Causes of groundwater salinization in the plain area of Kashgar River Basin in Xinjiang, China

In order to reveal the distribution characteristics and formation mechanism of groundwater salinization in the plain area of the Kashgar River Basin in Xinjiang of China, 398 groups of groundwater samples were collected in 2017. Hydrogeochemical methods coupling with stable isotope technology were used for sample analysis. Results showed that groundwater was weakly alkaline in general (pH ranged between 6.68 and 8.52), with total dissolved solids (TDS) ranging from 246.5 to 44,130.4 mg/L. The main groundwater hydrochemical types included SO4·Cl, SO4 and HCO3·SO4. Along groundwater flow direction, increased TDS and obvious salinization were observed with hydrochemical type change from HCO3·SO4 to SO4 and to SO4·Cl, respectively. Groundwater was mainly recharged by river infiltration in the piedmont. Groundwater salinization was affected by lixiviation, evaporation concentration and cation exchange. Continuous weathering and dissolution of evaporative rock minerals, such as gypsum and halite, were the main factors leading to the continuous salinization of groundwater. Regional deuterium surplus calculation results showed that lixiviation was the main cause of groundwater salinization in recharge areas in the piedmont, and controlled the whole runoff process. Meanwhile, the strongest evaporation concentration mainly occurred in discharge areas of the groundwater flow system. It was concluded that groundwater salinization mainly depended on lixiviation degree.