Wei Chao, Guo Huaming, Zhang Di, Wu Yang, Han Shuangbao, An Yonghui, Zhang Fucun
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China.
MOE Key Laboratory of Groundwater Circulation & Environment Evolution and School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China.
Environ Geochem Health. 2016 Feb;38(1):275-90. doi: 10.1007/s10653-015-9716-x. Epub 2015 May 20.
High-F(-) groundwater is widely distributed in Xiji County, which endangers the safety of drinking water. In order to evaluate the key factors controlling the origin and geochemical mechanisms of F(-) enrichment in groundwater at Xiji County, one hundred and five groundwater samples and sixty-two sediment samples were collected. Fluoride concentration in the groundwater samples ranged from 0.2 to 3.01 mg/L (mean 1.13 mg/L), with 17 % exceeding the WHO drinking water guideline value of 1.5 mg/L and 48 % exceeding the Chinese drinking water guideline value of 1.0 mg/L. High-F(-) groundwaters were characterized by hydrochemical types of Na-HCO3 and Na-SO4·Cl, which were found in Quaternary sediment aquifer and in Tertiary clastic aquifer, respectively. Conditions favorable for F(-) enrichment in groundwater included weakly alkaline pH (7.2-8.9), low concentration of Ca(2+), and high concentrations of HCO3 (-) and Na(+). Calcite and fluorite were the main minerals controlling F(-) concentration in groundwaters. The hydrolysis of F-bearing minerals in aquifer sediments was the more important process for F(-) release in Tertiary clastic aquifer, which was facilitated by long residence time of groundwater, in comparison with Quaternary sediment aquifer. Cation exchange would also play important roles, which removed Ca(2+) and Mg(2+) and led to more free mobility of F(-) in groundwater and permitted dissolution of fluorite, especially in Tertiary clastic aquifer. However, evapotranspiration and competing adsorption of B and HCO3 (-) were the more important processes for F(-) enrichment in Quaternary groundwater. Groundwater in Lower Cretaceous aquifer had relatively low F(-) concentration, which was considered to be the potential drinking water resource.
高氟地下水在西吉县广泛分布，危及饮用水安全。为了评估控制西吉县地下水中氟富集的成因及地球化学机制的关键因素，采集了105个地下水样品和62个沉积物样品。地下水样品中的氟浓度范围为0.2至3.01毫克/升（平均1.13毫克/升），其中17%超过了世界卫生组织1.5毫克/升的饮用水指导值，48%超过了中国1.0毫克/升的饮用水指导值。高氟地下水的水化学类型为Na-HCO₃和Na-SO₄·Cl，分别存在于第四纪沉积物含水层和第三系碎屑含水层中。有利于地下水中氟富集的条件包括弱碱性pH值（7.2-8.9）、低浓度的Ca²⁺以及高浓度的HCO₃⁻和Na⁺。方解石和萤石是控制地下水中氟浓度的主要矿物。与第四纪沉积物含水层相比，第三系碎屑含水层中含水层沉积物中含氟矿物的水解是氟释放的更重要过程，这得益于地下水的长时间停留。阳离子交换也起着重要作用，它去除了Ca²⁺和Mg²⁺，使氟在地下水中更易自由移动并促使萤石溶解，特别是在第三系碎屑含水层中。然而，蒸发蒸腾作用以及硼和HCO₃⁻的竞争吸附是第四纪地下水中氟富集的更重要过程。下白垩统含水层中的地下水氟浓度相对较低，被认为是潜在的饮用水资源。
