Organochlorine pesticides and enantiomers of chiral pesticides in Arctic Ocean water.

In the summers of 1993 and 1994, seawater samples from the surface layer (40–60 m) were collected to determine the spatial distribution of organochlorine pesticides on expeditions that crossed the Arctic Ocean from the Bering and Chukchi seas to the North Pole, to a station north of Spitsbergen, and then south into the Greenland Sea. Spatial differences in concentration were found that varied with the pesticide. Heptachlor exo-epoxide (a metabolite of heptachlor) and α-hexachlorocyclohexane (α-HCH) increased from the Chukchi Sea to the pole, and then decreased toward Spitsbergen and Greenland Sea. Chlorinated bornanes (toxaphene) followed a similar trend, but levels were also high near Spitsbergen and in the Greenland Sea. A reverse trend was found for endosulfan, with lower concentrations in the ice-covered regions. Little variation was seen in chlordane concentrations, although the ratio of trans-/cis-chlordane decreased at high latitudes. Several of these pesticides are chiral: α-HCH, cis- and trans-chlordane, and heptachlor exo-epoxide. Enantioselective degradation of (−)α-HCH was found in the Bering and Chukchi seas, whereas the (+) enantiomer was depleted in the Arctic Ocean and Greenland Sea. Enrichment of (+) heptachlor exo-epoxide was found in all regions. Trans- and cis-chlordane were nearly racemic.