Fluorine-Rich Shallow Groundwater in Weigan River Basin (Xinjiang): Enrichment Factors and Spatial Distribution

Abstract

Long-term usage of drinking water with excessive fluoride concentration (above 1.5 mg/L) is known to harm human health. Since the fluoride concentration in the shallow groundwater of the Weigan River Basin, China, exceeds this level, this study explored fluoride’s sources and enrichment mechanism for this basin. Based on information retrieval and regional geological environment analyses, 47 sets of shallow groundwater samples in the Weigan River Basin were collected and analyzed. The research results show that the fluoride content in the drainage basin of the research area ranged from 0.2 to 5.46 mg/L, with an average value of 1.14 mg/L. The test results showed that 40.43% of the water sample test results exceeded the national domestic drinking water safety standard (1.0 mg/L). The average pH value of the research area was 8.37, which was slightly basic. Type Na+–Cl−/(SO42−) was the primary hydrochemical type. In the research area, groundwater with a high fluoride concentration contained much sodium and little calcium. The main mechanism of excessive fluoride formation in the groundwater was the continued dissolution of fluorine-containing minerals (fluorite) in the research area, while the main fluorine source was weathering of silicate rocks and evaporites. Evaporation-crystallization and cation exchange were the main factors controlling fluorine enrichment. These findings indicate that physicochemical processes are the major mechanisms for controlling F− enrichment and that may be useful for studying F− occurrence in groundwater in arid and semi-arid areas.