AIR-WATER GAS-EXCHANGE AND EVIDENCE FOR METABOLISM OF HEXACHLOROCYCLOHEXANES IN RESOLUTE BAY, NWT

Paired air and water samples were collected at Resolute Bay (74 degree s N, 95 degrees W) in summer 1992 to estimate the direction of gas exc hange of hexachlorocyclohexanes (HCHs) and investigate possible loss p rocesses in the water column. Average concentrations of alpha-HCH and gamma-HCH in ocean surface water were 4.7 +/- 0.9 and 0.44 +/- 0.11 ng /l, respectively. These alpha- and gamma-HCH levels are similar to 66- 104% and 54-72% of values reported for the central Arctic Ocean at the Canadian Ice Island in 1986. Mean atmospheric concentrations of alpha -HCH and gamma-HCH(-1.4 +/- 16 and 9.8 +/- 1.3 pg/m(3)) were 2-3 times lower than summer Arctic levels in the 1980s. The ocean surface water (-1.4 degrees C) was approximately within Henry's law equilibrium wit h respect to atmospheric gamma-HCH levels. Water/air fugacity ratios w ere 1.03 for gamma-HCH and 1.57 for alpha-HCH, indicating a slight pot ential for volatilization of alpha-HCH. The two alpha-HCH enantiomers in air and water were separated by chromatography on a gamma-cyclodext rin capillary column. The enantiomeric ratio (ER = ratio of (+)alpha-H CH/(-)alpha-HCH) in air was 1.00 +/- 0.04. This agrees excellently wit h ER = 1.00 +/- 0.01 found for a racemic alpha-HCH standard. The (+) e nantiomer was depleted in seawater, resulting in ER = 0.93 +/- 0.06 in Resolute Bay. ERs of samples from Amituk Lake on Cornwallis Island ra nged from 0.65 to 0.99, depending on location, date and relative contr ibutions of fresh snowmelt and older lake water. These results suggest that microbial degradation of HCHs is taking place in Arctic lakes an d near-shore marine waters.