Hexachlorocyclohexanes in the Canadian Archipelago. 1. Spatial Distribution and Pathways of α-, β-, and γ-HCHs in Surface Water

Hexachlorocyclohexanes (HCHs) in the surface water of the Canadian Archipelago and south Beaufort Sea were measured in summer, 1999. Overall concentrations of HCH isomers were in order of abundance: α-HCH (3.5 ± 1.2 ng L-1) > γ-HCH (0.31 ± 0.07 ng L-1) > β-HCH (0.10 ± 0.03 ng L-1). Concentrations and ratios of α-HCH/γ-HCH decreased significantly (p < 0.001 to 0.003) from west to east, but there was no significant variation in α-HCH/ β-HCH. The (+) enantiomer of α-HCH was preferentially degraded, with enantiomer fractions (EFs) ranging from 0.432−0.463 and increasing significantly (p < 0.001) from west to east. Concentrations also varied latitudinally for α-HCH and γ-HCH (p < 0.002) but not for β-HCH. Principal component analysis with variables α-HCH and γ-HCH concentrations, EF, latitude, and longitude accounted for 71% (PC 1) and 16% (PC 2) of the variance. Mixing in the eastern Archipelago was modeled by assuming three end members with characteristic concentrations of α-HCH and γ-HCH. The model accounted for the observed concentrations and higher EFs of α-HCH at the eastern stations.