大同盆地高氟地下水水化学特征及其成因

Hydrochemistry and Occurrence of High Fluoride Groundwater in Datong Basin

为查明控制大同盆地高氟地下水形成的主要地球化学过程,对大同盆地地下水高氟区31个水样进行了水化学特征及因子分析研究。结果表明,研究区浅层和深层地下水中均检测出氟,且氟含量高,最大ρ(F)达10.37mg/L。该区高氟地下水以Na-HCO3型水为主,具有典型的富Na特征。PHREEQC饱和指数计算结果表明,地下水中萤石为不饱和状态,地下水中ρ(F)主要受到萤石溶解影响。因子分析研究表明,水-岩相互作用、碳酸盐矿物溶解沉淀及Na-Ca离子交换作用是控制大同盆地地下水氟富集的主要水化学过程。

To identify the main geochemical processes controlling the fluoride enrichment in groundwater at Datong Basin,total of thirty-one samples were collected for hydrochemical and factor analysis study.High fluoride concentration was detected in both shallow and deep groundwater.In shallow groundwater,the fluoride concentration ranges from 0.01 to 10.37 mg/L,while deep groundwater has lower fluoride concentration,ranging from 0.01 to 3.14 mg/L.High fluoride groundwater is typically Na-HCO3 type water and characterized by high Na concentration.The saturation indices calculated by PHREEQC indicate that fluorite is undersaturated in almost all groundwater samples,meaning that the fluoride concentration in groundwater is mainly controlled by fluorite solubility.Factor analysis indicates that processes including water-rock interaction,carbonate mineral precipitation and cation exchange are the dominant factors for the occurrence of high fluoride groundwater in Datong Basin.