Atmospheric concentrations and air-water flux of organochlorine pesticides along the Western Antarctic Peninsula

Air, seawater, sea ice, and snow were collected during the austral winter (September-October 2001) and summer (January-February 2002) along the Western Antarctic Peninsula. Hexachlorobenzene (HCB) > heptachlor > alpha- and gamma-hexachlorocyclohexane (HCH) and heptachlor epoxide, were the most frequently detected organochlorine pesticides in air. HCB and HCH levels declined over the past 20 years, with a half-life of 3 years for sigmaHCH in Antarctic air. However, heptachlor epoxide levels have not declined in Antarctic air over the past decade, possibly due to continued use of heptachlor in the southern hemisphere. Peak heptachlor concentrations in air were measured coincident with air masses moving into the region from lower latitudes. Levels of lindane were 1.2-200 times higher in annual sea ice and snow compared to alpha-HCH, likely due to greater atmospheric input of gamma-HCH. The ratio of alpha/gamma-HCH in Antarctic air, sea ice and snow was <1, illustrative of a predominance of influx of lindane versus technical HCH to the regional environment. However, alpha/gamma-HCH in seawater was >1, likely due to more rapid microbial degradation of gamma- versus alpha-HCH. Water/air fugacity ratios for HCHs demonstrate continued atmospheric influx of HCHs to coastal Antarctic seas, particularly during late summer.     

Some pesticides occurrence in air and precipitation in Québec, Canada

Air and precipitation samples were collected in three stations located in Quebec between January 1993 and March 1996 to determine spatial and seasonal variations of several organochlorine pesticides and metabolites (alpha-HCH, gamma-HCH, HCB, gamma-chlordane, DDT, DDE, Mirex). alpha-HCH, gamma-HCH, and HCB were more or less measured in large amounts at all sites, whereas gamma-chlordane, DDT, and DDE concentrations were lower and Mirex was undetectable. Higher concentrations levels were observed in air during hot spring/summer periods except for HCB, indicating a probable temperature dependence. Ln concentrations vs reciprocal temperature plots and Henry's law determinations helped to highlight the contribution of soil and/or water volatilization of those compounds. Itwas observed that alpha-HCH came mainly from Atlantic Ocean volatilization at Mingan, whereas sources of gamma-chlordane and DDE were mostly due to volatilization from soils in southern Quebec. DDT may be present in the atmosphere by the way of transport from remote regions. Lindane sources were multiple: it may be found in the atmosphere bythe processes of transport and volatilization coming from soil or water. Finally, a negative correlation between HCB and air temperature implies that processes other than volatilization are involved in transport of this compound.     

Hexachlorocyclohexanes in the North American atmosphere

Annually integrated air concentrations of alpha- and gamma-hexachlorocyclohexane (HCH) were determined in 2000/2001 at 40 stations across North America using XAD-based passive air samplers to understand atmospheric distribution processes on a continental scale. Elevated levels of gamma-HCH in the atmosphere of the Canadian Prairies are consistent with the ongoing use of lindane as a seed treatment on canola and confirm the feasibility of detecting the agricultural use of a pesticide using long-term integrated passive air sampling. In contrast to gamma-HCH, the atmospheric concentrations of alpha-HCH show a rather uniform distribution across Canada and the United States, which is expected for a chemical with no current use on the continent. Higher levels in the atmosphere over Atlantic Canada can be explained by alpha-HCH evaporating from the waters of the Labrador Current, which is supported bythe chiral composition of alpha-HCH and the temperature dependence of its atmospheric concentrations along the east coast of Canada. Similarly, alpha-HCH is volatilizing from Lake Superior. Atmospheric HCH levels increase with elevation in the Canadian Rocky Mountains. The results suggest that evaporation, in particular from cold water bodies, is an important source of alpha-HCH to the North American atmosphere. Low levels of HCHs in Central America hint at efficient degradation under tropical conditions. Chiral analysis shows that (+)-alpha-HCH is often enriched in air over continental areas and at the Pacific Coast, which is opposite to the enantiomeric enrichment in the proximity to the Great Lakes and the Atlantic Ocean. Passive air sampling is a powerful tool to discern the large-scale variability of semivolatile and persistent organic chemicals in the atmosphere.     

Atmospheric Hexachlorocyclohexanes in the North Pacific Ocean and the adjacent Arctic region: spatial patterns, chiral signatures, and sea-air exchanges

During the 2003 Chinese Arctic Research Expedition (CHINARE2003) from the Bohai Sea to the high Arctic (37 degrees N to 80 degrees N) aboard the icebreaker Xuelong (Snow Dragon), air samples were collected for the analysis of hexachlorocyclohexanes (HCHs) in the North Pacific Ocean and adjacent Arctic region. The sigma HCHs (alpha-HCH + gamma-HCH) ranged from 2.3 to 95.1 pg/m3 with the highest levels observed in Far East Asia (32.5 pg/m3), followed by the North Pacific Ocean (17.0 pg/m3) and the Arctic (7.3 pg/ m3). Compared to previous studies in the same areas in 1990s, our measurements were approximately 1 order of magnitude lower. Because of disproportionate chemical reduction and physical fractioning during long-range transport, the ratios of alpha-HCH to gamma-HCH (alpha/gamma-HCH) showed a significant increasing trend from low to high latitudes, suggesting thatthe alpha/gamma-HCH range of 4-7 could not be used to identify sources of technical HCHs especially in remote areas. The ratios of (+)-alpha-HCH to the sum of (+)-alpha-HCH and (-)-alpha-HCH were on average much more biased from 0.5 compared to previous observations in mid-1990s, indicating the exchange of atmospheric alpha-HCH with those in the oceans, where (+)-alpha-HCH was selectively depleted in biological degradation processes. Estimated fugacity ratios based on available data for both alpha-HCH and gamma-HCH further implied their net volatilization from seawater to air in the Arctic Ocean.     

Hexachlorocyclohexanes (HCHs) in the Canadian Archipelago. 2. Air-water gas exchange of alpha- and gamma-HCH

Air and water were sampled in the Canadian Archipelago during summer on the Tundra Northwest 1999 (TNW-99) expedition and air was sampled at Resolute Bay (RB), Nunavut, to determine the gas exchange of alpha- and gamma-hexachlorocyclohexanes (HCHs) and the enantiomers of alpha-HCH. Air concentrations of sigmaHCH during TNW-99 and at RB were similar, averaging 55 and 53 pg m(-3), respectively. The net gas exchange direction was volatilization for alpha-HCH and near equilibrium or deposition for gamma-HCH, whereas actual fluxes depended on the fraction of open water. Enantiomer fractions, EF = (+)/[(+) + (-)] of alpha-HCH in air sampled from shipboard were significantly correlated to those in surface water for events with >90% open water, but were closer to racemic and not correlated to EFs in water for events with 0-50% open water. Levels of alpha-HCH in air at RB averaged 37 +/- 9 pg m(-3) from June to early July, and EFs were close to racemic (0.496 +/- 0.004). In mid-July the ice pack broke up around RB. From this point through August, air concentrations increased significantly to 53 +/- 5 pg m(-3), and the mean EF decreased significantly to 0.483 +/- 0.009. Air concentrations of gamma-HCH at RB did not differ significantly before (8.0 +/- 3.7 pg m(-3)) and after (6.6 +/- 0.76 pg m(-3)) ice breakup. Results show that alpha-HCH enantiomers are sensitive tracers for following the impact of ice cover loss on gas exchange in the Arctic.     

Hexachlorocyclohexane (HCH) isomers and chiral signatures of alpha-HCH in the Arctic marine food web of the Northwater Polynya

Concentrations of hexachlorocyclohexane (HCH) isomers (alpha, beta, and gamma) and enantiomer fractions (EFs) of alpha-HCH were determined in the Northwater Polynya Arctic marine food web. Relative food web structure was established using trophic level models based on organic delta 15N values. Concentrations of HCH in the samples collected, including water, sediment, benthic invertebrates (four species), pelagic zooplankton (six species), Arctic cod, seabirds (seven species), and ringed seal, were in the range previously reported for the Canadian Arctic. The relative proportion of the HCH isomers varied across the food web and appeared to be related to the biotransformation capacity of each species. For invertebrates and fish the biomagnification factors (BMFs) of the three isomers were > 1 and the proportion of each isomer and the EFs of alpha-HCH were similar to water, suggesting minimal biotransformation. Seabirds appear to readily metabolize gamma- and alpha-HCH based on low BMFs for these isomers, high proportions of beta-HCH (62-96%), and high EFs (0.65-0.97) for alpha-HCH. The alpha- and beta-HCH isomers appear to be recalcitrant in ringed seals based on BMFs > 1 and near racemic EFs for alpha-HCH. The beta isomer appears to be recalcitrant in all species examined and had an overall food web magnification factor of 3.9. EFs of alpha-HCH and the proportion of beta-HCH in sigma-HCH in the food web were highly correlated (r2 = 0.92) suggesting that EFs were a good indicator of a species capability to biotransform alpha-HCH.     

Influence of Asian and Western United states agricultural areas and fires on the atmospheric transport of pesticides in the Western United States

Historic and current use pesticides (HUPs and CUPs), with respect to use in the United States and Canada, were identified in trans-Pacific and regional air masses at Mt. Bachelor Observatory (MBO), a remote high elevation mountain in Oregon's Cascade Range located in the United States, during the sampling period of April 2004 to May 2006 (n = 69), including NASA's INTEX-B campaign (spring 2006). Elevated hexachlorobenzene (HCB) and alpha-hexachlorocyclohexane (alpha-HCH) concentrations were measured during trans-Pacific atmospheric transport events at MBO, suggesting that Asia is an important source region for these HUPs. Regional atmospheric transport events at MBO resulted in elevated dacthal, endosulfan, metribuzin, triallate, trifluralin, and chlorpyrifos concentrations, with episodic increases in concentration during some spring application periods, suggesting that the Western U.S. is a significant source region for these CUPs. Endosulfan I, gamma-HCH, and dacthal concentrations were significantly positively correlated (p-value < 0.05) with increased air mass time in Western U.S. agricultural areas. Elevated gamma-HCH concentrations were measured at MBO during both trans-Pacific and regional atmospheric transport events, including regional fire events. In addition to gamma-HCH, elevated sigmachlordane, alpha-HCH, HCB, and trifluralin concentrations were associated with fires in Western North America due to revolatilization of these pesticides from soils and vegetation. Trans-chlordane/cis-chlordane and alpha-HCH/gamma-HCH ratios were calculated and may be used to distinguish between free tropospheric and regional and/or Asian air masses.     

The air-sea equilibrium and time trend of hexachlorocyclohexanes in the Atlantic Ocean between the Arctic and Antarctica

Hexachlorocyclohexanes (HCHs) were determined simultaneously in air and seawater during two cruises across the Atlantic Ocean between the Arctic Ocean (Ny-Alesund/ Svalbard, 79 degrees N; 12 degrees E) and the Antarctic Continent (Neumayer Station/ Ekstroem Ice Shelf, 70 degrees S; 8.2 degrees W) in 1999/ 2000. The concentrations of alpha-HCH and gamma-HCH in air and surface waters of the Arctic exceeded those in Antarctica by 1-2 orders of magnitude. The gaseous concentrations of gamma-HCH were highest above the North Sea and between 20 degrees N and 30 degrees S. Fugacity fractions were used to estimate the direction of the air-sea gas exchange. These showed for alpha-HCH thatthe measured concentrations in both phases were close to equilibrium in the North Atlantic (78 degrees N-40 degrees N), slightly undersaturated between 30 degrees N and 10 degrees S and again close to equilibrium between 20 degrees S and 50 degrees S. Y-HCH has reached phase equilibrium in the North Atlantic as alpha-HCH, but the surface waters of the tropical and southern Atlantic were strongly undersaturated with y-HCH, especially between 30 degrees N and 20 degrees S. These findings are significantly different from two earlier estimates around 1990 as a result of global emission changes within the past decade. Therefore, we investigated the time trend of the HCHs in the surface waters of the Atlantic between 50 degrees N and 60 degrees S on the basis of archived samples taken in 1987-1997 and those from 1999. A decrease of alpha-HCH by a factor of approximately 4 is observed at all sampling locations. No decrease of gamma-HCH occurred between 30 degrees N and 30 degrees S, but there was a decrease in the North Atlantic, North Sea, and in the South Atlantic south of 40 degrees S. The constant level of gamma-HCH in the tropical Atlantic confirms the conclusion that the tropical Atlantic acts as a sink for y-HCH at present time. The measured alpha-HCH seawater concentrations were compared with results from a global multimedia fate and transport model. Whereas the time trend over 13 years and the latitudinal gradient were well reproduced by the model, the absolute levels were too high by a factor of 4.5. This may be explained by the zonal averaging employed in the model as well as uncertain emissions and degradation rates.     

Hexachlorocyclohexanes in the Canadian archipelago. 1. Spatial distribution and pathways of alpha-, beta- and gamma-HCHS in surface water

Hexachlorocyclohexanes (HCHs) in the surface water of the Canadian Archipelago and south Beaufort Sea were measured in summer, 1999. Overall concentrations of HCH isomers were in order of abundance: alpha-HCH (3.5 +/- 1.2 ng L(-1)) > gamma-HCH (0.31 +/- 0.07 ng L(-1)) > beta-HCH (0.10 +/- 0.03 ng L(-1)). Concentrations and ratios of alpha-HCH/gamma-HCH decreased significantly (p < 0.001 to 0.003) from west to east, but there was no significant variation in alpha-HCH/ beta-HCH. The (+) enantiomer of alpha-HCH was preferentially degraded, with enantiomer fractions (EFs) ranging from 0.432-0.463 and increasing significantly (p < 0.001) from west to east. Concentrations also varied latitudinally for alpha-HCH and gamma-HCH (p < 0.002) but not for beta-HCH. Principal component analysis with variables alpha-HCH and gamma-HCH concentrations, EF, latitude, and longitude accounted for 71% (PC 1) and 16% (PC 2) of the variance. Mixing in the eastern Archipelago was modeled by assuming three end members with characteristic concentrations of alpha-HCH and gamma-HCH. The model accounted for the observed concentrations and higher EFs of alpha-HCH at the eastern stations.     

Fate of chiral and achiral organochlorine pesticides in the north atlantic bloom experiment

Organochlorine pesticides (OCPs) were measured in the surface seawater and lower atmosphere during the North Atlantic Bloom Experiment in the spring 2008 from samples collected on the R/V Knorr. The gaseous concentration profiles resulted from both long-range transport (LRT) from the Arctic by polar easterlies and local biogeochemical processes. Relatively constant α/γ-hexachlorocyclohexane (HCH) ratios and enantiomer fractions of α-HCH indicated that a single water mass was sampled throughout the cruise. Changes in dissolved phase concentrations were dominated by bloom processes (air-water exchange, partitioning to organic particles, and subsequent sinking) rather than LRT. α-HCH and dissolved phase trans-chlordanes showed depletion of (+) enantiomer, whereas depletion of the (-) enantiomer was observed for heptachlor exo-epoxide (HEPX) and cis-chlordanes. Fugacity ratio calculations suggest that hexachlorobenzene (HCB) and γ-HCH were depositing from air to water whereas heavier OCPs (chlordanes, HEPX) were evaporating. Dissolved phase concentrations did not decrease with time during the three-week bloom period; neither were lipophilic OCPs drawn down from air to water as previous studies hypothesized. Comparison with Arctic measurements suggested that the Arctic returned higher concentrations of α-HCH and HCB through both the atmospheric (polar easterlies) as well as oceanic transport (East Greenland Current) to the lower latitudes.     

Endosulfan and gamma-HCH in the arctic: an assessment of surface seawater concentrations and air-sea exchange

Arctic seawater concentrations of two currently used pesticides, endosulfan and gama-HCH, were collated from a variety of cruises undertaken throughout the 1990s up to 2000 for different regions of the Arctic Ocean. Surface seawater concentrations for alpha- and beta-endosulfan ranged from <0.1-8.8 (mean 2.3) pg/L and 0.1-7.8 (mean 1.5) pg/L, while gamma-HCH concentrations were approximately 100 fold higher than alpha-endosulfan, ranging between <0.70 and 894 (mean 250) pg/L. Geographical distributions for alpha-endosulfan revealed the highest concentrations in the western Arctic, specifically in the Bering and Chukchi Seas with lowest levels toward the central Arctic Ocean. In contrast, gamma-HCH revealed higher concentrations toward the central Arctic Ocean, with additional high concentrations in the coastal regions near Barrow, Alaska and the White Sea in northwest Russia, respectively. A fugacity approach was employed to assess the net direction of air-water transfer of these two pesticides, using coupled seawater and air concentrations. For alpha-endosulfan, water-air fugacity ratios (FR) were all <1 indicating net deposition to all regions of the Arctic Ocean, with the lowest values (0.1-0.2) evident in the Canadian Archipelago. Given the uncertainty in the temperature-adjusted Henry's Law constant (factor approximately10), it is plausible that equilibrium may have been reached for this compound in the western fringes of the Arctic Ocean where the highest water concentrations were observed. Similarly, FR values for gamma-HCH were generally <1 and in agreement     

Modeling the effect of snow and ice on the global environmental fate and long-range transport potential of semivolatile organic compounds

Snow and ice have been implemented in a global multimedia box model to investigate the influence of these media on the environmental fate and long-range transport (LRT) of semivolatile organic compounds (SOCs). Investigated compounds include HCB, PCB28, PCB180, PBDE47, PBDE209, alpha-HCH, and dacthal. In low latitudes, snow acts as a transfer medium taking up chemicals from air and releasing them to water or soil during snowmelt. In high latitudes, snow and ice shield water, soil, and vegetation from chemical deposition. In the model version including snow and ice (scenario 2), the mass of chemicals in soil in high latitudes is between 27% (HCB) and 97% (alpha-HCH) of the mass calculated with the model version without snow and ice (scenario 1). Amounts in Arctic seawater in scenario 2 are 8% (alpha-HCH) to 21% (dacthal) of the amounts obtained in scenario 1. For all investigated chemicals except alpha-HCH, presence of snow and ice in the model increases the concentration in air by a factor of 2 (HCB)to 10 (PBDE209). Because of reduced net deposition to snow-covered surfaces in high latitudes, LRT to the Arctic is reduced for most chemicals whereas transport to the south is more pronounced than in scenario 1 ("southward shift"). The presence of snow and ice thus considerably changes the environmental fate of SOCs.     

Air-water gas exchange of organochlorine pesticides in Taihu Lake, China

Previous research in the Taihu Lake Region (TLR) of China found high levels of atmospheric organochlorine pesticides (OCPs). To understand the sources and the environmental behaviors of these OCPs in the TLR, research on air-water gas exchange was performed in 2004. Hexachlorocyclohexanes (HCHs), DDT related compounds (DDTs), cis-chlordane (CC), trans-chlordane (TC), heptachlor (HEPT), and alpha-endosulfan in both air and water samples were analyzed, and air-water gas exchange fluxes of these compounds were calculated. The net volatilization flux of alpha-HCH was 58 ng m(-2) day(-1), suggesting that the residue of technical HCH in the lake sediment might have been an important source of alpha-HCH to the air of this region after the ban of technical HCH two decades ago. The main components of technical chlordane, TC, CC, and HEPT, each had net volatilization fluxes >230 ng m(-2) day(-1), suggesting that waste discharge from manufacturing plants in the upper region was the main source of chlordane to the lake. Unlike alpha-HCH and chlordane, o,p'-DDT and alpha-endosulfan had net deposition fluxes, suggesting that these compounds were transported through the atmosphere from land sources and then deposited into the lake. The correlation between air concentrations and ambient air temperature indicated that the current sources of o,p'-DDT and alpha-endosulfan were from land; alpha-HCH and chlordane were mainly from the lake.     

Passive air sampling of PCBs, PBDEs, and organochlorine pesticides across Europe

This study presents concurrently sampled ambient air data for a range of persistent organic pollutants at the continental scale. This was achieved using a passive air sampling system, deploying polyurethane foam disks, which was prepared in one laboratory, sealed to prevent contamination, sent out by courier to volunteers participating in different countries, exposed for 6 weeks, collected, resealed, and returned to the laboratory for analysis. Europe was the study area--a region with a history of extensive POPs usage and emission and with marked national differences in population density, the degree of urbanization and industrial/agricultural development. Samplers were deployed at remote/rural/urban locations in 22 countries and analyzed for PCBs, a range of organochlorine pesticides (HCB, alpha-HCH, gamma-HCH, ppDDT, ppDDE), and PBDEs. Calculated air concentrations were in line with those obtained by conventional active air sampling techniques. The geographical pattern of all compounds reflected suspected regional emission patterns and highlighted localized hotspots. PCB and PBDE levels varied by over 2 orders of magnitude; the highest values were detected in areas of high usage and were linked to urbanized areas. HCB was relatively uniformly distributed, reflecting its persistence and high degree of mixing in air. Higher gamma-HCH, ppDDT, and ppDDE levels generally occurred in South and East Europe.     

The role of the snowpack on the fate of alpha-HCH in an atmospheric chemistry-transport model

A dynamic snowpack module was implemented in the Danish Eulerian Hemispheric Model Persistant Organic Pollutants (DEHM-POP), an atmospheric chemistry-transport model designed to study the environmental fate of persistent organic pollutants in the Northern Hemisphere. The role of the snowpack on the fate of alpha-hexachlorocyclohexane (alpha-HCH) was investigated by making simulations both with and without the formation of a snowpack and comparing model results with data from 21 air monitoring sites. The inclusion of a dynamic snowpack module in the DEHM-POP model generally improves the fit between modeled and observed alpha-HCH air concentrations for the winter and spring seasons and the overall correlation coefficient between predicted and observed concentrations are improved at 8 of the sites. The predicted snowpack concentrations are in good agreement with the few available snow measurements from the Arctic. The presence of a snowpack increases surface boundary layer air concentrations of alpha-HCH at midlatitudes, while the effect is more pronounced in the Arctic due to the longer periods of snow cover. The results indicate that the snowpack module in DEHM-POP acts as a fast-exchanging temporary storage medium for alpha-HCH, as significant fractions were rapidly revolatilized back into the atmosphere following deposition with snowfall, although the current parametrization for vapor-exchange probably over emphasizes this process. Nonetheless, increased air concentrations observed between March and May ("spring maximum events"; SME) at several high latitude monitoring stations are also predicted by the model. The model results indicate that the SMEs are associated with the revolatilization of previously deposited chemical from the snowpack, following a reduction in the capacity of the snowpack to retain alpha-HCH with increasing temperatures toward the end of the winter period, rather than the actual melting of the snowpack. The SMEs are not predicted at all the Arctic monitoring sites by the model, and the significance of the snowpack in controlling these in the model is, therefore, open to question given the uncertainties in the snow-air partition coefficient (K(sa)) and the reliance of the model on a one-layer snowpack rather than a multilayered snowpack.     

A dynamic model to study the exchange of gas-phase persistent organic pollutants between air and a seasonal snowpack

An arctic snow model was developed to predict the exchange of vapor-phase persistent organic pollutants between the atmosphere and the snowpack over a winter season. Using modeled meteorological data simulating conditions in the Canadian High Arctic, a single-layer snowpack was created on the basis of the precipitation rate, with the snow depth, snow specific surface area, density, and total surface area (TSA) evolving throughout the annual time series. TSA, an important parameter affecting the vapor-sorbed quantity of chemicals in snow, was within a factor of 5 of measured values. Net fluxes for fluorene, phenanthrene, PCB-28 and -52, and alpha- and gamma-HCH (hexachlorocyclohexane) were predicted on the basis of their wet deposition (snowfall) and vapor exchange between the snow and atmosphere. Chemical fluxes were found to be highly dynamic, whereby deposition was rapidly offset by evaporative loss due to snow settling (i.e., changes in TSA). Differences in chemical behavior over the course of the season (i.e., fluxes, snow concentrations) were largely dependent on the snow/air partition coefficients (K(sa)). Chemicals with relatively higher K(sa) values such as alpha- and gamma-HCH were efficiently retained within the snowpack until later in the season compared to fluorene, phenathrene, and PCB-28 and -52. Average snow and air concentrations predicted by the model were within a factor of 5-10 of values measured from arctic field studies, but tended to be overpredicted for those chemicals with higher K(sa) values (i.e., HCHs). Sensitivity analysis revealed that snow concentrations were more strongly influenced by K(sa) than either inclusion of wind ventilation of the snowpack or other changes in physical parameters. Importantly, the model highlighted the relevance of the arctic snowpack in influencing atmospheric concentrations. For the HCHs, evaporative fluxes from snow were more pronounced in April and May, toward the end of the winter, providing evidence that the snowpack plays an important role in influencing the seasonal increase in air concentrations for these compounds at this time of year.     

Atmospherc deposition of organochlorine compounds to remote high mountain lakes of Europe

Bulk deposition samples were taken near three mountain lakes located in the Pyrenees (Estany Redó), Alps (Gossenk?llesee), and Caledonian Mountains (Ovre Ne?dalsvatn) for evaluation of the atmospheric deposition load of organochlorine compounds (OC), namely, polychlorobiphenyls (PCBs), hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), and endosulfans, in the remote European high mountain areas. The compounds of present use in agriculture, namely, endosulfans and gamma-HCH, exhibit large differences in mean deposition fluxes between the three sites. They occur in large amounts in Estany Redó (340 and 430 ng m(-2) month(-1) for endosulfans and gamma-HCH, respectively), reflecting the impact of agricultural activities in southern Europe. This lake showed also the highest proportion of the more labile endosulfan isomers (alpha and beta = 82%) whereas only the most recalcitrant species, endosulfan sulfate, was found in Ovre Ne?dalsvatn. In contrast, the OC whose use is now banned exhibit a more uniform geographic distribution with deposition fluxes of 31-40, 30-100, and 1.4-15 ng m(-2) month(-1) for alpha-HCH, PCBs, and HCB. Both compounds of present and past use exhibit a clear seasonal pattern, with higher deposition in the warm periods, which is consistent with enhanced volatilization at higher temperatures. In the case of the agricultural pesticides it may also reflect higher use during application periods. The OC distributions in the atmospheric deposition of the three sites are rather uniform and highly enriched in compounds with volatilities larger than 0.0032 Pa. However, more than 90% of these compounds are not retained in the lake waters or sediments. Comparison of OC composition in atmospheric and sedimentary deposition evidences a selective trapping of the less volatile compounds. Trapping efficiencies increase at decreasing air temperatures of the lacustrine systems.     

Spatial and temporal trends of chiral organochlorine signatures in Great Lakes air using passive air samplers

Passive air samples (PAS) were collected and analyzed to assess the spatial and temporal trends of chiral organochlorine signatures in the Laurentian Great Lakes. Samples were collected from 15 sites and analyzed for the concentrations and enantiomer signature of chlordanes and alpha-hexachlorocyclohexane (alpha-HCH). Levels of the chlordanes were typically 4 times higher in urban areas than what were observed at rural and remote locations, exhibiting strong urban-rural gradients. Near racemic residues were seen for the chlordane enantiomers in samples collected from sites located in Toronto and Chicago, which can be attributed to continued emissions of historical use of the technical chlordane mixture, while the chiral signature observed at sites located in rural and remote locations was indicative of an aged source. Knowledge of the spatial and temporal distribution of the enantiomer signatures of chlordane and alpha-HCH in air is useful for distinguishing sources of these compounds to ambient air. Results suggest that potential sources, such as those associated with Toronto and Chicago, have limited influence over the levels at rural and remote sites within the Great Lakes. Sources that are relatively close to sample sites, however, have a strong influence on levels observed at those sites. For instance, results indicate that Lake Superior continues to act as a source of alpha-HCH to sites located on its shores. Generally, it appears that during the warmer months, local enhanced surface-air exchange influences air concentrations and that during the cooler periods of the year, levels in the atmosphere are more strongly influenced by advective transport from source regions.     

Residue situation of DDT, HCH and HCB in grains in the years 1982-1987

In the GDR DDT-preparations are not admissible and the application of lindane-preparations is limited. In pursuance of the investigations of grain samples since 1971 DDT-, DDE-, alpha-, beta- and gamma-HCH as well as HCB-residues have been determined. These residues are to be attributed to an unwilled contamination by uptake from the soil. In comparison with the residue situation from 1971 up to 1980 a further decrease of the contamination of cereals with DDT- and HCH-residues was stated, whereas the HCB residues remained constant. In 1987 the mean values for the total DDT-, total HCH- and HCB-residues were found to be distinctly below the maximum residue limits stated in the regulations of admissible residue levels in the GDR or below the negigible residue levels according to the toxicity group II of 0.02 mg.kg-1 for DDT, HCH and HCB.