Hydrogeochemical analysis of the groundwater composition and risk to human health of an abandoned mine area, southwest China

Coal mining has resulted in pollution of groundwater in mining areas, which poses a risk to human health. However, understanding of groundwater evolution in mining areas and the associated implications remains insufficient. This study collected 13 groundwater samples from an abandoned coal mine in southwestern China. Ionic ratio analysis, hydrochemical simulation, health risk assessment, and entropy-weighted water quality index (EWQI) were applied to characterize the groundwater quality and the associated risks to human health. Monte Carlo analysis was used to quantify the uncertainty in the health risk assessment. The results indicated that the groundwater samples are of the HCO₃-Ca and SO₄-Ca water chemistry types. Water–rock interaction and mining activities were the main processes regulating groundwater hydrochemistry. Acid mine drainage was mainly responsible for elevated groundwater sulfate in the study area. EWQI ranged from 13 to 515 (mean of 111), and 75% of the samples fell within classes 1 and 2, meeting the World Health Organization (WHO) drinking water standards. Health risk assessment indicated adults to be more at risk from groundwater ingestion than children, with this result confirmed by uncertainty analysis. This study comprehensively examined groundwater evolution and its potential impacts through the example of a typical mining area. The results provides valuable insights into the identification of factors affecting groundwater, the evolution of hydrochemical processes, and the sustainable development of groundwater resources in mining areas globally.