化隆-循化盆地含水层沉积物地球化学特征及其对地下水氟富集的影响  

Geochemical characteristics of aquifer sediments and their influence on fluoride enrichment in groundwater in the Hualong-Xunhua basin

作　　者：邢世平 吴萍 胡学达 郭华明[1] 赵振 袁有靖 XING Shiping;WU Ping;HU Xueda;GUO Huaming;ZHAO Zhen;YUAN Youjing(School of Water Resources and Environment/MOE Key Laboratory of Groundwater Circulation and Environmental Evolution,China University of Geosciences(Beijing),Beijing 100083,China;Key Lab of Geo-environment Qinghai Province,Qinghai 906 Engineering Survey and Design Institute Co.,Ltd.,Environmental Geological Exploration Bureau of Qinghai Province,Xining 810007,China)

机构地区：[1]中国地质大学(北京)水资源与环境学院/中国地质大学(北京)地下水循环与环境演化教育部重点实验室,北京100083 [2]青海省环境地质勘查局青海九零六工程勘察设计院有限责任公司青海省环境地质重点实验室,青海西宁810007

出　　处：《地学前缘》2023年第2期526-538,共13页Earth Science Frontiers

基　　金：青海省科学技术厅重点实验室创建平台建设专项(2021-ZJ-Y11);国家自然科学基金项目(42130509,41825017)。

摘　　要：在干旱-半干旱地区天然成因的高氟地下水严重影响饮用水安全。前人对高氟地下水的化学特征和形成过程已开展了大量研究,但是对高氟含水层沉积物特征及其地下水氟富集的影响机理尚不明确。本文以化隆-循化盆地黄河河谷高氟区含水层地下水和沉积物为研究对象,分析了地下水化学特征、含水层沉积物的元素组成和可溶组分、含水层沉积物总氟和可溶态氟含量,探究了沉积物地球化学特征对地下水氟富集的影响。结果表明,地下水F^(-)-浓度为0.51~3.78 mg/L(平均值:1.38 mg/L),且随着井深的增加有增大的趋势。高氟地下水主要以Na^(+)为主,且F^(-)-浓度与Na^(+)浓度呈显著的正相关关系。沉积物中总氟含量为460~1030 mg/kg,可溶态氟的含量为0.53~19.9 mg/kg。萤石未达到饱和状态的地下水中,F^(-)-与Ca^(2+)的正相关关系表明萤石等矿物持续溶解向地下水中提供F^(-)-,而地下水中F^(-)-与Si和Al的正相关关系表明含氟硅酸盐风化也促进了地下水氟的富集。沉积物可溶态提取液和地下水pH值、HCO_(3)^(-)以及Na^(+)/Ca^(2+)均与F^(-)-浓度呈正相关关系,表明解吸以及离子交换是高氟地下水形成的重要水文地球化学过程。沉积物中可溶态氟与总铁、总锰的正相关关系表明,F^(-)-的解吸来源于铁、锰氧化物矿物表面的吸附态氟。此外,地下水盐度对地下水氟的富集有着积极的影响。研究成果对揭示高氟地下水的形成机理具有重要意义。Natural occurrence of high-fluoride groundwater in arid and semi-arid areas seriously threatens the safety of drinking water.The chemical characteristics and formation processes of high-fluoride groundwater have been well studied,but the characteristics of high-fluoride aquifer sediments and their influence on the enrichment of groundwater fluoride remain unclear.This paper investigated the hydrogeochemical characteristics of high fluoride groundwater and the elemental compositions and water-soluble components of high-fluoride aquifer sediments to reveal how sediment geochemical characteristics affect fluoride enrichment in groundwater in the Yellow River Valley of the Hualong-Xunhua basin.The results showed that groundwater fluoride concentrations ranged from 0.51 to 3.78 mg/L(average 1.38 mg/L)and tended to increase with depth.Na^(+) was the major cation in the high fluoride groundwater and positively correlated with F^(-).Total fluoride contents of sediments ranged from 460 to 1030 mg/kg,and water-soluble F^(-) contents ranged from 0.53 to 19.9 mg/kg.In groundwater at below fluorite saturation,a positive correlation between F^(-) and Ca^(2+) indicates that fluorite continues to dissolve and provides F^(-) to groundwater,and positive correlations between F^(-) and Si and F^(-) and Al illustrate that weathering of fluoride-containing silicate also promotes fluoride enrichment in groundwater.Positive correlations between F^(-) and pH,F^(-) and HCO_(3)^(-),and F^(-)and Na^(+)/Ca^(2+) in both water-soluble extract of sediment and groundwater indicate that desorption and cation exchange are important hydrogeochemical processes in the formation of high-fluoride groundwater.Positive correlations between water-soluble F^(-) and total Fe/Mn in sediments suggest that desorbed F^(-) originated from Fe/Mn oxide-bound fluoride.Additionally,groundwater salinity had a positive impact on fluoride enrichment in groundwater.The results of this study are of great significance for revealing the genetic mechanisms of high fluoride

关 键 词：化隆-循化盆地 高氟地下水 沉积物 地球化学特征 水-岩相互作用 

分 类 号：P641.3[天文地球—地质矿产勘探]