Enrichment of fluoride in groundwater under the impact of saline water intrusion at the salt lake area of Yuncheng basin,northern China |
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Authors: | Xubo Gao Yanxin Wang Yilian Li Qinghai Guo |
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Institution: | (1) School of Environmental Studies and MOE Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, 430074, People’s Republic of China |
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Abstract: | Long-term intake of high-fluoride groundwater causes endemic fluorosis. This study, for the first time, discovered that the
salt lake water intrusion into neighboring shallow aquifers might result in elevation of fluoride content of the groundwater.
Two cross-sections along the groundwater flow paths were selected to study the geochemical processes controlling fluoride
concentration in Yuncheng basin, northern China. There are two major reasons for the observed elevation of fluoride content:
one is the direct contribution of the saline water; the other is the undersaturation of the groundwater with respect to fluorite
due to salt water intrusion, which appears to be more important reason. The processes of the fluorine activity reduction and
the change of Na/Ca ratio in groundwater induced by the intrusion of saline water favor further dissolution of fluorine-bearing
mineral, and it was modeled using PHREEQC. With the increase in Na concentration (by adding NaCl or Na2SO4 as Na source, calcium content kept invariable), the increase of NaF concentration was rapid at first and then became slower;
and the concentrations of HF, HF2−, CaF+, and MgF+ were continuously decreasing. The geochemical conditions in the study area are advantageous to the complexation of F− with Na+ and the decline of saturation index of CaF2, regardless of the water type (Cl–Na or SO4–Na type water). |
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Keywords: | Fluoride Groundwater Hydrogeochemistry Salt lake Northern China |
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