Total gaseous mercury along a transect from coastal to central Antarctic: Spatial and diurnal variations

Total gaseous mercury (TGM) in the atmospheric boundary layer was investigated along a transect from coastal (Zhongshan Station; 69°22′25″S, 76°22′14″E) to central (Kunlun Station; 80°25′2″S, 77°6′47″E) Antarctic from December 16, 2012 to February 6, 2013. TGM varied considerably from 0.32 to 2.34 ng m−3 with a mean value of 0.91 ng m−3. Spatially, relatively high values occurred near the coastal region and on the central plateau with altitude higher than 3000 m above sea level. This distribution pattern cannot be accounted for simply by the influence of mercury emission from the ocean. Changes in TGM were also found to be related to the topography. TGM was higher in the inland flat region (290-800 km from the coast) than in the inland transition zones with steep slopes (800-1000 km from the coast). Temporally, diurnal cycling of TGM was clearly observed at Kunlun Station, with the lowest value occurring typically at midnight, and the peak value at midday. This diurnal pattern was attributed to the reemission of gaseous elemental mercury (GEM) from the snow pack, the oxidization of GEM and convective mixing.