 18 48 30 1.4 Pa4/4 02.11.97–03.11.97 3.5 71 0.0 5 130 20 2.9 Pa4/5 03.11.97–04.11.97 4.2 68 0.2 23 13 37 1.2 Pa4/6 04.11.97–05.11.97 3.5 74 0.0 1 138 9 2.5 Pa4/7 05.11.97–06.11.97 9.3 64 0.1 1 82 29 2.0 Pa4/8 06.11.97–07.11.97 17.5 47 0.1 16 51 30 1.6 Table 2 Total concentrations of fluoranthene (Fla), pyrene (Pyr), chrysene (Chr), benzo[b]fluoranthene+benzo[k]fluoranthene (Bbk), benzo[a]pyrene (BaP) and benzo[ ghi]perylene (Bgh) in the samples, totalled over all impactor stages Sample Sample Fla/ Pyr/ Chr/ Bbk/ BaP/ Bgh/ Total/ ID volume/m3 Site pg m-3 pg m-3 pg m-3 pg m-3 pg m-3 pg m-3 pg m-3 Pa1/1 113 A 880 1200 550 1000 510 1000 5140 Pa1/2 114 A 710 940 510 1000 520 900 4580 Pa2/1 103 A 560 100 390 660 290 630 2630 Pa2/2 110 A 640 240 550 740 330 560 3060 Pa2/3 115 A 500 200 490 810 350 710 3060 Pa3/1 103 B 970 850 500 1600 880 770 5570 Pa3/2 101 B 1600 1610 1900 3200 1400 1900 1610 Pa3/3 109 B 890 980 670 1900 820 1100 6360 Pa3/4 110 B 2100 2200 2000 4200 1700 3000 15200 Pa3/5 130 B 490 510 990 1500 760 1400 5650 Pa3/6 109 B 760 770 1100 1700 820 1300 6450 Pa3/7 108 B 750 850 1400 1800 1000 1800 7600 Pa4/1A 116 A 740 660 400 1000 360 510 3670 Pa4/1B 116 B 730 690 430 1000 370 440 3660 Pa4/2A 111 A 720 610 350 1000 300 370 3350 Pa4/2B 111 B 700 520 340 820 250 310 2940 Pa4/3A 112 A 1210 1100 680 1400 490 580 5460 Pa4/3B 112 B 1130 930 560 1300 410 490 4820 Pa4/4A 98 A 1010 1100 1000 1500 680 920 6210 Pa4/4B 98 B 1090 1100 1200 1900 810 940 7040 Pa4/5A 113 A 590 470 360 990 230 400 3040 Pa4/5B 113 B 620 490 360 1000 240 310 3020 Pa4/6A 107 A 1340 1200 1500 1800 850 960 7650 Pa4/6B 107 B 1370 1100 1700 2400 1000 1100 8670 Pa4/7A 112 A 1010 840 1100 4300 1600 2300 11150 Pa4/7B 112 B 1030 890 1000 4500 1600 1800 10820 Pa4/8A 111 A 450 570 450 610 300 400 2780 Pa4/8B 111 B 190 200 290 510 130 340 1660 Fig. 3 Average size distribution of particle adsorbed PAHs and wind Fig. 2 Comparison of size distributions of particle adsorbed PAHs with sampling at diVerent distances from the crossing (A=10 m, B= direction (number of 30 min averages) at the samplings Pa1/1, Pa1/2, Pa2/1, Pa2/2, Pa2/3, Pa4/8A and Pa4/8B.Wind coming from the 80 m). The mean wind directions were southeast to east with sampling Pa4/1 (a) and southwest to west with sampling Pa5/8 (b). crossing. PAH concentration range, 1.7–5.1 ng m-3. J. Environ. Monit., 1999, 1, 357–360 359The total PAH concentrations are not significantly influenced by the wind direction.The variability of the PAH concentrations detected with one wind direction is as high as the variability from direction to direction. The diVerent size distributions of particle adsorbed PAHs are correlated with the distance from the sampling site to sources of combustion aerosol. The shorter the distance to the source(s), the higher was the proportion of PAHs on small particles. With wind direct from the crossing area, a strong Fig. 4 Size distribution of particle adsorbed PAHs and wind direction local source of fine and ultrafine aerosol, the maximum PAH (number of 30 min averages) at the sampling Pa3/4. Wind coming concentration was found on the smallest particles. Wind from from built-up area. PAH concentration, 15.1 ng m-3.the built-up area near the sampling site, a diVuse and more distant source of aerosol, shows a shift in the PAH distribution to larger particles. A further shift to a higher proportion of the PAHs on larger particles was found with wind from the park and thus from the diVuse sources behind it. We conclude that the distribution of particle adsorbed PAHs within diVerent particle size classes is substantially influenced by the distance from the sampling site to strong sources of PAH loaded particulate matter.References Fig. 5 Average size distribution of particle adsorbed PAHs and wind direction (number of 30 min averages) at the samplings Pa2/1, Pa3/1, 1 J. Pekkanen, K. L. Timonen, J. Ruuskanen, A. Reponen and Pa3/2, Pa3/5, Pa3/6, Pa4/5A and Pa4/5B.Wind coming from the park A. Mirme, Environ. Res., 1997, 74, 24. nearby. PAH concentration range, 2.6–11.7 ng m-3. 2 P. Penttinen, K. L. Timonen, P. Tiittanen, M. Vallius, A. Mirme, J. Ruuskanen and J. Pekkanen, Resp. Crit. Care Med., 1998, 157, A878 (Abstract). 3 J. Schwartz, D. W. Dockery and L. M. Neas, J. Air Waste Manage. Assoc., 1996, 46, 927. 4 K. Ito and G. D. Thurston, J.Expos. Anal. Environ. Epidemiol., 1996, 6, 79. 5 P. Pagano, T. de Zaiacomo, E. Scarcella, S. Bruni and M. Calamosca, Environ. Sci. Technol., 1996, 30, 3512. 6 C. Venkataraman, J. M. Lyons and S. K. Friedlander, Environ. Sci. Technol., 1994, 28, 555. 7 C. Venkataraman and S. K. Friedlander, Environ. Sci. Technol., Fig. 6 Average size distribution of particle adsorbed PAHs and wind 1994, 28, 563. 8 V. M. Kerminen, T. E. Makela, C. H. Ojanen, R. E. Hillamo, direction (number of 30 min averages) at the samplings Pa3/3, Pa3/7, Pa4/6A, Pa4/6B, Pa4/7A and Pa4/7B. Wind coming from the park J. K. Vilhunen, L. Rantanen, N. Havers, A. von Bohlen and D. Klockow, Environ. Sci. Technol., 1997, 31, 1883. and main street. PAH concentration range, 6.3–11.1 ng m-3. 9 Z. D.Ristovski, L. Morawska, N. D. Bofinger and J. Hitchins, Environ. Sci. Technol., 1998, 32, 3845. 10 C. A. Noble and K. A. Prather, Environ. Sci. Technol., 1996, eter of 260 nm (Fig. 4). In this case the wind was blowing 30, 2667. from the built-up area near the sampling site. The third 11 T. Tuch, P. Brand, H. E. Wichmann and J. Heyder, Atmos. distribution with the maximum PAHconcentration on particles Environ., 1997, 31, 4193. 12 C. K. Li and R. M. Kamens, Atmos. Environ., Part A, 1993, with a geometric mean diameter of 920 nm we found on days 27, 523. with the main wind direction from northeast to east (Fig. 5). 13 D. Y. H. Pui and D. R. Chen, J. Aerosol Sci., 1997, 28, 539. On these days the wind was blowing mainly from the direction 14 A. Trier, Atmos. Environ., 1997, 31, 909. of the city park nearby. Distributions with no unique maximum 15 J. Schnelle, T. Ja�nsch, K. Wolf, I. Gebefu� gi and A. Kettrup, in PAH concentration in a distinct particle size range were Chemosphere, 1995, 31, 3119. observed on days with wind from the park and the main 16 J. Schnelle, K. Wolf, G. Frank, B. Hietel, I. Gebefu� gi and A. Kettrup, Analyst, 1996, 121, 1301. street. This is wind from northeast to south (Fig. 6). In this case we found a mixture of the distributions we observed on days with the wind mainly from northeast and southeast. Paper 9/01494B 360 J. Environ. Monit., 1999, 1, 357&nda

ISSN:1464-0325    

DOI:10.1039/a901494b

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Air sampling of fungal spores on filters. An investigation on passive sampling and viability† A° sa Na�sman,*ab Go�ran Blomquistb and Jan-Olof Levinab aUmea° University, Department of Public Health and Clinical Medicine, Occupational Medicine, S-901 85 Umea°, Sweden, E-mail: asa.nasman@niwl.se; Fax: +46 90 7865027; Tel:+46 90 7869071 bNational Institute for Working Life, Department of Chemistry, Box 7654, S-907 13 Umea°, Sweden Received 9th April 1999, Accepted 9th June 1999 In this study, glycerol was tested as a collection substrate for passive bioaerosol sampling.Filters (mixed cellulose acetate and nitrate) were soaked in glycerol and exposed for an aerosol from three diVerent fungal species: Penicillum commune, Aspergillus versicolor and Paecilomyces variotii.The passive sampling method was compared with a closed-face polycarbonate filter sampling method. Exposure was performed in an exposure chamber. The total number of spores was determined by microscopic techniques, and the cultivable number was determined by cultivation on Malt Extract Agar dishes. The glycerol soaked filter demonstrated a good correlation with the closedface sampler with regard to the total count.Spores stored in a pumped filter cassette were not aVected by storage for up to 7 days. On the other hand, the culturability of the spores was markedly decreased after 1 day when stored on glycerol soaked filters. liquid have been used.12 These instruments, however, are Introduction usually not suitable for personal sampling, and filters have The measurement of micro-organisms is an important tool for been used to monitor the exposure in the work environment.13 investigating diseases in the work environment.DiVerent tech- Currently, there is a need for small and easily handled niques, such as impaction, impingement or filtration, have samplers in the work environment. The sampler should not been used for sampling micro-organisms in diVerent work interfere with the working procedure, i.e.be small and light. environments.1 The determination of the number of micro- It should also be easy to use. The best situation would be if organisms in the sample is usually performed either by the worker was able to perform the sampling himself and send microscopy or by cultivation.2–4 Microscopic methods provide the sample by mail for analysis at the laboratory.In order to the total number of single micro-organisms, cultivable as well develop such a sampler, it is necessary to find a suitable as non-cultivable, while cultivable methods determine only collection substrate that works for passive sampling, and also colony forming units which may be composed of single spores to determine how storage aVects the culturability of the spores.as well as aggregates of spores. Several studies show that the Passive sampling has been used for sampling dust in diVerent cultivable number of spores is markedly lower than the total work environments. Brown et al.13 used electrostatically number.5–7 This may be caused by a loss of viability during charged substrates to collect airborne dust, while Vinzents14 sampling,8,9 an eVect of aggregation7 or by the use of inad- used a tape mounted on a sampler in three diVerent directions.equate growth substrate. Since there is always a fraction of So far these passive samplers have not been used to assess the non-cultivable spores that still may cause trouble for humans exposure of micro-organisms in the work environment.such as allergic reactions and fever, 10 it is important to make In this study, a collection substrate for passive sampling sure that all spores are taken into account. This implies that was investigated. A filter soaked in glycerol was used as a the sampling method used for assessing the exposure in the passive sampler. This sampling method was compared with work environment must not only collect precise aerosol frac- closed-face filter cassettes.Both the total count and the cultitions, as defined by the CEN standard EN 481,11 but also vable counts were compared after 0, 1, 2 and 7 days of storage. prevent the micro-organisms from losing their viability during sampling and analysis. How the viability of fungal spores is aVected by storage Materials and methods between sampling and analyses is poorly explored. The micro- Cultivation of fungal spores organisms may lose their viability due to stress during sampling (i.e.method of collection and handling of sample), the type of Penicillum commune (Pegasus LAB AB, Uppsala, Sweden) and growth medium used, the aerosolization method, the tempera- Paecilomyces variotii (UPSC 1766) were cultured in Petri ture and the humidity.9 These eVects diVer between diVerent dishes (9 cm in diameter) on Malt Extract Agar (MEA), micro-organisms and sampling methods employed.Bacteria composed of 1.5% Bacto-Agar (Difco, Detroit, MI, USA), are usually more sensitive than spores of fungi and acti- 2% Malt Extract (Oxoid L39, Basingstoke, Hampshire, UK) nomycetes when sampled on filters.8 Therefore, samplers or and deionized water.Aspergillus versicolor (UPSC 2027) was impactors that collect the bacteria on a semisolid gel or in a cultured on MEA plates plus 20% sucrose, M20 plates (J. T. Baker B. V., Deventer, Netherlands). P. commune was cultured for 7 days at 22 °C and afterwards the cultivation plates were †Presented at AIRMON ’99, Geilo, Norway, February 10–14, 1999.J. Environ. Monit., 1999, 1, 361–365 361stored at +5 °C for further usage after 8–32 days. A. versicolor the filter cassettes was 1.88±0.06 l min-1. The filter cassettes were analysed immediately after sampling. was cultured for 14–21 days at 22 °C and then either used immediately or stored for 5–36 days at +5 °C. P. variotii was cultured for 7 days at 22°C and then the cultivation plates were stored at+5 °C for another 6–13 days.After the sampling Determination of cultivable and non-cultivable spores procedure, the spores from P. commune and A. versicolor were After the sampling period, the inlet and the outlet connections cultivated on MEA plates. P. variotii was cultured on MEA of the filter cassettes were plugged.All filters were moved to with antibiotics [3 ml l-1 penicillin–streptomycin 10 000 a smaller sealed chamber for storage at either +22 °C or IU ml–10 000 ml ml-1 (Gibco BLR, Life Technologies, Ta� by, +5 °C (P. commune). Four HA filters and two polycarbonate Sweden)]. filters were analysed each time. Analyses were performed after 0, 1, 2 and 7 days. Laboratory generation and sampling of spores The passive filters were placed in a sterile beaker, covered HA (mixed cellulose acetate and nitrate) filters with a pore with a lid, and 3 ml of sterile filtered 0.05% Tween-80 was size of 0.45 mm and measuring 25 mm in diameter (Millipore added.Five ml of sterile filtered 0.05% Tween-80 was added Co., Bedford, PA, USA) were first soaked in glycerol (BDH to the filter cassettes.All filters were then vortexed for 30 s in Laboratory Supplies, Poole, Dorset, UK), and left hanging order to suspend the fungal spores. The total number of spores for 1 h to remove excess glycerol. The remaining droplet was was then determined by counting in a Bu� rker chamber. Nine removed with a Kleenex tissue. These filters were then used A-squares were counted three times per sample.When the for passive sampling. total number exceeded 200 spores, three diagonal A-squares Polycarbonate filters, with a pore size of 0.45 mm and a were counted. diameter of 37 mm, inside polypropylene aerosol monitors After the extraction procedure, 1 ml was used for serial (MSI, Westboro, MA, USA) were used for pumped sampling. dilution. Cultivable counts were analysed by spreading 100 ml The mean air flow through the filter cassette during sampling of the original solution, diluted 10, 100 and 1000 times for the was 1.06±0.07 l min-1.passive filters, and 100, 1000 and 10 000 times for the pumped All filters were placed in an even pattern in a chamber made filters, on MEA plates. P. variotii was cultured on MEA plates of polyacrylate with a voluproximately 1 m3 with antibiotics. Three cultivation plates were used for each (120×100×80 cm).The filters were divided into three diVerent dilution. These were cultivated for 7 days at 22 °C before the positions in the box corresponding to the left, the middle and number of colony forming units was determined. This number the right (Fig. 1). Air was blown (50 l min-1) at the culture represents the cultivable part of the fungi.The cultivable dish, placed in the middle of the chamber, through a tube number was then divided by the total number of spores in ending approximately 5 cm above the culture dish. This was order to obtain the percentage of cultivable spores. done to produce an aerosol in the chamber. The exposure time was 1 h in all experiments with P.commune and 2 h with A. versicolor and P. variotii. In order to investigate the cultivable number on a cultivation Results and discussion plate, a cultivation plate of P. variotii, which was matched Validation of the exposure chamber with the plate used for aerosolization, was rinsed with sterile filtered 0.05% Tween-80 (KEBO AB, Stockholm, Sweden) The mean value of the spore concentration in the exposure before the experiment was started.This sample is referred to chamber varied between 7×105 and 1×107 for the filter as the reference sample. The spore solution was then treated cassettes and between 3×105 and 1×106 for the passive filters as below. The same thing was done afterwards with P. in the diVerent P. commune experiments.In the A. versicolor commune or A. versicolor. Two plates of P. commune and A. experiments, the concentration varied between 8×105 and versicolor were used in each experiment; the spores were either 3×106 and 4.0×104 and 4.4×104 for the filter cassettes and rinsed by sterile filtered 0.05% Tween-80 (this sample is referred the passive filters, respectively. The corresponding values for to as the reference sample) or aerosolized in the exposure P.variotii were 3×105–8×105 and 3×104–6×104, respectchamber as above. During this experiment, four pumped ively. The number of spores that were aerosolized when air polycarbonate filters were used. The medium air flow through was blown at a cultivation plate varies considerably between diVerent species. Of the three diVerent species investigated in this study, P.commune was easiest to aerosolize. P. variotii and A. versicolor spores were harder to render airborne from the cultivation plate, and therefore the sampling time was increased to 2 h. Normalized values for the diVerent positions in the exposure chamber (Fig. 1) are shown in Tables 1 and 2. Positions closer to the walls gave lower spore counts.This is caused by the change in air flow close to the walls. No sampling was therefore performed closer than 20 cm to the wall. An ANOVA test was conducted at 95% confidence interval comparing the diVerent sampling positions in five P. commune experiments. The results showed that there was no significant diVerence between the diVerent positions for pumped sampling, however there was a significant diVerence between the passive sampling positions.The results are shown in Tables 3 and 4. As this study is based on the percentage of cultivable spores Fig. 1 The diVerent sampling positions in the exposure chamber. The sampled at each position, or mean values for a complete cones represent the filter cassette samplers and the circles represent experiment in comparison with other experiments, it is assumed the passive samplers.All samplers to the right are named R1–R9, the that the spread in concentration in the exposure chamber did samplers in the middle M1–M6 and the samplers to the left L1–L9 (see Tables 1 and 2). not aVect the results. 362 J. Environ. Monit., 1999, 1, 361–365Table 1 Distribution of spore concentrations at the diVerent sampling positions.Expressed as normalized values for passive sampling. Positions according to Fig. 1 Position P. commune A. versicolor P. variotii R1 0.4 1.8 0.9 R3 1.4 1.2 1.1 R5 1.0 1.3 0.8 R7 1.0 1.3 0.9 R9 1.0 1.5 1.2 M1 1.1 0.8 1.0 M2 0.7 0.7 0.8 M3 1.1 0.6 0.9 M4 1.5 1.5 1.6 Fig. 2 Correlation between filter cassette sampling and passive M5 1.1 1.0 1.7 sampling when total number was compared.Each point represents M6 1.0 0.8 1.1 the mean value of the total number from a single experiment, passive L1 0.7 0.9 0.8 sampling versus filter cassette sampling. Filled diamonds indicate L3 0.8 0.6 0.6 P. variotii, open squares A. versicolor and filled triangles P. commune. L5 1.0 0.9 0.8 L7 1.2 0.8 1.1 L9 1.0 0.9 0.8 Influence of sampling method on culturability Pumped sampling.Samples collected with the ordinary filter Table 2 Distribution of spore concentrations at the diVerent sampling cassette showed a decrease of about 50% in culturability positions. Values expressed as normalized values for filter cassette (Fig. 3, 5 and 6). The loss in culturability is seen immediately sampling. Positions according to Fig. 1 after sampling and is not significantly aVected by storage over several days. Previous studies have shown that the culturability Position P. commune A. versicolor P. variotii of fungal spores is decreased when a pumped sampling method is used.5–7 When the reference samples (samples not submitted R2 1.2 1.8 1.1 R4 0.9 1.1 0.8 to the sampling step) for all three species tested in this study R6 0.7 0.8 0.8 were analysed, the result showed a non-cultivable fraction of R8 1.2 1.3 0.7 about 30% (Fig. 4 and 6). This means that moulds consist of L2 0.7 1.0 0.7 quite a large fraction of spores that are already non-cultivable L4 1.4 0.9 1.8 before sampling is performed. A. versicolor and P. commune L6 0.9 0.7 1.0 showed no significant diVerence in culturability when the L8 0.9 0.4 1.0 reference sample was compared with spores collected by pumped sampling (Fig. 4). P. variotii showed a decrease in Table 3 ANOVA table for the diVerent positions in the exposure culturability of 30% after pumped sampling compared to the chamber for passive sampling. SS=square sum, df=degrees of free- reference sample (Fig. 6). A. versicolor and P. commune dom, MS=mean square, F=calculated F-value showed no decrease in culturability (Fig. 3 and 5) when sampled on pumped filters, compared with P. variotii that Source of variation SS df MS F P-value tended to loose culturability with storage time (Fig. 6). After Position 1.63×1011 15 1.1×1010 1.90 3.6×10-2 storage at +22 °C for 7 days, only half of the spores remained Experiment 2.08×1011 4 5.2×1010 9.3 6.2×10-6 cultivable.Error 3.35×1011 60 5.6×109 Total 7.05×1011 79 Passive sampling. All three species were aVected in a negative manner by glycerol. P. commune appeared to stand a short time of exposure to glycerol and was unaVected after 1 h of Table 4 ANOVA table for the diVerent positions in the exposure sampling (Fig. 7). After 1 day of storage, the cultivable chamber for filter cassette sampling.SS=square sum, df=degrees of fraction was 8% and decreased to zero after further storage. freedom, MS=mean square, F=calculated F-value A. versicolor and P. variotii were aVected immediately. P. variotii showed a cultivable fraction of 30% after 2 h of Source of variation SS df MS F P-value sampling, with no cultivable spores after 1 day of storage Position 4.3×1011 7 6.1×1010 0.76 6.2×10-1 (Fig. 8). A. versicolor was most aVected, i.e., after 2 h of Experiment 1.1×1012 4 2.7×1011 3.4 2.1×10-2 sampling only 14% was cultivable (Fig. 9). Further storage Error 2.2×1012 28 8.0×1010 reduced the cultivable fraction to zero. Total 3.8×1012 39 Passive filters soaked in glycerol reduce the culturability of EYciency of the sampling methods for total spore sampling The passive filter method was validated against a traditional pumped method, in order to compare two diVerent sampling techniques.Both the total count and cultivable count were compared. The total number of spores collected by the filter cassettes was 2–22 times larger than the amount collected on the passive filters. A coeYcient of correlation of 0.8 (Fig. 2) between the two sampling methods was achieved when the total number was compared.This indicates that these filters may have the potential to be used as collection substrate in a passive sampling device, if they are built into a sampling device Fig. 3 Cultivable number of P. commune for filter cassette sampling. Values expressed as the mean value of two experiments. and calibrated against a pumped sampler.J. Environ. Monit., 1999, 1, 361–365 363Fig. 7 Cultivable number of P. commune for passive sampling. Values expressed as the mean value of two experiments. Fig. 4 Cultivable number of reference sample and mean value of the four filter cassettes used in the same experiment. A, P. commune; B, A. versicolor. Fig. 8 Cultivable number of P. variotii for passive sampling.Values expressed as the mean value of two experiments. Fig. 5 Cultivable number of A. versicolor for filter cassette sampling. Values expressed as the mean value of two experiments. Fig. 9 Cultivable number of A. versicolor for passive sampling. Values expressed as the mean value of two experiments. Stability of experiment culture The purpose of the experiment was to study the influence of storage time and temperature on the culturability of the spores in order to investigate how a prolonged storage time before sampling and diVerent storage temperatures after sampling aVect the culturability.The cultivable fraction of P. commune was increased by 40% if the experiment culture was stored at +5 °C for 32 days before sampling (compared with 8 days), when pumped sampling was used (Fig. 3 and 10B). When passive sampling was Fig. 6 Cultivable number of P. variotii for filter cassette sampling. used, a longer storage time at +5 °C gave an increase of 10% Values expressed as the mean value of two experiments. Noll= (Fig. 7 and 10A). The largest eVect was observed when the reference sample (not submitted to sampling). filters were stored for more than 1 day.On the seventh day of storage, 7% of the spores were still cultivable. A. versicolor was not aVected by a longer storage phase. Regarding temperature stability after sampling, when all the fungi and are therefore not suitable for use when it is necessary to identify the species. This is probably due to filters were stored at +5 °C instead of +22 °C after sampling, an increased culturability of about 31% was seen for both dehydration since the glycerol used contained no water.Other substrates, such as polymer solutions with their rather sampling methods (Fig. 3, 7 and 11). Passive sampling showed an increased culturability after 24 h of storage; on day 2, the high water content (80–90%),15 might be better in this consideration. culturability was 9% (Fig. 7 and 11A). 364 J. Environ. Monit., 1999, 1, 361–365important as a large fraction of the spores are non-cultivable already before sampling. This means, regardless of the sampling method, a large fraction of spores will be missed if culture-based methods are used for determination. On the other hand, if a non-culture-based method is used, it is diYcult to determine what species are being dealt with.Pumped filter cassettes show good characteristics for sampling of fungal spores in both aspects. The cultivable fraction is stable during storage and is of the same magnitude as for normal growing conditions. Glycerol impregnated filters may be used as a collection substrate for passive sampling as long as only the total number of spores is determined.In order to produce a passive sampler that works for the cultural fraction as well, other substrates need to be investigated. An alternative could be water-based polymers, such as polyethylene glycols. Acknowledgements The excellent assistance of Sven-Olof Westermark (National Institute for Working Life, Department of Chemistry, Umea°, Sweden) and the helpful advice of Hans Stenlund (Department Fig. 10 Cultivable number of P. commune. Cultivation plate stored at of Epidemiology and Public Health, Umea° University, Umea°, +5 °C for 29 days before aerosolized. A, passive sampling; B, filter Sweden) are gratefully acknowledged. cassette sampling. References 1 G. Blomquist, Analyst, 1994, 119, 53. 2 U. Palmgren, G. Stro�m, G. Blomquist and P. Malmberg, J. Appl.Bact., 1986, 61, 401. 3 Air Quality Monographs, vol. 2 Health Implications of Fungi in Indoor Environments, ed. R. A. Samson, B. Flannigan, M. E. Flannigan, A. P. VerhoeV, O. C. G. Adan and E. S. Hoekstra, Elsevier, Amsterdam, 1994, ch. 2. 4 W. Eduard and D. Heederik, Am. Ind. Hyg. Assoc. J., 1998, 59, 113. 5 B. Crook, S. J. Futter, W. D. GriYths, L. C. Kenny, S. Stagg, J. D. StancliVe and I.W. Stewart, Ann. Occup. Hyg., 1997, 41, 677. 6 K. Karlsson and P. Malmberg, Scand J. Work Environ. Health, 1989, 15, 353. 7 W. Eduard, J. Lacey, K. Karlsson, U. Palmgren, G. Stro�m and G. Blomquist, Am. Ind. Hyg. Assoc. J., 1990, 51, 427. 8 B. Crook, L. C. Kenny, S. Stagg, J. D. StancliVe, S. J. Futter, W. D. GriYths and I.W. Stewart, Ann. Occup. Hyg., 1997, 41, 647. 9 W.D.GriYths and G. A. L. DeCosmo, J. Aerosol Sci., 1994, 25, 1425. 10 P. Malmberg, Arbete och Ha�lsa, 1991, 50, 39. 11 Workplace Atmospheres—Size Fraction Definitions for Measurement of Airborne Particles, EN 48151993, European Fig. 11 Cultivable number of P. commune. Cultivation plate stored at Standard, Brussels, 1993. +5 °C for 35 days before aerosolized. Samples stored at +5 °C. 12 E. Welam-Henningsson and M. S. Ahlberg, J. Aerosol Sci., 1994, A, passive sampling; B, filter cassette sampling. 25, 1459. 13 R. C. Brown, M. A. Hemingway, D. Wake and A. Thorpe, Analyst, 1996, 121, 1241. Conclusions 14 P. S. Vinzents, Ann. Occup. Hyg., 1996, 40, 261. 15 P-A° . Albertsson, Partition of Cell Particles and Macromolecules, Since it is important to determine both the total number and Wiley, New York, 3rd edn., 1986, pp. 73–111. the cultivable number of fungal spores, it is necessary to find a method that is reliable in both aspects. This is especially Paper 9/02832C J. Environ. Monit., 1999, 1, 361–3

ISSN:1464-0325    

DOI:10.1039/a902832c

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Assessment of occupational exposure to diesel fumes—parameter optimization of the thermal coulometric measurement method for carbon† Vincent Perret,* Cong K. Huynh, Pierre-Olivier Droz, Trinh Vu Duc and Michel Guillemin IST , Institute of Occupational Health Sciences, Rue du Bugnon 19, CH-1005 Lausanne, Switzerland Received 31st March 1999, Accepted 17th June 1999 ‘Elemental’ carbon (EC) is used as a surrogate to assess occupational exposure to diesel soot.EC thermal analysis needs complete desorption of organic compounds from the soot particles prior to analysis in order to minimize positive interferences and artefacts. The desorption of the organic compounds can be considered as the major step which influences the reliability of the EC determination. A systematic study was carried out to investigate the diVerent parameters of influence such as desorption temperature, desorption duration, heating rate and type of the sample on the desorption eYciency.It was found that temperature and duration are the major parameters of influence on the desorption eYciency. The influence of the sample load can be seen as a measure of the pyrolysis susceptibility of the sample.An optimized temperature program is proposed. EC, respectively). The organic fraction of the diesel particulate Introduction is first removed in helium, at ramps and steps going up to Diesel exhaust was classified in 1989 as probably carcinogenic about 850 °C. The evolved carbon is catalytically oxidized to to humans by the International Agency for Research on CO2, which is reduced (catalytically) to methane and quantified Cancer1 and is classified in category 2b because there is using a flame ionization detector (FID).The temperature is suYcient evidence for its carcinogenicity in animals and some lowered and an oxygen–helium mixture is introduced into the trends in epidemiological studies. Since that time, more results sample oven.The temperature is then raised to about 940 °C from additional epidemiological studies have confirmed that to remove the remaining carbon, which is again converted to Diesel exhaust represents a significant occupational and public methane for quantification. If the diesel particulate sample health problem.2,3 contains materials that pyrolyze (form char), a portion of the Although the gaseous phase of the exhaust of diesel engines carbon removed during the second part of the analysis is contains irritant gases such as oxides of nitrogen, sulfur dioxide assigned to the organic fraction.This correction for pyrolysis and aldehydes, leading to acute eVects on workers, the chronic is accomplished through continuous monitoring of the filter hazard related to lung cancer comes from the particulate phase transmittance.The correction assumes that a decrease in filter of the exhaust and is considered as a priority in the field of transmittance during the first part of the analysis (in helium) occupational health.1,4 Present toxicological knowledge sup- is caused by charring. To correct for the thermally deposited ports the use of the carbon core of the diesel particles as the char, the split between the organic and elemental carbon is most relevant index of exposure to assess the health risk of not made until enough is oxidatively removed to bring the exposed people.5–7 filter transmittance back to its initial value. The second method Taking into account that diesel particles are mainly com- was developed in Germany and is called the coulometric posed of a core of ‘elemental’ carbon (EC) coated by organic method.12 This is a simple thermal method were the ‘elemental’ compounds such as oil residues, polycyclic aromatic hydrocarbon is defined as the carbon not removed from the sample carbons and other derivatives, the measurement methods after a given thermal treatment under an inert gas.The oYcial developed up to now have been focused on the ‘elemental’ German method has defined a thermal treatment of 8 min at carbon, which is not pure carbon but something more complex 500 °C under nitrogen.After that, oxygen is introduced and with a high proportion of carbon.8,9 The analytical challenge the temperature is increased to 800 °C; the CO2 formed is here is diVerent from the usual one aimed at the analysis of a determined by coulometry in a solution of barium perchlorate.specific molecule. In our case, the aim is to be as close to the A round robin test has been carried out to compare these diesel carbon core as possible, knowing that this core is not a two methods.13 The tested samples were either filters spiked specific and well determined chemical and mineralogical with organic compounds such as sucrose and EDTA, field species.10,11 samples taken in diVerent environments or field samples spiked Two types of methods, based on the same basic principle, with cigarette smoke.The results showed that the simple have been developed. In both methods, diesel soot samples thermal method gave results biased towards higher levels of are collected on quartz or glass fiber filters according to usual ‘elemental’ carbon for the samples containing a high pro- occupational hygiene techniques. The first method (NIOSH portion of organic compounds compared with the thermal– analytical method No. 5040) is a thermal–optical technique optical method. The positive bias in the analysis of the OC for determination of organic and elemental carbon (OC and standards is attributed largely to inadequate removal of OC during the first part of the analysis.Lack of correction for pyrolytically formed carbon (char) is also a factor. †Presented at AIRMON ’99, Geilo, Norway, February 10–14, 1999. J. Environ. Monit., 1999, 1, 367–372 367By the end of 1998, there was still a limited availability of to the equation instruments on the market to perform NIOSH method 5040.Ba2++CO2+2 OH-�BaCO3+H2O On the other hand, the coulometer is an instrument which has been on the market for a long time and has been used, for The OH- ions consumed are electrolytically reformed accordinstance, for the determination of total organic compounds in ing to water. Its availability is still assured despite the bankruptcy of 2 H2O+2 e-�H2+2 OH- the manufacturer, and production is now continued by another representative.It was therefore decided to investigate the in the back-titration in parallel with this reaction. The carbon performance of the simple thermal method further by using content of the sample is determined from the number of the coulometer, looking at the main parameters of influence: coulombs required to restore the initial alkalinity (pH#9.7) desorption temperature and duration, sample loading, heating of the absorption solution.The integrated electrolysis current rate and type of samples (pure organic compounds, diesel soot is indicated by the coulometer in the form of counts, each and cigarette smoke). The objective of the study was to count corresponds to 0.2 mg of equivalent carbon (see the improve our knowledge of the influence of these factors on Coulomat response and linearity section).the determination of ‘elemental’ carbon by a simple thermal Organic carbon is determined by using an inert gas (N2) to method. desorb adsorbed compounds at high temperature (500– 800 °C). Formation of CO2 is assured by the catalytic oxidation of the desorbed compounds. The determination of elemental Experimental carbon is performed after the desorption by combustion of Products and materials the sample under a stream of pure O2.The drift of the Coulomat due to the atmospheric CO2 Coronene (purum), barium perchlorate (puriss p.a.) and infiltration was checked before each measurement. A drift barium carbonate (puriss p.a.) were obtained from Fluka below 2 counts min-1 was considered acceptable and sub- (Buchs, Switzerland). Analytical-reagent grade anthracene, tracted as background during the measurements. The response saccharose, oxalic acid and calcium carbonate and extra-pure of the Coulomat was tested every 10 measurements with two activated charcoal were obtained fMerck (Dietikon, oxalic acid controls (50 ml of aqueous oxalic acid, 3.8 and Switzerland).Activated charcoal was conditioned at 800 °C 0.4 mg L-1 carbon concentration). The reproducibility was for 4 h under an N2 atmosphere. Nitrogen 60 (99.9999%), tested using triplicates of increasing amounts of oxalic acid. oxygen 55 (99.9995%) and helium 60 (99.9999%) were obtained from Carbagas (Liebefeld, Switzerland).Sampling Coronene and anthracene were chosen as representative of PAHs adsorbed on diesel soot14 and saccharose was chosen All quartz fiber filters (Whatman, Maidstone, Kent, UK; as a representative of highly pyrolyzable organic compounds. QM-A) were conditioned under O2 at 1000 °C for 30 min. Saccharose samples were prepared by deposition of an aqueous Instrumentation solution (10 g L-1) on a 43 cm2 quartz fiber filter. Coronene and anthracene samples were prepared by deposition and A Stro�hlein 720 DR/C Coulomat was used, with the modifi- evaporation (15 min, 120 °C) of a toluene solution on a 43 cm2 cation that the pump was replaced by carrier gas overpressure quartz fiber filter.Passive cigarette smoke samples were in order to prevent any entry of air into the system through sampled using a cyclone (CasellaTM respirable dust) in a leaks (Fig. 1). laboratory-made sampling chamber. Diesel exhaust samples were obtained using a laboratory-made mixing chamber con- Measurement method nected to the exhaust of a Fiat Ducato 2.5 diesel powered The determination of carbon is based on converting carbon- light duty truck, using a cyclone (CasellaTM respirable dust).containing compounds to CO2 and H2O by catalytic oxidation or using an oxidizing atmosphere at high temperature. Calibrations To ensure complete conversion to CO2, the actual desorp- Temperature measurement. In the Coulomat (Fig. 1), tion/combustion unit (oven I ) is followed by a CuO/Pt catalyst measurements of oven temperature are made by using a at 900 °C (oven II ) for post-oxidation.Any sulfur oxides and thermocouple placed outside the desorption quartz tube. To hydrogen chloride formed are removed from the gas stream check the relationship between the measured temperature and in oven III, which is kept at 400 °C and packed with silver the temperature inside the tube (where the sample is intro- wool. As a safety measure, a PerhydritA absorber is further duced), a calibration has been performed with a reference connected upstream of the following absorption vessel to scrub thermocouple (chromel–alumel ) placed at the same location out any sulfur dioxide residues not removed by oven III, which as the sample.The relationship was linear from 200 to 900 °C could influence the pH-dependent CO2 determination. The (n=8, slope=1.04±0.01, intercept=-8.29±4.58, r= CO2 passes together with the gas stream into the absorption 0.99984).All temperatures cited in this paper are temperatures vessel and is absorbed in alkaline Ba(ClO4)2 solution according inside the oven tube and were calculated using the regression slope determined above. Coulomat response and linearity.To check the Coulomat response, a calibration was performed using increasing amounts of oxalic acid. The linearity was checked up to 500 mg of carbon (n=30, r=0.99989). A count is equal to 0.2000±0.0006 mg of carbon, which corresponds to the manufacturer’s specifications. Data analysis Statistical analysis of the results was carried out using Systat Fig. 1 Schematic diagram of the modified Stro� hlein 702 DR/C Coulomat (pump unit removed). 5.2 for multifactorial analysis and variance analysis. 368 J. Environ. Monit., 1999, 1, 367–372Results and discussion Factors of influence The desorption of the organic compounds can be considered as the major step which influences the reliability of the EC determination. Many factors are susceptible to influence the desorption eYciency.In this paper, factors to be studied were chosen based on two criteria: factors from the analysis process and technical feasibility. The factors selected were desorption temperature, desorption duration, sample load, heating rate and sample type. Influence of temperature The influence of temperature on the desorption eYciency of two types of organic compounds, saccharose and coronene, is Fig. 3 Desorption thermogram at (solid line) 550 °C under N2 and illustrated in Fig. 2. (dotted line) 750 °C under N2 of 50 ml of aqueous saccharose solution Saccharose is a compound with a high proportion of oxygen (2 mg of carbon per ml of solution). The curves are the desorption (C12H22O11) and coronene is a PAH (C30H14). Both are strictly kinetic in counts min-1 of the CO2 detector during desorption (1 count=0.2 mg of carbon).organic compounds (the carbon content is 100% organic carbon) and should lead to an EC response of zero within experimental error (EC/TC=0%). Fig. 2 shows that the posidesorption eYciency is increased compared with a lower tive interference decrease with increase in temperature for both temperature. types of compounds.As shown in Fig. 2, the coronene desorption eYciency seems The pyrolysis of organic compounds (also known as charto reach a maximum after 800 °C (EC/TC=2–3%). The ring) during the desorption process is a major cause of artefacts saccharose desorption eYciency reaches its maximum at the and this phenomenon increases with increase in temperature. highest temperature, without any step.This could be explained Another possible cause of artefacts is the non-desorption of by a diVerent sensitivity to pyrolysis. Coronene, a PAH, seems the organic compounds because of an insuYcient temperature not to be very sensitive to thermal degradation. of desorption. Although higher temperatures increase the desorption These two phenomena are opposed: a high temperature eYciency of organic compounds, an excessive desorption tem- increases the interference by pyrolysis but also decreases it by perature could desorb the ‘elemental’ carbon present in the increasing the desorption eYciency.The increase in desorption diesel samples ( leading to a positive interference during the eYciency with increase in temperature is illustrated in Fig. 3. OC determination) and inorganic carbonaceous compounds Fig. 3 clearly shows a diVerence in the kinetic behavior such as carbonates. Fig. 4 shows the desorption of elemental during the first 3 min. At 750 °C, more organics are volatilized carbon and calcium carbonate versus temperature. during the very beginning of the desorption process as com- Fig. 4 suggests that the loss of elemental carbon will not pared with 550 °C, and more thermal decomposition products occur below 800–850 °C under N2.However, some internal are removed. This is why the total count (total area under the oxidants (e.g., metal oxides) present in the sample could curves) related to the OC removed is higher at 750 °C. oxidize part of the EC fraction during desorption under a Depending on the kind of sample, thermal degradation neutral atmosphere.15 could take place at relatively low temperatures.A higher Calcium carbonate, which occurs naturally in environmental temperature increases the thermal degradation but, on the samples, could cause a positive interference during the desorp- other hand, also enhances the desorption eYciency of nontion and/or oxidation processes. Fig. 4 suggests that desorption volatile species.Both eVects act in opposite directions. The of CaCO3 will occur at temperatures higher than 800 °C. Other results in Fig. 3 tend to show that at a higher temperature the carbonates, such as MgCO3 and Na2CO3, could decompose at lower temperatures but are less common in occupational environments with the exception of specific situations where they are used in the working process.The interferences due to the presence of carbonates could be eliminated by acid treatment of the sample.16 Influence of the duration of desorption The influence of the duration of desorption on the desorption eYciency of an organic compound is illustrated in Fig. 5 for saccharose. The behavior of other pure organic compounds is expected to be similare behavior of mixtures such as diesel fuel is more complex and very sample dependent.Fig. 5 shows how long desorption should be to be as complete as possible. An essential point of the coulometric method is the necessity to ensure complete desorption of the organic compounds prior to the determination of the EC fraction. Excessive desorption causes many problems, such as Fig. 2 Ratio of elemental carbon (EC) to total carbon (TC) versus desorption of EC during OC determination, drift of the temperature of desorption of (&) saccharose (84 mg OC) and ($) apparatus and excessive cost of the analysis. A compromise coronene (100 mg OC). EC was determined by the combustion of the has to be found.We consider that the best strategy is to desorb sample for 8 min at 800 °C under O2 (100%) after 40 min of desorption until the signal does not increase over a period of 2 min, under N2 for saccharose and 15 min for coronene.TC is the sum of OC+EC. instead of waiting for a certain fixed time. This usually J. Environ. Monit., 1999, 1, 367–372 369contributes to a higher relative desorption eYciency. This can be easily explained.At the beginning of the desorption, a sample with a higher sample load will desorb relatively more compounds. This means that at the end of the desorption, a relatively smaller amount could be aVected by thermal degradation. This eVect does not appear for anthracene, which is less sensitive than saccharose to thermal degradation. Influence of the heating rate The influence of the heating rate on the desorption eYciency of saccharose is illustrated in Fig. 7. It shows a weak improvement of the desorption eYciency with increasing rate of heating for saccharose but not for anthracene. Saccharose is more sensitive to thermal degradation than anthracene (a PAH). At low heating rates, samples are heated longer at lower temperatures, which can be suYcient to pyrolyze the compound but Fig. 4 Desorption thermogram under N2 of activated charcoal, used not high enough to ensure its desorption. as an elemental carbon source, and of calcium carbonate under N2 and O2. Carbonates decompose on heating with CO2 emission. Each temperature was stepped during 5 min after reaching the target Hierarchy of influences temperature. The fitted curves were constructed by mathematical B-spline interpolation. To check the relative importance of the various parameters of influence, a combinatory based analysis was conducted.For four diVerent kinds of samples, four parameters at two levels (low and high) were tested. The types of samples, factors of influence and levels used in the combinatory analysis were as follows Samples Saccharose, coronene, cigarette smoke, diesel soot Desorption temperature 500, 800 °C Desorption duration 15, 30 min Heating rate 50, 500 °Cmin-1 Sample load Saccharose 50, 260 mg total control (TC) Coronene 40, 160 mg TC Cigarette smoke 40, 240 mg TC Diesel 24, 48 mg TC Fig. 5 Desorption at 500 °C under N2 of saccharose (630 mg OC) This combination leads to 64 analyses to be complete. versus time. 100% desorption corresponds to the total recovery of OC Table 2 presents the crude results for cigarette smoke and (OC=TC).Desorption kinetic refers to Dcount/Dtime= [count(time2)-count(time1)]/(time2-time1). diesel soot samples. Table 3 summarizes the crude analysis of variance of the results and Table 4 summarizes the crude analysis of variance of the interaction between factors. corresponds to about 20 min for the occupational hygiene The F-ratio can be used as a measure of the intensity of an samples treated in our laboratory.influence and therefore as a means to establish a hierarchy between the factors. Influence of the sample load It is interesting to note from Tables 1 and 3 that the The influence of the sample load on the desorption eYciency temperature and the duration of desorption are the main of organic compounds, saccharose and anthracene, is illustrated in Fig. 6, and suggests for saccharose that a higher sample load Fig. 7 Desorption at 800 °C under N2 40 min (total time meaning including heating time) of saccharose versus rate of heating. EC was Fig. 6 Desorption of saccharose and anthracene at 800 °C under N2 determined at 800 °C for 8 min under O2.The heating rate was adjusted manually. The graphs show the heating rate of the oven and for 20 min as a function of the equivalent carbon content of the sample (TC). EC was determined at 800 °C for 8 min under O2. not of the sample itself. Errors bars represent standard deviations on triplicates. Errors bars represent standard deviations on triplicates. 370 J.Environ. Monit., 1999, 1, 367–372Table 1 Summary of factors of influence on the EC recovery versus type of sample Factor Saccharose Coronene Cigarette smoke Diesel Temperature XXXX XXXX XXXX XXX Desorption duration XXXX XXX XX XXXX Rate of heating n.s.a n.s. n.s. X Sample load XX n.s. XXX XX an.s., non-significant factors (P>0.05). Table 2 Crude results for cigarette smoke and diesel soot samples.The ratio EC/TC is presented as a function of the diVerent parameters levels (1=high level, 0=low level; e.g., last line is temperature 800 °C, duration 30 min, heating rate 500 °Cmin-1, sample load 240 and 48 mg TC for cigarette smoke and diesel soot, respectively) Sample type Temperature Duration Heating rate Sample load Ratio EC/TC (%) Cigarette smoke 0 0 1 0 48 0 0 0 0 46 0 1 0 0 37 0 0 0 1 34 0 1 1 0 31 1 0 0 0 28 0 0 1 1 22 1 0 0 1 21 0 1 1 1 16 0 1 0 1 16 1 1 0 0 8 1 0 1 0 8 1 1 1 0 6 1 0 1 1 4 1 1 0 1 1 1 1 1 1 1 Diesel soot 0 0 0 0 73 0 0 1 0 70 1 0 0 0 65 0 0 0 1 56 1 0 1 0 54 0 1 0 0 54 0 0 1 1 53 1 0 0 1 49 0 1 1 0 49 0 1 0 1 44 0 1 1 1 43 1 0 1 1 37 1 1 0 1 31 1 1 0 0 31 1 1 1 0 22 1 1 1 1 21 Table 3 Analysis of variance of the temperature, desorption duration, heating rate and sample load influence on the EC/TC ratio.Bold figures indicate that the F-ratio does not reach a significance level of 5% (P>0.05) Cigarette smoke Saccharose Coronene Diesel Factor F-ratio P F-ratio P F-ratio P F-ratio P Temperature 45.677 0.000 72.246 0.000 81.308 0.000 33.707 0.000 Desorption duration 14.004 0.003 32.049 0.000 27.875 0.000 52.236 0.000 Rate of heating 4.163 0.066 1.587 0.234 3.216 0.100 5.373 0.041 Sample load 16.261 0.002 10.757 0.007 0.433 0.524 13.332 0.004 Table 4 Analysis of variance of the interaction between factors.Bold figures indicate that the F-ratio has reached a significance level of 5% (P<0.05) Cigarette smoke Saccharose Coronene Diesel Interaction F-ratio P F-ratio P F-ratio P F-ratio P Temperature–time 3.413 0.124 12.569 0.016 8.478 0.033 53.512 0.001 Temperature–rate 1.520 0.272 4.228 0.095 0.237 0.647 20.400 0.006 Temperature–load 1.321 0.302 1.719 0.247 5.543 0.065 0.312 0.601 Time–rate 3.741 0.111 4.162 0.097 0.339 0.585 1.761 0.242 Time–load 3.262 0.131 2.623 0.166 4.783 0.080 14.090 0.013 Rate–load 0.082 0.786 0.176 0.692 0.000 0.986 0.330 0.590 J.Environ. Monit., 1999, 1, 367–372 371Table 5 Temperature program proposed to determine EC/OC content of diesel soot using the thermal method. A first step (pre-analysis) of 3 min under an N2 atmosphere is used to purge the system of the ambient air. The second step (OC determination) is a fast increase in the temperature of desorption to 800 °C.This temperature is stepped until no count is observed during 2 min. The third step (EC determination) is a switch to an O2 atmosphere and a temperature of 800 °C stepped until no count is observed during 2 min Analysis Gas Temperature/°C Duration/min Pre-analysis High-purity N2 Ambient 3 Organic carbon (OC) High-purity N2 800 Stepped Elemental carbon (EC) High-purity O2 800 Stepped Table 6 EC recovery for pure organic samples (saccharose and eYciency of the Diesel organic fraction.To improve the EDTA). Saccharose solution 50 ml, carbon content 2 g l-1. EDTA desorption, we propose to adopt the highest possible temperasolution 50 ml, carbon content 2.2 g l-1. For the thermal method, ture whilst still avoiding EC desorption. Using the results desorption temperature and duration are indicated.A stepped temillustrated in Fig. 4, we propose to use 800 °C as a good perature is maintained until no count on the CO2 detector is observed compromise and to continue the desorption until there is no during 2 min count detected during 2 min (Table 5). EC recovery (%) Simple modifications of the method can lead to a substantial improvement of the organic desorption (Table 6).Method Saccharose EDTA NIOSH 5040a <0.1 <0.1 Acknowledgements Thermal, 550 °C, 8 min 66 87 Thermal, 550 °C, stepped 59 82 We thank Mr. J.-N. Lepdor for technical assistance. This Thermal, 800 °C, 10 mina 22 11 project was funded by the Swiss National Science Foundation, Thermal, 800 °C, steppedb 8 15 project number 32–42315–94. aThe ‘NIOSH 5040’ and the ‘Thermal, 800 °C, 10 min’ values are from an interlaboratory comparison.13 bThe step duration was around 35 min.References 1 IARC Monographs on the Evaluation of Carcinogenic Risks to factors of influence for all types of sample. The other factors, Humans, Vol. 46, Diesel and Gasoline Exhausts and Some especially the sample load, may act in a diVerent way according Nitroarenes.International Agency for Research on Cancer, Lyon, to the sample type. Cigarette smoke, for instance, is more 1989. sensitive to the load than to the duration of desorption. This 2 Health EVects Institute, Diesel Exhaust: a Critical Analysis of confirms that this very common pollutant in workplaces may Emissions, Exposure, and Health EVects, Special Report of the Institute’s Diesel Working Group, Health EVects Institute (HEI), cause significant interferences in the EC determination, as Cambridge, MA, 1995.already shown earlier,13 and should be looked for in any field 3 B. Bhatia, P. Lopipero and A. H. Smith, Epidemiology, 1998, 9, 84. sampling. Charring probably explains this interference, which 4 International Programme on Chemical Safety, Diesel Fuel and suggests that the influence of the sample load on the desorption Exhaust Emissions, Environmental Health Criteria No. 171, eYciency could be used as a measure of the charring sensitivity World Health Organization, Geneva, 1996. of the sample, but more data are needed to support this 5 U.Heinrich, R. Fuhrst and S. Rittinghausen, Inhal. Toxicol., 1995, 7, 533. conclusion. Saccharose is an organic compound representative 6 K.Steenland, D. Silvermann and D. Zaebst, Am. J. Ind. Med., of highly pyrolyzable species but probably not representative 1992, 21, 887. of common workplace pollutants. Saccharose readily decom- 7 E. Brich and R. A. Cary, Analyst, 1996, 121, 1183. poses. The charring process continues as the temperature is 8 J. Perez and R. L. Williams, SAE (Soc.Automot. Eng.) Tech. increased, but almost all of the decomposition products Pap., 1989, No. 894291. (including char) can be removed at high enough temperatures. 9 D. M. Smith, M. S. Akhter, J. A. Jassim, C. A. Sergides, W. F. Welch and A. R. Chugghtai, Aerosol Sci. Technol., 1989, 10, 311. Therefore, the char formed during analyses for sucrose and 10 B. K. Cantrell and W. F. Watts, Jr., Appl. Occup. Environ. Hyg., similar compounds is probably not a major source of EC 1997, 12, 1019. interference when a higher temperature is employed. 11 S.-J. Chen, S.-H. Lioa, W.-J. Jian and C.-C. Lin, Environ. Int., PAHs or the other compounds tested in this study are 1997, 4, 475. representatives of the fraction of the organic compounds 12 Von den Berufsgenossenschaften anerkannte Analysenverfahren zur suspected to be mutagenic which are coated on the carbon Festellung der Konzentrationen krebserzeugender ArbeitstoVe in der Luft in Arbeitsbereichen. Method No 44: Diesel Engine Emission, core of diesel soot. They are almost insensitive to the rate of ZH 1/120, Carl Heymanns Verlag, Cologne, 1995. heating and to the sample load for the ranges used in our 13 E. Birch, Analyst, 1998, 123, 851. experiments. This confirms that charring is not a problem for 14 N. R. Khalili, P. A. ScheV and T. M. Holsen, Atmos. Environ., these PAHs. 1995, 29, 553. 15 E. Birch, ECDSEMeeting, Berlin, personal communication, 1998. 16 H. Cachier, M.-P. Bremond and P. Buat-Me�nard, Tellus, 1989, Conclusion 41B, 379. The temperature and the duration of desorption seem to be the parameters of most influence acting on the desorption Paper 9/02622C 372 J. Environ. Monit., 1999, 1, 367–3

ISSN:1464-0325    

DOI:10.1039/a902622c

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Quantification of re-evaporated mass from loaded fibre-mist eliminators† Burkhard Riss*ab Ewald Wahlmu�llera and Wilhelm Ho�flingerb aPROFACTOR GmbH,Wehrgrabengasse 1–5, A-4400 Steyr, Austria. E-mail: briss@pr-steyr.ac.at bInstitute for Chemical Engineering, Fuel and Environmental Technology, Vienna University of Technology, Getreidemarkt 9/159; A-1060 Wien, Austria. E-mail: whoeflin@fbch.tuwien.ac.at Received 7th April 1999, Accepted 21st June 1999 Airborne lubricant emissions are a serious health hazard for employees in the metal working industry.The basic components of lubricants are oils and additives for adapting the properties to achieve the process demands. The oils used in lubricants are either mineral, synthetic or of biological origin. The lubricants are used as water-emulsions and also as straight oils.Extreme process conditions cause considerable amounts of aerosol and vapour emissions of lubricants into the working environment. Fibre filters are used in industrial demisters for pollution control and also for sampling purposes. Re-evaporation of separated lubricants from loaded fibre filters causes increased vapour emissions.Quantification of lubricant vapour emission was the subject of this research. An apparatus and an appropriate procedure for measuring the dynamic behaviour of evaporative losses from fibre filters were developed. The test piece of a loaded fibre filter was fixed in a sampling probe according to VDI 2066. The vapour concentration of organic compounds in downstream air was measured in real-time by using a photo-ionisation detector (PID).The PID was checked by sampling the vapour on an oleophilic adsorbent resin, solvent extraction and quantitative IR analysis and also gravimetrically. The two basic processes of filtering volatile aerosols are, on the one hand, collecting droplets on the fibres and, on the other hand, the evaporation of collected liquid. These two processes had to be separated in order to measure the increase of the vapour concentration caused by the tested fibre filter.The experiments were carried out using pure dodecane and hexadecane in order to avoid diYculties due to the unknown chemical composition of lubricant vapour. The variation of the air flow and the initial liquid mass on the filter covered the relevant range for industrial fibre demisters and for sampling methods based on collecting aerosols on fibre filters. It was found that the downstream air was saturated with lubricant vapour for a wide range of filter loads and filtration velocities.From the results obtained it can be concluded that loaded industrial filter systems emit air with saturation vapour concentration throughout their operation.Hence, vapour emissions can be estimated easily if the saturation vapour pressure and the mean relative molecular mass are known. Moreover, results obtained from measurements of filters with low loads confirm that the phase transition from liquid to vapour is influenced by the identified process parameters. This is relevant for measurement methods using fibre filters for sampling volatile aerosols.A semi-empirical model to estimate the evaporative losses for low loadings is proposed. However, further research is necessary to determine the full range of parameters that are relevant for evaporative losses from filters loaded with low masses of aerosols. of occupational health risks regarding aerosols and vapour is Introduction still under discussion.1,3,4 The assessment of occupational Extreme process conditions cause airborne emissions of metal health risks caused by airborne MWF emissions is either based working fluids (MWFs) at metal machining sites.Firstly, on the sum of aerosols and vapour (German approach: peripheral speeds of workpieces and cutting tools tear parts 10 mg m-3)1 or based on aerosols solely (Belgium, Finland of the MWFs into aerosols and fine droplets. Secondly, energy and UK: 5 mg m-3; Sweden: 3 mg m-3).In contrast, the dissipation at cutting processes and hot surfaces occurring at Austrian limit values at the workplace are 1 mg m-3 for thermal treatment applications cause considerable amounts of aerosols and 20 mg m-3 for the sum of aerosols and vapour.4 evaporated MWFs.1 A wide range of facilities such as electrostatic filters, sinter MWFs are applied either as oil-in-water emulsions or as plate element filters and centrifugal force filters are available straight oils.The basic ingredients of the lubricants are mineral to control airborne lubricant emissions at metal working sites. or synthetic oils and hydrocarbons of biological origin. Filter demisters are preferred frequently due to their high Additives adjust the properties (e.g.VT-index, corrosion, process reliability. The fact that loaded fibre mist collectors themselves can be a source of MWF vapour emissions was inhibiting the growth of micro-organisms) of the basic compothe subject of a recent investigation.5. nents to the specific process demands.2 In spite of the low Sampling lubricant aerosols on fine glass-fibre filters for vapour pressure of MWF components (‘semi-volatility’), conmeasurement purposes is common practice,6 although evapor- siderable amounts of vapour phase arise at ambient conditions.ative losses of collected aerosols during sampling may occur Exposure to airborne MWF emissions is known to be a due to the volatility of the MWFs.This results in systematic serious health hazard for employees.1 The current assessment underestimation of the aerosol phase. Recent measurements performed with diVerent sampling rates and equal sampling duration prove this assumption.7 †Presented at AIRMON ’99, Geilo, Norway, February 10–14, 1999. J. Environ. Monit., 1999, 1, 373–377 373Based on the results published in ref. 5 and 7, the goals of mass, the latter are proportional to the surface. The experiments were performed at loadings of the test piece below the this work are the identification and quantification of the most important parameters for evaporative losses from fibre filters saturation point of the filter material. The investigations should cover pure evaporative eVects, but exclude secondary emissions used for separation of liquid aerosol emissions.Therefore, an appropriate experimental set-up and a procedure to measure of liquid particles. Downstream aerosol loads indicated in Fig. 1(a) represent the dynamic behaviour of the evaporation process have to be developed. Losses of retained aerosols from fibre filters should penetrated and re-emitted particles.If the equilibrium between the liquid and vapour phase downstream of the filter is not be quantified. The variation of the selected parameters should include the range, which is important for industrial fibre filter achieved, evaporation still takes place if aerosols are present. Additional problems for in situ detection of the dynamic systems and for sampling devices.The results obtained are discussed in detail. behaviour of the evaporation process are caused by retention and distortion of the concentration front due to diVusion in the pipes and tubes between the filter and the measuring point. Experimental These eVects may not be negligible, taking account of the low air velocities present in sampling probes or highly eYcient Filtering volatile aerosols by using a fibre filter can be divided into two basic processes: collection of droplets on the filter industrial fibre filters.Penetration of aerosols was avoided by separating the filter loading process from the evaporation and evaporation of collected liquid. Evaporation takes place if the vapour pressure of the collected substance is below the process as mentioned above.Re-emission of aerosols downstream was neglected. Retention within the tube and lag time equilibrium (saturation vapour pressure) and liquid phase is still present. Evaporation of liquid induced by the filter takes of the detector were minimised by placing the suction inlet of the detector instrument as near as possible behind the test place if the vapour load downstream is higher than that upstream [Fig. 1(a)]. filter (approximately 5 cm). Because of the restricted suction city of the detector instrument with integrated pump, it The fundamental problem of measuring the concentration and ratio of liquid and vapour phase emissions by applying a was necessary to change the usual filtration process from pulling air through the filter to pushing it through by placing measurement method based on sampling the aerosols on a fibre filter (and collecting the vapour phase e.g.on an adsorbent the pump upstream as shown in Fig. 2. Flow conditions are regarded to be equal in these two operation modes. Pressure resin) is that the method itself causes a systematic error due to unknown evaporative losses of liquid from the filter during level diVers by about 1% (Dp#10 hPa) from absolute atmospheric pressure, so that changes of physical properties were sampling time.In order to avoid the diYculties in determining the ratio of aerosol and vapour load, the two basic processes regarded as negligible. The described phenomenon which had to be considered for were separated within the experiments. Therefore, the test filter was drizzled manually in calm air with liquid before separating volatile aerosols on fibre filters resulted in the experimental set-up given in Fig. 2. It consists of a standardised exposing it to the air flow. As given in Fig. 1(a), drain-oV mass flow of retained liquids filter holder according to VDI 2066,8 wherein a test filter of 50 mm diameter was implemented. The clearance of the filter may occur if the filter material becomes saturated itself. Saturation of filters implemented in a vertical position is given fixing was 40 mm.The variable air flow was provided by a gas sampler typically used for sampling applications (GS 312, by the balance of gravitational forces causing the tendency of drain-oV and forces caused by adherence of liquid to the fibre Desaga, Germany).The sampling device recorded automatically ambient air conditions and total air volume pumped surface. The former forces are proportional to the retained through the test filter. The pressure drop at the filter was detected by using a sensor based on a DMS bridge (Testo, Germany) and on-line recording (Testo 454, Testo). The dynamic behaviour of the downstream vapour concentration was measured with a portable photo-ionization detector (PID 2020, Perkin-Elmer, Canada).The PID works at 10.6 eV ionization radiation; thus, only organic air pollutants are detected. The permanent air gases (argon, carbon dioxide, nitrogen, oxygen, water vapour, etc.) require a higher energy of ionization and are not ionised by the UV photons. The PID enables in situ measurements of the downstream vapour concentration.The relevant parameters of the experiments are test filter properties, the range of air velocities penetrating the test filter, the upstream vapour load, the liquid load of the fibre filter, the Fig. 1 Model for filtration of mixed phase emissions (schematic). (a) Loaded air flow upstream: in industrial applications, liquid drain-oV is possible. (b) Situation of experiments with oil-wetted filter: vapour concentration downstream is filter induced only.SVC: saturation Fig. 2 Experimental arrangement (schematic). vapour concentration. 374 J. Environ. Monit., 1999, 1, 373–377ambient temperature, and the physical properties and chemical method for measuring hazardous substances, BIA 8000 (mineral oil, vapours and aerosols).6 Before starting the experimen- composition of the test fluid.Filter materials utilized for high performance filters in industrial systems applied for separating tal procedure, the PID was calibrated in a saturated atmosphere of the investigated liquid by placing the suction fine particles and those used for sampling are similar concerning the filter fibre diameter.The experiments were carried out inlet of the PID in a vapour saturated environment. Clean laboratory air for zero point adjustment was taken. using glass fibre filters (Type 13400, Sartorius, Austria; 50 mm diameter, 5–10 mm fibre diameter, #92% porosity), which are Changes in the procedure had to be made when quantitative analyses of evaporative losses of hexadecane were performed.usually used for sampling particulate matter. Filters used in industrial applications have the same range of fibre diameter The PID method was found not to be suitable, because the saturation concentration is very low, so that calibration of the and porosity. High performance fibre filters implemented in industrial device was not possible. For this reason the remaining hexadecane on the test piece after diVerent exposure times to the systems are normally operated at air velocities of 0.04–0.1 m s-1.For measurement purposes liquid aerosols are sampled air flow (120, 240, 360, 480, 720 min) was measured. The test filter was analysed by eluting the organic compounds with with filtration velocities from 0.06 (personal sampling according to BIA 31106) to 0.5 m s-1 (isokinetic sampling using 1,1,2-trichlorotrifluoroethane (quality for IR spectroscopy, Merck, Germany) and IR spectroscopy (PE Spectrum 1000, GSP-PD according to VDI 20668 and BIA 3110, respectively).The experiments covered the range of filtration velocities Perkin-Elmer, Canada). With this measurement method the dynamic behaviour of concentration values cannot be investi- between 0.04 and 0.2 m s-1, which resulted in flow rates of 3.5–12 l min-1.gated, but average values within intervals are feasible. The recommended limit value for the sum of lubricant aerosols and vapour at the workplace in Austria is 20 mg m-3. Results The vapour pressure of n-dodecane at 25 °C results in a saturation vapour concentration of 1100 mg m-3 while n- A typical time-dependent course of the PID-display and pressure drop is shown in Fig. 3. The course of the PID-display hexadecane reaches saturation at the same temperature when an 18 mg m-3 vapour load occurs. The experiments were represents the current evaporation rate. After a steep rise the vapour concentration shows a high level of saturation, then a carried out under zero vapour loads upstream of the tested filter because the maximum evaporation rates should occur flat phase followed by a rapid decrease towards zero.The recorded pressure drop has a decreasing course and reaches a [Fig. 1(b)]. This can be regarded as a worst case scenario. In contrast to industrial demisters where the masses loaded constant value at the end of the high phase of saturation. The final pressure drop of the filter is equivalent to unloaded, dry at fibre filters might reach the saturation point of the material for the retained liquid, the masses at filters used in sampling test filters.The area below the graph of saturation ratio w in Fig. 3 applications are very low. A total MWF mass of 2.1 mg would be expected at the filter if the workplace concentration of represents the evaporated mass, which is equal to the initial mass at the end of the experiment.The initial mass placed on aerosols were 5 mg m-3 and the total sampling air volume using BIA 3110 were 0.42 m3.6 Because of diYculties in the filter determines the width of the high level phase. By using the saturation ratio w, the temperature-corrected dispersing small masses on the one hand and avoiding draino V eVects at the test filter on the other hand, the range value of the saturated vapour pressure pS and the ideal gas equation, the evaporated mass me of the test liquid can be investigated covered initial masses between 6 and 200 mg (4–135 g m-2).calculated by numerical integration over the air volume VL: Temperatures of ventilated air in industrial filter systems are usually between 20 and 30 (35) °C.Sampling of MWF me= PVL r dVL= PVL w pS M R T dVL (1) emissions normally takes place at ambient temperatures within 20 and 25 °C. The temperatures during the experiments were at ambient values. where me [kg]=evaporated mass; R [J kmol-1 K-1]=univer- The experiments were executed with two pure n-alkanes— sal gas constant; w=saturation ratio; T [K]=temperature; pS dodecane (bp=216 °C; vapour pressure=16 Pa at 25 °C) and [Pa]=saturation vapour pressure; VL [m3]=air volume; M hexadecane (bp=287 °C; vapour pressure=0.21 Pa at [kg kmol-1]=relative molecular mass; and r [kg m-3]= 25 °C)—within the range of boiling-point and vapour pressure vapour concentration downstream.of common MWFs. For example, the vapour pressure of By plotting the results of the calculated evaporated mass me Macron H from Shell is about 0.5 Pa9 and for CUT XU from based on measured data against the air volume penetrated OMV the flash-point is specified to be 180 °C.10 Pure substances were chosen to avoid diYculties in detecting complex and unknown mixtures of real MWFs.The developed procedure for carrying out the experiments was as follows: The dry test filter stored at ambient conditions was weighed.In conditions of calm air, the testing fluid was drizzled rapidly onto the filter by using a simple sprayer. Then the initial mass at the filter was determined by weighing the test-piece again. Immediately afterwards the wetted filter was placed in the filter holder and clean laboratory air was pumped through at a defined flow rate.The time-dependent downstream vapour concentration and the pressure drop at the filter and the ambient conditions were recorded automatically. The completed evaporation of the substance on the test filter was indicated by the PID recording and additionally confirmed by gravimetric methods. The accuracy of the PID was checked by sampling the vapour on AmberliteA XAD-2 adsorbent, solvent extraction Fig. 3 Measuring data: PID instrument and pressure drop record. Test fluid: dodecane; air flow: 9.45 l min-1; initial mass 52.1 mg. and quantitative IR analysis according to the analytical J. Environ. Monit., 1999, 1, 373–377 375through the filter the graph given in Fig. 4 is obtained. The evaporated mass me shows a linear increase over a wide range.Fig. 5 indicates the saturation ratios found within the varied range of initial masses. The parameter air flow is represented by diVerent diameters of the bubbles. The saturation ratio w was calculated by using the current concentration r divided by the concentration of saturation rS: w= r rS = 1 rS me VLKprop. (2) For hexadecane, in situ measurement was not applicable.Therefore, the measurement was executed by quantitative IR spectroscopy. For hexadecane, the saturation ratio is given by eqn. (3): w[%]= r rS 100= ma-Mv Vÿ L t rS 100 (3) Fig. 6 Mass transfer coeYcient bmax depending on air flow. where ma [kg]=initial mass; mv [kg]=remaining mass on filter; and t [s]=test duration. Deviations of the overall evaporated mass, calculated by evaporation is restricted by the provided wetted surface.using PID-measurement and checked by gravimetric determi- Furthermore, errors due to the time lag of the measuring nation, did not exceed ±15%. A comparison performed using system probably occurred. quantitative IR spectroscopy confirmed these results. The experiments confirm that loaded fibre filters used for collecting semi-volatile liquids emit retained aerosols as vapour if they are penetrated by unsaturated vapour air flow.As a Discussion and conclusion result of this research, exhaust air of loaded industrial fibre Fig. 3–5 indicate that high rates of saturation occur if loaded filters has to be regarded as saturated with lubricant vapour. fibre filters are penetrated even with clean laboratory air.Over Hence, vapour emissions of industrial fibre filters can be simply a wide range of initial masses and air flow rates, the saturation estimated by calculating the equilibrium load using the saturatio shows no dependency on these parameters (Fig. 5), ration vapour pressure (SVP), the temperature of the ventilated except for very small initial loadings ( less than 10 mg) which air measured at the site and the mean relative molecular mass.result in a decreasing saturation rate. This indicates that Unfortunately, SVP and mean relative molecular mass are seldom specified in the safety data sheet. If only flash-point or boiling-point is given in the safety data sheet a reference value of saturation pressure for lubricants based on mineral oil fractions can be obtained from monographs in e.g.ref. 11. A rough estimation of lubricant vapour production by a typical industrial fibre filter at a 3000 m3 h-1 ventilated air flow gives a value of approximately 3.2 kg h-1 if the vapour pressure of the lubricant is similar to that of dodecane and approximately 55 g h-1 if the vapour pressure is similar to that of hexadecane.15 For very small masses on the filter, which occurs e.g.in measurement applications based on sampling aerosols on fibre filters, the situation might be more complex. Assuming that saturation downstream of the filter does not occur when deposited masses on the fibre filter are very low (e.g. less than 10 mg on a filter of 50 mm diameter), a characteristic, based on the theory of convective mass transfer, is proposed below Fig. 4 Evaporative loss of dodecane from fiber filter. Data points for predicting evaporative losses. calculated by using eqn. (1). Considering the theory of convective mass transfer,12–14 the actual mass-transfer coeYcient b is defined by eqn. (4). Taking the proportional section of the of drawn lines in Fig. 4, a maximum coeYcient bmax can be determined [eqn. (5)]: b= Vÿ L S rS dme dVL (4) bmax= Vÿ L S rS Dme DVLKprop.(5) where b[m s-1]=mass transfer coeYcient; bMAX[m s-1]= maximum mass transfer coeYcient; rs[kg m-3]=saturation concentration; Vÿ L[m3 s-1]=volume flow; and S[m2]=surface of fibres. For hexadecane, where in situ values for evaporative losses were not achievable, data acquired by quantitative IR spec- Fig. 5 Saturation ratio, w, depending on initial mass ma and air flow. Bubble diameters represent air flow. troscopy are used to calculate a coeYcient for mass transfer 376 J. Environ. Monit., 1999, 1, 373–377[eqn. (6)]: References 1 HVBG, Berufsgenossenschaftliches Institut f. Arbeitssicherheit, bmax= ma-mv t S rS (6) BIA Report 7/96, Ku�hlschmierstoVe, St. Augustin, 1996. 2 T. Mang, Die Schmierung in der Metallbearbeitung, Vogl, For the surface S in eqns. (4)–(6), the surface of fibres Wu� rzburg, 1983. calculated by eqn. (7) was used. S was regarded as a material 3 US Department of Health and Human Services (NIOSH), constant and therefore uncertainties in the amount of the Occupational Exposure to Metalworking Fluids—Criteria for a Recommended Standard, NIOSH, Cincinnatti, OH, Publication actual wetted surface have to be modelled by the mass transfer No. 98–102, 1998. coeYcient b. 4 AUVA Merkblatt M 368–1097, Ku�hlschmierstoVe, Unfallverhu �tungsdienst der Allgemeinen Unfallversicherungsanstalt, S=SV (1-e) D2 p 4 B with SV= Sfibre Vfibre = 4 d (7) Vienna, 1997. 5 D. Leith, F. A. Leith and M. G. Boundy, Am. Ind. Hyg. Assoc. J., 1996, 57, 1137.where SV [m-1]=specific surface; e=porosity; D [m]=eVective 6 HVBG, Messung von GefahrstoVen—BIA Arbeitsmappe, Erich diameter of filter piece (clearance of filter holder); B [m]= Schmidt Verlag, Bielefeld, 12. Lfg. IV/94, 1994. thickness of filter; Sfibre [m2]=surface of one fibre; Vfibre [m3]= 7 D. Breuer, unpublished work. volume of one fibre; and d [m]=diameter of one fibre. 8 Verein Deutscher Ingenieure, VDI-Richtlinien 2066 Blatt 2, In Fig. 6, bmax for all the experimental results (near and Du� sseldorf, 1993. below saturation) was calculated. In addition, the theoretical 9 Shell Austria, Sicherheitsdatenblatt gema�ß 93/112/EG zu Material value for saturation is plotted. Fig. 6 shows that most of the 56930, 1996. 10 OMV, Sicherheitsdatenblatt Pd. Nr. 177.615, 1996. calculated values for bmax are near the theoretical maximum 11 Arbeitsmappe fu�r Mineralo�lingenieure, Deutscher Ingenieur value. The points at an air flow of 9.5 l min-1, which are Verlag, Du� sseldorf. significantly below the saturation value, were obtained from 12 H. D. Gaehr and K. Stephan, Wa�rme- und StoVu� bertragung, measurements where the initial mass was at the lower end of Springer-Verlag, Berlin, 1994, p. 340. the range. Further investigations are needed to ascertain 13 H. Brauer, StoVaustausch Einschließlich Chemischer Reaktionen, whether evasurement applications with Sauerla�nder, Aarau, 1971, pp. 110 and 333. low loadings (<5 mg) are significant and if bmax is a proper 14 G. Hanel, Einfu�hrung in die Konvektive Wa� rme- und StoVu� bertragung, Verlag Technik, Berlin, p. 148. characteristic in these cases. 15 B. Riss, Diplomarbeit, TU Wien, 1999. Further investigation is necessary to determine the dependency of evaporation on fibre diameter, ingoing droplet size distribution and the change of composition during evaporation of a complex cooling lubricant. Paper 9/02767J J. Environ. Monit., 1999, 1, 373&ndash

ISSN:1464-0325    

DOI:10.1039/a902767j

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Classification of particles from the farm environment by automated sizing, counting and chemical characterisation with scanning electron microscopy-energy dispersive spectroscopy† Asbjørn Skogstad,* Lene Madsø and Wijnand Eduard National Institute of Occupational Health, P.O. Box 8149 Dep, 0033 Oslo, Norway. E-mail: asbjorn.skogstad@stami.no; Fax: +47 23 19 52 06; Tel:+47 23 19 53 25 Received 13th April 1999, Accepted 28th May 1999 About 60 000 particles in 288 aerosol samples collected during farm work have been characterised with automated particle analysis using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS).Based on EDS-analysis of materials with known composition (potato flour, a-quartz, K-feldspar and b-wollastonite), criteria were developed for classification of particles as: (1) organic, (2) silicon-rich (silica), and (3) other inorganic particles.The reproducibility of the relative mass proportions in dust samples collected during farm work was 0.078 when approximately 200 particles were characterised per sample. Field samples from the farm environment showed clear diVerences in composition. Generally, inorganic particles dominated the particle mass.The proportion of the organic particle mass was highest for tending of swine and poultry, 55 and 38% respectively. Silica particles amounted to 10 to 20% of the total mass during handling crops, e.g. grain, straw, hay, potatoes, and onions. It seems likely that the results can be used in etiologic studies, but further validation would be needed for quantitative purposes.automated particle analysis program for SEM-EDS was used Aim of investigation in the farmer study. Such instrumentation has been commer- In a study of farmers’ respiratory health and exposure to cially available for several years. However, a literature search bioaerosols (Melbostad et al.1), exposure to organic dust and revealed only a few studies (Ho� flich3 and Gunst4) on inorganic silica was considered to be of interest.Measurement of these particles collected in the work environment and no studies on components by ashing and X-ray diVraction or infrared spec- organic particles or particles from the farm environment. The trometry was not feasible as sample sizes were expected to be present paper therefore describes classification of particles by small, typically <0.5 mg.A method based on chemical charac- chemical type in samples collected during diVerent types of terisation of particles by combined scanning electron farm work. microscopy and energy dispersive spectroscopy (SEM-EDS) was therefore considered. Materials and methods The analytical scanning electron microscope can provide both chemical and morphological data of individual particles.Sampling It is frequently used for qualitative characterisation of aerosols, The farmers carried battery powered pumps (AFC 123, Casella e.g., in the work environment. However, particle mass esti- Ltd., London, UK) connected to a closed-faced, graphite- mation by microscopy is inaccurate. Particles with surface filled polypropylene filter holder with a 50 mm extension tube structure may not be recognised as single particles but counted (Gelman 25 mm Air Monitoring Cassette, Gelman Sciences, as several particles with smaller size.The recognition of Ann Arbor, MI, USA) loaded with a polycarbonate filter individual particles in complex aggregates can be diYcult and (Poretics, Osmonics, Livermore, CA, USA) with pore size particles may be obscured. The volume of a particle is estimated 0.4 mm.The airflow through the filters was approximately from the microscopic dimensions by assuming that the particle 1 Lmin-1 which was measured with a calibrated Brooks 2-65 height is half of the minimum observed diameter and the mass MM rotameter (Emerson Electric Co., Hatfield, PA, USA).is estimated from the estimated volume and the assumed Sampling time was dependent on the work task, and varied particle density. If these errors are systematic and comparable between 2 to 120 min. for all particle types their influence will be reduced when the relative composition of particle types is estimated and the combined mass is measured by another method, e.g., gra- Preparation vimetry.Finally, the counting process induces an error as a The particle mass on the filters was measured by gravimetry limited number of the particles are analysed. The latter error using an ultra-microbalance (Satorius model S4, Goettingen, and other random errors decrease if the number of analysed Germany) with a detection limit of 3 mg. Samples were resus- particles is increased.Therefore 1000 to 5000 particles have pended in filtered (<0.45 mm) Tween 80 solution (0.05% w/v) been characterised in samples from outdoor air (Hanna et al.,2 by treatment for 3 min in an ultrasonic bath with a frequency and personal communication with the author). of 35 kHz and a high-frequency power of 225W (Sonorex As manual counting would be extremely time consuming an RK510H, Bandelin Electric, Berlin, Germany).Sub-volumes of the particle suspension containing 20–40 mg were filtered through a second polycarbonate filter with pore size 0.4 mm †Presented at AIRMON ’99, Geilo, Norway, February 10–14, 1999. J. Environ. Monit., 1999, 1, 379–382 379using a funnel with a 15 mm internal diameter. This step was fractions were done in Microsoft Excel for Windows 95 version 7.0.necessary to achieve an appropriate density of particles on the filter without overlap and aggregates were also dispersed to The precision was estimated by one-way analysis of variance (ANOVA) of samples that had been analysed twice. The some extent. Specimens of 8 mm×8 mm were cut from the filter and gently fixed on carbon specimen stubs with double- composition of the dust during diVerent work operations was compared by one-way ANOVA and by the Kruskal-Wallis sided carbon adhesive discs.In addition spots of carbon cement were applied at each corner of the specimen to secure test on the proportions of the chemical types. Statistical analyses were carried out with SystatA 8.0 (SPSS Inc., Chicago, good conductivity to earth.Finally the sample was coated with approximately 30 nm carbon film in a sputter coater IL, USA). (Balzers SCD 050, Balzers, Liechtenstein) equipped with a carbon thread flashing unit. Results Analytical procedure Analysis Inorganic particles and most organic particles were observed The specimens were analysed with a Jeol (Akishima, Tokyo, with good contrast in the backscattered electron image mode.Japan) JSM-6400 scanning electron microscope (SEM) con- However, some organic particles appeared smaller in size or nected to a Series II energy dispersive X-ray spectrometer were counted as several smaller particles, Fig. 1A and B. (EDS)-system (NORAN Instruments, formerly Tracor Northern Middleton, WI, USA) equipped with a thin window Classification criteria detector allowing detection of elements with atomic number As the main focus of the project was to study organic dust 6 (carbon).The automated analysis was performed using exposure, classification into three categories was considered the software package ‘Particle Recognition and suYcient for our purpose: 1, organic, 2, silicon-rich, and Characterisation’ (PRC, NORAN Instruments Inc., 3, other inorganic particles.To define the particle types, Middleton, WI, USA) run on the Series II EDS-system. A classification criteria were developed from PRC analysis of a modified version of the PRC program (made locally at particle mixture of quartz, feldspar, wollastonite and starch. NORAN Instruments B.V., Naarden, The Netherlands) was Fig. 2 shows the number of particles (total number 363) as a used which was similar to a previous version of the program function of silicon and carbon content.Since specimens were (Fritz et al.5) where the spectrum was acquired while the flashed with carbon, the silicon counts were corrected for electron beam was scanning over 8 rotational cords through carbon counts by the formula the centroid of the particle.X-ray counts were more reproducible with this acquisition mode as emical inhomogeneities Sicorr= Sicount Totalcount-Ccount and geometric and absorption eVects are averaged over the entire particle during the scan (Johnson6). The SEM was operated under the following conditions: accelerating voltage 20 keV, working distance 8 mm, electron probe current ca. 3 nA, solid-state backscattered electron detection, magnifications 500×for particles 1–5 mm and 100× for particles >5 mm, and X-ray acquisition time 6 s per particle. The elements selected for chemical characterisation were: C, Na, Mg, Al, Si, P, S, K, Ca, Ti, Cr, Mn, Fe, Cu and Zn. The total net X-ray counts varied between 1000 and 5000. The net peak area for a given element was expressed as the percentage of the total X-ray counts.Classification criteria Criteria for classification of particles were based on PRC analysis data of well defined particle types: K-feldspar (Norfloat NGP 325), a-quartz (Fyle-quartz), b-wollastonite and potato flour (commercial domestic quality), prepared and analysed following the same protocol as the field samples. Quantification of field samples Particle volume was estimated using particle area×smallest diameter/2.A minimum of two frames per magnification were analysed. The analysis was terminated when 100 particles or 4 frames per magnification had been counted. The particle mass was estimated assuming that the particle density of inorganic particles, including quartz, was 3 times the density of organic particles.The proportions of three particle types were computed by division by the total estimated mass. Data analysis The particle data were transferred in ASCII format from the Fig. 1 Scanning electron micrographs of organic particles from the EDS-system to a PC using the terminal-emulator program farm environment (poultry house) as seen in (A), secondary electron Procomm Plus 3.0 (Datastorm Technologies, Inc., Columbia, image mode, SEI, and (B), backscattered electron image mode, BEI.MO, USA). A tailor-made Basic-program further made the Particles which are underestimated are indicated by arrows. data accessible for Microsoft-Excel. Computations of the mass 380 J. Environ. Monit., 1999, 1, 379–382combinations as the independent variable, Table 1.The overall precision of the proportions was 0.078. The precision of observations where both replicate analyses had found proportions <0.25 or >0.75 was 0.045, whereas the precision for observations with at least one proportion between 0.25 and 0.75 was 0.10. The diVerence was statistically significant, F36,39=5.14 and p<0.001. There was a tendency to a better precision when more than 200 particles were classified (arithmetic mean 270) compared to samples with less than 200 classified particles (arithmetic mean 127), 0.071 and 0.090 respectively, F24,51=1.61 and p=0.08.Characterisation of field samples Results from the classification of organic, silica and other inorganic particles in samples from diVerent farm work are Fig. 2 Distributions of relative X-ray counts from carbon (CcountM) shown in Table 2.One-way ANOVA showed that the pro- and silicon corrected for carbon (SicorrU) of 363 particles from a mixture of potato starch, quartz, feldspar and wollastonite. portions between tasks were significantly diVerent for all particle types, F213,9=4.4 to 15.8, p=0.01 to<0.001. However, the conditions for ANOVA are not satisfied as the proportions The particles were classified by the following criteria.First were not normally distributed and the variances were not were particles with Ccount80 classified as organic. Of the homogeneous. The non-parametric Kruskal-Wallis test was remaining particles were particles with Sicorr>90 classified as therefore also used, which also showed that the diVerences quartz.The following particles were classified as other inorbetween tasks were significant for all particle types, p<0.001. ganic particles: 1, particles 5 mm with Sicorr>35 and Sicorr90; 2, particles >5 mm with Sicorr>40 and Sicorr90; and 3, particles with at least one element count >10 except Discussion carbon. When these criteria were applied approximately 65% Detection of particles with the PRC program relies on a high of the particles were classified.The remaining particles were contrast, preferably binary image, with the particles as white classified as organic particles as the Sicorr and the counts of structures against a black background. As backscattered elec- single inorganic elements were too low for positive recognition tron production is strongly correlated with atomic number, as an inorganic particle.Of these particles 60–80% had inorganic particles are easily recognised using the signal from Ccount70 and 90–96% had Sicount10 for particles >5 and the back-scattered electron detector. Organic particles have a 5 mm respectively. high content of light elements and their average atomic number is close to that of the filter.It can therefore be diYcult to Reproducibility obtain suYcient contrast between organic particles and background. A satisfactory contrast was achieved by fixing the Twenty five specimens were reanalysed. A total of 50 to 500 particles were classified per analysis. The standard deviation backside of the filter to the specimen stub using double-sided carbon adhesive discs.Problems with static electric charging was estimated by one-way ANOVA with sample-particle type of the specimen were absent and a smooth background with a good signal-to-noise ratio was obtained. Although it is likely Table 1 One-way ANOVA of replicate counting of 25 samples colthat some particles are not correctly sized or recognised as lected during farm work.The precision was estimated from the residual variance two or more smaller particles, the underestimation of organic particles was minimised by the improved preparation Source of variance df Mean square F-test p technique. The PRC program classifies particles with low X-ray counts Between all combinations of as non-integratable and does not store the element counts for sample and particle type 74 0.142 23.5 %0.001 such particles.As non-integratable particles from the farm Residual 75 0.00604a environment are likely to be of organic origin, carbon was aPrecision=Ó0.00604=0.078. included in the X-ray acquisition. Very few non-integratable Table 2 Composition of the dust that farmers are exposed to during diVerent tasks Particle type Organic Silica Other inorganic Task Na AM b Median sc AM Median s AM Median s Threshing 21 0.26 0.24 0.21 0.17 0.15 0.12 0.58 0.56 0.28 Handling of hay 28 0.18 0.14 0.15 0.12 0.08 0.13 0.71 0.79 0.20 Handling of silage 15 0.12 0.08 0.10 0.06 0.03 0.07 0.82 0.87 0.13 Sorting of potatoes 20 0.02 0.01 0.02 0.11 0.10 0.06 0.88 0.88 0.06 Sorting of onions 16 0.03 0.02 0.02 0.12 0.11 0.03 0.85 0.86 0.04 Tending of— Dairy cows and cattle 23 0.32 0.31 0.20 0.08 0.02 0.14 0.61 0.62 0.20 Sheep/goats 26 0.22 0.14 0.27 0.15 0.10 0.15 0.64 0.71 0.28 Poultry 31 0.39 0.33 0.26 0.02 0.01 0.03 0.60 0.64 0.25 Swine 25 0.54 0.51 0.15 0.07 0.05 0.07 0.40 0.40 0.14 Handling of liquid manure 18 0.16 0.07 0.23 0.15 0.11 0.16 0.70 0.80 0.23 aSample size.bArithmetic mean. cSample standard deviation.J. Environ. Monit., 1999, 1, 379–382 381particles were observed thereafter. Analysis of the test materials Large diVerences between the proportions of the particle types during diVerent tasks were found. Except for tending of showed that potato starch particles could clearly be classified on the basis of the carbon count. Silicon counts were primarily swine and poultry, the proportion of organic particles was low.Although many work operations in farming involve used for chemical classification of particles. Inorganic particles showed substantial and variable carbon counts due to the handling of organic materials, the generated dust is dominated by inorganic particles. A possible explanation is that the carbon coating which complicated the classification.The carbon count was therefore subtracted from the total X-ray surface of farm materials like grain and hay is contaminated with particles from the soil which can settle from air or deposit count after which quartz could be clearly distinguished from the silicates wollastonite and feldspar (Fig. 2). As the total by rain-splash. During handling of farm materials particles on the surface are more likely to be dispersed into the air than X-ray count excluding carbon could be very small for organic particles, the relative silicon count could be high even with a the organic substrate itself.The soil as a source of inorganic contamination is also plausible since the mineral soils which low silicon count. Therefore carbon counts >80% of the total count were used as a primary criterion for classification of dominate in the region of the study have an organic content which is often less than 5% by weight (Singh et al.7).The organic particles. About 35% of the particles that were not classified as silica or inorganic were finally classified as organic silica content of the dust varied from 2 to 17% which also may point at soil as an important source of dust as soil is as they were relatively high in carbon and low in silicon.It is possible, however, that some of these particles were not organic probably the only likely source of silica dust in the farm environment. or were aggregates of both organic and inorganic particles. The proportion of organic particles may therefore have been overestimated. However, this error is counteracted by under- Conclusions estimation of size and number of some organic particles.Accuracy was further studied by the reproducibility of the An automated method for sizing, counting and chemical characterisation of particles collected in the farm environment estimated proportions of the particle types. The overall standard deviation was 0.078 when on average 200 particles were by scanning electron microscopy-energy dispersive spectroscopy was developed.It was possible to classify particles as analysed per analysis. The precision was suYcient for the comparison of field samples from the farm environment where organic, silicon-rich (silica) and other inorganic particles. Large diVerences in composition of the airborne dust were highly significant diVerences between tasks were found.The standard deviation was smaller in samples where a larger observed during diVerent types of farm work. Most of the dust was inorganic and probably due to contamination from number of particles had been analysed as should be expected. However, a much larger number of particles need to be the soil. It therefore seems likely that the results can be used in etiologic studies, but further validation is needed for quanti- classified to improve the precision substantially.Hanna et al.2 mention ranges of 5–11% and 26–37% for the proportions of tative purposes. two chemical particle types in samples collected in outdoor air. These data suggest standard deviations of 0.015 to 0.03 References which were found when 1000 or 5000 particles where classified per analysis (personal communication with the author).Low 1 E. Melbostad, W. Eduard and P. Magnus, Scand. J. Work Environ. Health, 1997, 23, 271. (<0.25) and high (0.75) proportions were estimated with 2 R. B. Hanna, K. J. Karcich and D. L. Johnson, Scanning Electron better precision which is similar to the binomial distribution. Microsc, 1980, 1, 323. The results probably have a bias due to many assumptions 3 B. Ho� flich, Diploma Thesis, Technical University of Darmstadt, that have been made in the quantification. In addition soluble 1997, (in German). particles as salts and sugars were lost as samples needed to be 4 S.Gunst, Diploma Thesis, Technical University of Darmstadt, 1997, (in German). resuspended to obtain an optimal particle density on the SEM 5 G. S. Fritz, J. J. McCarthy and R. J. Lee, in Proceedings of the 16th specimen. If the bias does not depend on the type of farm Annual Conference of the Microbeam Analysis Society, ed. work, i.e., particle types are similar, the results may still be R. H. Geiss, San Francisco Press, CA, 1981, pp. 57–60. useful in etiologic research. As the farmer study aims at 6 D. L. Johnson, Scanning Electron Microsc, 1983, 3, 1211. identifying the most important components in airborne dust 7 B. R. Singh, T. Børresen, G. Uhlen and E. Ekeberg, in Management for respiratory eVects among farmers, further validation of of Carbon Sequestration in Soil, CRC Press, Boca Raton, New York, 1988, pp. 195–208. the method, e.g., by comparison to standard methods, was postponed until more was known about the importance of organic dust. Paper 9/02941I 382 J. Environ. Monit., 1999, 1, 379–3

ISSN:1464-0325    

DOI:10.1039/a902941i

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Determinations of PCB within a project to develop cleanup methods for PCB-containing elastic sealant used in outdoor joints between concrete blocks in buildings† M. Sundahl*, E. Sikander, B. Ek-Olausson, A. Hjorthage, L. Rosell and M. Tornevall SP Swedish National Testing and Research Institute, P.O. Box 857, SE-501 15 Bora° s, Sweden. E-mail: mikael.sundahl@sp.se; Fax: 46-33-120254; Tel: 46-33-165666 Received 29th March 1999, Accepted 1st June 1999 Determinations of PCB were carried out as part of a project aimed at developing cleanup methods for PCBcontaining elastic sealant used in outdoor joints between concrete blocks.The goals of the project were to develop methods, which minimise the spread of PCB to the outdoor environment and to indoor air, and which keep the PCB levels as low as reasonably possible in the workplace environment whilst removing the elastic sealant.The following PCB determinations were carried out: (1) concentration in the elastic sealant; (2) concentration in the concrete close to the sealant; (3) concentration in soil; (4) concentration in the indoor air; and (5) concentration in the air in the workplace environment.The cleanup process consisted of a number of diVerent steps: (1) cutting the elastic sealant with an oscillating knife; (2) grinding the concrete with a mechanical machine; (3) sawing the concrete with a mechanical saw and (4) cutting the concrete with a mechanical chisel. In all these diVerent steps a high capacity vacuum cleaner connected to the machines was used. The elastic sealant contained 4.7 to 8.1% total PCB of a technical product with a composition most similar to Clophene A40.The concrete close to the sealant (first 2 mm) contained 0.12 and 1.7% total PCB at two diVerent places. The pattern of the PCB in the concrete resembled that of the sealant. PCB concentrations in the soil from the ground close to the building were 0.1 and 0.3 ppm at two diVerent places before the remedial action.The source of the PCB in the soil is most likely the sealant as the PCB pattern is similar for the two materials. The PCB levels in the workplace air at the beginning of the project, when the techniques were not fully developed, were generally above the occupational exposure limit of 10 mg m-3 (up to 120 mg m-3). Later when the techniques were optimised to better take care of dust and gases produced during the cutting and grinding etc., the levels were below or close to 10 mg m-3.The pattern of the PCB in the workplace air was diVerent from that of the sealant and contained higher levels of lighter components. The PCB concentrations in the indoor air were measured before and during the remedial process. The levels were around 600 ng m-3 and there was no significant increase during the removal of the sealant.The PCB level after the remedial action will be measured later. The pattern of the PCB in the indoor air was diVerent from that of the sealant as well as from that of the workplace air. Higher levels of the lighter PCB were present indoors compared to the composition in both workplace air and in sealant.Extracts of PCB were analysed by GC-MS with a SIM method (selected ion monitoring). Standard procedures were used for extraction of solid materials. For the air samples an OVS tube was used with XAD-2 as adsorbent. The filter and adsorbent were extracted with toluene. This work shows that it is important to perform remedial action of PCB-containing elastic sealant as: (1) there is a spread of PCB to the indoor air giving high enough concentrations to make this the main PCB load on humans living in the apartments studied in this project; (2) large amounts are spread to the soil from these sealants; and (3) many of the PCBcontaining elastic sealants used need to be changed from a functional perspective.amount of PCB added in such sealants ranges from 100 to Introduction 500 tonne.3 It has been shown that PCB from sealants leak to PCB are persistent organic pollutants; their eVects on the the environment, into the surrounding ground4 as well as to environment have been described in numerous papers.In this indoor air.5 It is most likely that PCB from sealants have paper we refer to a single source with the aim of neither already spread to refuse dumps for used building materials, choosing the most extensive papers nor of selecting the first due to a previous lack of knowledge about the problem.Many or most recent ones.1 PCB is a collective name for 209 diVerent of the sealants are getting old and need to be changed from a chemical compounds, congeners, with biphenyl and chlorine functional perspective and it is far more expensive to take care as the common parts in the molecules.Several diVerent PCB of PCB when it is diluted with other garbage on a refuse dump technical products have been produced; these include Clophene than to take care of it at source. Thus, there is a need for A40, A50, A60 and Arochlor 1242, 1248, 1254 and 1260. eYcient methods for exchanging these sealants with new PCB free materials, which minimise the spread of PCB to the From 1956 to 1972 PCB were extensively used in Sweden as environment, to indoor air and to the workplace environment.plasticizers in elastic sealants used in joints between concrete In this paper results are presented mainly from chemical blocks in buildings. In particular, products based on thiokol,2 measurements from a project to develop cleanup methods for a polysulfide, often contain PCB.In Sweden, the estimated PCB-containing elastic sealants. Technical descriptions of the cleanup process, where relevant, are given as background information.6 †Presented at AIRMON ’99, Geilo, Norway, February 10–14, 1999. J. Environ. Monit., 1999, 1, 383–387 3831 l min-1.The flow rate was checked using a calibrated flow Methods and background information meter. The filter and first section of the adsorbent were Taking away the sealant extracted together and the backup section of the adsorbent was extracted separately. The materials were mixed with The cleanup process consisted of diVerent steps: (1) cutting toluene (5 ml ) with 1,2,3,4-tetrachloronaphthalene (50 ml with the elastic sealant with an oscillating knife; (2) grinding the concentration 10 ng ml-1) added and extracted in an ultrasonic concrete with a mechanical machine; (3) sawing the concrete bath for 0.5 h.The method is partly validated by OSHA. with a mechanical saw; and (4) cutting the concrete with a Extraction eYciencies were greater than 93%. Breakthrough mechanical chisel.In all these diVerent steps a high capacity was not detected, for 125 l air, and the average recoveries were vacuum cleaner connected to the machines was used. The 95%. The breakthrough in all our measurements was less than vacuum cleaner had a capacity of 425 m3 h-1 (maximum 2%. Blank tubes were also extracted and no PCB could flow). The dust was separated in three steps with cyclone, fine be detected. filter and micro filter.Analysis of PCB extracts Description of the building All extracts were analysed by a gas chromatography mass The building was eight storeys high and was located in spectrometry selected ion monitoring (GC-MS-SIM) method. Bergsjo� n, Go�teborg, Sweden. Wall structures were constructed The instrument used was an HP 5890 GC with an MSD 5970.of concrete blocks and the joints were filled with a PCBThe column used for the GC separation was a BPX containing elastic sealant which was in bad condition and had 25 m×0.25 mm. The parameters used were as follows: to be replaced. The length of the sealants was about 4000 m 70 ml min-1 split flow, 300 °C injector temperature splitless which corresponds to about 1500 kg sealant; with an average injection, 100 °C for 1 min then 5 °Cmin-1 to 300 °C.MSD content of 6% PCB this corresponds to about 90 kg of PCB. parameters: SIM detection 3- and 4-Cl congeners starting at Extraction and sampling of PCB 6 min, Cl m/z 256.0, 258.0, 254.0, 220.0 and 292.0; 4-Cl congener starting at 23.4 min, m/z 292.0, 290.0 and 288.0; To determine the PCB concentration in the sealant an extraction internal standard starting at 24.3 min, m/z 263.9, 265.d with heptane was performed. Sealant (100 mg) was immersed in 194.0; 5-Cl starting at 25.5 min, m/z 326.0, 324.0 and 322.0; heptane (3 ml ) and extracted in an ultrasonic bath (1 h).The 6-Cl congener starting at 30.4 min, m/z 360.0, 362.0 and 356.0; extraction procedure was repeated twice.The extracts were col- 7-Cl congener starting at 33.0 min, m/z 393.9, 395.9 and 390.0. lected and washed with concentrated sulfuric acid (1 ml ) and To secure the identification, retention times and relative peak then diluted with heptane (100 ml final volume). heights of the SIM masses were used. The PCB congeners 28, 1,2,3,4-Tetrachloronaphthalene (100 ml with concentration 10 ng 52, 101, 118, 138, 153 and 180 were quantified by this method ml-1 to 10 ml extract) was added as an internal standard.The and the sum of these is denoted by S7PCB. To determine the internal standard was added after the extraction procedure. The total PCB content the results were compared with the PCB extraction eYciency was not determined, but the repeated procontents in the technical products and then S7PCB was ceduremost likely gives eYciencies greater than 90% (by comparimultiplied by the appropriate correction factor.7 For air son with similar compounds in similar matrices).samples which do not have the same composition as any To determine the PCB concentration in soil an extraction with technical product a conversion factor of 6 was used to obtain heptane was performed.Larger stones were taken away and soil the total PCB concentration from S4PCB.5 S4PCB is the sum (1–3 g) was mixed with heptane (3 ml ) and extracted in an of the congeners 28, 52, 101 and 138. ultrasonic bath (1 h). The extraction procedure was repeated three times. The extracts were collected and washed (50 ml 0.2M Quantification and detection limits and accuracy and precision NaCl in 0.1M H3PO4).The water phase was extracted with in the measurements heptane. The collected heptane phase was evaporated (ca. 3ml) and washed with concentrated sulfuric acid (1 ml ) and then The quantification limit of a single congener was 4 pg ml-1 diluted (5 ml ). 1,2,3,4-Tetrachloronaphthalene (50 ml with con- and the detection limit was 1 pg ml-1.The total accuracy for centration 10 ng ml-1 to 5 ml extract) was added as an internal the diVerent measurements was estimated to be better than standard. The internal standard was added after the extraction ±21%. The accuracy was estimated by adding an estimated procedure. The extraction eYciency was not determined, but the accuracy for the sampling–extraction step of ±15% and for repeated procedure most likely gives eYciencies greater than the analytical step of±15%. To obtain a value of the combined 90%.To determine the dry weight (dw) of the soil sample, soil repeatability in the analysis and extraction step, 18 sealants was dried (24 h, 105 °C) and weighed before and after drying. were extracted and analysed twice. The results gave at 95% To determine the PCB concentration in concrete, ground confidence level a spread of ±12%.concrete was collected and the powder was extracted with heptane. Ground concrete (0.3 g) was mixed with heptane (3 ml ), Results and discussion extracted in an ultrasonic bath (1 h) and the sediment was then Elastic sealant allowed to settle. The extraction procedure was repeated twice.The extractswere collectedandwashedwith concentrated sulfuric The elastic sealant contained from 4.7 to 8.1% PCB of a acid (1 ml) and then diluted with heptane (100 ml final volume). technical product similar to Clophene A40 (Table 1). Most 1,2,3,4-Tetrachloronaphthalene (100 ml with concentration likely, the original PCB content in the sealant was higher as 10 ng ml-1 to 10 ml extract) was added as an internal standard.PCB certainly was added from a functional perspective to The internal standard was added after the extraction procedure. plasticize the sealant. The sealant is 30 years old and PCB The extraction eYciency was not determined, but the repeated have leaked to the surrounding ground and to indoor air as procedure most likely gives eYciencies greater than 90%.is shown below. To determine the PCB concentration in air an OVS tube with XAD-2 as an adsorbent was used. An air sampling pump, Soil SKC aircheck sampler model 224-PCXR7, was used and depending on whether the air was from indoor or from the The soil from the ground was contaminated by PCB. The results are summarised in Table 2. A 2 cm portion was taken workplace environment the air volumes sampled were around 60 l and around 1500 l, respectively at a flow rate of around from the top layer of the soil from a 0.5×0.5 m surface.The 384 J. Environ. Monit., 1999, 1, 383–387Table 1 Partial content (normalised to highest) of the 7 selected PCB congeners in sealant and the technical product Clophene A40 and sum concentrations of PCB. For Clophene A40 the conversion factor from S7PCB to total PCB concentration is 5.3.The results reported in the same row are results obtained for the same sample but with separate extractions and analyses, thus giving an indication of the repeatability Partial content of the respective PCB in sample and product content PCB Congener 28 52 101 118 138 153 180 Content S7PCB Total content Clophene A40 0.19 0.39 0.14 0.13 0.05 0.06 0.01 Sealant 0.17 0.30 0.29 0.17 0.05 0.03 0.01 9.4 and 8.8 g kg 5.1 and 4.7% Sealant 0.19 0.38 0.24 0.15 0.04 0.02 0.01 14 and 15 g kg 7.4 and 8.1% Table 2 Results obtained for soil samples taken from the ground before and after the refinishing process.The results reported in the same row are results obtained for the same sample but with separate extractions and analyses, thus giving an indication of the repeatability S7PCB (mg kg-1 dw), before S7PCB (mg kg-1 dw), after Soil 1 1–1.5 m from building 0.013 and 0.028a 0.080 and 0.088 Soil 2 1–1.5 m from building 0.048 and 0.062 Soil 3 10–10.5 m from building Below detection limit 0.026 and 0.025a aThese values are below the quantification limit, at this dw, S7PCB 0.04 mg kg-1 dw.The detection limit is, at this dw, S7PCB 0.01 mg kg-1 dw. results obtained indicate that the soil was contaminated during We conclude that no significant increase of the PCB levels indoors occurs during the remedial process. The PCB sample the work involved in removing the sealant. See below for an estimate of the amount of PCB that was spread during the of indoor air taken after the remedial action was taken shortly after the process was finished and we believe that the concen- remedial process.tration will drop considerably within the next half year. Concrete Workplace air The concrete close to the sealant was contaminated by PCB The results are summarised in Table 4. The air was sampled in but the concentrations drop quickly with the distance from the breathing zone of the worker.The quantification limit of the joint. The results are summarised in Fig. 1. The first layer PCB in used air was #2 mg m-3 with an operating range of up from which the sealant was cut has a high PCB concentration to #80 mg m-3. An important conclusion drawn from the which shows the need for grinding the concrete surface to get measurements is that workers should use some kind of breathing rid of the PCB in this layer.It is reasonable from a practical protection due to the levels of PCB present in workplace air. point of view to grind a few millimetres of the concrete but Furthermore, smallmistakes in the remedial procedure can result not much more. in high PCB concentrations; therefore it is important to be careful during all the steps involved in the procedure.Indoor air Measurements of the PCB concentration in the air located after The results are summarised in Table 3. The quantification limit the vacuum cleaner at the vent were also carried out and the with the used air sampling volumes was #50 ng m-3 with an total PCB concentrations were found to be 15 and 17 mg m-3 in operating range up to #2000 ng m-3.Rather high levels of the new and used filter, respectively. PCB were found in the indoor air in the building. This can most likely be coupled to the PCB present in the sealant. Comparison of the PCB pattern in diVerent samples Previous investigations of buildings in Germany showed that The relative contents of the 7 indicator congeners are diVerent PCB from sealants can leak to indoor air and particularly for diVerent types of samples taken in the project reported in when lower chlorinated technical products are used as sealants this paper (Table 5).Some important conclusions can be higher concentrations are found indoors.8 There is also a drawn. The concentration of the PCB with low chlorine correlation between PCB concentration in indoor air and content is important for the level of the concentrations in air outdoor temperature.5 At higher temperatures the concenas the PCB found in air is dominated by lighter more volatile tration indoors gets higher.We have not attempted to study PCB. The PCB found in soil and concrete most likely originate this correlation further in this project due to limited resources.from the sealant as there is a similarity between the PCB pattern found for these three materials. The diVerent air measurements that is, workplace environment, air located after the vacuum cleaner and indoor air, show diVerent patterns. Looking at the 7 indicator congeners, indoor air is dominated by PCB 28 and 52, air after the vacuum cleaner is dominated by 28, 52 and 101 and workplace environment is dominated by PCB 28, 52, 101 and 118.It is also important that there is no significant diVerence between the PCB pattern of the indoor air before and during the remedial action which indicates that the remedial action does not aVect the PCB level indoors. Fig. 1 Total PCB concentration in diVerent layers of concrete close to Estimation of the PCB spread during the remedial action the surface where the sealant was cut away.The results reported in the same column at the same depth are results obtained for the same The estimations are rough but give a feeling of the magnitude sample, but with separate extractions and analyses, thereby giving an of the PCB spread and the amount of PCB left in the building indication of repeatability. The diVerent columns represent results obtained for samples taken from diVerent locations.after remedial action had been taken. J. Environ. Monit., 1999, 1, 383–387 385Table 3 PCB concentrations in indoor air before, during and after remedial action Total PCB concentration Total PCB concentration Total PCB concentration Outdoor temperature in indoor air in indoor air in indoor air before, during before remedial during remedial after remedial and after action action action remedial action Apartment a, 530 ng m-3 910 ng m-3 11 °C, 12.5 °C, — uninhabited Apartment b, 610 ng m-3 570 and 660 ng m-3 810 ng m-3 15.5 °C, 7–8 °C, 0–5 °C inhabited Apartment in <50 ng m-3 7–10 °C, —, — building without PCB-containing sealant Long term target 30 ng m-3 level in Germany9 Guideline level 300 ng m-3 in Germany9 Level of 3000 ng m-3 concern in Germany9 Table 4 PCB concentrations in workplace air.The results in the same row were not obtained during the same period, thus giving an indication of the variation in the concentrations during the work Total PCB concentration in Working operation Vacuum cleaner breathing zone Comments Cutting with an oscillating knife Not connected 14 and 49 mg m-3 Not optimised Grinding with a mechanical machine Connected method, beginning Cutting with a mechanical chisel Not connected of the project Cutting with an oscillating knife Connected 5.6 and 9.4 mg m-3 Optimised method Grinding with a mechanical machine Connected 11.0 and 5.5 mg m-3 Optimised method Threshold limit value for 10 mg m-3 workplace environment in Sweden Cutting with an oscillating knife Connected 42 and 30 mg m-3 Vacuum cleaner tubing got loose Sawing with a mechanical saw Connected 34 mg m-3 Vacuum cleaner Cutting with a mechanical chisel Connected tubing got loose Grinding with a mechanical machine Connected 120 mg m-3 a Vacuum cleaner tubing got loose Grinding with a mechanical machine Connected 80 mg m-3 Sampling during Sawing with a mechanical saw Connected all the time of the Cutting with a mechanical chisel connected two measurements above aConcentrations of individual PCB congeners in samples higher than those in the highest standard might give a higher uncertainty in the value compared to other values.The amount of PCB spread to the air during the remedial We estimate the increase in the PCB concentration in the soil as being an average of 0.05 ppm in the first 4 cm, no action should mainly be that located in the air after the vacuum cleaner.The sealants in the entire building took 120 d increase deeper into the soil, and in the first 20 m from the house. The soil samples were taken at 0–2 cm depth, and 1 to cleanup and change.In a normal day, two vacuum cleaners were run 4 h each. A flow of 300 m3 h-1 per machine at a and 10 m from the house. The house was 77 m long×13 m wide. The amount of soil contaminated by 0.05 ppm is equival- concentration of 16 mg m-3 gave a total amount spread to the air of 120×2×4×300×16×10-6=5 g PCB during the entire ent to [(77+20+20)×(13+20+20)-(77×13)]×0.04= 208 m3×1000 kg m-3×0.05×10-6×5.3 (from S7PCB to cleanup process.It is reasonable to assume that the PCB spread to the air during the remedial action mainly goes this total concentration)=55 g PCB. We estimate the amount left in the concrete to be as follows: way as the flow is so high through the vacuum cleaner. This can be compared to the amount that is oV-gassed to the indoor first 2 mm ground away; then, 2 mm×2 (number of edges)×3 cm (width of ground surface)×4000 m× environment during one year: Volume of the house×air exchange rate (not measured, 0.5 per hour is a usual value 2300 kg m-3 (density of concrete)=1104 kg concrete, 2 to 4 mm contains 400 ppm, 4 to 6 mm contains 90 ppm and for mechanical ventilated apartments)×hours in 1 year ×PCB concentration indoors (representative value for deeper no PCB, giving 1104×(400+90)×10-6=0.54 kg PCB.The 2 mm grinding of the concrete is a minimum value, in the measurements 600 ng m-3)=77×13×22×0.5×24×365 ×600×10-9=60 g PCB spread to the indoor air during one most cases more than 2 mm are ground. Therefore 0.54 kg is probably too large an estimate. year. 386 J. Environ. Monit., 1999, 1, 383–387Table 5 The relative contents of the 7 indicator PCB for diVerent samples PCB28/31a PCB52 PCB101 PCB118 PCB138 PCB153 PCB180 Concrete 0.67 1 0.99 0.60 0.12 0.063 0.010 Concrete 0.49 0.85 1 0.60 0.19 0.13 0 Concrete 0.80 1 0.79 0.49 0.11 0.055 0.007 Concrete 1 0.83 0.98 0.63 0.14 0.069 0.008 Concrete 0.44 0.84 1 0.56 0.20 0.11 0.036 Soil 0.47 0.76 1 0.56 0.88 0.81 0.53 Soil 0.52 1 0.90 0.56 0 0 0 Soil 0.64 1 0.68 0.34 0.17 0 0 Soil 0.66 1 0.95 0.51 0.18 0.14 0 Vacuum cleaner 1 0.63 0.19 0 0 0 0 Vacuum cleaner 1 0.49 0.15 0.040 0 0 0 Sealant 0.53 1 0.96 0.56 0.14 0.091 0.027 Indoor air before work 1 0.44 0 0 0 0 0 Indoor air before work 1 0.50 0.042 0 0 0 0 Indoor air during work 1 0.52 0.048 0.012 0 0 0 Indoor air during work 1 0.42 0.033 0 0 0 0 Workplace environment 1 0.94 0.49 0.22 0 0 0 Workplace environment 1 0.88 0.37 0.19 0.037 0.016 0 Workplace environment 1 0.90 0.36 0.14 0.051 0 0 Workplace environment 1 0.90 0.35 0.13 0 0 0 Workplace environment 1 0.82 0.35 0.16 0 0 0 Workplace environment 1 0.88 0.40 0.17 0.054 0.022 0 Workplace environment 1 0.89 0.40 0.17 0.045 0.022 0 aIn this table the sum of PCB28 and 31 are used for the comparison, since there is a poor chromatographic separation between these two congeners.To summarise 540 g+55 g+5 g=0.6 kg PCB is either spread developing the cleanup methods and cooperation during the measuring periods. Bjo�rn Lundgren is gratefully acknowledged or left in the building compared to the 90 kg PCB taken away. Thus more than 99% of the PCB are removed, which must be for his valuable comments. considered a good result.References Conclusions 1 C. Bernes, in Monitor 16, Persient Organic Pollutants, A Swedish View of an International Problem, Swedish Environment Protection It is important to remove PCB-containing elastic sealant in Agency, Stockholm. order to reduce the spread of PCB to indoor air and to the 2 Thiokol is a polysulfide which often has PCB added as a plasticizer. outdoor environment.Some kind of breathing protection 3 T. Hammar, PCB i fogmassor, La�nstyrelsen i Kalmar informerar should be used by workers during the work involved in (The County Government Board in Kalmar, Sweden informs), removing the sealant. There is no significant increase in PCB 1992, 10. 4 B. Jansson, J. Sandberg, N. Johansson and A. A° stebro, PCB i levels indoors during the remedial process. A few millimetres fogmassor—Stort eller litet problem? Swedish Environmental of the concrete should be taken away as the concentration in Protection Agency, Stockholm. the concrete closest to the sealant is high. 5 C. Benthe, B. Heinzow, H. Hessen, S. Mohr and W. Rotard, It is possible to remove PCB-containing elastic sealant with Chemosphere, 1992, 25, 1481. minor spread of PCB to the environment. A rough estimate 6 E. Sikander, M. Sundahl, M. Tornevall, B. Ek-Olausson, suggests that more than 99% of the PCB is removed. A. Hjorthage, L. Rosell and P.-O. Johnnesson, Utveckling och utva�rdering av metoder fo�r PCB-haltiga fogmassor, SP Swedish National Testing and Research Institute, Bora°s, Sweden, 1999, 07. Acknowledgements 7 D. E. Schultz, G. Petrick and J. C. Dulnkner, Environ. Sci. Technol., 1989, 23, 852. ‘Kretsloppsmiljarden’ a Swedish governmental fund for a 8 E. Balfanz, J. Fuchs and H. Kieper, presented at Dioxin ’93, 13th sustainable development, ‘Miljo� teknikdelegationen’ a Swedish International Symposium on Chlorinated Dioxins and Related governmental fund for environmental technology, The Swedish Compounds, Organohalogen Compounds 1993. 9 Internet address: http://www.mtm.de/pcbnrw.htm Council for Building Research, and others are gratefully acknowledged for financial support. Hans Zackrisson, Fogspecialisten AB, is gratefully acknowledged for help in Paper 9/02528F J. Environ. Monit., 1999, 1, 383&ndash

ISSN:1464-0325    

DOI:10.1039/a902528f

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Reduction and avoidance of lubricant mist demands an integrated assessment approach† Ewald Wahlmu�ller,*a Heribert Neubauera and Wilhelm Ho�flingerb aPROFACTOR GmbH, Wehrgrabengasse 1–5, A-4400 Steyr, Austria. E-mail ewahlm@pr-steyr.ac.at bInstitute for Chemical Engineering, Fuel and Environmental Technology, Vienna University of Technology, Getreidemarkt 9/159, A-1060 Wien, Austria. E-mail: whoeflin@fbch.tuwien.ac.at Received 7th April 1999, Accepted 21st June 1999 A case study to identify major factors for lubricant mist exposure covered 15 metal machining sites.The investigation included milling, turning, drilling and grinding applications. Systematic analysis considered all relevant data concerning the machine tool, the lubricant and the suction plant. The eYciency of the implemented maintenance program at the installed filter systems was checked by concentration measurements immediately before and after service.All performed measurements of lubricant aerosol and vapor loads upstream and downstream of the installed filter systems were carried out according to VDI 2066 and BIA 3110, respectively. The selection criteria for the sites to be investigated, the systematic nature of the data acquisition and the procedure of the analysis are demonstrated in detail by performing comparisons between selected applications using emulsions and those employing straight oil for lubrication. The results of the study identify recirculation of ventilated air as the major source of workplace exposure to airborne lubricant emissions.More than 60% of the demisters investigated emit air at total lubricant loads (aerosols and vapor) above the limit of 20 mg m-3 at any time of operation; which also means immediately after service. A common reason for exceeded aerosol loads in recirculated air is e.g. the fact that the type of filter system applied is often not suitable for the separation problem. Loads of lubricant vapor are usually higher at the processes which use water emulsions as lubricant.In a quarter of the cases the limits were exceeded solely due to high vapor loads even immediately after service. The exposure can be reduced by replacing the lubricant, installation of a vapor separation plant or avoiding air recirculation. Maintenance time of the demisting system and aerosol separation eYciency of state-of-the-art demisting systems can be expanded by implementation of enhanced preliminary filter stages.This study confirms that appropriate service measures lower both aerosol emissions and lubricant vapor concentrations due to the reduction of exposed oil-wetted surfaces. The performed measurements show no significant relationship between loads of airborne lubricants and the type of machining process.Therefore, investigations at a much more detailed level have to be performed. However, the individual assessment of any workplace due to the complex situation remains essential. industry.6 The four metal working sites included in this study Introduction employed 3380 people. Approximately 45% of these employees Metal working fluids (MWFs) are necessary to secure high were exposed to lubricant emissions.The annual consumption quality surfaces and to extend tool life in metal cutting of MWF concentrates and oils of the companies investigated applications. In thermal treatment processes lubricants guaran- is 650 tons. tee defined cooling rates. Extreme process conditions cause Exposure data reported in ref. 2 provide results of several airborne emissions of MWFs into the workspace. Aerosols are studies performed during the period 1950–96 in the USA. The generated due to high peripheral speeds of workpieces and collected data represent aerosol concentrations of MWFs cutting tools. Evaporation of MWFs due to hot surfaces and measured in the ambience of diVerent types of metal cutting re-condensation as well as combustion of components causes processes.Measurement results of lubricant aerosols and vapor very fine particles with diameters down to 0.1 mm. Vapor at 13 diVerent types of metal working processes in Germany emissions occur due to the (semi-) volatility of MWF compo- during 1988 and 1994 were published in ref. 1. Three-quarters nents. Airborne emissions of cutting fluids are expected to of the samples were taken at milling, turning, drilling and have a serious health impact on exposed employees.1–5 grinding sites.Further investigations covered measurements at Condensed oilfilms in the work environment are potential 28 mist separation plants. The recorded data set contains sources of accidents due to slippery surfaces and increase the upstream and downstream loads of airborne MWFs drawn by risk of fire.Micro-organisms growing in organic compounds isokinetic sampling according to VDI 2066 and BIA 3110 as cause hygiene problems. Furthermore, environmental pol- well as particle size distributions at the investigated site. The lution as well as machine failures and elevated cleaning costs data set is related to area measurements using a sampling are relevant.In 1982 in the USA approximately 1.2 million system relying on the German standard TRGS 402. employees were potentially exposed to MWFs.3 In Austria in In contrast to earlier investigations, the aim of the work 1996 approximately 190 000 people were employed in the metal within this field study was to identify major sources of lubricant mist exposure at metal working sites by applying an integrated assessment approach. In addition to systematic measurements †Presented at AIRMON ’99, Geilo, Norway, February 10–14, 1999.J. Environ. Monit., 1999, 1, 389–394 389the investigation should include relevant aspects of the machine nation of the method is 0.25 mg m-3 for aerosols and 0.5 mg m-3 for vapor at a sampled air volume of 5.6 m3.tool, physical and chemical properties of the MWF used as well as details about the suction plant installed. An assessment Depending on the aerosol concentration of the sampled air the measurement time was 15, 30, 60, 90 or 120 min in order of the eVectiveness of currently applied maintenance programs at the filter systems by concentration measurements immedi- to avoid overloading the sampling filter.Upstream of the demisting system the measurement time never exceeded 30 min ately before and after service is the innovative aspect of this study. The goal was to check whether recirculation of venti- due to high concentration of aerosol. An important requirement of the performed measurement was to ensure that one lated air into the workroom was permissible or not.The collected data should provide a basis to optimise maintenance pair of samples, upstream and downstream of the filter system, was drawn during machining the same workpiece at the procedures and to propose eVective measures to reduce and avoid emissions. machine tool to ensure equal upstream concentration when the downstream sample was drawn.Concentration limits for airborne lubricant emissions Description of the experimental procedures The approach aimed to enable comparisons of data collected In Germany threshold limit values for airborne lubricant concentrations at the workplace were issued in 1996 for at diVerent types of metal cutting processes and data derived from diVerent companies. Therefore, systematic measurements aerosols and for the sum of aerosols and vapor (Table 1).The Austrian limit values for loads of airborne MWFs at the of aerosol and vapor loads had to be related to technical data of the configuration system investigated which includes the workplace are of the quality of recommended standards. Furthermore, the Austrian approach diVers from the German machine tool, the lubrication and the suction plant system.The capability of the integrated assessment approach applied standard in qualifying the toxic potential of the vapor phase. In contrast to the German approach the Austrian legislation within this study should be validated. The selection of the sites investigated was determined by does not limit airborne lubricant emissions of recirculated air.In Germany recirculation is permissible if the sum of aerosols the following criteria: The study shoulver investigations (i) at the four most important metal cutting processes (occur- and vapor does not exceed 20% of the threshold limit value (ZH 1/248 and VDI 2261 Bl. 3) at the workplace (Table 1). ring in regional metal industries); (ii) in diVerent companies; (iii) at applications which employ emulsions for lubrication Recirculation of ventilated air is forbidden in Austria as well as in Germany if the lubricant contains substances that are and straight oils at the same type of metal cutting process; and (iv) at sites which were expected to generate relevant expected to cause cancer.In this paper, exceedence of the limit value is deemed to emissions (visual inspection).Criteria of minor priority covered technical details such as have occurred if the Austrian limits at the workplace, which are given as 1 mg m-3 for aerosols and 20 mg m-3 for the requirements for putting up measurement equipment and production schedule at the plant. sum of aerosols and vapor, are exceeded. The goals of the study, to identify major factors for exposure to airborne lubricant emissions and to propose eVective meas- Results ures for reduction and avoidance, required detailed analyses of configuration and process parameters at the site.The type The performed study covered systematic analysis and measurements at 15 metal machining sites. Table 2 provides infor- of metal cutting process, the type of lubricant employed, the phase of operation (e.g.smooth/rough work), the temperature mation about numbers of diVerent system configurations. The investigation included milling, drilling, turning and grinding of the ventilated air, the integrity of the machine tool housing and the type of suction plant (centralised/decentralised) were processes. Drilling was either performed together with milling or turning work. One-third of the machine tools were equipped considered as relevant for upstream concentrations of the demisting equipment installed.The filter system was character- with full-integrated housing. The MWFs employed divided into two diVerent sorts of straight oil and five qualities of ised by the main eVect, part or stage utilised for demisting although most of the state-of-the-art filter systems combine water emulsion (3–6%).All decentralised suction plants were equipped with compact filter devices and recirculated ventilated diVerent mechanisms or eVects (e.g. several fiber filter stages for pre-separation of large droplets and an electrostatic force air into the workroom. Centralised plants drew oV air after separation. filter stage to collect the finest particles such as smoke and combustion residues).In addition to upstream and down- At processes where straight oil was used for lubrication, smoke appeared frequently during operation (e.g. rough work). stream parameters of the ventilated air and details about the maintenance program employed the number of working shifts These applications were either equipped with electrostatic filters or fiber filters enhanced by using a HEPA (high eYciency at the machine tool was recorded. Air samples drawn for measuring lubricant loads upstream particulate air filter, according to EN 1822) filter stage for separation of particularly fine aerosols.Sinter plate element and downstream of the demisting system installed were taken by isokinetic sampling according to VDI 2066.Loads of filters occurred only together with milling/drilling applications. All centrifugal force filters were more than 10 years old. At lubricant aerosols and vapor were measured separately by using a sampling system recommended by the German BIA one single milling/drilling site, lubricant vapor separation was performed by utilising activated charcoal. (BIA 3110).7 The sampling system relies on collecting the particle phase on a glass-fiber filter and adsorbing the vapor All four diVerent types of demisting systems installed at the sites investigated are listed in Table 3.As mentioned above phase on AmberliteA XAD-2 adsorbent resin. The analysis of the sample was performed by eluting the charged filter and they are characterised by the main eVect, part or stage utilised for separation, despite the fact that most of the devices adsorbent resin with 1,1,2-trichlorotrifluoroethane (quality valid for IR spectroscopy, Merck, Darmstadt, Germany) and combine several diVerent types of demisting stages.Table 4 gives details of applied maintenance programs and rates. quantitative FTIR spectroscopy (PE Spectrum 1000, Perkin- Elmer, Norwalk, CT, USA) in the spectral region between Maintenance rates depended mainly on the type of filter system, upstream concentrations of aerosolised lubricants, 2800 and 3000 cm-1.Spectra of standard concentrations were prepared with cutting fluid samples drawn from the machine loads of chips and dust, the number of working shifts at the machine tool, and also on specific properties of the lubricant at the site investigated.According to ref. 7 the limit of determi- 390 J. Environ. Monit., 1999, 1, 389–394Table 1 Threshold limit values of airborne lubricant emissions at the workplace and for recirculation of exhaust air after mist separation. All values in mg m-3 Austria Germany Limit at the Limit for air Limit at the Limit for air workplace recirculation workplace recirculation Aerosols 1 — — — Sum of aerosols 20 — 10 2 and vapor Table 2 Number of system configurations investigated (machine tools, lubrication and suction plant including demisting) Machine toola Lubrication Suction plantb Ventilated Housing Type Demisting systemc air Emulsion Straight Process FI PI (3–6%) oil C D EF SPE FF CFF R O Milling/ 3 4 6 1 3 4 3 4 2 — 4 3 drilling Turning/ 5 — 4 1 — 5 1 — 2 2 5 — drilling Grinding 2 1 1 2 — 3 1 — 4 2 3 — aMachine tool housing: FI, full integrated housing; PI, partial integrated housing.bSuction plant: C, central suction plant; D, decentralised suction plant; R, air recirculated to workroom; O, outgoing air. cDemisting system: EF, electrostatic filter; SPE, sinter plate element filter; FF, fiber filter; CFF, centrifugal force filter.Table 3 Service programs of industrial demisting systems Maintenance program Demisting system Rate/months Work 1–1.5 Cleaning/replacement of wiremesh or synthetic preliminary demister stages; Electrostatic filter cleaning the collector of the electrostatic stage Sinter plate element filter 1.5 Backsweeping and washing of the sinter plate elements; replacement of broken parts Fiber filter 1–6 (18) Cleaning/replacement of wiremesh or synthetic demister stages; replacement of HEPA elements Centrifugal force filter 3–6 Cleaning and/or replacement of wiremesh and/or fiber filter stages used as preliminary and/or fine filter stages Table 4 Airborne lubricant emissions of industrial demisters measured immediately before and after service (average and range, containing all measured exhaust air loads at milling, turning, drilling and grinding processes) Total lubricant load Load of lubricant aerosols (sum of aerosol and vapor load)/mg m-3 Before service After service Before service After service Minimum 0.3 0.1 Minimum 1.2 0.9 Average 1.7 1.2 Average 20 18 Maximum 6.1 3.5 Maximum 63 48 and organisational demands. Sinter plate element filters and was at the limit at service time and slightly underneath immediately afterwards.some fiber filter systems utilise the pressure drop at the system for indicating service demand. Fig. 1 gives the percentage of sites investigated where the preliminary defined limit loads for recirculation of ventilated In conformity with the results published in ref. 1, aerosol and vapor loads upstream and downstream of the demisting air were exceeded immediately before and after service. The results show that immediately before service 70% of the cases system were scattered over a wide range and were not signifi- cant for the type of metal cutting process. Vapor loads were recirculate exhaust air into the workroom at inadmissible loads of airborne lubricants. Immediately after maintenance the usually higher at sites where emulsions were used.Table 4 provides the range and average of aerosol loads and total measurements indicate that total lubricant loads are still exceeded at 60% of the sites. Regarding the aerosols solely, lubricant loads (sum of aerosols and vapor) measured in ventilated air after demisting immediately before and after 54% of the measured downstream concentrations exceeded the limit of 1 mg m-3.Before service 30% of downstream samples service. As indicated by the values of Table 4 the average aerosol load at all the sites investigated exceeded the defined exceeded the total limit value solely due to vapor loads. The applied service program reduced the exceeded concentrations limit value of 1 mg m-3 in both cases, immediately before and after maintenance.The mean value of the total loads of due to high vapor loads to a quarter of the sites checked. In the following, the systematic nature of the assessment airborne lubricants (aerosols and vapor) in the ventilated air J. Environ. Monit., 1999, 1, 389–394 391The phase shift induced by the high-pressure drop at the filter system results in zero separation eYciency for aerosol loads at the end of the service time.A comparison between applications using water emulsion for lubrication and those which employ straight oil indicates significantly that vapor loads were less when straight oil was used for lubrication. In addition to the fact that high vapor loads are usually associated with high concentrations of aerosols, high temperatures in the machine housing as well as the physical properties of the lubricant employed also determine the load of gaseous phase.This is significantly demonstrated if vapor loads at Ecocut 1 (milling/drilling, checkpoint No. F2/F3) and Hu� ller Hille 11/12 (milling/drilling, checkpoint No. F4/F5) are Fig. 1 Analysis of lubricant loads exceeding the limit values immediately before and after service. compared. For sampling volatile particles ( liquid and also solid materials) on fiber filters several points have to be considered in order to avoid measurement errors or to assess the reliability approach applied within this field study and the results achievable are demonstrated in detail by presenting some selected of the results obtained.For sampling aerosolised MWFs, there is the risk that some of the collected liquid adhering to the examples of the sites investigated. In addition to the results of the measurements performed, Table 5 provides relevant back- sampling filter will be stripped oV during sampling if the gaseous phase is not saturated with MWF vapor.Evaporative ground information about the configuration of the machine tool, the lubrication and the demisting system at the selected losses of sampled aerosols result in an underestimation of the liquid phase. However, quantification of evaporative losses is processes. For each type of process an example site employing emulsion and an application for using straight oil is listed. complex.The amount of losses depends mainly on the vapor pressure of the sampled MWF aerosols, the degree of saturation of the sampled gas, the gas velocity penetrating the Discussion and conclusion sampling filter and the sampling time. The saturation rate of the air in the suction plant depends In the following, the integrated assessment approach applied within this study will be demonstrated by performing detailed on the retention time in the connecting pipes between the machine tool and the filter system.Hence, upstream of filter analysis and comparison of the measurement results given in Table 5. Its capability to identify major sources of airborne systems in central suction plants the ventilated air can be regarded as saturated. Ventilated air upstream of filter systems lubricant emission and to formulate eVective measures will be verified. installed in decentralised suction plants often remains unsaturated.Further relevant factors determining the conditions of Changes in the quality of capturing generated emissions at the site are dominated by the decrease of ventilated air during the ventilated air are the integrity of the machine tool housing, the vapor pressure of the MWF employed and the temperature maintenance time due to the elevated pressure drop of a clogged filter system.For example, the filter at the machine of the ventilated air. Unsaturated conditions may also be present during phases of operation where workpieces are tool Ecocut 1 (milling/drilling, checkpoint No. F2/F3) was operated at approximately 50% of the nominal air flow of the changed.Ideal isokinetic sampling of volatile particles requires equal electrostatic demister installed. The intended expansion of residence time for the charged air in the demister system filtration velocities at the sampling filter, which means the same by-pass flow rate, respectively. DiVerences in the velocit- results in extremely low downstream loads of lubricant aerosols as attested by the measurement results provided (checkpoint ies of the sampling air flow penetrating the sampling filter cause diVerent amounts of evaporative losses of the collected No.F2/F3). The measured loads of lubricant vapor are extremely high at Ecocut 1, even immediately after service. lubricant. In reality it is impossible to ensure equal flow rates if isokinetic sampling is performed.The velocity in the pipe Forty-two days after service downstream loads of aerosols are still less than 1 mg m-3. The appropriate measure at this site of the suction plant and the selected diameter of the nozzle at the sampling probe determine the rate of the by-pass flow is to check the vapor pressure of the lubricant in order to avoid high loads of gaseous phase. The volume of ventilated during isokinetic sampling.Realising a constant flow rate would require continuous adjustable nozzles at the sampling air at the fiber filter, which is part of the suction plant at Gildemeister (turning/drilling, checkpoint No. D5/D6), probe. Uncertainties resulting from diVerences in the sampling time decreased by approximately 25% within less than 25 d. Even worse is the situation at Karstens (grinding, checkpoint No.have to be taken into account when measurements between upstream and downstream loads of MWF particles are com- S1/S2) where the HEPA filter stage of the fiber filter system installed was completely clogged. This example demonstrates pared. Upstream sampling time normally has to be kept short in order to avoid overloading the sampling filter.the consequences of belated service drastically: Exposure to hazardous emissions is caused due to the reduction of venti- Measurements downstream of highly eYcient filter systems may need to be performed for a prolonged period in order to lated air and by re-emission of lubricants from dirty filters (checkpoint No.S1/S2). The centrifugal force filter installed reach the detection limit of the method. However, further research is required to quantify uncertainties in the field of at the Oerlikon Boehringer (turning/drilling, checkpoint No. D1) was not serviced within 6 months. The diVerence of the sampling volatile particulate matter. The described assessment approach identifies recirculation vapor load measured upstream and downstream of the filter system indicates a measurement error due to an overloaded of ventilated air into the workroom as the major source of workplace exposure at metal working sites. More than half of sampling filter (turning/drilling, checkpoint No.D1). Sinter plate element filters cause a high pressure drop due the state-of-the-art filter equipment investigated, which was designed for aerosols separation only, was not able to ensure to the fine pores necessary for highly eYcient aerosol separation.The measured loads at Hu� ller Hille 11/12 (milling/drilling, exhaust aerosol loads below the limit for workplace recirculation. For a high upstream load of aerosols, enhanced prelimi- checkpoint No. F4/F5) indicate a certain transformation of lubricant aerosols into vapor caused by the filter system itself.nary filter stages can be an eYcient measure to elevate the 392 J. Environ. Monit., 1999, 1, 389–394Table 5 Measurement results of selected sites investigated within the described field study Demisting sy Machine tool Lubrication Technical information Measurement results Separation Upstream load/ Downstream load/ eYciencyh Nominal Measured Time mg m-3 mg m-3 (%) Exhaust Manufacturer, air flow/ Checkpoint air flow/ after Temperature/ Name Housinga Typeb Manufacturer Typec aird date m3 h-1 no.m3 h-1 service/d °C Ae Vf A+Vg A V A+V A A+V Milling/drilling— Ecocut 1 FI WE Aral Sarol EF R Ifs Industrie- 4.800 F2 2.209 15 24.5 2 55.2 57.2 0.1 44.9 45 94.2 21.4 474 EP, Aral filter-Service, F3 1.997 42 27.5 8.4 61.6 70 0.6 62.4 63 92.5 9.9 IFE 5000 D, 1996 Hu� ller Hille PI WE Estramet S SPE O Heimpel & 5000 F4 7.901 6 23.5 4.3 7 11.3 1.3 7.1 8.4 69.7 25.7 11/12 33, Oemeta Besler, F5 7.558 135 30 3.7 5.2 8.9 0.5 8.5 9 86 (-1.1) Sinterstar 7,1, >10 years Liebherr FI SO OMV CUT EF R CZECH, EP 1.700 F11 1.154 3 28 20.6 0.1 20.7 0.8 0.1 0.9 96 95.5 LC 255 XU, OMV 1000, 1998 F12 1.063 50 26 12.7 0.8 13.5 0.9 0.3 1.2 92.9 91.3 AG T urning/drilling— Oerlikon FI WE BIO KS 3 CFF R Ing.G. 1.000 D1 846 6 6 35 33.8 68.8 3.5 19.3 22.8 90 66.8 Boehringer HoVmann, Type 12, >10 years R.N.F.90 FI SO OMV CUT EF R CZECH, EP 1.400 D5 1.459 3 27 14.5 5.6 21.1 0.6 4.7 5.3 95.9 73.9 Gilde- XU 1000, 1997 D6 1.086 25 30 9.7 8.9 18.6 0.4 5.5 5.9 96.1 68.3 meister Grinding— Karstens PI WE BIO KS 3, FF R ISI-Industrie- 1.800 S1 633 9 23.5 5.7 7.3 13 1.1 7.5 8.6 80.8 33.7 Quaker Produkte, FIB S2 102 152 26 8.9 34.8 43.7 6.1 26.7 32.8 31.5 25 Chemical 1800, 1992 Gleason- FI SO Excelene 416, FF R HoVmann No info S5 471 4 31 1.5 1.2 2.7 1.8 1.3 3.1 (-20) (-14.8) Phoenix D.A. Stuart Filter, DLT 40 R, 1991 aAccording to Table 2.bWE=water emulsion; SO=straight oil. c,dAccording to Table 2. eA=aerosol. fV=vapor. gA+V=sum of aerosol and vapor. h(Upstream load-downstream load)/upstream load×100 (%). J. Environ. Monit., 1999, 1, 389–394 393aerosol separation eYciency and also the maintenance rate. References The performed comparison demonstrates that high loads of 1 HVBG, Berufsgenossenschaftliches Institut f.Arbeitssicherheit, lubricant vapor are mainly related to the physical properties BIA Report 7/96, Ku�hlschmierstoVe, St. Augustin, 1996. of the lubricant in use. Changing the MWF is a suitable and 2 US Department of Health and Human Services (NIOSH), eVective measure to reduce vapor emissions in addition to the Occupational Exposure to Metalworking Fluids—What you need to installation of a vapor separation plant or avoiding air recircu- know about, National Institute for Occupational Safety and Health (NIOSH), Publication No. 98–116, 1998. lation. This study confirms that appropriate service measures 3 US Department of Health and Human Services (NIOSH), lower both aerosol and vapor concentrations due to the Occupational Exposure to Metalworking Fluids—Criteria for a reduction of oil-wetted surfaces exposed to the air flow. In Recommended Standard, Education and Information Division of conformity with the results published in ref. 1, aerosol and the National Institute for Occupational Safety and Health vapor loads upstream of the demisting system were scattered (NIOSH), Cincinnati, Publication No. 98–102, 1998. 4 AUVA Merkblatt M 368–1097, Ku�hlschmierstoVe, Unfallver- over a wide range even for the same type of metal cutting hu�tungsdienst der Allgemeinen Unfallversicherungsanstalt, Wien, process or phase of operation, respectively. However, an 1997. assessment at each individual workplace is still essential. 5 T.Mang and H. Kraner, Mineraloel-Tech., 1978, 23 (7/8), 1. The described assessment approach is capable of analysing 6 Wirtschaftskammer O� sterreich, Statistisches Jahrbuch 1997, the complex situation at metal-working sites and of identifying Wirtschaftskammer O� sterreich, Wein,May 1998. 7 HVBG, Messung von GefahrstoVen—BIA Arbeitsmappe, Erich major sources of airborne lubricant emissions. The background Schmidt Verlag, 12th edn. IV/94, 1994. information provided about the machine tool, the lubrication and the suction plant system enables eVective measures for reduction and avoidance of exposure to be proposed. Paper 9/02768H 394 J. Environ. Monit., 1999, 1, 3

ISSN:1464-0325    

DOI:10.1039/a902768h

出版商:RSC    

年代:1999

数据来源: RSC

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The fate and persistence of polychlorinated biphenyls in soil Stephen Ayris and Stuart Harrad* Environmental Health, Institute of Public & Environmental Health, University of Birmingham, Birmingham, UK B15 2TT . Tel:+44 (0) 121 414 7298; Fax:+44 (0) 121 414 3078; E-mail: S.J.Harrad@bham.ac.uk Received 15th April 1999, Accepted 25th May 1999 The fate and persistence of PCBs 28, 52, 101, 138, and 180 artificially introduced into three soils was studied under a variety of field conditions for up to 415 d following initial contamination.A relationship was detected between ln Koa (octanol/air partition coeYcient) and the experimentally observed first-order loss rate constant that was statistically significant at at least the 90% level in all but one instance. In nearly all experiments, PCB persistence was greater in soils of higher organic carbon content.Soil temperature and moisture content were also indicated as important influences on persistence. Significantly longer half-lives were observed in a soil in which initial PCB contamination had occurred ca. 1 year previously. A mass balance showed the most likely mechanism of loss to be volatilisation. Losses attributable to aerobic biodegradation could not be ruled out, but those due to leaching, uptake by biota, and soil erosion were demonstrated to be negligible.First-order rate constants (kv) were determined for volatilisation of the same congeners from soil under a variety of controlled laboratory scenarios. Multiple linear regression analysis (MLRA) showed the most important influences on kv to be ln Koa (adjusted for soil temperature) and soil organic carbon content.Limited evidence was observed for a relationship between kv and soil moisture content, but not water flux. When tested against field measurements, the MLRA-derived relationship between kv and independent variables predicted to within a factor of 2.5, the persistence of PCBs 28, 52, and 101.However, it did not account for the influence of the age of contaminant association with the soil, soil moisture content or water flux, and failed to function for soils of high organic content, or where ln Koa exceeds ca. 23. The laboratory-based experiments directly measured volatil- Introduction isation of PCBs from soil. Their principal aim was to evaluate In recognition of the continued potential health threat posed the relationship between the first-order volatilisation rate by polychlorinated biphenyls (PCBs),1 the UK government constant (kv) and the octanol air partition coeYcient (Koa) recently announced an action plan to phase out and destroy adjusted for soil temperature, soil organic carbon content remaining stocks.2 While this is to be welcomed, there remains ( foc), soil moisture content (MC), and the water evaporation a considerable burden of PCBs associated with topsoil,3 which flux (WF).These data were subjected to multiple linear represents an important reservoir of material that is essentially regression analysis (MLRA), to provide an equation to predict beyond human control. One route via which PCBs enter soils the persistence of PCBs in soil.The accuracy of this equation is by accidental spills of PCB-contaminated fluids associated was tested against our field measurements. with transformers and large capacitors. If the risk arising from such incidents is to be understood and eVectively managed, Experimental methods the rate of decline in soil contamination must be accurately predicted, along with the relative significance of the diVerent Field experiments fate mechanisms involved, i.e., volatilisation, biodegradation, General.For each experiment, 30 cm diameter and 12 cm leaching, uptake by biota, and physical mass transport. depth containers were filled to 5 cm depth (between ca. 1.25 Furthermore, volatilisation from soil has been identified as the and 2.5 kg depending on soil density) with soil. This layer was most important single source of PCBs to the UK atmosphere.3 covered with a further 5 cm of the same soil artificially enriched It is therefore important that our understanding of the kinetics with a known quantity of PCBs 28, 52, 101, 138, and 180.of soil air exchange of PCBs is improved, if the contribution This was achieved by applying a mixture of these congeners of such volatilisation to the contemporary emission inventory (dissolved in 50 ml acetone) to the soil using a spray gun is to be accurately determined, and the likely influence of pesticide applicator with thorough mixing.To permit volatilis- current eVorts to reduce environmental contamination by ation of acetone and more intimate PCB binding to soil, 72 h reducing primary emissions is to be assessed.elapsed before the first soil samples were taken and the This paper reports the results of experiments monitoring experiments begun. One hundred 1 mm diameter holes were the fate of PCB congeners 28, 52, 101, 138 and 180 in soils drilled into the base of each pot to facilitate leachate collection under field and controlled laboratory conditions.The aims of these experiments were: (i) to assess the relative significance via a plastic funnel draining directly into an amber glass bottle. of potential mechanisms influencing PCB fate in soil, viz, Leachate samples were collected on an approximately volatilisation, leaching, soil erosion, uptake by biota, and monthly basis.degradation; (ii) to evaluate the influence of edaphic and Experimental conditions. These are summarised in Table 1. pollutant properties on PCB persistence in soil; and (iii) to Soil A was a sandy loam, soil B a clayey loam, while soil C determine how closely PCB loss from soil approximates to a first-order process over the time scales studied. was a commercially available peat-based compost.J. Environ. Monit., 1999, 1, 395–401 395Table 1 Conditions for field experiments Experiment/ Mean Mean moisture Duration (no. of soila temperature/°C foc/g g-1 content/g g-1 measurements) 1/A 10 0.0113 0.363 13/5/96–5/7/97 (24) 1/B 10 0.0213 0.353 13/5/96–5/7/97 (24) 1/C 10 0.207 0.736 13/5/96–5/7/97 (24) 2/A 3 0.0113 0.425 11/11/96–5/2/97 (12) 2/B 3 0.0213 0.403 11/11/96–5/2/97 (12) 2/C 3 0.207 0.87 11/11/96–5/2/97 (12) 3/A 14 0.0113 0.19 5/5/97–27/7/97 (9) 3/WA 14 0.0113 0.271 5/5/97–27/7/97 (9) aWA-‘weathered’ soil A.Sampling procedures Topsoil monitoring. Soil sampling was initially conducted with bidaily frequency but as the experiment proceeded this frequency was reduced. To ensure only the contaminated layer was sampled, the total depth to the base of each pot was measured and samples taken to this depth less 5 cm.Each sampling event comprised five cores taken over the soil surface using a steel tube of 1 cm diameter. These sub-samples were Fig. 1 Schematic diagram of the volatilisation chamber. homogenised and a 1.5 g sample taken for analysis, with unused sample being returned to the pot. using a Hi-Vol sampler, with volatilised PCBs retained on a Mass balance measurements.To provide an additional single polyurethane foam (PUF) plug. The sampling flow rate measurement of PCB persistence, a mass balance was conduc- and duration were identical for all samples (0.75 m3 min-1 ted for each soil in experiment 1. In summary, the mass and 24 h, respectively). balance for each pot is described by eqn.(1): To ensure that PCBs detected in the sampling PUF were due to volatilisation from the soil sample alone, the air entry Mu=M0+MD-ML-MS-Mt=415 (1) for the chamber was fitted with two PUF plugs to remove in which Mu is the ‘unaccounted for’ congener mass loss; M0 PCBs from incoming air. The PCB removal eYciency, is the congener soil burden at time zero (the start of the expressed as the percentage of incoming PCB removed by the experiment); MD is the increase in congener mass due to bulk ‘pre-chamber’ cleaning PUFs, was measured by conducting a atmospheric deposition; ML is the congener mass loss due to ‘chamber blank’, i.e., conducting an experiment but in the leaching; MS is the congener mass loss from sampling; and absence of soil, after each five experiments.Mean ‘chamber Mt=415 is the congener soil burden at the end of the experi- blank’ values for each congener were subtracted from all ment (415 d). experimental data. To facilitate mass balance calculation, at the end of experi- Prior to use, the chamber was thoroughly cleaned and dried. ment 1,Mt=415 was calculated by determining the PCB content The soil heater was installed on the base of the soil tray and of a single 5 cm diameter core to the base of the pot, and the experimental soil loaded into the soil tray to a depth of multiplying this by the total soil mass.M0 was determined by 7 cm. The platinum film detectors and the thermocouple probe measuring the soil bulk density, volume, and the PCB concen- were laid on the surface of this soil layer before being evenly tration in both the contaminated and non-contaminated soil covered to a depth of 1 cm with soil artificially enriched with layers, ML was estimated by summing the leached masses a known quantity of PCB congeners 28, 52, 101, 138, and 180.recorded in each sample over the duration of the experiment, MS was taken to be the total mass of PCB removed over all Measurement of edaphic properties the soil sampling events, and MD was calculated as the product Soil temperature was measured at a 1 cm depth via four evenly of the exposed soil surface area and the bulk atmospheric spaced sheathed platinum film detectors connected to a cali- deposition fluxes measured at the sampling site during the brated digital voltmeter.The temperature over the duration experiment.Our atmospheric deposition sampling method is of each experiment was maintained within ±2 °C. described elsewhere,4,5 but in summary, bulk (i.e., wet and PCB concentrations in the top 1 cm soil layer were deter- dry, vapour and particulate) deposition was collected on a mined at the beginning and end of each experiment, by monthly basis using an Al foil-lined inverted frisbee connected analysing a representative sample of approximately 1 g.This to an amber glass vessel. was obtained by taking ten sub-samples of 1 g each in an X pattern across the soil surface. After homogenization and Measurement of edaphic properties removal of the sample for analysis, the remaining soil was Mean air temperatures were taken from a weather station spread evenly over the surface layer.located near the experimental site. The soil foc was measured The soil foc was measured by elemental analysis, while the by elemental analysis, and the soil MC, determined by drying soil MC was taken as the mean of that determined for to constant mass, taken as the mean of that determined for representative soil samples taken before and after each experieach sampling event.ment. The water flux (WF) was calculated using eqns. (2) and (3). Laboratory experiments WF=ydkw (2) Volatilisation chamber. PCB volatilisation fluxes were studied kw=( ln W0-ln Wt)/t (3) using a custom-built chamber, illustrated in Fig. 1. Essentially, air was pulled via suction over the surface of a soil sample, where yd is the vertical diVusion distance assumed to be 396 J.Environ. Monit., 1999, 1, 395–4010.005 m (half the distance of the enriched soil layer); kw is the Results and discussion water flux rate constant in d-1; W0 and Wt are the masses of Field experiments water present (kg) in the soil at the beginning and end of each experiment, respectively, calculated as the product of MC and Applicability of first-order kinetics.PCB loss from a number the total mass of the spiked soil layer; and t is the duration of of Arctic soils was reported to follow first-order kinetics for the experiment (d). at least the first 5 years after initial contamination.6 However, Twenty-two laboratory experiments were conducted. The it has been suggested that first-order kinetics may not relevant conditions of each are detailed in Table 2.After each adequately describe long term PCB loss.7 To assess whether experiment, the PCB content of the sampling PUF was deter- first-order kinetics were appropriate to describe PCB loss from mined and converted to kv values using eqns. (4) and (5): soil over the time scales studied in this project, we plotted the concentration of each congener n in soil at time=t ( ln Ctn) kv=( ln M0-ln Mt)/t (4) against time (t) for each experiment.Table 3 summarises the kinetic information obtained from such plots for each congener Mt=M0-Mv (5) and experiment. Out of 40 such plots, linear correlation at the 99.9% confidence level was observed in 31 cases, and in only where M0 and Mt are the congener masses (mg) present in the one instance was the confidence level below 90%.These data soil at the beginning and end of each experiment, respectively; clearly show that PCB loss from soil over the relatively short and Mv is the congener mass (mg) present on the sampling duration of these experiments is a first-order process, with PUF (corrected for chamber blank). apparent deviations most likely due to a combination of soil inhomogeneity, particularly likely for soil C, and an inadequately low ratio of experiment duration to the rate of PCB Sample purification and analysis.PCB analyses were conduc- loss from a given soil. ted using well-validated GC-MS-based procedures.4,5 Soil samples were homogenised with Na2SO4 and Soxhlet extracted Comparison of half-life measurement methods.Table 4 sumwith hexane5acetone (40560 v/v), bulk deposition samples marises the mass balance data obtained. Half-lives obtained were filtered through a glass fibre filter (GFF) and PUF in by this method are consistently longer than those obtained via series before soxhlet extraction with dichloromethane, leachate the ‘topsoil monitoring’ approach (Table 3). We believe the samples were passed through a PUF prior to Soxhlet extraction discrepancies are predominantly due to the influence of soil with dichloromethane, and PUF samples of volatilised PCB compaction during experiment 1, which when combined with were Soxhlet extracted with dichloromethane.Following con- the sampling method adopted for the ‘topsoil monitoring’ centration, extracts were subjected to acid washing, Florisil approach means that as the experiment progressed, PCB chromatography, lipid removal via solvent exchange between concentrations were measured in an increasingly narrower DMSO and hexane, and concentration prior to GC-MS analy- depth of soil from which PCB loss via volatilisation would be sis on a Fisons’ MD-800 instrument, fitted with an HP-5 Trace more facile.It is therefore considered that the half-lives Analysis column (60 m×0.25 mm i.d.×0.25 mm film thick- reported in Table 3 are underestimates where soil compaction ness). One ml of sample extract was injected in the splitless occurs. mode (injector and transfer line temperatures both 300 °C), and the oven program was 140 °C for 2 min; 5 °Cmin-1 to Comparison with previously reported half-lives. The variation 200 °C; and 2 °Cmin-1 to 280 °C.Ten ions were monitored in in half-lives that we observed for diVerent congeners, soils, EI selected ion monitoring (SIM) mode (ionisation voltage= and climatic conditions, is consistent with the range reported 70 eV) for the analysis of the trichlorinated biphenyls through by other studies. Individual PCBs in artificially contaminated the heptachlorinated biphenyls, two ions for each homolog Arctic soils displayed half-lives of 0.7–2.3 years,6 half-lives in group.These ions were 255.95, 257.95, 289.95, 291.95, 325.90, sewage sludge-amended UK agricultural soils ranged from <1 327.90, 359.90, 361.90, 393.85, and 395.85. to 8.5 years for PCBs 18, 28 and SPCB,7 those for di-, tri-, and tetrachlorobiphenyls were 0.5, 0.75, and 3.2 years, respectively, in field studies of PCB loss from sewage sludge-amended Quality control and quality assurance.Sampling eYciency soil,8 while data extrapolated from temporal trends in PCB standards (SESs, PCB congeners 19 and 147) were added to levels in UK soils indicated a mean half-life for PCBs in 5 the bulk deposition sampler, the leachate capture vessel, and diVerent soils of ca. 5 years.9 It is therefore interesting that the sampling PUF used in the laboratory experiments before the average half-life for congeners 28, 52, 101, 138, and 180 each measurement. SES recoveries (which reflect analyte losses in ‘weathered’ soil A in experiment 3, which we consider the due to both sampling and analysis) ranged between 45 and most applicable to ‘typical’ UK conditions, is ca. 5.5 years. It 75% for the field experiments and between 55 and 86% for the is important to note, however, that our experiments measured laboratory experiments. Sample data were not corrected for PCB loss in the absence of vegetative cover, which appears to SES recoveries. Recoveries of internal standards added to retard PCB loss from soil,6 and thus are likely to underestimate check analyte losses during sample analysis alone (PCB con- PCB persistence in many environmental scenarios.geners 34, 62, 119, 131, and 173) ranged between 47 and 90% for all samples. To measure the combined uncertainty due to Congener-specific diVerences in persistence. Table 3 reveals a marked increase in persistence with increasing chlorine soil sampling and analysis combined, five replicate soil samples were analysed for each experiment.The coeYcients of variation number. The octanol air partition coeYcient (Koa), which is negatively correlated with increasing chlorination within a for individual congeners ranged between 4 and 16% (arithmetic mean=6.8%). compound class, has been suggested as the most suitable physico-chemical parameter for predicting semivolatile organic compound (SOC) partitioning between air and organic environmental media, such as soil.10 To evaluate the relation- Multiple linear regression analysis (MLRA).MLRA was conducted using SPSS for Windows version 7 in a ‘retro- ship between Koa and PCB persistence in our experiments, we derived Koa values for each congener at the mean temperature analytical’ manner.Inclusion of independent variables in the final regression equation depended on significant T not of each experiment using appropriate algorithms,11,12 and plotted ln Koa against k. The relationship between ln Koa and exceeding 0.1. J. Environ. Monit., 1999, 1, 395–401 397Table 2 Conditions and volatilization rate constants (kv d-1) for laboratory experiments Mean soil concentration of congener/mg kg-1 kv for congenerd Experiment foc a MCb WFc T /K 28 52 101 138 180 28 52 101 138 180 1 0.011 0.40 0.24 303 46.8 51.9 37.3 42.1 48.5 0.0094 0.0073 0.0029 0.0031 0.0003 2 0.011 0.40 0.26 303 49.1 47.3 36.1 41.5 55.0 0.0113 0.0085 0.0037 0.0012 0.0003 3 0.207 0.63 0.02 303 116.5 134.5 126.5 113.7 131.8 0.0037 0.0021 0.0008 0.0002 0.0001 4 0.021 0.26 0.07 303 30.0 30.9 34.0 31.7 30.9 0.0145 0.0111 0.0046 0.0023 0.0005 5 0.011 0.33 0.16 285 44.6 48.8 41.0 44.8 48.7 0.0058 0.0043 0.0018 0.0003 0.0001 6 0.011 0.40 0.06 286 30.7 32.9 31.5 29.2 31.9 0.0082 0.0061 0.0025 0.0004 0.0002 7 0.011 0.25 0.29 278 28.2 25.0 23.1 27.0 23.6 0.0034 0.0009 0.0013 0.0004 0.0004 8 0.011 0.18 0.07 293 32.8 31.3 27.5 32.1 29.7 0.0035 0.0054 0.0021 0.0006 0.0003 9 0.011 0.36 0.41 286 20.0 24.1 22.3 22.7 23.3 0.0098 0.0076 0.0030 0.0004 0.0001 10 0.011 0.19 0.16 286 16.5 21.1 19.6 21.7 20.3 0.0033 0.0029 0.0010 nc nc 11 0.011 0.20 0.25 286 16.9 19.8 18.3 18.0 19.3 0.0054 0.0049 0.0016 0.0002 nc 12 0.011 0.18 0.39 286 16.7 18.1 17.1 18.2 18.5 0.0027 0.0027 0.0008 nc nc 13 0.011 0.12 0.28 286 14.6 15.9 14.1 9.2 14.9 0.0009 0.0010 0.0008 0.0001 nc 14 0.011 0.34 0.35 286 61.7 63.3 59.9 58.8 58.4 0.0051 0.0042 0.0023 0.0005 nc 15 0.011 0.29 0.20 287 73.7 74.7 70.3 69.5 69.8 0.0044 0.0039 0.0024 0.0006 nc 16 0.011 0.27 0.14 286 79.4 79.5 78.5 77.1 77.8 0.0042 0.0039 0.0023 0.0006 nc 17 0.044 0.33 0.43 303 9.6 7.7 10.0 11.3 14.0 0.0146 0.0109 0.0044 0.0007 0.0003 18 0.017 0.08 0.26 303 8.0 7.6 7.5 9.1 7.7 0.0144 0.0101 0.0036 0.0014 0.0012 19 0.021 0.11 0.29 303 9.3 8.9 9.1 11.9 8.8 0.0271 0.0195 0.0102 0.0016 0.0013 20 0.207 0.87 0.03 303 44.0 43.2 43.5 37.7 39.0 0.0016 0.0014 0.0007 0.0002 0.0001 21 0.011 0.31 0.17 303 18.3 21.5 20.3 17.4 12.4 0.0178 0.0128 0.0051 0.0029 0.0015 22 0.011 0.27 0.18 303 13.2 14.6 14.4 12.6 12.7 0.0217 0.0162 0.0061 0.0035 0.0014 afoc is organic carbon content of soil (g g-1).bMC is moisture content of soil (g g-1). cWF is water evaporation flux (cm d-1). dnc is not calculable. 398 J. Environ. Monit., 1999, 1, 395–401Table 3 Summary of kinetic data for field experiments Half-life (rangea)/d Experiment soilb Congener 28 Congener 52 Congener 101 Congener 138 Congener 180c 1/A 94 (90–98) 100 (95–107) 126 (120–133) 173 (160–188) 217 (204–230) 1/B 91 (88–95) 105 (99–112) 139 (133–144) 198 (178–223) 210 (198–224) 1/C 178 (157–204) 187 (169–211) 257 (210–329) 239 (198–303) 433 (347–578) 2/A 148 (122–187) 193 (131–363) 231 (165–385) 239 (173–386) 224 (161–367) 2/B 161 (147–179) 217 (187–258) 301 (247–386) 347 (257–533) 85 (301–535) 2/C 267 (217–346) 239 (187–332) 495 (315–1151) 630 (435–1146) 866 (385–nc) 3/A 122 (117–127) 154 (144–166) 217 (192–249) 315 (289–346) 408 (364–463) 3/WA 193 (178–209) 267 (247–290) 462 (432–497) 495 (434–576) 8664 (5776–17239) aRange calculated using percent error in k.bWA=‘weathered’ soil A. cnc is not calculable. Table 4 Mass balance data for field experiment 1 Soil Congener M0/mg MD/mg ML/mg MS/mg Mt=415/mg MU/mg Half-life (rangea)/d A 28 65.1 0.29 0.13 0.50 6.1 58.7 121 (112–133) A 52 70.6 0.37 0.10 0.61 7.8 62.5 131 (120–144) A 101 62.5 0.24 0.09 0.51 15.0 47.1 202 (175–239) A 138 63.7 0.17 0.07 0.57 29.1 34.1 367 (298–477) A 180 91.4 0.07 0.05 0.72 51.4 39.2 500 (402–661) B 28 74.2 0.29 0.02 0.75 5.9 67.8 114 (106–122) B 52 77.4 0.37 0.02 0.87 10.2 66.7 142 (134–151) B 101 79.5 0.24 0.03 1.00 20.7 58.1 214 (199–231) B 138 67.2 0.17 0.01 1.03 31.0 35.3 372 (308–469) B 180 99.8 0.07 0.01 1.33 53.9 44.7 467 (402–558) C 28 41.2 0.29 0.02 0.89 15.0 25.5 285 (223–395) C 52 50.3 0.37 0.02 1.12 24.2 25.3 393 (302–563) C 101 41.1 0.24 0.01 0.97 28.9 11.5 817 (469–3172) C 138 45.2 0.17 0.01 1.06 34.9 9.5 1112 (495–nc)b C 180 54.3 0.07 0.01 1.34 49.3 3.2 3325 (781–nc)b aRange calculated from measured combined sampling and analytical coeYcient of variation for each congener and each soil.bnc=not calculable. k for soil A over the entire duration of experiment 1 is significant at the 99.9% confidence level. Similar plots for other soils and experiments reveal linear relationships between ln Koa and k that, for all but one experiment, are significant at at least the 90% confidence level.Clearly, our field experiments indicate PCB persistence to be positively linearly correlated with ln Koa. Influence of soil organic carbon content. With very few exceptions, PCB persistence in the three soils studied in experiments 1 and 2 followed the order soil C&soil B>soil A. While there are insuYcient data to permit firm conclusions to be drawn, this observation is consistent with the hypothesis that SOC persistence in soils is positively correlated with foc.Fig. 2 PCB half-lives in soil A over the first 86 d of experiments 1 and 3. Influence of temperature and soil moisture content. Table 3 demonstrates that over the full durations of experiments 1 and 2 the half-lives of all congeners in all soils were significantly longer in experiment 2.As discussed above, there appears to used for the 2 experiments were not absolutely identical with be a positive correlation between PCB persistence and Koa. respect to their PCB sorption potential, the only other detected The latter is negatively correlated with temperature, and it is diVerence between the two experiments was that the mean soil thus unsurprising that PCB persistence is greater in experimoisture contents were 0.363 and 0.190 g g-1, respectively, ment 2 (mean temperature=3 °C) than experiment 1 (mean over the first 86 days of experiments 1 and 3.temperature=10 °C). However, there is evidence that a Furthermore, half-lives in soil A were comparable in experi- straightforward temperature-related seasonal eVect on PCB ments 2 and 3, despite the higher mean temperature observed persistence does not occur in all instances, and that edaphic in experiment 3 (14 °C compared with 3 °C).Again, mean soil properties other than temperature may play an important ro� le. moisture content was higher in experiment 2 (0.425 g g-1) To illustrate, Fig. 2 shows the half-lives of PCBs measured in than in experiment 3 (0.190 g g-1).Such eVects on persistence soil A over the first 86 days of both experiment 1 and 3. It is associated with increased soil moisture content, are consistent apparent that despite the mean temperatures over both periods with the concept that such increases enhance competition being similar (13 °C and 14 °C for experiments 1 and 3, between water and PCB molecules for sorptive sites in the respectively) PCBs were clearly more persistent in experiment 3.Aside of the possibility that the sub-samples of soil A soil matrix. J. Environ. Monit., 1999, 1, 395–401 399Influence of soil ‘weathering’. While the majority of our Extrapolation to field conditions. To test the field validity of eqn. (6), we used it to predict half-lives for individual con- experiments studied PCB fate in ‘freshly-enriched’ soils, experiment 3 compared PCB loss from two portions of soil A (one geners under the conditions prevailing in the field experiments.Table 5 compares these predicted values with those observed ‘freshly-enriched’, the other subjected to 1 year of ‘weathering’, i.e., exposure to environmental conditions following artificial in field experiments 1, 2, and 3.Clearly, eqn. (6) is only applicable under specific conditions; it functions poorly, if at enrichment in the same fashion as the other soils). Half-lives in the ‘weathered’ soil are clearly longer for all congeners all, for soils with a high foc, is inapplicable to both PCBs 138 and 180 under the conditions of our field experiments, and despite the fact that its mean moisture content was higher than that of the ‘freshly-contaminated’ soil.This is consistent cannot distinguish between PCB persistence in a freshlycontaminated soil and an identical ‘weathered’ soil. Despite with the suggestion that SOC persistence in soils is strongly dependent on the length of the SOC–soil interaction, i.e., the such limitations, eqn.(6) predicts the persistence of congeners 28, 52, and 101 to a reasonable degree of accuracy (mean extent of ‘weathering’, and that laboratory studies where PCBs are added as spikes underestimate PCB persistence.7 observed5predicted ratio=1.04; s=0.55; range=0.10–2.32). Evidently, although eqn. (6) may only be used under certain conditions, it is capable of predicting to within at least a factor Relative significance of potential loss mechanisms.Five possof 2.5, the persistence of PCBs 28, 52, and 101 in soils of ible mechanisms may account for PCB loss during our experitypical foc values at the annually averaged temperatures prevail- ments: leaching, soil erosion, uptake by biota, degradation, ing in the UK. There are several likely factors why this and volatilisation.Table 4 shows that PCB losses due to equation is not more accurate, the majority associated with leaching (ML) were minimal compared with the ‘unaccounted the influence of excluded variables. These are: MC, WS, and for’ mass loss (MU). A quantitative expression of this obserconsideration of the length of PCB association with the soil vation was obtained by calculating ML/MU for each congener matrix (‘weathering’).Each of these is likely to exert an and soil. Values ranged from 0.0002 to 0.0031, with an influence on PCB persistence under field conditions, and their arithmetic mean and s of 0.0013 and 0.00086, respectively. omission from eqn. (6) inevitably impairs its eYcacy. It should Similarly, we consider losses due to soil erosion to be minimal also be noted that predicted half-lives consider loss due to for two reasons: first, the magnitude of MU could only be volatilisation only.The correspondence between predicted and assigned to soil erosion if a significant proportion of the total observed half-lives therefore provide further indirect evidence soil mass was lost during the experiments, such loss was not that volatilisation was the major loss mechanism operating observed; secondly, soil erosion would aVect all congeners during the field experiments. equally, and thus significant losses via this mechanism are Given the mechanistic simplicity and potential wider generic inconsistent with the observed congener-specific losses.Uptake applicability of eqn. (6), it is instructive to compare its ability by biota is not considered significant in our experiments as to forecast PCB fate in soil with that of the more mechan- weeds were removed regularly and PCB translocation from istically detailed mathematical modelling approach developed soil to foliage is considered minimal, and also because fauna by Jury and coworkers to predict volatilisation fluxes of such as earthworms were either absent or included in the final surface applied chemicals from soils.14 As we had not measured ‘mass balance’ measurement.Although we did not measure all of the input parameters required to evaluate the Jury any PCB degradation products, aerobic degradation has been approach, direct evaluation of its predictive performance with shown to be significant under favorable conditions for lower respect to our data was not possible.Instead, we referred to chlorinated PCBs,7 with one study reporting that although no the work of Cousins et al.15 who assessed the ability of the degradation of Aroclor 1260 was observed, 4–7% of the PCB Jury approach to predict PCB volatilisation fluxes measured associated with a soil contaminated with 100 mg kg-1 of under controlled laboratory conditions for a number of sewage Aroclor 1242 was aerobically degraded by indigenous microsludge- amended soils.For surface layer sludge applications, flora over a 60 d period.13 Over the first 63 d of experiment 1, they measured volatilisation fluxes of PCBs 18, 33, 47, 52, 87, k for the loss of congener 28 from soil A was 0.0143.This and 101 over three consecutive time periods. Using the Jury equates to a loss of ca. 60% of the initial loading of PCB 28 in 63 d, and thus the estimated maximum contribution of aerobic degradation to the overall loss of congener 28 is 12%. Table 5 Observed field and predicted half-lives using equation 6a In addition to biodegradation, there may also have been losses Observed field due to photolysis, but we have been unable to measure the half-life Predicted significance of this pathway.By implication therefore, we Experiment Soila Congener (rangeb)/d half-life/d conclude that the principal PCB loss mechanism in our field experiments is volatilisation; a hypothesis supported by our 1 A 28 121 (112–133) 115 observed correlation between ln Koa and k. 1 A 52 131 (120–144) 132 1 A 101 202 (175–239) 467 1 B 28 114 (106–122) 115 Laboratory experiments 1 B 52 142 (134–151) 132 1 B 101 214 (199–231) 467 In seven experiments the volatilised mass of PCB 180 was 1 C 28 285 (223–395) 2963 below the average ‘chamber blank’ value, while in the remain- 2 A 28 148 (122–187) 188 der, volatilised mass was frequently close to the blank level. 2 A 52 193 (131–363) 210 2 B 28 161 (147–179) 204 We therefore eliminated data for this congener before con- 2 B 52 217 (187–258) 231 ducting a multiple linear regression analysis on this reduced 3 A 28 122 (117–127) 99 data set (Table 2). This analysis yielded eqn. (6) relating kv, 3 A 52 154 (144–166) 115 to foc and temperature-dependent ln Koa. 3 A 101 217 (192–249) 295 3 WA 28 193 (178–209) 99 kv=5.17×10-2-2.21×10-3 ln Koa-2.97×10-2 foc (6) 3 WA 52 267 (247–290) 115 3 WA 101 462 (432–497) 295 n.(6) was significant at the 99.99% confidence level. b aWA denotes ‘weathered’ soil A. bOnly those experiments for which values were derived for both independent variables, and predictions were calculable are shown. For all other experiments, revealed ln Koa (b=-0.79) to exert amore significant influence predicted half-lives were not calculable.on k, than foc (b=-0.31). 400 J. Environ. Monit., 1999, 1, 395–401model provided predicted fluxes that consistently underesti- ditions. Multiple linear regression analysis of these data revealed the most important independent variables to be ln mated measured values by a mean factor of 12.4 (s=9.99; range=3.4–40.7).Clearly, although we were unable to conduct Koa (adjusted for soil temperature), and to a lesser extent, foc. The multiple linear regression equation derived was tested direct comparison of the relative eYcacy of our empirically derived equations with that of the Jury model, when used against our field measurements of PCB persistence in soils, and found to perform well for PCBs 28, 52, and 101 under appropriately eqn.(6) appears to be a useful ‘screeninglevel’ tool. conditions consistent with those typically prevailing in the UK. However, caution is needed if the findings of this work Observations on the influence of specific parameters on kv are to be extrapolated to other situations. Specifically, the regression equation does not account for the influence of the Soil organic carbon content.The foc was negatively correlated age of contaminant association with the soil (‘weathering’), with kv, a finding consistent with previous theoretical treatthe eVect of varying soil moisture content, and fails to function ment.16 Further support for this relationship is supplied by for soils of high organic content, or in situations where ln Koa other experimental studies, each demonstrating a negative exceeds ca. 23, e.g., for congeners 138 and 180 at soil tempera- relationship between SOC evaporative loss from soil and tures approaching 0 °C.foc.17–19 Soil moisture content and water evaporation flux. In contrast Acknowledgements to MLRA of the whole data set, analysis of laboratory We gratefully acknowledge the Royal Society and the West experiments 9–14 inclusive, suggests that kv may be positively Midlands Regional OYce of the National Health Service linearly related to MC.In these experiments, MC was varied, Executive for supporting our work on PCBs, and Gian Marco while other independent variables were essentially held con- Currado and Lee Hoon Lim for assistance with sampling stant.Plots of kv against MC for PCBs 28, 52, and 101, atmospheric deposition. respectively, in these experiments (there were insuYcient data to permit similar plots for congeners 138 and 180) revealed good Pearson correlation coeYcients (0.947>R>0.831, i.e., References significant at the 95–99% confidence level ) for these congeners. These findings suggest that MC does exert an influence on kv, 1 F.X. R. van Leeuwen and M. Younes, Organohalogen Compd., 1998, 38, 295. but that the eVect detected in our laboratory experiments is 2 Department of the Environment, United Kingdom action plan for very small compared to that of ln Koa and foc. the phasing out and destruction of polychlorinated biphenyls (PCBs) It has also been suggested that PCB volatilisation fluxes are and dangerous PCB substitutes, Department of the Environment, positively correlated with water flux.16 However, neither the London, 1997.MLRA conducted on the full data set, nor regression of WF 3 S. J. Harrad, A. Sewart, R. Alcock, R. Boumphrey, V. Burnett, versus kv for experiments 9–14, revealed any significant R. Duarte-Davidson, C. Halsall, G.Sanders, K.Waterhouse, S. R. Wild and K. C. Jones, Environ. Pollut., 1994, 85, 131. relationship between these two variables. 4 S. Ayris, G. M. Currado, D. Smith and S. Harrad, Chemosphere, 1997, 35, 905. Octanol air partition coeYcient. In addition to our field 5 S. Harrad and D. Smith, Sci. Total Environ, 1998, 212, 137. experiments, other recent experimental studies support the 6 S.L. Grundy, D. A. Bright, W. T. Dushenko and K. J. Reimer, broad validity of eqn. (6). Chiarenzelli et al.20 observed that Environ. Sci. Technol., 1996, 30, 2661. approximately 60%, 55%, 35% and 20% of the PCBs contained 7 R. E. Alcock, J. Bacon, R. D. Bardget, A. J. Beck, P. M. in Aroclors 1242, 1248, 1254, and 1260, respectively, volatilised Haygarth, R. G. M. Lee, C. A.Parker and K. C. Jones, Environ. Pollut., 1996, 93, 83. over one day from subaqueous sand. Cousins et al.15 measured 8 R. Gan and P. M. Berthoux, Water Environ. Res., 1993, 66, 54. volatilisation fluxes of individual tri-through pentachloro PCBs 9 R. E. Alcock, A. E. Johnston, S. P. McGrath, M. L. Berrow and from sewage sludge ameliorated soils. MLRA of this dataset K. C. Jones, Environ. Sci. Technol., 1993, 27, 1918. showed that fluxes were positively correlated with the sludge 10 T. Harner and D. Mackay, Environ. Sci. Technol., 1995, 29, 1599. concentration and negatively correlated with log Koa. 11 T. Harner and T. F. Bidleman, J. Chem. Eng. Data, 1996, 41, 895. This study shows that over periods of up to 415 d, PCB loss 12 R. L. Falconer and T. F. Bidleman, Atmos. Environ., 1994, 28, 547. 13 B. Guilbeault, M. Sondossi, D. Ahmad and M. Sylvestre, M. Int. from soil under field conditions typically prevailing in the UK Biodeterior. Biodegrad., 1994, 33, 73. follows first-order kinetics. It reports first-order rate constants 14 W. A. Jury, W. F. Spencer and W. J. Farmer, J. Environ. Qual., for the loss of five PCB congeners from three soils, and 1983, 12, 558. provides evidence that they are correlated with ln Koa and 15 I. T. Cousins, N. Hartlieb, C. Teichmann and K. C. Jones, influenced by temperature as well as soil moisture and organic Environ. Pollut., 1997, 97, 229. carbon content. The age of PCB association with one soil 16 G. H. Eduljee, Chemosphere, 1987, 16, 907. 17 B. Lindhardt and T. H. Christensen,Water, Air, Soil Pollut., 1996, (‘weathering’) was shown to influence persistence, with signifi- 92, 375. cantly longer PCB half-lives observed in soil subjected to ca. 18 R. Haque and D. W. Schmedding, J. Environ. Sci. Health, Part B, 1 year’s prior ‘weathering’. Indirect evidence suggests that the 1976, 11, 129. primary loss mechanism is volatilisation, and although the 19 Y. Iwata, W. E. Westlake and F. A. Gunther, Bull. Environ. significance of aerobic biodegradation could not be dismissed, Contam. Toxicol., 1973, 9, 204. losses due to leaching, soil erosion, and uptake by biota were 20 J. R. Chiarenzelli, R. J. Scrudato and M. L. Wunderlich, Environ. Sci. Technol., 1997, 31, 597. shown to make negligible contributions to the overall loss. First-order rate constants for the volatilisation of PCBs from soil were determined under controlled laboratory con- Paper 9/03017D J. Environ. Monit., 1999, 1, 395–401 401

ISSN:1464-0325    

DOI:10.1039/a903017d

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

An investigation of the origin and mobility of phosphorus in freshwater sediments from Bort-Les-Orgues Reservoir, France V. Ruban,* S. Brigault, D. Demare, and A.-M. Philippe Laboratoire Central des Ponts et Chausse�es, B.P. 19, 44340 Bouguenais, France Received 22nd March 1999, Accepted 25th May 1999 In order to assess the origin and the potential mobility of phosphorus (P) in the sediment of the Bort-Les-Orgues Reservoir, France, two sequential extraction schemes, i.e., the SMT (modified Williams method)and the Golterman schemes, were compared. Finally, the potential mobility of P in this sediment was estimated from results of sequential extraction.The SMT method appeared to be more satisfactory than the Golterman method, which is in accordance with results from a study currently carried out in the framework of the European programme Standards, Measurements and Testing.Iron-bound P and organic P were the dominant forms of P in the sediment; these forms are likely to be released at the sediment/water interface in case of anoxia and could diVuse into the water column, thus increasing the risk of eutrophication in this sensitive reservoir.The P stock (330±66 t) is not negligible and should be taken into account in any restoration project of the reservoir. The SMT procedure seems promising and will provide, in the near future, a valuable tool for water managers in the field of lake restoration. potential mobility of P species, they also allow the assessment Introduction of the origin of the sediment phosphorus. Water management of lakes, reservoirs and watercourses has In this paper, two sequential extraction schemes, modified become an increasing problem due to the development of Williams (SMT) and Golterman, aimed at determining the eutrophication.This excessive supply of phosphorus (mainly origin of phosphorus in the sediment of the Bort-Les-Orgues from anthropogenic origin) to water systems, induces a degra- Reservoir (France) are compared.Finally, the potential dation of their quality through the proliferation of algae, thus mobility of phosphorus in this sediment is assessed. hindering various water uses. Much eVort and money have been spent on combating this form of pollution, but eutrophication remains one of the most important water quality prob- Description of the study site lems in Europe. This clearly appears through the Urban The hydroelectric reservoir of Bort-Les-Orgues is located in Wastewater European Directive of May 21, 1991, in which the upper part of the Dordogne River, not far from its source; eutrophic waters are defined as ‘sensitive areas’ requiring it is the largest reservoir of the French Massif Central.The stricter standards for phosphorus and nitrogen discharge to drainage basin is 1745 km2 (1010 km2 for the Dordogne River, receiving waters. 735 km2 for the Rhue River). The reservoir is 20 km long with Phosphorus is regarded as the key factor in freshwater a mean depth of 43.7 m and a maximum depth of 110 m. For eutrophication.1–3 It has two origins, i.e., external and internal. the normal elevation of exploitation (542.5 m above sea level ), Phosphorus from external origin comes from diVuse sources it has an area of 10.91 km2 and a volume of 477 ×106 m3.It (natural, agricultural ) or point sources (industrial and domshould be noted that these data apply for 1996, the year during estic eZuents). This nutrient is also released from the sediment, which this study was carried out.The main set of characteristics which acts as an internal source.4 Sediment can contribute regarding hydrology, land use and population are given in phosphate to the overlying waters at levels comparable to the Ruban and Demare.12 external source.5 However, not all the forms of P are likely to be released and thereby increase eutrophication. The ability of a sediment Sampling and preservation to store or release P has repercussion on the trophic state of a lake, hence on its productivity.The study of the sediment Three sediment cores were taken in the reservoir in 1997, behaviour is, therefore, a key factor which helps understanding down to a depth of 25 cm, the CEMAGREF sampler was the P cycle in rivers and lakes. It is also of prime importance used.A surface sample (0–5 cm) was also collected by means in the framework of water management and restoration of of a grab sampler. The cores were sliced as follows : 0–2 cm, water bodies. 2–5 cm, 5–10 cm and then every 5 cm to the bottom. The The various forms in which P occurs in sediments has samples were put into glass bottles and stored at a temperature received considerable attention during the past decades and of 4 °C until analysis. The sediment was passed through a many extraction schemes have been developed. Good extrac- 200 mm sieve in order to eliminate coarse plant fragments and tion methods are operationally defined on the basis of the then freeze dried.Though not perfect, this technique induces reactivity of a particular phase in a given extractant.There little change in the sediment and allows reproducible analyses are two types of methods: the ‘strong’ ones using HCl– even after several months, which is not always the case with NaOH6–9 and the ‘soft’ ones in which chelators such as nitrilo fresh sediment. triacetic acid or EDTA are used.10,11 pH and redox potential (Eh) were measured in situ by means of Ponselle probes (Ponselle PVRT).Extraction methods not only provide information on the J. Environ. Monit., 1999, 1, 403–407 403with de-ionised water. A quality control procedure was applied Sample analysis throughout the diVerent steps of sample preparation and The following determinations were carried out on the fraction analysis. The quality control procedure mentioned was that in of the sediment with a particle size of less then 200 mm: (i) loss use at the Water Division of Laboratoire Central des Ponts et on ignition (calcination at 550 °C for 2 h); (ii) water content Chausse�es.The materials and equipment (e.g., glassware, (drying at 105 °C until stable weight); (iii) particle size distri- balances, pH meters, pipettes, spectrophotometers) were regubution ( laser diVraction, Malvern Mastersizer MS1005) larly checked and the traceability of the samples was ensured Kjeldahl nitrogen13 (distillation with concentrated H2SO4); thanks to data reported in specific books.Furthermore, blanks (iv) iron, calcium (FAAS,Varian Spectra A300); (v) organic and standards were regularly run with each series of analyses carbon14 (oxidation with potassium dichromate); (vi) total in order to check the validity of the data.phosphorus (persulfate digestion+colorimetry according to Murphy and Riley15); and (vii) sequential extraction of P. Characteristics and origin of the sediment Two operationally defined extraction schemes were used in this study, i.e., a modified version of the Williams method Fig. 1 shows the main characteristics of the sediment in the (SMT), which has been proposed in the frame of the Bort-Les-Orgues Reservoir. The sediment was mainly silt (87% ‘Standards, Measurements and Testing’ programme of the on average) and was homogeneous with depth.Furthermore, European Commission, and the Golterman method (G). The there was little variation from upstream to downstream. initial version of the Williams method and the Golterman Organic carbon slightly increased from upstream (5.4%) to scheme are widely recognised for the determination of P downstream (6.2%); these values are in the range of concencompounds in lake sediments,10,11,16–18 and the SMT protocol trations for sediments in reservoirs from crystalline watersheds seems promising19 because it is relatively easy to implement, (4.9–6.4%) as reported by Rofes.20 can be used for all kinds of sediments (either calcareous, Calcium concentration was low (7.2 mg g-1), whereas iron siliceous or organic), and has a good reproducibility.concentration was high (58 mg g-1). Again, these elements The SMT method is composed of five steps and involves were homogeneous with depth (Table 2).As the iron concenthe of aqueous solutions of NaOH and HCl19 (Table 1). tration was much higher than the calcium concentration, iron The following forms are determined : iron-bound P, calcium- would probably be a key factor in phosphorus exchange at bound P, inorganic P, organic P and total P. the sediment/water interface. Note that the abundance of iron The Golterman method, (G) utilises chelators (Ca–EDTA, is characteristic of crystalline regions such as the French Na2EDTA) and is carried out at a pH similar to the sediment Massif Central.pH. It also comprises five steps as shown in Table 1: labile P, The C/N ratio is a good indicator of organic carbon iron-bound P, calcium-bound P, acid soluble organic P and sources.17 Sediments of terrestrial origin have a C/N ratio of reductant organic P.around 14–20 (by weight), while phytoplankton, the major Both methods have shortcomings, e.g., the partial resorption source of autochthonous organic matter in lakes, produces of P extracted by NaOH onto CaCO3 in the case of SMT, ratios of from 5 to 9. In the Bort-Les-Orgues sediment, C/N and possible solubilisation of a very small part of organic averaged 13 upstream and 11 downstream.These values are matter by NaOH in the first step. In the case of the G method, slightly higher than the average for the Pareloup Reservoir chelators interfere with P determination and the method is (9.8) located about 100 km south from Bort-Les-Orgues. This very long and lacks precision. ratio results from the mixing of two pools of organic matter The detection limits were 0.01 mg g-1 for the forms of P (OM), autochthonous and allochthonous, on which is superand total phosphorus (TP), 1 mg g-1 for Fe and 0.1 mg g-1 imposed biogeochemical modification of the particulate matter.for Ca. Allochthonous organic matter prevailed but it can be seen Five replicate determinations were made for each form of that autochthonous material increased downstream.P (for both methods). The coeYcient of variation ranged from 0.5 to 5%. For the SMT scheme, the precision of the method Sequential extraction of P is ±5% for HCl–P, inorganic P and concentrated HCl extractable P, ±10% for NaOH–P and organic phosphorus (OP). Comparison of the SMT and Golterman methods Regarding the G method, the precision is around ±20%, ±50% for labile P because of the very small quantities Total phosphorus (TP) concentrations in the surface sediment (SMT method) are presented in Fig. 2. Although TP concen- extracted in this step. The Murphy and Riley colorimetric method15 was used to trations were rather high (2–2.5±0.1 mg g-1 on average), these values are comparable to those reported by Bostro�m measure P in the extracts. The quantification of phosphate was based upon calibration curves of standard solutions.These et al.21 for lake sediments and they are in the upper range of concentrations for sediments from crystalline reservoirs as curves were determined several times during the period of analysis. reported by Rofes.20 There was no significant tendency with depth as shown in Table 2.The small variations observed All the reagents used were analytical-reagent grade; the glassware and plasticware were soaked in 0.3% HCl and rinsed probably resulted from changes in phosphorus inputs over Table 1 Reagents used and corresponding P fractions in the two sequential extraction procedures tested in this study Step 1 Step 2 Step 3 Step 4 Step 5 SMT NaOH 1 mol L-1, HCl 1 mol L-1 HCl 3.5 mol L-1 HCL 1 mol L-1, HCl 1 mol L-1 iron-bound P, +3.5 mol L-1, +calcination, inorganic P +calcination, bioavailable Ca-bound P, total P organic P, partly non-available available Golterman H2O, labile P, Ca–EDTA+dithionite Na2–EDTA H2SO4 NaOH 2 mol L-1, bioavailable 0.05 mol L-1, 0.1 mol L-1, 0.25 mol L-1, reductant organic P, iron-bound P, Ca-bound P, acid soluble non-available bioavailable non-available organic P bioavailable 404 J.Environ. Monit., 1999, 1, 403–407Fig. 1 Characterization of the sediment in the Bort-Les-Orgues Reservoir. time (dry year/wet year), but these changes remained small, since P concentration in the Rhue River is higher than that of other tributaries of the lake. The influence of the Rhue River within the precision of the method.Besides, TP concentrations tended to increase from upstream (1.99±0.1 mg g-1) to down- was observed up to station 3, 2 km from the dam.23 In order to know whether the diVerence between upstream stream (2.55±0.13 mg g-1), as did organic C concentrations. This has been observed in other reservoirs, e.g., in St Etienne and downstream TP was significant, a statistical test was carried out.Because the number of observations was small, Cantale`s Reservoir.22 In the case of Bort-Les-Orgues, the increase in P could result from inputs from the Rhue River the non-parametric test of White was used. For a=0.05, the J. Environ. Monit., 1999, 1, 403–407 405Table 2 Concentration of the forms of P, Fe, and Ca in a sediment core collected at station 4 (deeper part of the lake) Depth/ Ca/ Fe/ TP/ HCl–P/ NaOH–P/ OP/ cm mg g-1 mg g-1 mg g-1 mg g-1 mg g-1 mg g-1 0 7.3 5.8 2.69 0.38 1.55 0.67 2–5 7.2 59 2.65 0.42 1.60 0.62 5–10 7.1 58 2.60 0.40 1.62 0.65 10–15 7.2 58 2.70 0.40 1.50 0.69 15–20 7.2 57 2.72 0.42 1.65 0.63 20–25 7.3 59 2.67 0.42 1.60 0.63 Mean 7.2 58 2.67 0.41 1.59 0.65 SD 0.08 0.75 0.05 0.02 0.05 0.03 Fig. 2 Total phosphorus concentrations in the Bort-Les-Orgues Reservoir. TP was measured by the SMT and Golterman extraction schemes, and by persulfate digestion. Five replicates were made, the mean value and standard deviation are reported on the figure. hypothesis of equality between the means was rejected, therefore, it can be admitted that upstream P values are diVerent from downstream P values.Fig. 3 shows the distribution of phosphorus forms at the four stations in the Bort-Les-Orgues sediments, the SMT and Golterman methods were used. Concentrations were homogeneous within a core (Table 2), consequently, average values are presented here. The test of White was again applied to test the diVerence between the two methods. As shown in Table 1, step 1 (SMT) and 2 (G) are equivalent, so are step 2 (SMT) and 3 (G), and step 4 (SMT) and 4+5 (G).Consequently, for each station, HCl–P (SMT)/Ca–P (G), NaOH–P (SMT)/Fe–P (G), OP (SMT)/acid soluble OP+reductant OP (G) were compared. For a=0.05 the comparison of means carried out according to this test showed a significant diVerence. This confirms that the SMT and Golterman methods are not equivalent.The validity of the SMT scheme and the accuracy with which it has been carried out may be tested by comparing the sum of the single fractions with the total (concentrated HCl–P) measured separately.24 Such a comparison shows that TP-S(NaOH–P+HCl–P+OP)=0.05, the mean diVerence is thus negligible. Furthermore, TP values measured by persulfate Fig. 3 Sequential extraction of phosphorus (SMT and Golterman digestion were close to those obtained following the SMT schemes) at the 4 stations in the Bort-Les-Orgues Reservoir.Five protocol. replicates were made, the mean value and standard deviation are reported on the figure. As TP was not measured separately in the G method, it is not possible to check the validity of this scheme as was done for the SMT scheme.However, it has to be noted that the are in agreement with a series of interlaboratory comparisons currently carried out in the framework of the European project sum of the diVerent fractions yielded by the G method is significantly lower than TP measured by persulfate digestion SEPHOS (sequential extraction of phosphate in freshwater sediments) supported by the Standards, Measurements and and SMT method (Fig. 2). It seems reasonable to conclude then, that the SMT method gives better results in the case of Testing Programme of the European Commission.19 The discrepancy between the two methods enhances the necessity of the Bort-Les-Orgues sediments. This is not surprising as the G method was mainly designed for calcareous sediment and a harmoned sequential extraction scheme, which would enable water managers and researchers to compare their the Bort-Les-Orgues sediments are crystalline.Also, it is important to note that the better results of the SMT scheme results. 406 J. Environ. Monit., 1999, 1, 403–407(18 mg m-2 d-1) was measured through a laboratory experiment12 before the reservoir was emptied in 1995. The partial emptying of the reservoir induced a reduction of P release due to the oxidation of iron compounds to which P was adsorbed.Also, it is important to keep in mind that a large releasable P stock exists in the reservoir, which could delay the recovery of the lake even when measures to reduce P inputs are taken. Quantification of the P stock, together with the release rate will help in predicting this restoration delay. Acknowledgements The authors thank the Adour-Garonne Water Agency as well as the Councils of the Cantal, Corre`ze and Puy-de-Do�me Fig. 4 Relative distribution of phosphorus according to the SMT Departments for their financial support; they are also grateful protocol, in the Bort-Les-Orgues Reservoir. to E.P.I.DOR (Etablissement Public Interde�partemental de la Dordogne).The help of the CEMAGREF in core sampling The relative percentages of phosphorus forms according to was very much appreciated. the SMT method are presented in Fig. 4 for the Bort-Les- Orgues Reservoir. NaOH–P was 60% of TP, OP 24%, and References HCl–P 16%. The potentially releasable P (NaOH–P+OP) in the sediment is around 80%, which is in agreement with 1 R. A. Vollenweider, Technical Report OECD, DAS/CSI 68-27, previous results12.OECD, Paris, 1968. Therefore, in the Bort-Les-Orgues Reservoir, phosphorus is 2 OECD, Synthesis report (Eutrophisation des eaux. Me�thodes d’e�valuation et de lutte), OECD, Paris, 1982. mainly of anthropogenic origin (NaOH–P+OP partly), 3 P. C. M. Boers and D. T. Van der Molen, Eur. Water Pollut. whereas Ca–P, which is of detrital origin, accounts for less Control, 1993, 19.than 20%. These results also show that most sediment P in 4 B. Bostro�m and K. Pettersson, Hydrobiologia, 1982, 170, 229. the lake is allochthonous. Brigault and Ruban25 have shown 5 G. Premazzi and A. Provini, Hydrobologia, 1985, 120, 23. that among the sources of allochthonous P, about 30% comes 6 J. D. H. Williams, J.-M.Jaquet and R. L. Thomas, J. Fish. Res. from domestic or industrial eZuents (mostly NaOH–P), 60% Bd. Can., 1976, 33, 413. 7 J. D. H. Williams, T. Mayer and J. O. Nriagu, Soil Sci. Soc. Am. from agriculture (NaOH–P+OP). J., 1980, 44, 462. 8 A. H. M. Hieltjes and L. Lijklema, J. Environ. Qual., 1980, 3, 405. Estimation of the phosphorus stock in the sediment 9 R. Psenner, R. Pucsko and M.Sager, Arch. Hydrobiol., Suppl., 1985, 70, 111. An estimation of the sediment stock in the reservoir of Bort- 10 H. L. Golterman and A. Booman, Verh. Int. Ver. Limnol., 1988, Les-Orgues was made. 23, 904. Taking into account the volume (477×106 m3) and the 11 H. L. Golterman, Hydrobiologia, 1996, 5, 1–9. mean depth (43.7 m) of the reservoir (the surface of the 12 V. Ruban and D.Demare, Hydrobiologia, 1998, 373/374, 349. sediment was estimated to 10.91 km2) and assuming that P is 13 AFNOR, NF T90 110, in Qualite� de l’eau, recueil de normes franc�aises, AFNOR, Paris, 1996. active in the upper 5 cm of the sediment,26 it is possible to 14 AFNOR, NF X31 109, in Qualite� des sols, recueil de normes calculate the available P stock, since the concentration is franc�aises, AFNOR, Paris, 1996.known. The sediment stock (5 cm) was 545 500 m3, with a 15 J. Murphy and J. P. Riley, Anal. Chim. Acta, 1962, 27, 31. mean water content of 75%, the volume of dry sediment was 16 J. Armengol and A. Vidal, Ergeb. Limnol., 1988, 30, 61. 130 625±10% m3. The density of the sediment was 1.1, hence 17 P. G. Manning and K. R. Lum, Can. Mineral., 1983, 21, 121.the sediment mass was 150 012 t. The concentrations of 18 R. L. Thomas, S. Santiago, V. Gandais, L. Zhang and J.-P. Vernet, Water Pollut. Res. J. Can., 1991, 26, 433. NaOH–P and OP were 1.62 and 0.58 mg g-1, respectively, 19 V. Ruban, J. F. Lopez-Sanchez, P. Pardo, G. Rauret, H. Muntau and their mass in the sediment was then: and P. Quevauviller, J. Environ. Monit., 1999, 1, 51. 20 G. Rofe`s, in Gestion inte�gre�e des milieux aquatiques, Presses de mNaOH--P=1.62 10-3×150 012=243±48 t l’ENPC, Paris, 1994, pp. 89–99. mOP=0.58 10-3×150 012=87±18 t 21 B. Bostro�m, M. Jansson and C. Forsberg, Ergebn. Limnol., 1982, 18, 5. The stock of P likely to be released averaged 330±66 t, which 22 V. Gandais-Ruban, D. Demare and A. Fournier, Bull. Labo. Pont is far from negligible if compared to the annual TP input of Chausse�es., 1993, 186, 79. 121 t.25 However, this value is only indicative as it supposes 23 S. Brigault, E. Sacchi, R. Gonfiantini and G. M. Zuppi, C. R. Acad. Sci., Ser. IIa: Sci. Terre Plane`tes, 1998, 327, 397. that the release occurs on the whole reservoir, which is 24 A. Barbanti and G. P. Sighinolfi, Environ. Technol. Lett., 1988, probably not the case. 9, 117. Nurnberg27 has shown that significant correlations between 25 S. Brigault and V. Ruban, Water, Air, Soil Pollut., 1999, to be anoxic release rates and sediment P fractions can be used to published. predict phosphate release rates in lakes with known sediment 26 H. S. Jensen, P. Kristensen, E. Jeppesen and A. Skytthe, P concentrations. Applying this relationship to the sediment Hydrobiologia, 1992, 235/236, 731. 27 G. Nurnberg, Can. J. Fish. Aquat. Sci., 1988, 45, 453. of Bort-Les-Orgues leads to a release rate of about 5 mgm-2 d-1, which is typical of meso-eutrophic lakes in this area. It has to be noted that a much higher flux Paper 9/02269D J. Environ. Monit.,

ISSN:1464-0325    

DOI:10.1039/a902269d

出版商:RSC    

年代:1999

数据来源: RSC