文安县高氟地下水的分布特征及关键水化学性质分析

为进一步认清河北省文安县高氟地下水的水化学性质,在水文地质调查以及取样分析的基础上,采用水化学特征分析、多元统计分析和水化学成因分析等手段阐明文安县高氟地下水的分布特征和关键水化学性质.结果表明：文安县深层地下水氟化物含量0.56～4.19 mg/L,总体分布是中北部偏高;其关键水化学特征是pH值7.7～8.7、总碱度高于211 mg/L、总硬度低于90 mg/L,水化学类型为典型的Na-HCO3型;在文安县地下水环境条件下,总碱度、碳酸氢根以及钠离子是促进高氟地下水形成的关键水化学因素;当2.0 mg/L＜F-＜ 3.5 mg/L时,地下水中Ca2＋与F-有拮抗作用.通过氯碱指数和饱和指数分析可知,研究区域高氟地下水的形成主要是水-岩间的阳离子交换反应和氟矿物的溶解-沉淀反应.

Analysis of distribution and key hydrochemistry of high-fluoride groundwater in Wen＇an city

In order to clarify the distribution and hydrochemistry characteristics of high-fluoride groundwater in Wen＇an city, Hebei province, based on hydrogeological investigations and water samples analysis, hydrochemistry status analysis, multivariate statistical analysis and geochemical modeling have been carried out in this paper. Results show that the fluoride concentration ranges from 0.56 mg/L to 4.19 mg/L with 99% of the samples exceeding the maximum allowable limit （1.0 rag/L）, pH values range from 7.7 to 8.7, the values of total alkalinity and hardness ranges from 211 mg/L to 296 mg/L and 4 mg/L to 90 mg/L and all the high-fluoride groundwater belongs to Na-HCO3 type. A positive correlation between total alkaline, bicarbonate, sodium and fluoride indicates that the hydrochemistry status promotes the formation of high-fluoride groundwater. Ca2＋ plays a reverse role in fluorite dissolution when fluoride concentration ranges from 2.0 mg/L to 3.5 mg/L. With regard to the occurrence of fluoride, geochemical modeling indicated that cation exchange between the groundwater and the surrounding minerals and mineral weathering and dissolution are major determinants in this region.