Environ. Sci. Technol. 1999, 33, 2340-2345
Polychlorinated Biphenyls in the Atmosphere of Southern Norway J O H N - E R I K H A U G E N , †,| F R A N K W A N I A , * ,‡ A N D Y I N G D U A N L E I § NILU Norwegian Institute for Air Research, P.O. Box 100, N-2007 Kjeller, Norway, WECC Wania Environmental Chemists Corp., 280 Simcoe Street, Suite 404, Toronto, Ontario, Canada M5T 2Y5, and Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontario, Canada M5S 3E5
Atmospheric concentrations of seven polychlorinated biphenyl (PCB) congeners (IUPAC No. 101, 105, 118, 138/ 163, 153, 156, 180) were measured every week from 1992 to 1995 in Lista, a coastal station in Southern Norway. This data set of 200 samples was analyzed with respect to the influence of time, temperature, air mass origin, and wind speed on both the absolute level and the relative congeneric composition of the PCBs. The geometric mean concentration of the sum of the seven PCB congeners was 114 pg‚m-3, which is in the range observed at urban locations in Europe during the early 1990s. No obvious concentration decrease could be observed during the 4 years. PCB concentrations showed a clear seasonal fluctuation with higher levels during the summer. The temperature dependence of the air concentrations of individual congeners increased with the number of chlorine atoms per molecule resulting in an increase in the relative importance of the higher chlorinated congeners during warm periods. Air arriving in Southern Norway from southwesterly directions had slightly higher concentrations than air coming from the North, whereas the relative composition of the PCB congeners was not influenced by air mass origin. At higher wind speed the concentrations of PCBs decreased. Episodes of conspicuously elevated PCB concentrations neither were associated with a particular air mass origin nor had an unusual congeneric composition. The data analysis suggests that whereas regional air transport from central Europe contributes to the occurrence of PCBs in Lista, a large fraction of the PCBs stems likely from local sources.
Introduction Decades after restrictions on the use of polychlorinated biphenyls (PCBs) have been introduced in Europe and North America, PCB concentrations in the biotic and abiotic environment seem to have reached a steady level, which decreases only slowly or not at all (1, 2). It is believed that the atmosphere is now the major source of PCBs to many * To whom correspondence should be addressed: phone: (416) 977 8458; fax: (416) 977 4953; e-mail:
[email protected]. † NILU Norwegian Institute for Air Research. ‡ WECC Wania Environmental Chemists Corp. § University of Toronto. | Present address: MATFORSK, Norwegian Food Research Institute, Osloveien 1, N-1430 Ås, Norway. 2340
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aquatic ecosystems (3). However, it is not clear what maintains atmospheric concentrations of PCBs at relatively constant levels in a country such as Norway which has not used PCBs in more than a decade. It has been suggested that the major source of PCBs to the atmosphere is volatilization from the terrestrial environment, a process that may account for 80-90% of the PCBs in the atmosphere over Britain (4). Additionally, PCBs may enter the atmosphere from a number of diffuse sources such as combustion of municipal and industrial wastes, volatilization from contaminated buildings, and leakage of PCB-containing electrical installations (capacitors, transformers) which are still in use or stored at landfills (5). Is it possible to discern to what extent the atmospheric levels in Norway are controlled by continuous recycling of material that has entered the environment a long time ago versus relatively recent releases of PCBs from a number of diffuse sources within Norway and the more densely populated countries of Central Europe? Long-time monitoring data of air concentrations can provide some insight into the dynamics of persistent organic pollutants at a location (6-8). Because the weather systems common at midlatitudes cause variations in the patterns of long-range and regional atmospheric transport on a time scale of a few days, it is important to have monitoring data at a relatively high temporal resolution. Such highly resolved data for PCBs for the European atmospheric environment are rare and have so far been reported only for urban sites (5, 9). Here we report weekly measurements of the concentrations of three pentachlorobiphenyls, three hexachlorobiphenyls, and one heptachlorobiphenyl in the atmosphere of Southern Norway during 1992-1995. The data are analyzed with respect to the influence of year, air mass origin, temperature, and wind speed on absolute levels and congeneric composition.
Materials and Methods Sampling Site and Sampling Method. The Lista station, a rural coastal site 14 m above sea level, is located at the southernmost tip of Norway (58°06′N, 6°34′E). The prevailing wind direction is from west-southwest, the annual mean temperature during the 4 years of sampling was 8 °C, and the mean annual precipitation varied from 886 to 1419 mm. From the beginning of 1992 to the end of 1995, samples of approximately 500 m3 of air were collected over a period of 24 h once every week. A previously described high-volume sampler (10) was employed using a flow of approximately 20 m3‚h-1. Particles were collected on glass fiber filters of 142mm diameter (Gelman type AE, type 61635, cutoff >99% for 0.2 µm), which had been pretreated at 450 °C for 8 h. Compounds in the vapor phase were adsorbed on two sequential polyurethane foam (PUF) plugs (100-mm diameter, 50-mm thickness, density 25 kg‚m-3). Further details on the sampling method are given in ref 11. Reference Compound. Crystalline PCB-101 (2,2′,4,5,5′pentaCB), PCB-105 (2,3,3′,4,4′-pentaCB), PCB-118 (2,3′,4,4′,5pentaCB), PCB-138 (2,2′,3,4,4′,5′-hexaCB), PCB-153 (2,2′,4,4′,5,5′-hexaCB), PCB-156 (2,3,3′,4,4′,5-hexaCB), and PCB-180 (2,2′,3,4,4′,5,5′-heptaCB), officially certified at >99% purity, were purchased from Dr. Ehrenstorfer GmbH (Germany) and used as reference substances in the quantification. Isotope-labeled [13C]PCB-118, -153, and -180 from Cambridge Isotope Laboratory (U.K.) were used as internal standards. Sample Extraction and Cleanup. Prior to sample extraction, isotope-labeled standards in isooctane were added to the first PUF plug of the air sample. The glass fiber filter and the PUF plugs were Soxhlet extracted separately for 8 h with 10.1021/es9812397 CCC: $18.00
1999 American Chemical Society Published on Web 05/29/1999
FIGURE 1. Time profile of the sum of the concentrations of seven PCB congeners in Lista, Norway, from 1992 to 1995. Given is also the ambient temperature at the time of sampling. The Roman numerals next to elevated peak concentrations indicate the sector of air mass origin (I, Northern Scandinavia; II, Eastern Europe; III, Western Europe; IV, U.K.; V, Norwegian Sea; VI, no assignment possible). 150 or 300 mL of n-hexane/diethyl ether (9:1). The extracts were combined since earlier studies had shown that typically less than 5% of the PCBs in the atmosphere at Lista were sorbed to particles, and the very low amounts in the filter extract were thus often close to detection limits and blank levels. After volume concentration the extracts were treated with concentrated sulfuric acid. The hexane phase was dried with sodium sulfate and eluted on a silica gel column with n-hexane/diethyl ether. After volume reduction to approximately 0.5 mL, 2 ng of tetrachloronaphthalene and 10 ng of octachloronaphthalene were added as recovery standards. Then the sample was concentrated further to 100 µL by applying a gentle stream of purified nitrogen. Further details on sample cleanup are given in ref 11. Quantification by Low-Resolution Mass Spectrometry. High-resolution gas chromatography (HRGC) combined with low-resolution negative ion chemical ionization mass spectrometry (NICI-LRMS) was used for the quantification of the PCBs. A Hewlett-Packard (HP) 5890 series II gas chromatograph with a mass spectrometer HP 5989A (MS-Engine) was employed. NICI was carried out at an ion source temperature of 200 °C and an ion source pressure of 0.6 hPa using methane (Messer Griesheim, 99.95% purity). The ion source was tuned for optimum performance with perfluorotributylamine at m/z 312, 414, and 464. The electron energy of the primary electrons was about 170 eV, and the high-energy dynode voltage was set to 10 kV. Selected ions were recorded for each compound employing a dwell time of 50 ms/ion. For the pentachlorobiphenyls the masses 326 and 328 were recorded, for the hexachlorobiphenyls masses 360 and 362, and for the heptachlorobiphenyls masses 394 and 396. For the respective isotope-labeled congeners we recorded the masses 338 and 340, 372 and 374, and 406 and 408. More volatile tri- and tetrachlorobiphenyls such as PCB-28, -31, and -52 were not quantified because of the low sensitivity of the NICI-LRMS technique for these congeners. PCB-163 coeluted with PCB-138, and the concentrations given are therefore for both congeners. For quantification the most abundant ions were used. The HRGC conditions were as follows: separation on fused silica gel capillary column (HP Ultra 2, 25-m × 0.2-mm i.d. coated with 0.11 µm of 5% diphenyl-, 95% dimethylpolysiloxane); carrier gas helium at a flow of 35-40 cm‚s-1 (180 °C); splitless injection of 1 µL; splitless time of 2 min; injector temperature of 250 °C; transfer line of 260 °C; temperature program of 60 °C for 2 min, then 20 °C/min to 150 °C, and 4 °C/min to 280 °C (10 min isothermal).
Quality Control. Comprehensive quality control procedures were performed during the determination of PCBs in air based on the requirements of the European Quality Norm EN 45001 (12). Blank and control samples were run through the complete cleanup procedure frequently and parallel with the samples. The method blanks for the PCB congeners varied from 0.03 to 0.3 pg‚m-3. All measured PCB concentrations were at least 10 times higher than the blank levels. The precision of 23 air control samples analyzed from 1992 to 1995 was within 15% of the mean concentration of the single PCB congeners (13). At regular intervals air samples were analyzed separately for filter, PUF plugs I and II. The particle-bound fraction of PCBs typically made up less than 5% for all the PCB congeners. Between 1% and 7% of the single congeners were found on the second back-up PUF plug with concentrations similar to method blanks. This suggested that no significant breakthrough had taken place during sampling. Lower limits for determination for the single PCB congeners varied between 0.04 and 0.85 pg‚m-3. The PCB concentrations measured in all air samples exceeded these limits. Regular analysis of an extract of an ambient air control sample was carried out during the year parallel with the Lista air samples. Further quality assurance measures and criteria are discussed in detail elsewhere (11, 13). Control samples suggested that there were minor problems with PCB contamination during the first half of 1992 (13). This may partly explain the higher concentrations measured during this year. However, during the second half of 1992, the PCB concentrations of the control sample were within the range of the following years, confirming that the problem had been corrected. Meteorological Data and Trajectory Calculations. Meteorological data from the Lista station were provided from the Norwegian Meteorological Institute. Details of the trajectory calculations are given in ref 14.
Results and Discussion Mean Levels and Interannual Trends. In Figure 1 the sum of the atmospheric concentrations of the seven PCB congeners (Σ7PCB) is shown as a function of time. The geometric mean Σ7PCB during the entire 4-year period (200 samples) was 114 pg‚m-3. The lowest and highest measured concentrations were 22 and 747 pg‚m-3. Table 1 gives geometric mean, maximum, and minimum concentrations for all seven quantified PCB congeners. The interannual variability of the average Σ7PCB concentration was low during the 4 years (Figure 2A). Other data from the Northern European enviVOL. 33, NO. 14, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Annual Geometric Mean and Range (Minimum and Maximum) of Concentrations (pg‚m-3) of PCBs in Air in Lista, Norway congener year
101
105
118
138/163
153
156
180
sum
1992 (n ) 45) 1993 (n ) 52) 1994 (n ) 51) 1995 (n ) 52) 1992-1994 (n ) 200)
48.2 (11.2-220) 31.5 (9.5-92.6) 31.6 (7.7-125.1) 30.2 (6.1-85.2) 34.3
1.6 (0.2-19.4) 1.2 (0.4-3.5) 1.1 (0.3-3.9) 0.8 (0.2-2.6) 1.1
9.6 (2.8-57.7) 7.3 (1.8-25.4) 6.4 (1.5-21.9) 7.0 (1.9-22.3) 7.5
48.4 (16.2-237) 34.3 (5.9-165) 32.9 (9.5-111) 36.9 (8.1-116) 37.4
37.3 (10.3-201) 25.7 (4.7-130) 23.8 (6.0-89.7) 23.8 (4.4-78.0) 26.9
1.0 (0.2-4.4) 0.9 (0.2-4.4) 0.8 (0.2-2.7) 0.7 (0.1-2.6) 0.9
6.6 (1.8-32.3) 5.2 (0.7-28.0) 3.8 (1.2-12.8) 3.9 (0.6-15.2) 4.7
155 (48-747) 107 (23-444) 101 (27-366) 105 (22-317) 114
FIGURE 2. Box and whisker plots showing the sum of the concentrations of seven PCB congeners in Lista, Norway, sorted based on year of sampling (A), mean temperature (B), sector of air mass origin (C), and mean wind speed (D) at the day of sampling. The line shows the median, the box delineates the 25 and 75 percentiles, and the whiskers delineate the 10 and 90 percentiles. The diamonds show outliers. ronment confirm that PCB concentrations have not seen any significant decline during the early 1990s (2). However, the concentrations in 1992 (geometric mean 155 pg‚m-3) were approximately 1.5 times higher than in the following years (1993, 107 pg‚m-3; 1994, 101 pg‚m-3; 1995, 105 pg‚m-3). As mentioned earlier this may partly be explained by contamination during the first half of 1992. During the 4 years the intraannual variability of the air concentrations decreased as reflected by the disappearance of pronounced high-concentration episodes (Figure 1) and decreasing values for the 75 and 90 percentile concentrations (Figure 2A) with time. The average congeneric pattern of the PCBs is given in Figure 3. This pattern did not change significantly during the sampling period, but there may be a hint that PCB-138/163 increased relative to PCB-153 (Figure 4A). This possibly reflects different persistences of these hexachlorobiphenyl congeners. Comparison with Other European Measurements. Comparing PCB data from various studies is complicated because 2342
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FIGURE 3. Average relative composition of the seven PCB isomers measured in Lista, Norway. of the various quantification techniques and reporting conventions used by different laboratories. To assess to some extent how the concentrations at Lista compare with other locations, congener-specific concentration data (arithmetic means) reported for various European locations in the early 1990s are compiled in Table 2. This comparison suggests
FIGURE 4. Difference in the fractions of various congeners from the average congener composition of all samples (Figure 3) if the data are sorted based on year of sampling (A), mean temperature (B), sector of air mass origin (C), or mean wind speed (D) at the day of sampling.
TABLE 2. Arithmetic Mean Concentrations of Selected PCB Congeners (pg‚m-3) Reported for the European Atmosphere in the Early 1990s sample information Lista, Norway Kårvatn, North Norway Svanvik, North Norway Ny-Ålesund, Spitsbergen Ny-Ålesund, Spitsbergen Lancaster, U.K. London, U.K. Stevenage, U.K. Cardiff, U.K. Manchester, U.K. Augsburg, Germany Swedish West Coast Swedish West Coast a
time period 1991-1995 Mar-Apr 1992 Mar-Apr 1992 Mar-Apr 1992 Apr-Dec 1993 Aug 1995 1991-1992 1991-1992 1991-1992 1991-1992 Mar 1992-Feb 1993 Feb+May 1990 1991-1994
n 200 28-29 26-30 16-20 52 28 ? ? 48 55 64 4 21
101 41.6 2.41 2.27 1.87 1.28 15 117 31.1 91.5 84.5 16 9.8 4.5
118
138
153
180
ref
9.2 0.79 1.60 0.81 0.53 2.7 52.9 11.9 38.6 29.9
46.2a
34.0 0.99 1.58 0.99 0.61 12 26.2 12.9 32.5 36.9 11 8.8 4.5
6.1 0.31 0.45 0.23 0.16 2.5 12.0 6.15 17.0 24.0 2.4 2.7 1.6
this study 11 11 11 13 18 9 9 9 9 15 16 17
3.0 1.7
2.12a 3.14a 1.82a 0.54a 7.1 23.0 9.20 33.4 28.0 10 8.5 4.2
Includes congener PCB-163.
that the PCB levels in Southern Norway are rather high, namely, in the range of concentrations reported in recent years for urban areas in the U.K. (9) and Germany (15). Whereas it is not surprising that the concentrations are more than 1 order of magnitude higher than what has been measured in Northern Norway and European Arctic (11, 13), they are also considerably higher than levels reported for other European nonurban locations (16-18). They are, for example, higher than PCB concentrations measured during the same time period at several coastal stations at Sweden’s west coast (16, 17), which is approximately 300 km further east across the Kattegat. This may partly be explained by the fact that these Swedish samples were primarily taken during winter when PCBs levels are lower. However, when using the data from the station Ro¨rvik measured during the summer of 1992 as a reference (17), the levels at Lista were still 4 times higher. We have no obvious explanation for these rather high concentrations, but they may suggest that the vicinity of the Lista station has been or still is contaminated by PCBs from a local source. Seasonal Changes and Temperature Dependence. The PCB time profile (Figure 1) shows a temperature-driven seasonal variation with increased levels during summer, which is typically observed for PCBs in midlatitudes (see examples listed in ref 6). Summer concentrations (200-300 pg‚m-3) were approximately 3 times higher than winter concentrations (50-130 pg‚m-3) during all 4 years (Figure
FIGURE 5. Plot of the partial pressure of the three PCB congeners 105, 138/163, and 180 in air versus reciprocal absolute temperature. The slope of these relationships increases with molecular mass. 2B). We converted concentrations of the PCB congeners into partial pressures and regressed their logarithm against reciprocal temperature (Figure 5). The regressions (Table 3) were all highly significant, and the slopes of these relationships increased with an increasing number of chlorine atoms in the molecule. This implies that the concentrations of the VOL. 33, NO. 14, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 3. Temperature Dependence of the Partial Pressure of Individual PCB Congeners at Lista, Norwaya congener
slope m
r2
PCB-101 PCB-105 PCB-118 PCB-138/163 PCB-153 PCB-156 PCB-180 Σ7PCB
-5209 ( 591 -6158 ( 659 -6498 ( 542 -7216 ( 518 -7348 ( 560 -7487 ( 539 -8367 ( 570 -6607 ( 537
0.28 0.31 0.42 0.49 0.47 0.49 0.52 0.43
a Given is the slope m and the regression coefficient r2 for the relationship ln(p/Pa) ) m/(T/K) + b, obtained from 200 samples. All regressions were highly significant.
more highly chlorinated congeners have a stronger temperature dependence than the less chlorinated congeners, and there is thus a significant seasonal shift in the PCB pattern favoring the more highly chlorinated congeners, in particular PCB-138/163, -153, and -180, during summer (Figure 4B). The relatively strong temperature dependence suggests that revolatilization from the Earth’s surface may be quite significant in controlling PCB concentrations at the Lista site (6-8). Influence of Air Mass Origin. We investigated the influence of the origin of the air masses arriving in Lista on the measured PCB concentrations by calculating air mass trajectories and assigning those to five geographical sectors as described in detail before (14). The five sectors were (I) Northern Scandinavia, (II) Eastern Europe, (III) Western Europe, (IV) U.K., and (V) Norwegian Sea. Those sampling dates which could not be clearly assigned to one of these five sectors were grouped into category VI. Σ7PCB concentrations measured in air arriving from these various sectors are summarized in Figure 2C. Air masses arriving from sectors III (Western Europe) and IV (U.K.) have somewhat higher levels of PCBs (median concentrations above 130 pg‚m-3) than those arriving from sectors I (Northern Scandinavia) and V (North Atlantic) which had medians below 100 pg‚m-3, but the differences are not significant. Somewhat surprisingly the pattern of PCBs was hardly influenced by the origin of the air masses. There was a hint that the air arriving from Northern Scandinavia had a slightly higher fraction of PCB101, whereas air from the U.K. had slightly higher proportions of the heavier congeners (in particular 153 and 180) relative to the pentachlorobiphenyls (Figure 4C). Influence of Wind Speed. Σ7PCB concentrations clearly decreased with increasing wind speed (Figure 2D), whereas the congeneric composition was not influenced by this parameter (Figure 4D). As the influence of revolatilized PCBs from the ground is likely to become less important at higher wind speeds (19), this is a further indication of revolatilization of PCBs from the Earth’s surface. Episodes of Elevated Concentrations. Throughout the sampling period episodes of significantly elevated concentration levels were observed, illustrated by “spikes” in the otherwise smooth time profile of Figure 1. A Σ7PCB concentration was considered elevated if it exceeded the 90 percentile for a particular year (Figure 2A). Such episodes were most notable in 1992 and occurred typically during summer. The sector of trajectory origin for these episodes is noted next to these “spikes” in Figure 1. Generally no clear relationship between elevated levels and air mass origin could be observed. During 1992, for example, the five highest concentrations were measured during five completely different air-transport situations. The highest concentrations during 1992 (June 6) and 1994 (May 12) were associated with air mass transport from sector I (Northern Scandinavia), which usually was characterized by low PCB concentrations 2344
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(Figure 2C). Interestingly, on those two sampling dates, R-hexachlorocyclohexane concentrations were also elevated at Lista (14). Elevated PCB levels were not associated with unusual congeneric patterns, but they were often slightly depleted in the pentachlorobiphenyls relative to the heavier congeners. This, however, can be explained by the fact that elevated levels occurred mostly in summer. Exceptions to this lack of unusual aspects associated with elevated levels are the three events with highest concentrations during the summer of 1993. These were all associated with air mass transport from sector IV (U.K.) and had a congener pattern which was clearly shifted toward the heavier congeners. A more thorough analysis of congener patterns, which would allow a clearer identification of source contributions (20), requires data for more congeners covering a wider range of physical chemical properties. The fact that air masses arriving from the South and the West have slightly higher concentrations than those arriving from the North suggests that regional atmospheric transport from the more densely populated countries in central Europe contributes to the occurrence of PCBs in the atmosphere in Southern Norway. However, the differences are not very large, and no clear link between episodes of high concentrations and air mass transport from central Europe could be established. The measured concentrations, which (i) are relatively high for a nonurban location, (ii) have an intermediate temperature dependence, and (iii) decrease with wind speed, as well as the rather constant congeneric composition of PCBs at Lista suggest that revolatilization of PCBs from the vicinity of the station may be quite significant. It is not at all clear what could have caused PCB contamination of the environment around the Lista station to the extent that revolatilization now should lead to concentrations in air which are comparable to those measured in urban areas in central Europe. This may be due to high deposition rates in the past driven by high precipitation rates and a location downwind from the major source areas of PCBs in Europe or by local sources in the vicinity of the sampling station. The latter explanation is in our opinion more likely. Marine sediments from two sites, Farsund Harbour and Lundefjorden, which are located less than 10 km east of Lista have been found to be highly contaminated with PCBs (21). Other potential sources of local contamination are an aluminum plant and the airport in Lista which for many years was used by the military (21).
Acknowledgments This study, funded by the Norwegian State Pollution Agency (SFT), was carried out as part of the Norwegian contribution to the CAMP monitoring program, which itself is part of the OSPARCOM program. F.W. acknowledges financial support through the Environment and Climate Research Programme of the European Union (Contract No. ENV4-CT96-0214).
Supporting Information Available Table with the concentrations of the seven PCB congeners in all 200 samples, including meteorological data such as temperature and wind speed. This material is available free of charge via the Internet at http://pubs.acs.org.
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(4) Harrad, S. J.; Sewart, A. P.; Alcock, R.; Boumphrey, R.; Burnett, V.; Duarte-Davidson, R.; Halsall, C.; Sanders, G.; Waterhouse, K.; Wild, S. R.; Jones, K. C. Environ. Pollut. 1994, 85, 131-146. (5) Granier, L. K.; Chevreuil, M. Atmos. Environ. 1997, 31, 37873802. (6) Wania, F.; Haugen, J.-E.; Lei, Y. D.; Mackay, D. Environ. Sci. Technol. 1998, 32, 1013-1021. (7) Hoff, R. M.; Brice, K. A.; Halsall, C. J. Environ. Sci. Technol. 1998, 32, 1793-1798. (8) Halsall, C. J.; Gevao, B.; Howsam, M.; Lee, R. G. M.; Ockenden, W. A.; Jones, K. C. Atmos. Environ. 1999, 33, 541-552. (9) Halsall, C. J.; Lee, R. G. M.; Coleman, P. J.; Burnett, V.; HardingJones, P.; Jones, K. C. Environ. Sci. Technol. 1995, 29, 23682376. (10) Oehme, M.; Stray, H. Fres. Zeitsch. Anal. Chem. 1982, 311, 665673. (11) Oehme, M.; Haugen, J.-E.; Schlabach, M. Sci. Total Environ. 1995, 160/161, 139-152. (12) Haugen, J.-E.; Oehme, M. Seminar on Pesticides in Precipitation and in Surface Water - Appearance and Effects; Nordic Council of Ministers: Tune, Denmark, Nov. 14-16, 1994; p 94. (13) Oehme, M.; Haugen, J.-E.; Schlabach, M. Environ. Sci. Technol. 1996, 30, 2294-2304.
(14) Haugen, J.-E.; Wania, F.; Ritter, N.; Schlabach, M. Environ. Sci. Technol. 1998, 32, 217-224. (15) Kaupp, H.; Do¨rr, G.; Hippelein, M.; McLachlan, M. S.; Hutzinger, O. Chemosphere 1996, 32, 2029-2042. (16) Brorstro¨m-Lunde´n, E. J. Sea Res. 1996, 35, 81-90. (17) Brorstro¨m-Lunde´n, E.; Lindskog, A.; Mowrer, J. Atmos. Environ. 1994, 28, 3605-3615. (18) Lee, R. G. M.; Hung, H.; Mackay, D.; Jones, K. C. Environ. Sci. Technol. 1998, 32, 2172-2179. (19) Honrath, R. E.; Sweet, C. I.; Plouff, C. J. Environ. Sci. Technol. 1997, 31, 842-852. (20) Stern, G. A.; Halsall, C. J.; Barrie, L. A.; Muir, D. C. G.; Fellin, P.; Rosenberg, B.; Rovinski, F.; Konovov, E.; Postoukov, B. Environ. Sci. Technol. 1997, 31, 3619-3628. (21) Konieczny, R. M.; Juliussen, A. Norwegian State Pollution Authority/Norwegian Institute for Water Research, Report No. 587/94, 1995.
Received for review November 30, 1998. Revised manuscript received April 12, 1999. Accepted April 19, 1999. ES9812397
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