Potentially Toxic Elements in Soil of a Historical Mining Region in Serbia: Geochemical Fractionation, Ecological Impact, and Health Risk Assessment.

Natural metal enrichment, combined with centuries of mining activity in the Rudnik Mountain region of Serbia, has led to the long-term accumulation of potentially toxic elements (PTEs) in the soil. Although the investigated area lies outside the current zone of active exploitation, the persistence and mobility of accumulated PTEs, historical contamination can still affect the local population. This study integrated assessments of soil characterization, enrichment, sequential extraction-based fractionation, mobility, and bioavailability of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn, as well as the associated ecological and human health risks. Geochemical and environmental pollution indices further identified As, Pb, and Cd as the main contributors to environmental risk. Sequential extraction results based on the BCR protocol indicated significant bioavailability of Cd (32% in the exchangeable fraction) and Pb (74% in the reducible fraction). In contrast, over 80% of As was present in the residual fraction, indicating limited mobility and low bioavailability. Health risk assessment for the local rural population revealed significant potential health concerns at the investigated sites, with exceedances of the hazard index (HI) and carcinogenic risk (CR) values, primarily associated with As as the main contributing pollutant.