Hydrochemical and Stable Isotope (δD and δ18O) Characteristics of Groundwater and Hydrogeochemical Processes in the Ningtiaota Coalfield, Northwest China

Understanding the sources and mechanisms of groundwater recharge in the Ningtiaota Coalfield, an arid area in northwest China, is important for water resources management and coal mine safety. Hydrochemical and stable hydrogen and oxygen isotopic data were used to study water-rock interactions and groundwater recharge in the area. A total of 45 water samples, including surface water, Quaternary groundwater, and Jurassic Zhiluo Group (J(2)z) and Yan'an Group (J(2)y) groundwater, were collected for major ions and stable isotope (delta D and delta O-18) analyses. Our results showed that the groundwater originated from atmospheric precipitation, and experienced weak evaporation during infiltration. Water in the study area has a low salinity and is dominated by HCO3-Ca type. The dominant water-rock interactions in the Jurassic Zhiluo Group (J(2)z) groundwater were dissolution of silicate minerals, gypsum, and halite and cation exchange. The results may aid in water resources management and groundwater inrush prevention in the coalfield and at other coal mines.