Arsenic and heavy metals in reclaimed soils of sulfide-containing waste dumps: contamination levels, spatial distribution, bioavailability, and health risk assessment.

Long-term storage of metallurgical and mining wastes has resulted in severe contamination of surrounding soils with arsenic and other potentially toxic elements, highlighting the importance of understanding the post-remediation behaviour of these contaminants for evaluating the effectiveness and ecological stability of rehabilitated soils. This study investigates the concentrations, chemical speciation, and bioavailability of As and heavy metals (Pb, Cd, Hg, Cu, Zn) in remediated Spolic Technosols formed on the site of the former Angarsk Metallurgical Plant (Svirsk, Eastern Siberia, Russia). Multiple indices - including geoaccumulation index (Igeo), enrichment factor (EF), pollution index and pollution load index (PI and PLI), ecological risk factor, and potential ecological risk index (Er and PERI) - were employed to evaluate contamination levels and ecological risks. Median Igeo values for As (>8), PERI (>6500) indicate that significant environmental risks still remain. The non-carcinogenic hazard index for children varied markedly among sites, with median values of 0.7-37.5 and a maximum values of 144 at the arsenic hotspot. The total carcinogenic risk exceeded commonly accepted regulatory limits (1 × 10-6-10-4) the area of former arsenic waste dumps, reached values classified as high carcinogenic risk 1.98 × 10-3 for children and 1.44 × 10-3 for adults. The perennial grass Elytrigia repens L. (wheatgrass) was used as a biological indicator to assess element uptake, translocation, and bioavailability. Wheatgrass exhibited substantial accumulation of As in root tissues (up to 1205 mg kg-1), supporting its potential role in phytostabilization. The results demonstrate that, even after remediation, Technosols retain elevated concentrations of PTEs that may be re-mobilized through ongoing soil-forming processes. These findings emphasize the importance of long-term monitoring, natural attenuation studies, and the integration of ecological soil-forming dynamics into post-remediation management strategies at legacy metallurgical sites.