Mercury in fish in Swedish lakes ? Linkages to domestic and European sources of emission

Abstract

The work deals primarily with data from 894 Swedish lakes. The following parameters are discussed: Hg- and Se-concentrations and Hg-quantity in the mor layer reflecting the atmospheric deposition of Hg and Se-, Hg- and S-emissions deposition from Swedish and continental sources, precipitation, Hg in pike, lake area, lake mean depth, pH, color, alkalinity, hardness, S and chloride in lake water. The results are focused on geographical variations and statistical correlations for the Hg-content in 1-kg pike (=FHg), and on computer simulations to get insights and data on the linkages between various historical Hg-emissions and FHg. Selected results: Increased FHg-values may be attributed to atmospheric emissions of Hg and to acid rain. Southern Sweden is significantly influenced by continental Hg-emissions. East Germany, Great Britain, West Germany and Poland seem to have contributed with the largest foreign Hg-amounts in the Swedish mor layer and, at the end, to increased Hg-concentrations in Swedish fish. We have calculated that there are about 10 300 Swedish lakes with FHg > 1 mg Hg kg−1 (= the Swedish blacklisting limit). What would happen with FHg if atmospheric depositions of Hg and S were significantly reduced? Reductions of S would be beneficial primarily for lakes in S. Sweden. About 50% of the elevated levels of Hg in Swedish pike in the 1980s may be linked to Swedish Hg-emissions during the last 100 yr, about 10 to 15% could be attributed to foreign Hg-emissions and 35 to 40% to acid rain. There is a long lag phase between emission reduction and reduction of FHg. The known, major Swedish emissions of Hg have already been significantly reduced, but new point sources of Hg have appeared. There has been a significant change in the character of the Hg-emissions during the last decades. High FHg-values in fish in Swedish lakes will be a major environmental problem for decades to come.