Lake Susser See as a natural sink for heavy metals from copper mining

Lake Susser See, west of Halle, Germany, is a natural sink for heavy metals , which are abundant in the streams crossing the Mansfeld copper shale mini ng and smelting district in Central Germany. The lake and its environment s erve as a recreational area for the local residents. We investigated the ve rtical distribution of key metals such as Cu, Pb and Zn in the lake sedimen ts. To estimate the future stability of the heavy metals in the lake sedime nts, speciation analysis of the metals was carried out on selected samples using several analytical methods, including X-ray diffraction, synchrotron- based X-ray fluorescence imaging, microprobe X-ray absorption near-edge str ucture spectroscopy and scanning electron microscopy. The lake sediments co ntain up to 5% Zn, 5000 ppm Pb, 4500 ppm Cu and 2000 ppm As. These maximum values are reached within the upper 60 cm of the sediment. There is a gener al trend of decreasing metal concentrations with depth. Several potential m etal sources of geogenic and anthropogenic pollutants have to be taken into account. Pollutants of geogenic origin are mainly heavy metals from the ou tcropping copper shale at the periphery of the Mansfeld geosyncline. Man-ma de pollutants are dominated by seepage from the mine tailings and smelting products of copper shale mining (in particular scrubber dust, `Theisen-slud ge'). Trace elements and their ratios in the lake sediments can serve as ge ochemical tracers. These tracers could help to identify the main sources of pollution. The data show that scrubber dust is the main carrier of the hea vy metal contamination in the lake sediments. (C) 2001 Elsevier Science B.V . All rights reserved.