Divergent temporal evolution of potentially toxic elements contamination and health risks in agricultural soils...

The environmental behavior of potentially toxic elements (PTEs) in soils surrounding uranium mines depends heavily on the operational status of the facilities, yet longitudinal comparisons between active and decommissioned sites remain scarce. This study presents a three-year (2018-2020) comparative assessment of agricultural soils located around an active uranium mine (AUM) and a decommissioned uranium mine (DUM) in southern China. Soil samples were analyzed for pH and concentrations of As, Cd, Pb, Th, U, Mn, and Zn, integrating contamination indices (the Geo-accumulation Index and Potential Ecological Risk Index) and the USEPA health risk model (ingestion, skin contact, inhalation). As, Cd, and U are the main contaminants at both regions, with contrasting temporal dynamics. At the AUM, U and Pb increased significantly over time (average U: from 0.274 to 0.515 in non-carcinogenic contribution for children), while at the DUM, Th decreases and U remains consistently high. The hazard index (HI) for ingestion in children exceeds 1 at both regions (up to 2.46 at AUM in 2020). As accounts for > 98% of the total carcinogenic risk, with TCR values exceeding 10^-4 (e.g., 1.01 × 10^-3 at DUM, 2019). The oral route accounts for nearly 100% of the total risk. Contamination mechanisms evolve after the mine ceases operations: the active mine generates a steady increase in risks, while the DUM exhibits delayed release (peaking in 2019). Environmental management tailored to each operational status is necessary, targeting both active anthropogenic inputs and long-term weathering processes.