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

DOI: 10.1180/minmag.2012.076.5.14 DOI Help

Authors: David Kossoff (Birkbeck College, U.K.) , Karen Hudson-edwards (Birkbeck College, U.K.) , William Dubbin (Natural History Museum, U.K.) , Maria Alfredsson (University of Kent at Canterbury, U.K.) , Tina Geraki (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Mineralogical Magazine , VOL 76 (5) , PAGES 1209-1228

State: Published (Approved)
Published: October 2012
Diamond Proposal Number(s): 6543

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, microscale 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.

Journal Keywords: mine tailings; floodplain; soil; Bolivia; Potosi; arsenic; lead; phosphorous; antimony; As; Pb; P; Sb; XANES; column leaching

Subject Areas: Environment, Chemistry

Instruments: I18-Microfocus Spectroscopy

Other Facilities: No