氧化还原条件对地下水中砷释放迁移的影响——以通榆县高砷地下水为例  

EFFECT OF REDOX CONDITIONS ON ARSENIC RELEASE AND TRANSPORT IN GROUNDWATER SYSTEMS:A CASE STUDY IN THE TONGYU COUNTY

作　　者：张迪[1,2] 郭华明[1,2] 倪萍[2] 吴旸[2] 

机构地区：[1]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]中国地质大学(北京)水资源与环境学院,北京100083

出　　处：《第四纪研究》2014年第5期1072-1081,共10页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:41222020和41172224);中国地质调查局项目(批准号:1212010813104)共同资助

摘　　要：研究区位于吉林西部通榆县,松嫩平原的西南部,总面积8468km^2。采集地下水样品87件,其中第四系浅层潜水井29件、第四系承压水井和新近系承压水井水样58件。在现场测定、实验室分析的基础上,研究了氧化还原条件对地下水中砷释放和迁移的影响。结果表明在空间上,从向海水库到四井子乡,水中的砷浓度逐渐增高,浅层地下水中的高砷点集中在四井子乡,深层高砷地下水分布在中部,霍林河两岸的冲湖积平原内。以我国标准0.05mg/L为限值,砷超标率达61%,以世界卫生组织(WHO)标准0.01mg/L为限值,有86%的地下水样超标。总体上,高砷地下水主要存在于还原环境中,地下水中溶解铁以Fe(Ⅱ)为主,As(Ⅲ)占总As的60%以上,NO_3^-含量较低,而NH_4^+浓度较高。还原环境是控制地下水系统中砷释放的关键因素。利用PHREEQC的模拟计算表明,地下水中不同氧化还原电对(Fe(Ⅱ)/Fe(Ⅲ)、N(-Ⅲ)/N(Ⅲ)、N(-Ⅲ)/N(Ⅴ)、N(Ⅲ)/N(Ⅴ)、S(-Ⅱ)/S(Ⅵ)和As(Ⅲ)/As(Ⅴ))计算得到的电子活度(pE值)存在很大差异,其中,Fe(Ⅱ)/Fe(Ⅲ)计算得到的pE值与现场实测Eh值换算得到的pE值较为接近。表明,Fe(Ⅱ)/Fe(Ⅲ)是研究区地下水的决定电位体系,其氧化还原状态主要受Fe(Ⅱ)/Fe(Ⅲ)的氧化还原控制。Fe氧化物/氢氧化物的还原性溶解,使吸附在其表面的As释放到地下水中,是高砷地下水的形成的主要原因;而人类农业活动促进了浅层地下水中As的运移和富集。High As groundwater has been found both in shallow and deep aquifers of the western Songnen basin,which seriously impacts health of local residents.Our study area is located in Tongyu County of Jilin Province,southwest of Songnen Plain （44°13′05＂～45°16′27＂N,122°02＂13＂～ 123°30′37＂E）,with a total area of 8468km2.Eightyseven groundwater samples were collected,among which 29 samples were taken from shallow Holocene-Upper Quaternary sand aquifers and 58 samples from deep Lower Quaternary and Upper Neogene confined aquifers.Based on groundwater sampling,on-site measurement and laboratory analysis,effect of redox conditions on arsenic release and transport in groundwater systems has been investigated.Results showed that the concentration of As in groundwater gradually increased from Xianghai to Sijingzi,the spatial distribution of high As shallow groundwater mainly occurs in Sijingzi,high As deep groundwater mainly occurs in the central of the study area and Huolin river alluvial plain.About 61％ samples exceed the Chinese drinking water guideline in rural areas （0.05mg/L）,and 86％ samples exceed the World Health Organization standard （0.01 mg/L）.High As groundwater is generally observed in reducing conditions,where Fe（Ⅱ） is the major dissolved Fe species in groundwater and about 60％ of As is in the form of As（Ⅲ）.Concentrations of NO3-are low,but NH4＋ concentrations are high in high As groundwater.Reducing conditions are the major causes for As mobilization in the aquifers.Calculation of pE values using PHREEQC shows that calculated pE values are different with different redox couples （Fe（Ⅱ）/Fe（Ⅲ）,N（-Ⅲ）/N（Ⅲ）,N（-Ⅲ）/N（Ⅴ）,N（Ⅲ）/N（Ⅴ）,S（-Ⅱ）/S（Ⅵ） and As（Ⅲ）/As（Ⅴ））.Calculated pE values of Fe（Ⅱ）/Fe（Ⅲ） couple are close to the measured pE values on the site,indicating that Fe（Ⅱ）/Fe（Ⅲ） is the determinant redox couple in the groundwater system.Redox reaction of Fe（Ⅱ）/Fe（Ⅲ�

关 键 词：高砷地下水 氧化还原电对pE值 水化学 PHREEQC 

分 类 号：P641.3[天文地球—地质矿产勘探]