Environmental impact and mobility of thallium and other metal(oid)s in soils and tailings near a decommissioned Zn-Pb mine (Raibl, NE Italian Alps).

Abstract

The potential impact of decommissioned mining areas on environmental quality is of major concern for local communities, posing a risk to water resources and human health. This study aims to investigate the impact of extraction activities on the surface environment by evaluating the occurrence of metal(oid)s, including potentially toxic elements (PTEs, i.e. As, Cd, Fe, Tl, Zn, Pb) and critical elements (As, Ge), at the Zn-Pb Raibl mining area (northeastern Italy). Elevated concentrations of metal(oid)s are found near mine waste heaps (< 100 mg/kg for Tl, Sb, Cd, Ge; > 1,000 mg/kg for As; > 1% for Pb and > 10% for Zn and Fe), which are made up of flotation tailings and waste rocks scattered around the mining village and stored in the tailings impoundments. Conversely, upstream from the mine, the environment is largely uncontaminated. According to the results, total and leachable metal(oid) concentrations are positively correlated. Tailings (65.1-754 mg/kg of Tl) are identified as the primary source of leachable Tl (11.4-255 mg/kg) and metal(oid)s are generally more mobile in organic-rich soils, suggesting increased metal(oid) mobility with soil ageing due to low soil pH and potential soluble organometallic complexes. Furthermore, the findings suggest that reprocessing of mine tailings could be a potential solution to recover valuable elements together with residue backfilling. Lastly, results from this study highlight how crucial mining site management is to limit PTE dispersion and reducing risks to the environment and public health.