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(15-10) Antarctic springtime depletion of atmospheric mercury. Ebinghaus, Ralf*,1, Temme, Christian1,2, Kock, Hans1, Löwe, Astrid3, Schroeder, William4, 1 GKSS Research Centre Geesthacht, Geesthacht, Germany2 University of Jena, Jena, Germany3 Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany4 Meterological Service of Canada, Downsview, Canada ABSTRACT- The background concentration of total gaseous mercury (TGM) in the lower troposphere of the northern hemisphere is generally around 1.7 ng m-3 and 1.3 ng m-3 in the southern hemisphere respectively. Recently, highly time resolved TGM measurements in the Arctic have shown that TGM levels are significantly depleted during the months after polar sunrise. A possible explanation may be a sequence of oxidation, adsorption and deposition of TGM leading to an increased input of atmospheric mercury into the Arctic ecosystem. The Arctic TGM depletion is strongly correlated with ground level ozone concentrations. Ozone depletions have also been observed in the Antarctic however, highly time resolved measurements of TGM covering longer time periods have not yet been reported for Antarctica. Two Tekran gas phase mercury analyzers (Model 2357A) have been installed at the German Antarctic research station Neumayer in January 2000 and were continuously in operation until February 2001. The site is located on the Ekstroem Shelf Ice, about 8 km from the Atka Bay and is operated by the Alfred Wegener Institute for Polar and Marine Research.The analyzers have been installed at the Neumayer Air Chemistry Observatory, which is approximately 1.5 km south of the main site. The prevailing wind directions are from the east, (and) northerly winds are very rare. The TGM data can briefly be characterized by three different periods: 1. Between January and February 2000 and December to February 2000/01 (i.e. during antarctic summer) TGM concentrations were highly variable with pronounced diurnal patterns and daily average concentrations between 0.6 and 1.8 ng -3 2. Between March and July 2000 the TGM concentration levels remained on a fairly constant concentration level of about 1.2 ng m-3. 3. Between August and November 2000 several depletion events have been detected with minimum daily average concentrations of about 0.1 ng m-3. The annual time series measured at Neumayer Station gives clear evidence that mercury depletion events (MDE) do occur in the Antarctic. It could also be shown that MDE coincides with ozone depletion in the lower troposphere and with the enhanced occurrence of BrO radicals in the Antarctic atmosphere, measured from the satellite borne GOME instrument and at Neumayer Station as BrO column densities. Key words: Mercury, Antarctic, Springtime depletion |
