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This article in JEQ

  1. Vol. 36 No. 1, p. 61-69
     
    Received: Apr 13, 2006


    * Corresponding author(s): thilo.hofmann@univie.ac.at
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doi:10.2134/jeq2006.0148

Vertical Distribution and Speciation of Trace Metals in Weathering Flotation Residues of a Zinc/Lead Sulfide Mine

  1. Nele Schuwirtha,
  2. Andreas Voegelinb,
  3. Ruben Kretzschmarb and
  4. Thilo Hofmann *c
  1. a Institute of Geosciences, Mainz Univ., Becherweg 21, D-55099, Mainz, Germany. Present address: Swiss Federal Institute of Aquatic Science and Technology (Eawag), CH-8600 Duebendorf, Switzerland
    b Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Universitätstrasse 16 CHN, CH-8092 Zurich, Switzerland
    c Vienna Univ., Center of Earth Sciences, Dep. of Environmental Geoscience, Althanstraße 14, A-1090 Vienna, Austria

Abstract

Sulfide-bearing mine tailings are a serious environmental problem around the world. In this study, the vertical distribution and speciation of Zn and Pb in the fine-grained flotation residues of a former sulfide ore mine in Germany were investigated to assess the inorganic weathering processes that effect the environmental risk arising from this site. Total metal contents were determined by X-ray fluorescence spectroscopy (XRF). Mobilizable fractions of Zn, Pb, Fe, and Mn were quantified by sequential chemical extractions (SCE). Furthermore, the speciation of Zn was analyzed by Zn K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) to identify the residual Zn species. The variations in pH and inorganic C content show an acidification of the topsoil to pH 5.5. EXAFS results confirm that Zn is mainly bound in sphalerite in the subsoil and weathering reactions lead to a redistribution of Zn in the topsoil. A loss of 35% Zn and S from the topsoil compared with the parent material with 10 g kg−1 Zn and neutral pH has been observed. If acidification proceeds it will lead to a significant release of Zn, S, and Pb to the ground water. In contrast to Zn, Pb is enriched in the mobile fraction of the topsoil by more than a factor of two compared with the subsoil which contains a total of 2 g kg−1 Pb. Thus, the high bioavailability of Pb and the potential for Pb uptake by plants and animals currently represent the most severe threat for environmental health.

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