Source analysis and risk assessment of fluorine and boron in Ruoqiang Oasis groundwater, Xinjiang

Groundwater quality in Ruoqiang County, situated on the southern margin of the Taklimakan Desert, is critical to sustaining local livelihoods, economic production, ecological stability, and high-quality development. This study analyzed 30 groundwater samples collected from Ruoqiang Oasis from 2023 to 2025 to investigate its hydrochemical characteristics and compositional controlling factors. The absolute principal component score-multiple linear regression model was employed to identify the source of fluoride and boron in the groundwater. The groundwater quality was assessed using the entropy-weighted water quality index. A health risk assessment model was applied to quantify the risks posed to different demographic groups by the fluoride and boron in drinking water. The findings of this study are as follows: (1) Groundwater in the study area is predominantly neutral to weakly alkaline. Fluoride and boron exceedance rates are 61.54% and 82.35% in single-structure phreatic water, and 0.00% and 29.41% in multi-structure phreatic-confined water, respectively. The hydrochemical facies are mainly Cl∙SO4-Na and Cl∙SO4-Na∙Ca, governed by evaporation concentration, rock weathering, and cation exchange. (2) Weathering and dissolution of boron-bearing silicate minerals and fluorite are the major sources of fluoride and boron. The groundwater chemical composition is primarily influenced by leaching and enrichment (71.76%), followed by primary geological conditions (13.32%) and anthropogenic activities (8.43%). (3) The groundwater quality exhibits a deteriorating trend over time, with fluoride posing a substantially higher health risk than boron, particularly to children. Mitigating fluoride concentrations is essential to reducing health risks in the region.