Distribution and source identification of dissolved sulfate by dual isotopes in waters of the Babu subterranean river basin, SW China

Sulfur and oxygen isotopes were employed to identify SO 4 2− sources in surface water and groundwater in the Babu subterranean river basin (BSRB). Our study revealed SO 4 2− enrichment in the BSRB waters compared with adjacent areas. The SO 4 2− in some samples originated mainly from precipitation; in others, it was derived mainly from sulfide dissolution in coal seams or from gypsum dissolution. In the water at the subterranean river exit, 13% of SO 4 2− originated from precipitation, 40% from sulfide oxidation in coal seams, and 47% from gypsum dissolution.