桂南地下热水系统中氟的分布及迁移富集规律

Distribution,Migration and Enrichment of Fluoride in Geothermal Water in Southern Guangxi,China

选取广西桂南地区地下热水系统为研究对象,利用氢氧同位素及锶同位素研究手段,对研究区内地下热水中氟的空间分布规律及其控制因素进行研究。结果表明：研究区内地下热水中氟含量变化范围为〈0.01～17.93mg/L,其中43%地下水样品中氟含量超过饮用水氟骨症临界值1.5mg/L,高氟地下热水的主要水化学类型为Na-HCO3型,水体中氟含量与温度呈明显正相关性;地下热水氢氧同位素特征显示,研究区地下热水的主要来源为大气降水,同时受一定程度蒸发浓缩及水-岩作用影响,地下热水锶同位素特征显示,研究区地下热水水化学组成明显受长石、云母等铝硅酸盐风化及碳酸盐岩溶解影响;对地下热水水化学开展的因子分析结果显示,研究区地下热水系统中影响氟迁移释放的主要因素为萤石的溶解与沉淀过程。

This paper deeply studies the spatial distribution and the affecting factors of fluoride（F）in the geothermal water in Southern part of Guangxi Province by the isotopic study of hydrogen,oxygen and strontium.The results indicate that the F concentration of geothermal water ranges from 0.01 to 17.93mg/L with 43% of water samples containing F above 1.5mg/L,and the geothermal water containing high fluoride is dominated by the hydrochemical type of Na-HCO3.In addition,there is a significant positive correlation between F concentration and the temperature of geothermal water.The hydrogen and oxygen isotope compositions indicate that the geothermal water is mainly originated from the meteoric water and influenced by the water-rock interaction and evaporation concentration to some degree.The strontium isotope analysis suggests that the weathering of silicate and carbonate rock contributes to chemistry of the geothermal water.The factor analysis results of the hydrochemistry of the geothermal water demonstrate that the migration and release of F in geothermal water is governed by the precipitation and dissolution of fluorite.