ORGANOCHLORINE PESTICIDES AND ENANTIOMERS OF CHIRAL PESTICIDES IN ARCTIC-OCEAN WATER

In the summers of 1993 and 1994, seawater samples from the surface lay er (40-60 m) were collected to determine the spatial distribution of o rganochlorine 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 differ ences in concentration were found that varied with the pesticide. Hept achlor exo-epoxide (a metabolite of heptachlor) and alpha-hexachlorocy clohexane (alpha-HCH) increased from the Chukchi Sea to the pole, and then decreased toward Spitsbergen and Greenland Sea. Chlorinated borna nes (toxaphene) followed a similar trend, but levels were also high ne ar Spitsbergen and in the Greenland Sea. A reverse trend was found for endosulfan, with lower concentrations in the ice-covered regions. Lit tle variation was seen in chlordane concentrations, although the ratio of trans-/cis-chlordane decreased at high latitudes. Several of these pesticides are chiral: alpha-HCH, cis- and trans-chlordane, and hepta chlor exo-epoxide. Enantioselective degradation of (-)alpha-HCH was fo und in the Bering and Chukchi seas, whereas the (+) enantiomer was dep leted in the Arctic Ocean and Greenland Sea. Enrichment of(+) heptachl or exo-epoxide was found in all regions. Trans- and cis-chlordane were nearly racemic.