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(15-06) Air-Snow/Firn Transfer of HCHs at Neumayer Station/ Antarctica. Lakaschus, Soenke*,1, Schrems, Otto1, 1 Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Niedersachsen, Germany ABSTRACT- Some semi volatile organic compounds have the potential to accumulate in polar regions and high mountain areas. The transfer processes between air and snow are of general interest for understanding the global fate and behaviour of these compounds.The aim of the present study was to determine the concentrations of Hexachlorocyclohexanes (HCHs) in Antarctic snow/firn and second to relate these to the corresponding atmospheric concentrations. Therefore snow/firn and air samples were collected simultaneously on the Ekstroem Ice Shelf at Neumayer Station/Antarctica (70S; 8W) during summer 1999/2000. The concentrations in snow/firn expressed as melt water equivalents were 7.7 pg/L (range 4-12) gamma-HCH and 2.4 pg/L (range 0.5-9) alpha-HCH. These concentrations are two orders of magnitude lower than reported northern hemispheric snow concentrations of HCHs. We observed a similar north/south gradient in air and seawater during a transect cruise between the Arctic and Antarctica. Theoretical snow/firn concentrations were calculated from the measured gaseous concentrations, recently reported interfacial sorption coefficients (KIA) for HCHs and literature estimates of snow surface areas. This comparison suggested that the measured snow and air concentrations were close to equilibrium. A clear relationship between the atmospheric HCH level and that in fresh snow was observed. In aged snow/firn- samples higher gamma-HCH concentrations, as would be expected from the gaseous concentrations, were found.We assume seasonal differences in the atmospheric long-range transport to Antarctica, which may explain the predominance of gamma -HCH in firn at Neumayer Station. Further investigations of the air/snow transfer and post depositional processes would require a suitable method to determine the specific surface area of snow under field conditions. Key words: HCHs, air-snow transfer, Antarctica, cold condensation |
