MERCURY IN SWEDISH FOREST SOILS AND WATERS - ASSESSMENT OF CRITICAL LOAD

As a result of air pollution, the content of Hg in fish has significantly increased in a large part of Scandinavia and North America. In this paper, the occurrence and fluxes of Hg in Swedish forest soils and waters are reviewed and synthesized. The main objective is to describe and evaluate the present transport of anthropogenic Hg from atmospheric deposition, through the terrestrial compartment and running waters to lake basins and also to comprehend the main factors influencing these fluxes. The transportation and distribution of Hg in forest soils and waters is closely related to the flow of organic matter. The content of Hg in humic matter is higher in southern and central areas compared to the north of the country. Compared to background concentrations, the Hg content has increased in the southern and central part by about a factor of 4-7, while the overall increase in the north is by about a factor of 2 to 3. The increased content of Hg in forest soils may have an effect on organisms and biological processes in the soil. Regarding budget calculations for whole catchment areas and for the mor layer of the soil, a reduction of about 80 % from present atmospheric wet deposition must be obtained to reach "critical load" with respect to conditions in Scandinavia.