The Mansfeld region in Sachsen-Anhalt, Central Germany, has a long tradition of mining Kupferschiefer, a marine copper-containing black shale of Permian age. One of the residues from the processing of that low-grade copper ore is 'Theisen Sludge', a very fine-grained scrubber dust composed of metal sulphide particles in a matrix of highly viscous hydrocarbons. The Theisen Sludge is considered to be the main source for heavy metal releases into the local environment. The most important discharge point for contaminated water is the 'Stadtborn Spring'. The extremely high metal and sulphate concentrations in the spring water cause the precipitation of a mineral phase exceptionally rich in heavy metals. This precipitate is the focus of the current investigation. It is shown that a gel with adsorbed metals first is formed from spring water. Then zinc-copper-aluminium hydroxides start to crystallise from the gel at an early stage, forming (Zn,Cu,Al)(O,OH)(2) brucite-type layers, which are positively charged owing to a remarkable Al content. These precursor layers take up SO42- for charge compensation and H2O into interlayers and begin to form zinc-copper-aluminium hydroxide-sulphates such as Al-rich zincowoodwardite within a few weeks of aging. Further maturation of the precipitate took place in the gaseous environment of atmospheric CO2 after part of the brook dried up several decades ago. This 'maturation' due to the long-term interaction of the precipitate with atmospheric CO2 is characterised by the transformation of the zinc-copper-aluminium hydroxide-sulphates into zinc hydroxide-carbonates with a residual copper content. The resulting crystalline phase is characterised structurally as disordered hydrozincite. The results described are the first step in a study which aims to optimise the natural precipitation process observed as a part of a remediation strategy for the local surface water system. It also is noticed that the fresh precipitate may be of use as a precursor material for copper/zinc co-precipitated oxide catalysts for industrial hydrogenation processes.

In metal mining districts, element and radionuclide patterns in contaminated stream sediment can be used as tracers to detect and track the sources of pollution, and to distinguish geogenic from anthropogenic input, a prerequisite for rehabilitation planning. An example is given from the Mansfeld mining district in central Germany, where mining of 'Kupferschiefer' was conducted for over 800 years and led to extensive environmental pollution, considered to be mainly of geogenic origin. In consequence, only emergency measures have been implemented. The aim of the present study was to identify the metal sources in the mining district and to assess the range of pollutant migration. In combining conventional geochemistry, mineralogy and radiometry, it was shown that most of the multi-metal pollution in the Mansfeld mining district is of anthropogenic origin. The major sources of metals are low-grade ore, metalliferous flue dust and slag. Conventional geochemistry provided information on the spread of contamination in the rivers of the mining district. Mineralogy and microchemistry added data on the composition of the source material and pointed to the potential sources of contamination. Finally, the fraction of these sources in environmental pollution was estimated by gamma-spectroscopy.

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.

In metal-mining districts containing outcropping ore bodies, mining waste heaps and dumped residues from ore-smelting, it is often difficult to distinguish between the various sources of environmental pollution due to their very similar geochemical composition. One example is the copper-mining district of Mansfeld in Central Germany, where uraniferous copper shale has been mined and processed For more than 800 years. The abundance of key radionuclides of the U-238 decay series in sediments and soils is a powerful tool for distinguishing between geogenic and anthropogenic metal sources, as well as for detecting pollutant migration pathways.

Reservoir minerals of the hydrotalcite group, especially glaucocerinite [Zn5Al3(OH)(16)] [(SO4)(1.5) (H2O)(9)], are able to extract metals from leachates by incorporation in their crystal lattice. The formation of these minerals strongly depends on the pH and the availability of trivalent cations such as Al, Fe and Cr. Leachates from smelting residues in the former "Kupferschiefer" mining district in Germany contain up to 2000 mg/l zinc, 6000 mg/l sulphate and about 15 mg/l aluminium. Natural precipitation of glaucocerinite occurs around the outflow of a slag heap and immobilises 6-10% of the zinc and about 10% of the sulphate in the leachate. We showed in lab experiments that adding trivalent cations (Al, Fe, Cr) to the leachate and increasing the pH from 6 to 7 results in increased glaucocerinite precipitation and eventually immobilises more than 95% of the zinc in leachate. If applied on an industrial scale, metal-absorbing reservoir minerals may become powerful tools for leachate treatment and a future resource for economically important metals.