Extended environmental risk assessment of the lake Långsjön within the Bofors Test Center Artillary Range area

On behalf of Bofors Test Center AB, the Swedish Defence Research Agency, divison of NBC Defence, has performed an extended environmental risk assessment of the lake Långsjön within the Bofors Test Center Artillery Range area. The company has earlier, with permission from the Swedish Environmental Authorities, been allowed to dump environmentally dangerous waste in Långsjön. Dumping has most extensively been performed during the period 1954 to 1975. The last dumping took place in 1993. Enhanced levels of heavy hetals (especially lead) have earlier been detected in lake sediment and in aquatic moss in the outflow of Långsjön (mostly mercury and lead). Generally, the water shows low pH values, which results in an increased risk for leakage of heavy metals. It may be possible that there is a leakage of mercury from the lake. The aim of this investigation has been to describe the impact of the dumping in the lake, with sediment sampling, bottom water sampling and investigation of the benthic fauna being indicators for this impact. The results showed that the upper sediment layers in Långsjön consequently show high to very high levels of mercury, while the bottom water seems to be less affected. The benthic fauna is also highly affected, especially at the inflow of the lake. An increased pH would probably give positive effects on the lake, since heavy metal leakage would decrease, as well as improve the life condition for the benthic life.