Abstract: Kuitun River Basin in Xinjiang is a typical endogenous high-fluorine area. By using a combination of mathematical statistics, qualitative and quantitative analysis, we investigated the correlation between chemical composition of borehole sediments and fluorine content, the chemical composition characteristics of groundwater and sediment, and the release mechanism of fluorine in the water-soil system of Kuitun River Basin. Results reveal a positive correlation between the fluorine (F) content and the content of magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), and arsenic (As) in borehole sediments. The occurrence state of fluoride ions in the water-soil system changes continuously through hydrogeochemical processes such as mineral dissolution- precipitation and complexation-dissociation. Moreover, the fluorine content at a particular depth is influenced by hydrogeochemistry and soil humus, causing variations in the storage environment. The fluorine content in groundwater initially increases and subsequently decreases with the rise in fluorine content in sediments.

Key words: chemical composition of groundwater, chemical composition of sediment, water-soil system, fluorine release mechanism, mathematical statistics, hydrogeochemical process, Kuitun River Basin