Distribution of fluoride in groundwater around Chagan Lake and its risk assessment under the influence of human activities

Chagan Lake is located in the area of Western Jilin for which waterways have high fluorine content. Because of the construction of water conservancy projects and agricultural irrigation areas, the groundwater replenishment and drainage conditions there have changed. Groundwater test data were used to analyze the status of groundwater fluoride with this changing hydrodynamic gradient. The paper established a health risk assessment model based on triangular fuzzy number. The results show that the samples of phreatic water and confined water with excessive fluoride content accounted for 68.74% and 29.4%, respectively. Samples that exceeded standards of fluoride content were mainly distributed in the northwest and southwest. The chemistry of phreatic water is more complicated than that of confined water. The water quality categories are mainly poor and very poor. The formation of major anions and cations was mainly controlled by evaporation and rock weathering. It was also found that non-carcinogenic risks of fluoride in phreatic water are greater than those in confined water. The risk indices for children and adults were [1.1, 1.6] and [0.6, 0.9], respectively (α = 0.8). The non-carcinogenic risk assessment model based on triangular fuzzy numbers has a higher reference value than that of traditional models.