Multi-year observations of organohalogen pesticides in the Arctic atmosphere

Abstract

Atmospheric measurements of organohalogen pesticides (OCs) have been made in both the Canadian and Russian Arctic. A full quality-controlled database of weekly samples is now available for the years 1992–94. Hexachlorobenzene (HCB) and the hexachlorocyclohexanes (HCHs) were the most predominant compounds in the atmosphere, followed by the chlordanes and endosulfan. Evidence of a seasonality in air concentrations was apparent particularly for the pesticide metabolites, compounds such as oxychlordane, heptachlor epoxide and dieldrin showing a significant positive correlation with temperature ( p<0.01). An exception to this was p, p′-DDE which showed elevated levels during the winter. Large spatial differences in mean annual concentrations of most OCs were not evident; however, spatial differences were apparent in α/γ-HCH ratios between the high Arctic site of Alert and the Yukon site of Tagish. The influence of both the European sector and the regional effect of the Arctic Ocean on the high Arctic probably accounted for this difference. A decline in the trans-chlordane/ cis-chlordane ratio compared to studies during the 1980s may indicate a more weathered source of chlordane to be present in the Arctic by the mid-1990s. Slopes generated from plots of partial pressure (ln P) versus 1/ T for selected compounds were considerably less steep than those derived from temperate studies. It is inferred here that long-range transport has a large influence on contaminant levels in the arctic atmosphere.