Migration of Cu, Zn, Cd and As in epikarst water affected by acid mine drainage at a coalfield basin, Xingren, Southwest China

Epikarst water, which is one of the most important water resources in karst mountain areas, is extremely sensitive to mining activities. Acid mine drainage (AMD) with high levels of heavy metals can degrade the water quality. A typical coalfield basin was chosen to research the migration process of heavy metals. It was found that the chemical compositions of the stream water in the research field were controlled by the dissolution of carbonate rocks or/and the weathering and oxidation of pyrite in the mining area. Excluding a few sites in the mining area, As(V) was dominant species of arsenic in the form of H2AsO4 − or HAsO4 2− in the research field. Based on the mass balance concept, it was found that fluxes of As, Zn, Cu and Cd in water from the mining area (site 17) affected by AMD were 18, 871, 281 and 12 kg year−1, respectively. Also, concentrations of Cd, Zn, As and Cu in the stream water decreased along the flow, because these ions deposited from the water to the stream bed as the redistribution processes in environment.