沉积物中砷的赋存特征及对地下水砷富集的控制:以内蒙古河套盆地为例  

Distribution characteristics of arsenic in sediments and its control on groundwater arsenic enrichment:A case study of Hetao Basin,Inner Mongolia

作　　者：张卓 郭华明[3] 韩双宝[4] 牛笑童 ZHANG Zhuo;GUO Huaming;HAN Shuangbao;NIU Xiaotong(Tianjin Center,China Geological Survey,Tianjin 300170,China;Tianjin Key Laboratory of Coast Geological Processes and Environmental Safety,Tianjin 300170,China;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Beijing 100083,China;Center for Hydrogeology and Environmental Geology,China Geological Survey,Baoding 071051,Hebei,China)

机构地区：[1]中国地质调查局天津地质调查中心(华北地质科技创新中心),天津300170 [2]天津市海岸带地质过程与环境安全重点实验室,天津300170 [3]中国地质大学(北京)生物地质与环境地质国家重点实验室,北京100083 [4]中国地质调查局水文地质环境地质调查中心,河北保定071051

出　　处：《中国地质》2024年第4期1331-1341,共11页Geology in China

基　　金：国家自然科学基金项目(42102298,41825017);中国地质调查局项目(DD20230426,DD20230431)联合资助。

摘　　要：【研究目的】河套盆地西侧存在原生高砷地下水,查明含水层沉积物中砷的空间分布和赋存特征,分析地下水砷的富集机理,有利于保障当地居民用水安全。【研究方法】本研究在河套盆地山前冲洪积扇区的钻孔K02和河套盆地平原区的钻孔K01中分别采集25和26个沉积物样品,用于分析岩性特征与地球化学组分,并开展砷的分步提取与解吸附实验。【研究结果】山前冲洪积扇区含水层处于相对氧化的环境中,而平原区含水层处于封闭的还原环境中。后者沉积物电导率普遍高于前者,两者沉积物电导率随深度均有递减趋势。山前冲洪积扇区和平原区沉积物总固相砷含量相差不大,但固相砷的赋存形态差别较大,前者沉积物固相砷以无定形态的铁氧化物或氢氧化物共存的砷为主,后者则以强吸附态砷为主。【结论】沉积物中砷赋存特征的差异是造成平原区地下水砷浓度高于山前冲洪积扇区的主要原因。解吸附实验表明弱碱性环境或高Na/Ca^(0.5)摩尔比值均能促进砷的解吸附,导致地下水中砷的富集。This paper is the result of hydrogeological survey engineering.Objective Higharsenic(As)groundwater occurred in the west of Hetao Basin.Investigating the spatial distribution and occurrence characteristics of As in aquifer sediments and studying the enrichment mechanism of As ingroundwater are beneficial to ensure the safety of water for local residents.Methods Twenty five sediment samples from borehole K02 in the piedmont alluvial fan and twenty sixsamples from borehole K01 in the plain were collectedto analyze lithological characteristics and geochemical components.These samples were further to conduct sequential extraction and desorption experiments of As in sediments.Results The aquifers in the piedmont alluvial fan were in a relatively oxidized environment,while the aquifers in the plain area were in a closed reducing environment.Salinity of the latter sediment was generally higher than that of the former,and salinity of both sediments had a decreasing trend with depth.Total solid As content in the sediments of the piedmont alluvial vans and the plain area displayed little difference,but the occurrence pool of solid Aswas quite different.The former sediment solid As was dominated by the As incorporated in very amorphous Fe−(oxyhydr)oxides,while the latter was dominated by strongly adsorbed As.Conclusions The differences of As occurrence characteristics in sediments were the main reason why groundwater As concentration in the plain area was higher than that in piedmont alluvial vans.Desorption experiments showed that weak alkalinity or high Na/Ca^(0.5) molar ratio could promote the desorption of As.

关 键 词：沉积物 固相砷 赋存特征 水文地质调查工程 河套盆地 内蒙古 

分 类 号：P641.8[天文地球—地质矿产勘探]