Lake Süßer See, west of Halle, Germany, is a natural sink for heavy metals, which are abundant in the streams crossing the Mansfeld copper shale mining and smelting district in Central Germany. The lake and its environment serve as a recreational area for the local residents. We investigated the vertical distribution of key metals such as Cu, Pb and Zn in the lake sediments. To estimate the future stability of the heavy metals in the lake sediments, 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 structure spectroscopy and scanning electron microscopy. The lake sediments contain up to 5% Zn, 5000ppm Pb, 4500ppm Cu and 2000ppm As. These maximum values are reached within the upper 60cm of the sediment. There is a general trend of decreasing metal concentrations with depth. Several potential metal sources of geogenic and anthropogenic pollutants have to be taken into account. Pollutants of geogenic origin are mainly heavy metals from the outcropping copper shale at the periphery of the Mansfeld geosyncline. Man-made pollutants are dominated by seepage from the mine tailings and smelting products of copper shale mining (in particular scrubber dust, ‘Theisen-sludge’). Trace elements and their ratios in the lake sediments can serve as geochemical tracers. These tracers could help to identify the main sources of pollution. The data show that scrubber dust is the main carrier of the heavy metal contamination in the lake sediments.

An exact morphometric description of Mining Lake 111, Brandenburg, Germany, was obtained after a new survey in 1996 by the staff of the water research department. Volume and surface area of ML111 were calculated based on values of this survey. An actual bathymetric map was created from the datapool which was the basis for the selection of sampling sites where we obtained sediment cores to describe the geochemistry of the lake sediments. Principal Component Analysis (PCA) was carried out to examine patterns and similarities between concentrations of different heavy metals. The patterns are different for the three basins within the lake. The spatial distributions of 12 elements in the sediment surface were estimated with a geostatistical procedure (Ordinary Kriging) as well as with a conventional interpolation method. The structure found with PCA was confirmed by the plots from spatial interpolation. Due to the complexity of the lake morphometry and bathymetry 66 sediment cores taken at 47 sampling sites were not sufficient to reduce the spatial variance distributions to acceptable values.