新疆阿克苏典型山前洪积扇内高氟地下水的化学特征及氟富集机制  

Hydrochemical characteristics and fluoride enrichment mechanisms of high-fluoride groundwater in a typical piedmont proluvial fan in Aksu area,Xinjiang,China

作　　者：潘欢迎 邹常健 毕俊擘[3] 刘运德 黄丽文 Pan Huanying;Zou Changjian;Bi Junbo;Liu Yunde;Huang Liwen(School of Environmental Studies,China University of Geosciences(Wuhan),Wuhan 430078,China;Geological Survey Institute,China University of Geosciences(Wuhan),Wuhan 430078,China;Xi'an Geological Survey Center,China Geological Survey,Xi'an 710054,China)

机构地区：[1]中国地质大学(武汉)环境学院,武汉430078 [2]中国地质大学(武汉)地质调查研究院,武汉430078 [3]中国地质调查局西安地质调查中心,西安710054

出　　处：《地质科技通报》2021年第3期194-203,共10页Bulletin of Geological Science and Technology

基　　金：国家重点研发项目课题(2017YFC0406105);中国地质调查局“新疆阿拉尔-图木舒克-昆玉综合地质调查”(DD20179605)。

摘　　要：在内陆干旱区,作为重要饮用水源的地下水常面临氟含量超标问题。查明内陆干旱区高氟地下水的分布规律,了解氟在地下水中的富集过程及其影响因素,既可丰富高氟地下水的研究体系,也是保证内陆干旱区饮水安全的重要基础。以新疆阿克苏地区典型山前洪积扇——依格齐艾肯河-喀拉玉尔滚河河间地带为研究区,基于水文地球化学调查结果,刻画了高氟地下水的分布区;结合氟离子含量与特征性水化学指标间的关系,揭示了高氟地下水的成因机制。结果表明:①地下水中氟含量的变化范围为0.8~6.1 mg/L,83%的水样氟含量超过《生活饮用水卫生标准》(GB 5749-2006)规定的上限(1.0 mg/L);②总体上,氟含量沿地下水流动路径逐渐增大,低氟地下水(ρ(F^(-))≤1.0 mg/L)分布在国道314以北的补给区,高氟地下水(ρ(F^(-))>1.0 mg/L)分布在国道314以南的径流区和排泄区;③高氟地下水的水化学类型以Cl·HCO_(3)-Na型为主,而低氟地下水则以Cl·SO4-Na型为主,高氟地下水相比于低氟地下水优势阴离子偏向于HCO_(3)^(-);④地下水的pH值范围为7.9~8.9(均值为8.4),表明其处于弱碱环境中。地下水中ρ(F^(-))与pH值呈正相关,此外构成浅层含水层的上更新统沉积物中含有黑云母、氟磷灰石等矿物,其表面存在一定数量的可交换F^(-),这表明水中OH-与矿物表面F^(-)间的阴离子交换可能对氟的富集有一定贡献;⑤地下水的F^(-)含量与Ca^(2+)含量呈负相关,即高氟地下水中ρ(Ca^(2+))小于低氟地下水。考虑到氟化钙(CaF_(2))是自然界中的主要含氟矿物,也是地下水中氟的主要来源,ρ(F^(-))与ρ(Ca^(2+))间的这种负相关指示着高氟地下水中可能存在去Ca^(2+)、Mg^(2+)作用,如阳离子交替吸附或碳酸盐岩沉淀等。研究区地下水样中ρ(F^(-))与ρ(Mg^(2+))间也呈负相关关系,且和ρ(F^(-))与ρ(Ca^(2+))间的关系高度相似,也佐证了高氟地下水中去In inland arid regions,high fluoride concentrations are frequently reported in groundwater which is an important source of drinking water.Investigating its distribution,enrichment and controlling factors could provide insights for better understanding the geochemistry of high-fluoride groundwater,and are critical foundation to ensure the safety of water supply in inland arid regions.To delineate the distribution of high-fluoride groundwater,a comprehensive hydrogeochemical investigation has been conducted in a typical piedmont proluvial fan in Aksu area,Xinjiang,China.The relationship between fluoride concentration and various geochemical parameters has been analyzed for identifying the controlling processes of groundwater fluoride enrichment in this region.The results are:①Fluoride concentrations in groundwater range from 0.8 to 6.1 mg/L,and 83%of the samples exceed the maximum limit of 1.0 mg/L set by the sanitary standards for drinking water(GB 5749-2006).②The fluoride concentration was found increasing along groundwater flow paths,and low-fluoride groundwater(ρ(F^(-))≤1.0 mg/L)mainly distributed in recharge areas by the north of National Highway 314 while high-fluoride groundwater(ρ(F^(-))>1.0 mg/L)mainly occurred in runoff and discharge areas by the south of National Highway 314.③The groundwater with high and low fluoride concentration is classified as Cl·HCO_(3)-Na type and Cl·SO4-Na type,respectively,indicating the dominant anion of high-fluoride groundwater is biased towards HCO_(3)^(-).④The pH range of groundwater is 7.98.9 with an average value of 8.4,demonstrating a weakly alkaline environment.The groundwater F^(-)content is positively correlated with the pH value.Anion exchange between OH-in groundwater and F^(-)on mineral surface might contribute to the enrichment of fluoride,since there is a certain amount of exchangeable F^(-)in black mica,fluorapatite and other minerals in surrounding Upper Pleistocene sediments.⑤The F^(-)concentration is negatively correlated with the Ca^(2+)conce

关 键 词：高氟地下水 富集机制 萤石溶解 离子交换 方解石沉淀 

分 类 号：X523[环境科学与工程—环境工程]