Air-water gas exchange and evidence for metabolism of hexachlorocyclohexanes in Resolute Bay, N.W.T.

Abstract

Paired air and water samples were collected at Resolute Bay (74°N, 95°W) in summer 1992 to estimate the direction of gas exchange of hexachlorocyelohexanes (HCHs) and investigate possible loss processes in the water column. Average concentrations of α-HCH and γ-HCH in ocean surface water were 4.7 ± 0.9 and 0.44 ± 0.11 ng/l, respectively. These α- and γ-HCH levels are ∼ 66–104% and 54–72% of values reported for the central Aretic Ocean at the Canadian Ice Island in 1986. Mean atmospheric concentrations of α-HCH and γ-HCH (114 ± 16 and 9.8 ± 1.3 pg/m3) were 2–3 times lower than summer Arctic levels in the 1980s. The ocean surface water (−1.4°C) was approximately within Henry's Law equilibrium with respect to atmospheric γ-HCH levels. Water/air fugacity ratios were 1.03 for γ-HCH and 1.57 for α-HCH, indicating a slight potential for volatilization of #x003B1;-HCH. The two α-HCH enantiomers in air and water were separated by chromatography on a γ-cyclodextrin capillary column. The enantiomeric ratio (ER = ratio of (+)α-HCH/(−)α-HCH) in air was 1.00 ± 0.04. This agrees excellently with ER = 1.00 ± 0.01 found for a racemic α-HCH standard. The (+) enantiomer was depleted in seawater, resulting in ER = 0.93 ± 0.06 in Resolute Bay. ERs of samples from Amituk Lake on Cornwallis Island ranged from 0.65 to 0.99, depending on location, data and relative contributions of fresh snowmelt and older lake water. These results suggest that microbial degradation of HCHs is taking place in Arctic lakes and near-shore marine waters.