Hydrochemical investigation of shallow groundwater in northwest margin of Lop Nur, northwest China

A hydrochemical investigation was conducted in northwest margin of Lop Nur to evaluate the groundwater chemical patterns and the main hydrological processes occurring in the groundwater system. Fourteen representative groundwater samples were collected from different springs and boreholes. Hydrochemical data of the groundwater showed that SO4, Cl-Na and Cl, SO4-Na water types were dominant in this area, and the total dissolved solid (TDS) content rose along the flow path of the groundwater. Ionic relation analysis was used in conjunction with geochemical modeling to investigate the evolution of the chemical composition of groundwater. PHREEQC was used for inverse geochemical modeling. It is demonstrated that the groundwater, recharged mainly in the northern low mountains, acquired its mineralization properties principally from water–rock interactions, i.e., dissolution of evaporates and reverse cation exchange. The dissolution of halite, Glauber’s salt, dolomite and calcite determined the Na+, Cl−, Mg2+, Ca2+, SO42− and HCO3− chemistry, but evaporation and precipitation also influenced the water composition. The shallow groundwater of Lop Nur was characterized by high salinity and slow circulation.