Trace metal concentrations in lake and overbank sediments in southern Norway

As, Be, Cd, Co, Cr, Cu, Hg, Ni, Pb, V, Se and Zn concentrations were determ ined and compared in lake and overbank sediments from 33 catchments without local pollution sources in southern Norway. There were no significant diff erences in concentrations of Be, Co, Cr, Cu, Ni, and V in overbank and pre- industrial lake sediments. In areas with shallow overburden, and significan t influence from long-range atmospheric pollution, concentrations of As, Cd , Hg, Pb, Se, and Zn in overbank sediments were probably modified by vertic al percolating water. In such areas, we suggest using lake sediments as a b etter sampling medium for mapping pre-industrial concentrations. Pre-indust rial lake sediments yield natural concentrations of Hg and Se, which consis t of both geogenic and natural atmospheric deposition. Important covariable s like organic carbon content, Fe oxides, and fine mineral fraction were ge nerally higher in preindustrial lake sediments as compared to overbank sedi ments. By adjusting for such differences overbank sediments could be used a s an alternative in mapping background concentrations of trace metals in re gions with few lakes.