A methodology for ranking potential pollution caused by abandoned mining wastes: application to sulfide mine tailings in Mazarrón (Southeast Spain)

Mining wastes often contain high concentrations of toxic elements, whose mobility and dispersion may pose an environmental hazard for soils, water, ecosystems and people. This article describes the partial application of a methodology designed to evaluate the pollution potential of abandoned mining wastes, using two indices for potential pollution evaluation: an index of contamination (IC) and a hazard average quotient (CPP). Composite samples, consisting of at least 30 subsamples, were taken at three sulfidic tailings impoundments in the mining area of Mazarrón (SE Spain). Mineralogical, physical, and chemical characteristics were analyzed: color, particle size, powder XRD analysis, pH, total content of toxic elements, and concentrations in leachates by the standard procedure EN-12457-2. Tailings were extremely acid (pH 2.30–2.52). Some ranges of total content (in mg/kg) were: As (381–565), Pb (2602–4487), Sb (139–170), and Zn (3254–5652). The concentration measured in the EN-12457 leachates (µg/L) was as high as 367,000 for Zn, 2030 for Cu, and 974 for Cd. The IC and CPP values were among the most high of the tailings inventoried in Spain. The combination of the indices provided a good estimation of the potential toxicity of these wastes, and it can be useful to rank abandoned mining waste facilities.