Unveiling priority control toxic metal in cover soil of anti-seepage tailings ponds: Insights from multi-media and probabilistic risk model

Abstract

Pollution from tailings ponds is a major environmental concern, yet systematic studies on anti-seepage tailings ponds remain scarce. This study assesses the environmental and health risks posed by heavy metals (HMs) contamination in an anti-seepage copper-nickel tailings pond located in Southwest China. Long-term monitoring and pollution assessment were conducted for cover soil, leachate, groundwater, surface water, and river sediments, along with a health risk assessment for the cover soil. Results showed that while groundwater remained uncontaminated, the concentrations of Cr, Cd, Ni, and Cu in cover soil exceeded background values by 5.8, 5.4, 4.7, and 3.6 times, respectively, surpassing regulatory limits. Leachate samples exhibited strong seasonal variation, with HM concentrations peaking during the rainy season, and Ni exceeded regulatory limits in all samples. The reuse of leachate for dust suppression was identified as a major contributor to cover soil contamination. Health risk assessment revealed unacceptable non-carcinogenic and carcinogenic risks, primarily driven by Cr exposure. Further analysis using positive matrix factorization, health risk assessment models, and Monte Carlo simulation quantified industrial contributions at 8.83 % for non-carcinogenic risk and 7.5 % for carcinogenic risk. This study provides a novel framework for integrating pollution source analysis and risk assessment in anti-seepage tailings ponds, offering valuable insights for environmental risk management and process safety.