Evolutional processes of groundwater in Xinglong County based on hydrochemistry and hydrogen and oxygen isotopes

The study of the hydrochemical characteristics and water-rock interaction processes of groundwater is of important significance in the evolutional processes, rational development and utilization of groundwater and the prevention of groundwater pollution. This research aims to investigate the groundwater quality and its water conservation conditions in Xinglong County, and to provide support for regional groundwater pollution prevention and safety of drinking water supply sources. Based on hydrochemical and hydrogen-oxygen stable isotope analyses, the hydrochemical characteristics, recharge sources and hydrogeochemical evolutional processes of groundwater in Xinglong County were discussed in detail. The results show that the main hydrochemical type of groundwater is of HCO₃-Ca·Mg type in Xinglong County. The groundwater is mainly recharged by precipitation, and is less affected by evaporation. The Gibbs diagram, major ion ratio method and correlation analysis show that the hydrochemical compositions are mainly controlled by the weathering and dissolution of carbonate rocks such as calcite and dolomite, and is less controlled by silicate dissolution. The content of strontium in groundwater in the east and south of the study area is significantly higher than that in the west, indicating that it may be affected by intrusive dykes and metamorphic rocks. In some areas, groundwater is affected by human activities, resulting in excessive concentration of NO₃^- in groundwater. The study may provide an indication of the hydrochemical evolution of regional groundwater and offer technical support for drinking water safety.