Multi-compartmental migration and ecological-health risks of trace metals in Dexing mining concentration areas: A holistic quantitative assessment

Abstract

To address the critical gap in linking multi-compartmental transfer with risks of trace metals (Cd, Pb, As, Cr, Ni) in mining environments. This study systematically investigated the trans-media migration of Cd, Pb, As, Cr, and Ni in China’s Dexing copper mining district through paired sampling of water-amphibians, soil-earthworms, and air-lichens. Advanced methodologies were employed, including ICP-MS quantification for heavy metals, geochemical indices (Igeo, BCF, BAF) to assess bioavailability, NMDS for source apportionment, and HPLC to detect DNA methylation alterations. Aquatic systems exhibited severe Cd/Pb enrichment (16.25–24.42 μg/L; 11–15× WHO limits), while agricultural soils showed extreme Cd contamination (1.5 mg/kg; 15× background). Biota displayed metal-specific accumulation: frogs achieved BCFs >1,000 for Pb/Cd, earthworms showed pH-modulated BAFs >2.5 for Cd/As, and lichens recorded 100–1,000× atmospheric Cr enrichment. NMDS resolved three contamination pathways: mining-derived Cd/Pb/As (MDS1 = 2.56), atmospheric Cr (PC2 = 1.84), and geogenic Ni. Cd dominated ecological risks (Eri = 554.25; RI 300), while atmospheric Cr drove carcinogenic risks (TCR = 4.11×10⁻⁵) exceeding safety thresholds. The source-media-biota-risk framework pioneers the integration of geochemical transport with epigenetic toxicity biomarkers, demonstrating that sub-lethal Cd/Pb exposure induces genome-wide DNA hypomethylation (2.4%–6.6% reduction; ρ = −0.71 to −0.91). This paradigm shift prioritizes bioavailability-informed regulations over concentration-based metrics, offering actionable strategies for sustainable development goals-aligned mining pollution control.