Identification of the sources of mine drainage in a multiaquifer area: a case study of the abandoned Dashu pyrite mine in southwest China

Environmental pollution by acid mine drainage (AMD) can have serious consequences, and water is necessary for the production of AMD. Studying the source of mine water is of great significance for revealing the causes of pollution and controlling environmental degradation. Taking the abandoned Dashu pyrite mine in southwest China as an example, hydrogeological and hydrochemical analyses and environmental isotope analysis, combined with principal component analysis (PCA), were used to find the hydraulic relationship between the mine's decline roadway and the surrounding aquifer, and to identify the source of mine water. Using deuterium-excess and tritium-content values, the recharge sources of the mine water were identified quantitatively, and a conceptual model of the groundwater flow was established, taking into consideration the hydrogeological conditions. Thus, the hydrogeological context associated with the pollution was determined. The results showed that the mine drainage mainly originates from the central groundwater recharge zone of the Quaternary accumulation platform in the northwest section of the mine, and a small part comes from the karst water recharge zone of the Maokou Formation. A quantitative identification method appropriate for multiple aquifers is established, which can provide a reference for the identification of the drainage sources of abandoned mines in similar multiple-aquifer settings, and it could provide important guidance for environmental managers dealing with the remediation of abandoned mine drainage.