The transport of beta-hexachlorocyclohexane to the western Arctic Ocean: a contrast to alpha-HCH.

A large database for alpha-hexachlorocyclohexane (alpha-HCH), together with multimedia models, shows this chemical to have exhibited classical 'cold condensation' behavior. The surface water of the Arctic Ocean became loaded between 1950 and 1990 because atmospheric transport of alpha-HCH from source regions to the Arctic was rapid and because alpha-HCH partitioned strongly into cold water there. Following emission reductions during the 1980s, alpha-HCH remained trapped under the permanent ice pack, with the result that the highest oceanic concentrations in the early 1990s were to be found in surface waters of the Canada Basin. Despite a much stronger partitioning into water than for alpha-HCH, beta-HCH did not accumulate under the pack ice of the Arctic Ocean, as might be expected from the similar emission histories for the two chemicals. Beta-HCH appears to have loaded only weakly into the high Arctic through the atmosphere because it was rained out or partitioned into North Pacific surface water. However, beta-HCH has subsequently entered the western Arctic in ocean currents passing through Bering Strait. Beta-HCH provides an important lesson that environmental pathways must be comprehensively understood before attempting to predict the behavior of one chemical by extrapolation from a seemingly similar chemical.