In this study, content distribution analysis and quantificational source apportionment of F^– in groundwater in the Sulin coal district, northern Anhui Province, China, were carried out. In addition, the health risk assessment of F^– exposure was evaluated for individuals in different groups, such as infants, children, teens, male adults, and female adults. Results can be summarized as follows.

The F^– concentrations in the groundwater samples ranged from 0.16 to 2.06 mg/L, with a mean value of 1.10 mg/L. Among the samples, 53.33% had elevated F^– concentrations, which exceeded China’s national standards for drinking water (1.00 mg/L) and 20.00% of the samples showed much higher F^– concentrations beyond the WHO’s recommended limit (1.50 mg/L). High F^– groundwater (>1.00 mg/L) was mostly located in the central and the northeastern parts of the study region, including Xutong, Jougou, Wugou, Yuanyi, Tongting, Suntong, Yangliu, Taoyuan, and Zhuxianzhuang. Spatial variations of F^– concentrations revealed that 48.47% of the geographical area had F^– concentrations below 1.00 mg/L, 41.65% of the geographical area had F^– concentration in the range of 1.00–1.50 mg/L, and 9.88% of the geographical area had F^– concentration above 1.50 mg/L.

The F^– concentration in the groundwater samples had a positive relationship with pH, Na⁺, and HCO₃^–, and was negatively correlated with Ca²⁺ and Mg²⁺, indicating weathering of F-bearing minerals as a F^– source. Quantificational source apportionment results explained that the weathering of F-bearing minerals was the main source of F^– in the groundwater samples, accounting for 66.20% of the total dissolved F^–, followed by cation exchange (16.30%), agricultural activities (13.20%), and natural geochemical processes (4.30%).

The percentages of infants, children, teens, male adults, and female adults, whose F^– intake exceeded the HQ safety limit (1.00) were 20.00%, 70.00%, 6.67%, 20.00%, and 10.00%, respectively. With the highest HQ value, children were the most vulnerable age group in high F^– regions. Apart from Qinan, Linhuan, and Qidong, children in the rest of the Sulin coal district were more likely to develop fluorosis. In addition, infants and male adults in Wugou, Taoyuan, and Xutong, as well as teen and female adults in Wugou, were at high risk of developing fluorosis. Wugou had the highest ED and HQ values due to the high level of F^– in the groundwater of this region. The optimum F^– content in the groundwater of the study region was calculated to be 1.05 mg/L, which provided a reference for local water management authorities to reduce fluorosis caused by excess F^– intake from drinking water.

Despite F^– enriched groundwater in the study area, most residents are not aware of the risks of fluorosis from drinking. Our findings are limited to assisting the informed management of groundwater resources for drinking within the study area. Overall, it is highly suggested for all parts of the geochemical cycle that efforts should be made to find the pathways, mobilization mechanisms, and reduction measures for fluoride that should be taken in the future in efforts to improve public safety.

The authors gratefully acknowledge the financial support provided by the Open Fund of State Key Laboratory of Groundwater Protection and Utilization by Coal Mining (no. SHJT-17-42.17), the Ecological restoration project in Lengshuijiang Antimony Mine area (no. LCG2020009), and Fundamental Research Funds for the Central Universities of China (no. 3142018011). We would like to thank Editage (www.editage.cn) for English language editing.