Hydrochemical characteristics and cause analysis of high fluoride groundwater in Zhuanlongwan coal mine

In order to gain insight into the hydrochemical characteristics and formation mechanism of high fluoride groundwater in Zhuanlongwan Coal Mine, we conducted a comprehensive analysis of 48 samples including quaternary groundwater (QGW), sandstone groundwater (SGW), and mine water (MGW) using statistical analysis and hydrochemical methods. The findings demonstrate that the groundwater in Zhuanlongwan Coal Mine generally exhibits weak alkalinity, with predominant cations comprising of Ca2+ and Na+, and anions consisting of HCO3– and Cl–. The mean mass concentration of SO4 2–, Cl–, TDS, pH, and CO3 2– in groundwater follows the order of MGW>SGW>QGW, whereas HCO3– and F– exhibit the trend of SGW>MGW>QGW. Specifically, the average mass concentration of F– in QGW, SGW, and MGW is 0.76 mg/L, 4.55 mg/L, and 4.35 mg/L, respectively. Notably, most samples from SGW and MGW significantly exceed the permissible F−concentration threshold of 1.0 mg/L. The hydrochemical type of low fluoride (\begin{document}$\rho_{{\mathrm{F}