Abandoned mine sites as a source of contamination by heavy metals:: A case study in a semi-arid zone

Mining and milling operations, including grinding, concentrating ores and disposal of tailings, along with mine and mill waste water, provide obvious sources of contamination in the surface environment. Climatic effects such as heavy rainfall events, have a great impact in the dispersion of metals in semi-arid areas, since soils are typically scarcely vegetated. The dispersion and influence of soluble and particulate metals present in the materials from an abandoned mine, Cabezo Rajao, in SE Spain, was evaluated. Tailings and soils were sampled and analysed for pH, EC, CaCO3, grainsize, mineralogical composition and heavy metal content, while water samples were collected and analysed for pH, EC, soluble metals and salts. The mean concentrations of Pb, Zn, Cd, Cu and As in solid samples were 8.3 g kg(-1), 12.5 g kg(-1), 40.9 mg kg(-1), 332.1 mg kg(-1), 314.7 mg kg(-1) respectively, and 1.5 mg l(-1), 50.3 mg l(-1), 13.6 g l(-1), 17.2 mg l(-1), 1.7 mg l(-1) in water samples respectively. These metals can be dispersed downstream and downslope from the tailings by water after rainfall. Soil samples collected in the surroundings of Mar Menor Lagoon were analysed, reflecting the influence of the transport of soluble and particulate materials from Cabezo Rajao, especially of Pb and Zn. However, the presence of high amounts of carbonate in the soils around the mine area revealed the stabilization of all the metals studied. (c) 2007 Elsevier B.V. All rights reserved.