Pyrite ore cargo spills as a source of soil pollution and ecological risk along the abandoned railway corridors of the Tharsis and Rio Tinto mines (Spain)

Abstract

Abandoned mining railways are a prominent legacy environmental issue facing many metalliferous regions with a long mining history. However, there is a general lack of information on potentially hazardous trace elements occurring in soils alongside railroad lines as a result of hazmat cargo spills. This paper explores for the first time the effects of pyrite ore transportation on soil pollution along the old railways of Tharsis and Rio Tinto, two historical mining districts of world-class importance in the Iberian Pyrite Belt. The railroad-side topsoil was found to be extremely acidic in reaction and contains abundant pyrite, spilled on the tracks during transit, and its oxidation products (jarosite, iron oxyhydroxides, and efflorescent sulfate minerals). Compared to local background concentrations, highly elevated levels of Pb, Zn, Cu, As, Hg, Sb, Bi, Cd, Ag, and Tl were detected in both railroad lines, indicating serious anthropogenic contamination. Exposure to soil contaminants, notably Pb, As, and Tl, could pose hazards to human health and the environment. Accordingly, a specific-site risk assessment is needed before the mining railway lines are converted into recreational trails.

Keywords: Hazmat cargo spills; Iberian Pyrite Belt; Mining railway; Pyrite; Soil quality index.