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Geochemistry of mine tailings and behavior of arsenic at Kombat,northeastern Namibia |
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| Authors: | O Sracek M Mihaljevič B Kříbek V Majer J Filip A Vaněk V Penížek V Ettler B Mapani |
| Institution: | 1. Department of Geology, Faculty of Science, Palacky University, Olomouc, Czech Republic 2. Institution of Geochemistry, Mineralogy and Natural Resources, Faculty of Science, Charles University, Praha, Czech Republic 3. Czech Geological Survey, Praha, Czech Republic 4. Regional Center of Advanced Technologies and Materials, Faculty of Science, Palacky University, Olomouc, Czech Republic 5. Department of Soil Science and Soil Protection, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences, Praha, Czech Republic 6. University of Namibia, Windhoek, Namibia |
| Abstract: | The mine tailings at Kombat, in semiarid northeastern Namibia, were investigated by the combination of solid-phase analyses, mineralogical methods, leaching tests, and speciation modeling. Dissolution of the most abundant primary sulfides, chalcopyrite and galena, released copper and lead which were adsorbed onto ferric oxyhydroxides or precipitated in the form of malachite, Cu2CO3(OH)2, and cerussite, PbCO3, respectively. Arsenic released from arsenopyrite was incorporated into ferric oxyhydroxides. Based on sequential extraction and 57Fe Mössbauer spectroscopy, a large amount of ferric iron is present as low solubility hematite and goethite formed rapidly (<10 years) under warm semiarid climatic conditions, and arsenic in these phases is relatively tightly bound. It seems that Cu and especially Pb in carbonate minerals represent a more serious environmental risk. Immobilization of As in hematite has implications for other mining sites in regions with similar climatic conditions because this process results in long-term immobilization of As. |
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