Air-sea exchange of mercury vapour over the Gulf of Gdansk and southern Baltic Sea

The total gaseous mercury (TGM) in air over the coastal station at Hel and over the southern Baltic Sea was measured during the summer and winter cond itions. Recorded 30-min resolution TCM data showed both higher concentratio ns and variability during the summer compared to the winter conditions. The summer TGM data ranged from 1.1 to 7.5 ng m(-3) while the winter data rang ed from 0.8 to 4.4 ng m(-3). The TGM content in air over the southern Balti c Sea indicated that, in general, during the summer conditions, the sea-to- air transport of gaseous mercury dominated, while during the winter season, a tendency of gaseous mercury to sink into the water has been found. The e vidences of enhanced water-to-air transfer of mercury vapour were noted, in particular, over the shallow waters of the Gulf of Gdansk under the strong water-to-air temperature gradients. Obtained results indicate that under s uch conditions, the coastal waters could act as a significant source of mer cury vapour that may contribute to the overall budget of atmospheric mercur y over the Baltic proper. (C) 2001 Elsevier Science B.V. All rights reserve d.