Hydrogeochemical characteristics and solute sources of groundwater in the Yuhengbei mining area, Shaanxi Province, China

Abstract The hydraulic connection between aquifers directly determines whether deep coal mining activities affect water quality in shallow aquifers. This study was conducted to investigate the hydrogeochemical characteristics and identify the solute sources of groundwater (including surface water, Quaternary water, water from Cretaceous and Jurassic coal strata aquifer) in the Yuhengbei mining area, Western China, using conventional, multivariate statistical analysis, and dissolved organic matter (DOM) analysis. All water samples were slightly alkaline, and the water from the shallow aquifers (surface water, Quaternary and Cretaceous aquifers) was predominantly of the HCO3-Ca type. The groundwater in deep Jurassic aquifer was mostly of the SO4-Na type. Major ion and DOM (total organic carbon and ultraviolet absorbance) concentrations decreased with increasing aquifer depth. Water-rock interaction and cation exchange were the main mechanisms controlling the chemical constituents of groundwater. The DOM was mainly derived from autogenous biological sources. Based on the indicator values, the hydraulic connection between the deep aquifers and the upper shallow aquifers was generally weak. The knowledge of hydrogeochemical characteristics and formation mechanisms will provide a technical basis for local groundwater management and support the sustainable use of water resources.