Integrated assessment of heavy metal dynamics, ecological risk, and plant-mediated phytostabilization in...

Mining-affected soils are complex geochemical systems characterized by long-term heavy metal accumulation, ecological degradation, and altered vegetation structure. Understanding the interactions among soil properties, contaminant mobility, ecological risk, and plant responses is essential for evaluating remediation potential in post-mining ecosystems. This study provides the first integrated assessment of soil properties, ecological risk, vegetation structure, landscape heterogeneity, and plant-mediated phytostabilization in the Belousovka mining area.

Soil physicochemical properties, granulometric composition, heavy metal concentrations, pollution indices, multivariate statistics, spatial analysis, and plant accumulation characteristics were investigated at 17 representative sampling sites, including two reference locations. Concentrations of Zn, Cu, Cd, and Pb were determined in soils and in root and shoot tissues of Helianthus annuus L. and Triticum aestivum L., two dominant agricultural crops representative of local agroecosystems, using 12 plant samples collected from two representative contaminated sites selected for detailed plant accumulation assessment. Pollution Load Index (PLI), Potential Ecological Risk Index (RI), bioconcentration factor (BCF), and translocation factor (TF) were calculated.

Zn and Cu were the dominant contaminants (1641 and 205 mg·kg^-¹, respectively), whereas Cd represented the principal ecological risk factor. Severe localized contamination was observed (PLI = 74.67; RI = 3992.46). PERMANOVA confirmed significant differences among ecological risk groups (R² = 0.72, p = 0.001). Heavy metal distribution was strongly influenced by soil texture, pH, carbonate content, and terrain-related redistribution processes. Vegetation surveys revealed dominance of ruderal, perennial, and phytostabilizing species in industrial areas, indicating ongoing spontaneous succession. Helianthus annuus L. exhibited substantially greater biomass and metal accumulation capacity than Triticum aestivum L., particularly for Zn, Cu, and Cd. Root tissues consistently accumulated higher metal concentrations than shoots, with TF values predominantly below 1.

Ecological risk was controlled by technogenic contamination and soil properties, whereas predominant root sequestration indicated phytostabilization as the principal adaptive response under contaminated conditions.