Pollution Characteristics, Ecological Risks, and Source Apportionment of Trace Elements in the Water and Soils of a Legacy Pb-Zn Mining Area

This study investigated the pollution characteristics, ecological risks, and sources of six trace elements in the water, riparian soils, and benthic sediments of the Taohuajiang lead–zinc mining area, Guangxi. Water, soil, and sediment samples were evaluated using pollution indices and source apportionment models. The results show zinc (Zn) is the primary water pollutant, spatially correlated with mining sites. Conversely, both soils and sediments exhibit severe composite contamination, with cadmium (Cd), lead (Pb), Zn, and silver (Ag) significantly exceeding background values. Notably, sediment trace elements accumulate intensely downstream of the mining zone and at river meander bends driven by hydrodynamic deposition. The area is classified as an extremely high risk zone (mean ecological risk index > 1200), predominantly driven by Cd. Source apportionment identified three factors governing the soils and sediments: legacy mining constitutes the principal source of Pb, Zn, Cd, Ag, and copper (Cu); natural geological processes govern arsenic (As); and agricultural/domestic activities partially contribute to Cu and Ag. Overall, historical mining primarily drives the regional contamination across multi-phase media, which is further exacerbated by agriculture, collectively threatening the local benthic and terrestrial ecosystem.