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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。
The research area is located in Tongyu County, western part of Jilin Province, southwest of Songnen Plain with a total area of 8468km ~ 2. A total of 87 groundwater samples were collected, of which 29 Quaternary shallow diving wells, Quaternary pressurized water wells and 58 newly constructed well water samples. Based on field measurements and laboratory analyzes, the effects of redox conditions on arsenic release and migration in groundwater were studied. The results show that in space, the concentration of arsenic in water gradually increases from Xianhai Reservoir to Sijingzi Township, the high arsenic concentration in shallow groundwater concentrates in Sijingzi Township, the deep arsenic groundwater distributes in the middle, Lake plain within. According to the standard of 0.05mg / L in our country, the exceeding standard rate of arsenic reaches 61%, and the limit of WHO (World Health Organization) standard 0.01mg / L is 86%. In general, high-arsenic groundwater mainly exists in the reducing environment. The dissolved iron in groundwater is dominated by Fe (Ⅱ), As (Ⅲ) accounts for more than 60% of total As, and NO_3 ~ - is lower, while NH_4 ~ + high. Restoring the environment is a key factor in controlling the release of arsenic from groundwater systems. The simulation results of PHREEQC show that the different redox couples in groundwater such as Fe (Ⅱ) / Fe (Ⅲ), N (-Ⅲ) / N (Ⅲ), N (-Ⅲ) / N (PE value) calculated from the calculated values of Fe (Ⅱ) / N (Ⅴ), S (-Ⅱ) / S (Ⅵ) and As (Ⅲ) / As The value of pE calculated by Fe (Ⅲ) is close to the value of pE calculated by field measured Eh. It is indicated that Fe (Ⅱ) / Fe (Ⅲ) is the decisive potential system of groundwater in the study area, and its redox state is mainly controlled by the redox of Fe (Ⅱ) / Fe (Ⅲ). The reductive dissolution of Fe oxides / hydroxides causes the release of As adsorbed on its surface to groundwater, which is the main reason for the formation of high-arsenic groundwater; and human agricultural activities promote As transport and enrichment in shallow groundwater set.