Risk-Informed Screening of Locally Occurring Plants for Nature-Based Restoration of Heavy-Metal-Contaminated Soils in Central Kazakhstan

Industrial emissions and legacy contamination from metallurgical activities can constrain sustainable land use by degrading soil quality and limiting vegetation establishment. This study combines a site-based contamination assessment with an early-stage plant tolerance screening to inform nature-based restoration planning in Central Kazakhstan. Soils were collected around three metallurgical complexes and analysed for heavy metals; exceedance relative to maximum permissible concentrations (MPC) was used to prioritise contaminants of concern. Seven locally occurring plant species were then screened in controlled Petri-dish assays using metal salt solutions (Pb, Zn, Cu, Cr, Cd and Ni), and germination percentage, germination dynamics, seedling shoot length and a growth inhibition index were quantified. Soil results showed elevated metal loads with frequent MPC exceedance, supporting the selection of these metals for biological screening. Plant responses were strongly species-specific: Brassica juncea and Medicago sativa maintained comparatively higher germination and early growth across treatments, whereas Suaeda salsa, Artemisia absinthium and Trifolium repens exhibited very low germination. These findings provide an evidence-based shortlist of candidate species for subsequent soil-based trials (including uptake and stabilisation assessment) and support risk-informed revegetation strategies for contaminated industrial landscapes.