| Abstract
| - Arctic seawater concentrations of two currently usedpesticides, endosulfan and γ-HCH, were collated from avariety of cruises undertaken throughout the 1990s up to 2000for different regions of the Arctic Ocean. Surface seawaterconcentrations for α- and β-endosulfan ranged from <0.1−8.8 (mean 2.3) pg/L and 0.1−7.8 (mean 1.5) pg/L, while γ-HCHconcentrations were ∼100 fold higher than α-endosulfan,ranging between <0.70 and 894 (mean 250) pg/L.Geographical distributions for α-endosulfan revealed thehighest concentrations in the western Arctic, specifically inthe Bering and Chukchi Seas with lowest levels towardthe central Arctic Ocean. In contrast, γ-HCH revealed higherconcentrations toward the central Arctic Ocean, withadditional high concentrations in the coastal regions nearBarrow, Alaska and the White Sea in northwest Russia,respectively. A fugacity approach was employed to assessthe net direction of air−water transfer of these twopesticides, using coupled seawater and air concentrations.For α-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 CanadianArchipelago. Given the uncertainty in the temperature-adjusted Henry's Law constant (factor ∼10), it is plausiblethat equilibrium may have been reached for this compoundin the western fringes of the Arctic Ocean where the highestwater concentrations were observed. Similarly, FRvalues for γ-HCH were generally <1 and in agreementwith other separate studies, although, like α-endosulfan,net deposition predominated over the Canadian Archipelago.In the central and eastern regions of the Arctic Ocean,as well as in the two coastal areas of this study, the fugacityratios for γ-HCH where ∼1 indicating conditions approachingequilibrium. The elevated water concentrations andhigher FRs in these coastal areas support the assessmentthat riverine/coastal sources are important for thischemical, but less so for α-endosulfan for which air towater transfer during the ice-free summer months is likelyto be the major contemporary source to the Arctic. It isrecommended that archived extracts of river water bereanalyzed for α-endosulfan to confirm this.
|
