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    Cycling of As, P, Pb and Sb during weathering of mine tailings: implications for fluvial environments

    Kossoff, David and Hudson-Edwards, Karen A. and Dubbin, W.E. and Alfredsson, M. and Geraki, T. (2012) Cycling of As, P, Pb and Sb during weathering of mine tailings: implications for fluvial environments. Mineralogical Magazine 76 (5), pp. 1209-1228. ISSN 1471-8022.

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    Abstract

    The weathering and oxidation of mine tailings has the potential to contaminate water and soil with toxic elements. To understand the mechanisms, extent and products of the long-term weathering of complex Bolivian tailings from the Cerro Rico de Potosí, and their effects on As, Pb, P and Sb cycling, three-year long laboratory column experiments were carried out to model 20 years of dry- and wet-season conditions in the Pilcomayo basin. Chemical analysis of the leachate and column solids, optical mineralogy, X-ray diffraction, scanning electron microscopy, electron probe microanalysis, micro-scale X-ray absorption near edge structure spectroscopy, Bureau Commun de Référence sequential extraction and water-soluble chemical extractions, and speciation modelling have shown that the weathering of As-bearing pyrite and arsenopyrite, resulted in a loss of 13–29% of the original mass of As. By contrast, Pb and Sb showed much lower mass losses (0.1–1.1% and 0.6–1.9%, respectively) due to the formation of insoluble Pb- and Sb(V)-rich phases, which were stable at the low pH (~2) conditions that prevailed by the end of the experiment. The experiment also demonstrated a link between the cycling of As, Sb, and the oxidation of Fe(II)-bearing sphalerite, which acted as a nucleation point for an Fe-As-Sb-O phase. Phosphorus was relatively immobile in the tailings columns (up to 0.3% mass loss) but was more mobile in the soil-bearing columns (up to 10% mass loss), due to the formation of soluble P-bearing minerals or mobilization by organic matter. These results demonstrate the influence of mine tailings on the mobility of P from soils and on the potential contamination of ecosystems with As, and strongly suggest that these materials should be isolated from fluvial environments.

    Metadata

    Item Type: Article
    Keyword(s) / Subject(s): mine tailings, floodplain, soil, Bolivia, Potosí, arsenic, lead, phosphorous, antimony, As, Pb, P, Sb, XANES, column leaching
    School: Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences
    Depositing User: Sarah Hall
    Date Deposited: 26 May 2016 09:08
    Last Modified: 29 Jun 2017 09:15
    URI: http://eprints.bbk.ac.uk/id/eprint/15335

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