MILJØ2015-Norsk miljøforskning mot 2015

Mercury (Hg) pollution is becoming an environmental problem of great concern in boreal areas across the entire northern hemisphere, especially because of bioaccumulation of methylmercury (MeHg) in fish and consequences of this toxic substance for human he alth. There is an urgent need for better knowledge on causes and pathways of spreading of Hg in the environment, as a basis for policy on reduction of Hg emissions and abatement measures of human exposure to Hg. Here we propose an interdisciplinary proje ct that aims to increase the understanding of environmental factors that control levels of Hg and MeHg in surface waters and fish. We will employ a catchment perspective to estimate a budget of inputs and outputs of Hg in a boreal catchment, assess effect s of forest management on concentrations of Hg in streams and fish, and aim to link the catchment fluxes to accumulation of Hg in the food chain by studying the role of organic matter as a carrier for Hg and MeHg and a diet source at the bottom of the aqu atic food chain. Norwegian experts with a background in environmental chemistry, forest management, catchment science and ecosystem modelling are joined with internationally acknowledged experts in the field of environmental Hg chemistry in catchments an d transfer mechanisms of Hg into and in the food chain. The project is organised along two linked pillars: 1) inputs and outputs of Hg and effects of forest management will be studied in a paired catchment study in a boreal lake catchment in southcentral Norway, where also MeHg accumulation in zooplankton will be studied; 2) in a synoptic study of nutrient-poor forested lakes located in an area with considerable logging activities, effects of forest management and catchment characteristics on Hg on aquat ic biota will be assessed. A focus on transfer of MeHg in catchments unites both pillars. A catchment model of Hg will be used to synthesize measurements in pillar 1 while also serving as a conceptual framework.