Abstract:

Insufficient or excessive intake of fluoride can create health problems for humans. The objective of this study was to understand the occurrence of fluoride in groundwater as well as its spatiotemporal variation and reasons in Tuoketuo County, Hohhot, Inner Mongolia, in view of the factors influencing the sources, migration and enrichment of fluorine. Sixty water samples(30 phreatic and 30 confined sources) were conducted a statistical analysis, water chemistry characteristics analysis, cluster and correlation analysis. The fluoride concentration in water samples varied from 0.40 to 7.20 (2.30±1.80) mg/L and 0.29-12.70(1.67±2.48)mg/L in phreatic and confined water, respectively. An analysis of the hydrogeochemical characteristic of samples indicated that the high fluoride content of groundwater was caused by the alkaline environment with high levels of TDS, HCO^-₃, Na⁺, EC and with a Ca²⁺ deficiency. High F^- concentrations were mainly observed in ground-water of HCO₃·Cl-Na type. The highest concentration of fluoride (>5 mg/L) in phreatic water was located in the groundwater discharge area because this water was affected by the groundwater flow field. In confined aquifers, the concentration of fluoride was mainly controlled by lithology; a high fluoride content (>1.5 mg/L) was only observed in lacustrine platform zone in confined aquifers in the study area.

Key words: groundwater, fluoride, hydrogeochemistry, water-rock interaction, Tuoketuo County, Inner Mongolia