Identification of priority pollutants and key factors affecting environmental risks of lead‑zinc mine tailing sites

Lead‑zinc mine tailing sites are widely distributed in China. Tailing sites with different hydrological settings tend to have different susceptibilities toward pollution and hence different priority pollutants and environmental risks. This paper aims to identify priority pollutants and key factors influencing environmental risks of lead‑zinc mine tailing sites with different types of hydrological settings. A database with detailed information on hydrological settings, pollution, etc. of 24 typical lead‑zinc mine tailing sites in China was built. A rapid classification method of hydrological settings was proposed considering the groundwater recharge and migration of pollutants in the aquifer. Priority pollutants in leach liquor of tailings, soil, and groundwater of sites were identified using the osculating value method. The key factors affecting environmental risks of lead‑zinc mine tailing sites were identified using the random forest algorithm. Four types of hydrological settings were classified. Pb/Zn/As/Cd/Sb, Fe/Pb/As/Co/Cd, and nitrate/iodide/As/Pb/Cd are identified as priority pollutants of leach liquor, soil, and groundwater, respectively. The lithology of the surface soil media, slope, and groundwater depth were identified as the top 3 key factors that affect the environmental risks of sites. Priority pollutants and key factors identified in this study can provide benchmarks for the risk management of lead‑zinc mine tailing sites.