Impact of acid mine drainage on water quality in receiving watersheds and associated potential adverse effects

Abstract

Mining activities have emerged as an important source of heavy metals (HMs) pollution in receiving watersheds, yet the ecological risks of HMs are primarily assessed using index-based methods with metal concentrations, lacking toxicity evaluation from a molecular biological perspective. This study integrated geochemical assessments with toxicogenomics assays to comprehensively evaluate the HMs contamination in a receiving watershed (Wenyu River and Luo River) affected by acid mine drainage (AMD). Results showed that the average concentrations of six HMs (Fe, Mn, Zn, Cu, Pb, and Ni) in surface water samples exceeded the environmental quality standards in China, and the average concentration of Fe was 28.9 times higher than the regional background values. The concentrations of Mn, Zn, and Cu in sediments ranged in 736.7–1654.6, 123.4–789.2, and 27.4–1114.0 mg∙kg⁻¹, respectively. Geochemical calculation showed that both surface water and sediments of the receiving watersheds were contaminated with HMs. Principal component analysis and cluster analysis suggested that Co, Zn, Cd, Cu, and Pb in sediments were likely of anthropogenic origin, whereas Cr, Ni, Mn, and As appeared to derive primarily from natural erosion processes. The highest toxicity level of 1.63 ± 0.09 as PELI_total was observed at sampling site W7 located downstream of the Wenyu River. Exposure to HMs pollution induced up-regulation of functional genes in yeast cells associated with chemical and oxidative stress pathways. This study provides a scientific basis for health risk assessment and the development of targeted mitigation strategies for HMs pollution in watersheds impacted by AMD.