MERCURY IN BALTIC AND NORTH-SEA WATERS

Improved determination methods for very low Hg concentrations in sea water using cold vapor AAS with pre-enrichment and purification on gold as well as a new sampling system ('MERCOS' PTFE water samplers) have been applied to extensive investigations for reactive and total Hg levels. The first research cruises concentrated on the southwestern Baltic Sea. Concentrations found in the surface water were around 2 ng L-1. Since 1979, Hg has been regularly monitored in the German Bight of the North Sea as a part of German and international monitoring programs. Two investigations have been performed in the lower course of the river Elbe, from Hamburg to the sea. Results show that the Elbe is the predominant 'point source' for Hg in the German Bight. In a large multidisciplinary research project 'ZISCH', a closely spaced station network has been sampled twice, in 1986 and 1987, to survey the entire North Sea, i.a. for Hg. Over most of the area, the median of Hg values in the surface water was 0.5 ng L-1; in a distinct field, however, extremely high levels were found, of more than 200 ng L-1.