Geochemical occurrence, enrichment and distribution of fluoride in groundwater in the Jilantai Desert Basin

【Objective】 The purpose of this study is to analyze the distribution pattern of high fluoride groundwater in the Jilantai Desert Basin and explore the impact mechanism of groundwater overexploitation on fluoride dissociation, migration, and enrichment in oasis runoff areas. 【Method】 The hydrochemical characteristics of groundwater were analyzed by using SPSS 24.0 and ArcGIS software and on the basic of groundwater monitoring data and mining data from 1980 to 2020 in the Chahaertan oasis, the distribution and genesis of high fluoride groundwater were studied by methods such as Piper’s trilinear diagram, ion ratio, Gibbs diagram, and saturation index. 【Result】 The groundwater chemistry presented zonal distribution, and the concentration of TDS and ions of potassium, sodium ion, fluoride increased from mountain recharge region, oasis runoff area to the desert salt lake discharge region. and the concentration of F- ranged from 0.2 to 3.4 mg/L. In particular, the content of fluoride ion in groundwater around salt lake increased outward. Research result showed that the formation of groundwater hydrochemistry in desert basins was mainly influenced by natural factors such as weathering of fluorinated rocks and evaporation concentration. On the other hand, under excessive extraction of groundwater, poor quality groundwater of salt lakes with high content of fluoride ion invaded into aquifer in desert oases, the irrigation return water leached soil salt, and also affected the migration of fluorine. 【Conclusion】 The enrichment of fluoride in groundwater reflected degeneration of eco-environment in the Jilantai Desert Basin. Therefore, in order to mitigate these issues and maintain the ecological balance of desert oases, the amount of groundwater exploitation in Chahaertan oasis should be restricted to 7 million cubic meters per year, thereby restraining the worsening trend of groundwater contamination.