Long term measurements of wet deposition and precipitation scavenging of hexachlorocyclohexanes in Southern Norway

Concentrations of alpha- and gamma-hexachlorocyclohexane (HCH) were measured in precipitation samples on a weekly basis between 1991 and 1995 at Lista, a coastal station in Southern Norway. The levels averaged at 1.9 ng/l alpha-HCH and 4.4 ng/l gamma-HCH. The time profile of gamma-HCH concentrations in rain was characterised by a generally low base line level with a few spring time episodes of highly elevated concentrations in excess of 100 ng/l. Such episodes could account for a large fraction of the total annual deposition of gamma-HCH, but could not be observed for alpha-HCH. Whereas gamma-HCH concentrations in Lista are considerably lower than those determined in Central European rain, alpha-HCH concentrations are similar. Total annual wet depositional fluxes are on the order of 2-4 mu g/m(2) alpha-HCH and 10-35 mu g/m(2) gamma-HCH. Vapour scavenging ratios of 31,000 and 91,500 for alpha- and gamma-HCH, which were derived using concentrations in air measured at the same location, agree well with previous determinations, but indicate higher-than-equilibrium partitioning. Neither interfacial sorption, nor temperature differences can explain this discrepancy. Scavenging ratios of alpha-HCH increased significantly at lower temperature. (C) 1999 Elsevier Science Ltd. All rights reserved.