Hydrochemical characterization of drinking groundwater with special reference to fluoride in an arid area of China and the control of aquifer leakage on its concentrations

The objective of the study is to determine the distribution and origin of fluoride in two confined aquifers within the depth of 80–240 m (mid-deep confined aquifers) in Shizuishan City, an arid area in Northwest China. Based on geological and hydrogeological conditions, the distribution patterns of fluoride in the two confined aquifers were studied. Correlation analysis was used to reveal the mechanisms and reactions influencing the groundwater chemistry. The control of aquifer leakage induced by intense groundwater abstraction on fluoride concentrations was also discussed. The results show that the concentration of F⁻ in some locations of the study area is beyond the limit of the Standards for Drinking Water Quality of China. Correlation analysis shows that the major reactions occurring in the confined aquifers are dissolution of gypsum, fluorite and halite, and precipitation of calcite and dolomite. Groundwater leakage from shallow aquifers is also responsible for the elevation of fluoride in mid-deep confined aquifers. The research is a scientific basis for the rational development and utilization of groundwater in this area, and it may be referenced by international scholars for similar research in other parts of the world.