RESUMEN
As an important water supply source in Beijingï¼ karst groundwater has played an irreplaceable role in the security of urban water supply and ecological environment protection in the past 70 years. The Xishan karst groundwater systemï¼ located in the upper reaches of western Beijingï¼ belongs to ecological conservation areas. There are several centralized water supply fields in this area. In this studyï¼ the Xishan karst groundwater system was taken as the research object. A total of 120 karst groundwater samples in this area were investigated by using statistical analysisï¼ ion ratioï¼ and principal component analysis ï¼PCAï¼ methods to explore the spatial distribution characteristics and formation mechanism of groundwater hydrochemistry. The research results showed thatï¼ â the groundwater quality of the Xishan system was generally goodï¼ with the characteristics of neutral pH and low salinity. A total of 84.17% of the water samples were classified as hard water. The chemical type of groundwater was mainly HCO3-Ca·Mg. â¡ The chemical composition of groundwater was mainly affected by the water-rock interactionï¼ and the weathering source of rock was mainly the dissolution of carbonate. ⢠The results of principal component analysis showed that 34.41% of the chemistry formation of groundwater could be explained by carbonate dissolutionï¼ 27.33% by rock salt and evaporate dissolutionï¼ 11.76% by aquifer sediment dissolutionï¼ and 10.30% by domestic sewage discharge. From the recharge area to the runoff area and then to the discharge areaï¼ the TH and TDS gradually increased. Coal mining drainage and human activities were the main factors that caused groundwater degradation and variable hydrochemical types in the piedmont. In the futureï¼ it is necessary to further strengthen environmental governanceï¼ control point and non-point source pollutionï¼ and continuously monitor key areas to provide scientific support for ecological and environmental protection.