Seasonality in Exchange of Organochlorines between Arctic Air and Seawater

Decreases in atmospheric concentrations of organochlorine (OC) pesticides in the Northern Hemisphere during the last decade have resulted in Arctic Ocean surface layer water that is now supersaturated for some compounds. Seasonal measurements of several OCs in air and seawater in the Canadian arctic archipelago during 1993 were made to study changes in air−sea exchange over an annual cycle. Fugacity ratios and Henry's law constants, with cor rection for seasonal changes in ice cover, were used to calculate net air−sea fluxes on a monthly basis. The lack of concentration gradients between 1 and 50 m indicated that advection of polar mixed layer water flowing southward from under the polar ice cap was an important factor controlling seawater concentrations. Out-gassing of HCHs, HCB, and dieldrin during the ice-free period could have lowered surface layer inventories by 4−20%. In contrast, net deposition of CHBs, chlordanes, and endosulfan-I during the open water period was equivalent to 50−>100% of the surface layer inventory. Air−sea fluxes of OCs were influenced by the combined effects of changes in atmospheric vapor pressure and water mass advection. Potential removal of OCs on sedimenting particles was calculated to be less important in controlling surface layer concentrations.