Combining stable isotope (2H, 18O, and 87Sr/86Sr) and hydrochemistry to understand hydrogeochemical processes in karst groundwater system, Xin’an, northern China

Karst groundwater is the most important source of water supply for Shanxi province, northern China. In this study, different hydrogeochemical indices along with multiple isotope (2H, 18O, and 87Sr/86Sr) were used to identify main factors controlling salinization processes in Xin’an karst system at Shanxi. The region’s was divided into three geologically distinct subsystems, namely, Changzhi–Xiangyuan subsystem (C–X), Huguan–Pingshun (H–P), Licheng (LC). HCO3–Ca·Mg dominant chemical type system. H–P LC subsystems experienced similar processes; from recharge zone discharge zone, Sr2+ content, Sr2+/Ca2+ ratio, TDS concentrations gradually increase flow direction. However, C–X subsystem, deep buried decrease due mixing fresh water. meteoric water, it also recharged by surface shallow groundwater. water–rock interactions conjunction cation exchange absolutely predominated evolution Major ions, such as Ca2+, Mg2+, HCO3−, SO42−, originated dissolution carbonate sulfate minerals. Dissolution minerals major process salinity. NO3−, Cl−, K+ could be attributed agricultural human activities, Na+ intense mining activities study area. results will facilitate understanding pollution enable effective management utilization resources.