Temporal and spatial distribution, sources and health risk assessment of trace elements in a typical karst river basin in Southwest China: Influence of acid mine drainage from abandoned coal mines

Karst water serves as a crucial water source in global karst regions. However, acid mine drainage (AMD) produced by coal mining, characterized by low pH and elevated concentrations of trace elements (TEs), threatens karst water quality. Thus, identifying priority control elements is key to controlling TEs pollution in karst water. In this study, a typical karst river basin affected by abandoned coal mines in Southwest China was taken as the research object to comprehensively analyze the spatiotemporal distribution of TEs, quantitatively identify pollution sources and associated human health risks, and determine the priority factors for health risk management. Spatiotemporal analysis revealed that elevated TEs were near abandoned coal mines, indicating their distribution was closely associated with AMD discharge, and TEs showed higher concentrations in the wet season. Furthermore, Fe, Mn, Ni, and As exceeded World Health Organization (WHO) guidelines to varying degrees in both seasons, while Cd only exceeded these guidelines in the wet season. Positive Matrix Factorization (PMF) identified four primary sources of TEs: abandoned coal mine drainage source, natural geological weathering source, water-rock reaction and agricultural activity superimposed source, and sewage-agricultural activity composite sources. Health Risk Assessment (HRA) based on Monte Carlo simulation indicated that non-carcinogenic risks and total carcinogenic risks for children exceeded safety thresholds during the wet season, with As posing cautionary risk. The relationship between TEs, pollution sources, and health risks indicated that abandoned coal mine drainage, Fe, and As were identified as priority control factors. These findings could offer critical guidance for safe health risk control in karst basins globally affected by similar mining activities.