Geochemical Characterization of Fluoride in the Groundwater of the Huaibei Plain, China

Abstract

Forty-two groundwater samples were collected for the geochemical characterization of fluoride in the Huaibei Plain, a high fluorine area, in Northern China. The concentration of fluoride in the groundwater was from 0.20 to 3.75 mg/l, and 23.81% (n = 9) of the samples exceeded the drinking water standard of 1.5 mg/l recommended by the World Health Organization. The groundwater was alkaline (pH 7.14 to 8.67), brackish (total dissolved solids 421 to 1196 mg/l), and the water was classified as bicarbonate-sodium, bicarbonate-calcium, bicarbonate-calcium·sodium, and bicarbonate chloride-sodium. This prevailing characteristics may be attributed to mineral weathering, water-rock interactions, and ion exchange in the aquifer. The main source of fluorine in the groundwater may be from the leaching of minerals.The elevated concentration of fluoride in groundwater may be derived from the calcite-fluorite minerals. This study also discusses a number of factors affecting the fluoride concentrations in groundwater. High fluoride concentrations are associated with weakly alkaline conditions, moderate total dissolved solids, and calcium and sodium ions as the dominant ions. Correlations between fluoride and sample depth and SO4 2− were not observed. All samples were below the solubility product curve of CaF2, which may be explained by positive correlation between fluoride and total dissolved solids. Evapotranspiration and runoff conditions also favor fluoride enrichment in groundwater.

Spatial distribution and potential health risk of fluoride in drinking groundwater sources of Huaibei, Anhui Province

“…Meanwhile, drought climate and alkaline environment will lead to the increasing of fluoride content in groundwater. Some studies shown that the concentrated distribution area of high fluoride in groundwater is consistent with the high fluorine waste discharge sites such as coal mines and power plants 28 .…”

“…Therefore, alkaline and alkalescent water is favorable for F − enrichment. The pH value of groundwater in Huaibei Plain is generally between 7.14 and 8.67 28 , which is alkaline and alkalescent, which is favorable for the enrichment of F − . Furthermore, F − adsorbed on the clay surface is easily replaced by OH − which leads to the enrichment of F − in alkaline environment.…”

“…It has been reported that NO 3 − in groundwater is mainly originated from human activities, For example, coal mines, power plants and other high fluorine waste emissions 28 . NO 3 − contamination in groundwater may be the result of agricultural factors such as fertilizers or animal wastes 42 .…”

“…Groundwater is the main water source to ensure its social and economic development 27 . For the high concentration of fluoride in the groundwater of Huaibei City (China), and the prevalence of dental fluorosis is more than 50–90% 28 . In recent years, the demand for water resources is increasing greatly with the accelerate development of socioeconomic and urbanization.…”

Fluorine in shallow groundwater in China: A review of distribution, occurrence and environmental effects

“…Studies have shown that the occurrence of fluoride in groundwater is related to the incidence rate of endemic fluorosis and has a negative effect on the human body (Ren et al, 1996;Marimon et al, 2013;Wang et al, 2015). There is no elemental form of F − in nature, which usually exists widely in the form of ions (Rafique et al, 2008;Ramachandran et al, 2012;Li et al, 2014;Hu et al, 2017). Moreover, F − also shows strong complexation and the ability to replace hydrogen atoms in organic compound molecules .…”