Beräkning av massbalanser för metaller i vatten samt miljöriskbedömning av Nerån vid Österbyverken i Östhammars kommun

Österbyverken is an industrial estate in Östhammars municipality in Uppland, Sweden. Many different activities have taken place on the estate the last 600 years. During the last 15 years both health and environmental studies have been made by different companies. At the most recent study a great increase of metals in Nerån, a river that runs partly through and partly next to the estate, was identified with mass balances. The purpose of this thesis is to accomplish a deepened study about the reasons for the increase of metals in Nerån. The aim is to identify knowledge gaps in the mass balances and try to complete these. From the outcome an environmental risk assessment will be attempted for Nerån and its outlet in the lake Filmsjön. The method went through steps and started with data analyses after which calculations for new mass balances were made. Beginning by acknowledge the increase of metals from the groundwater, both through measured results and through calculated confidence intervals. In addition, among other methods, calculations of theoretical leakage data from Kd-values were made. Surface water concentrations were also compared with levels of metals in sediments to see whether any connection existed between them. Additional mass balances were calculated to take suspended solids in the surface water under consideration. From the results an environmental risk assessment was made using guidelines from Netherland and Canada and the state division from the Swedish Environmental Protection Agency. The results of the study show that the differences of metal content between surface water and groundwater and between surface water and sediments might be smaller than first revealed, but there is still a great increase caused by another, unknown source. The environmental risk assessment shows that there are hazards for both Nerån and Filmsjön because of the leakage of metals from Österbyverken. For the surface water in Nerån it is mainly cobalt, copper and zinc that contributes with risks, for the sediment in Nerån it is mainly barium, cobalt, copper, chromium and nickel and for the sediments in Filmsjön it is mainly lead, cobalt, copper, chromium, nickel and zinc. Reasons for the differences between metal contents and medias might be from surface water outlet from the Österbyverken or because of differences in methods of taking specimens in surface and groundwater. Conclusions that have been drawn of the study is that further studies of the knowledge gaps needs to be done, particularly regarding the metals cobalt, copper, chromium, nickel and zinc. Further, the biodiversity in Nerån and Filmsjön is at risk, partly because several metals in the sediments reaches such high concentrations, partly because high concentrations of several metals in one area may increase risks.