Hexachlorocyclohexane (HCH) Isomers and Chiral Signatures of α-HCH in the Arctic Marine Food Web of the Northwater Polynya

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Abstract
Concentrations of hexachlorocyclohexane (HCH) isomers (α, β, and γ) and enantiomer fractions (EFs) of α-HCH were determined in the Northwater Polynya Arctic marine food web. Relative food web structure was established using trophic level models based on organic δ15N values. Concentrations of HCH in the samples collected, including water, sediment, benthic invertebrates (four species), pelagic zooplankton (six species), Arctic cod, seabirds (seven species), and ringed seal, were in the range previously reported for the Canadian Arctic. The relative proportion of the HCH isomers varied across the food web and appeared to be related to the biotransformation capacity of each species. For invertebrates and fish the biomagnification factors (BMFs) of the three isomers were >1 and the proportion of each isomer and the EFs of α-HCH were similar to water, suggesting minimal biotransformation. Seabirds appear to readily metabolize γ- and α-HCH based on low BMFs for these isomers, high proportions of β-HCH (62−96%), and high EFs (0.65−0.97) for α-HCH. The α- and β-HCH isomers appear to be recalcitrant in ringed seals based on BMFs >1 and near racemic EFs for α-HCH. The β isomer appears to be recalcitrant in all species examined and had an overall food web magnification factor of 3.9. EFs of α-HCH and the proportion of β-HCH in Σ-HCH in the food web were highly correlated (r2 = 0.92) suggesting that EFs were a good indicator of a species capability to biotransform α-HCH.
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