Distribution, origin and key influencing factors of fluoride groundwater in the coastal area, NE China

Evolution of shallow fluoride groundwater, in the Lower Liaohe River Plain in northeastern China, a typical coastal area, has been studied to assess the controls of geology, geochemistry and human activity on high-fluoride groundwater. A total of 212 shallow groundwater samples were collected. The range of the measured F– concentration was 0.11–4.9 mg/L with the mean value of 0.71 mg/L. Durov diagram classification, variation function calculation, thermodynamic calculation and factor analysis were used to analyze the distribution, origin and key influencing factors of high-fluoride groundwater. The distribution of high-fluoride samples was mainly concentrated in the southwestern and northeastern Lower Liaohe River Plain. The main origin of high fluoride in shallow groundwater was the lixiviation of fluorine-rich rocks in the northern plain and the alluvial fan of Da Linghe and Xiao Linghe Rivers. Additionally, through the migration and enrichment of fluoride in Xinmin, Linghai, a higher fluoride area was formed. The key influencing factors of fluoride groundwater was the fluoride lixiviation, regional hydraulic gradient, hydrochemical types and ion composition. Meanwhile, human pollution, evaporation and local irrigation were comparatively weak influencing factors. The process of calcite dissolution controlled the regional distribution of high fluoride in shallow groundwater.