Release of arsenic and iron in aquifer to groundwater under the variation of REDOX environment during bank infiltration: a case study in Huangjia groundwater source area, Northeastern China

Groundwater exploitation along a river bank can not only induce the river water infiltrating but also affect the biogeochemical reactions in the riverbank infiltration zone. Due to the differences in water chemistry in river water and groundwater, there are obvious physical, chemical and biological gradients in the riverbank infiltration zone, resulting in a series of strong and complex biogeochemical processes. In this study, Huangjia groundwater source area along the Liao River is selected as the case study area. To explore the REDOX environment in the infiltration zone induced by groundwater exploitation, and to deduce the major geochemical reactions of release arsenic and iron in aquifer to groundwater under different REDOX environment during bank infiltration. A number of highlighted conclusions has been obtained through this study: arsenic and iron in the sediments are mainly released to groundwater through desorption and reductive dissolution of iron minerals. The content of exchangeable and iron-manganese oxides bound state changes significantly. Co-evolution characteristics of As and Fe release processes are strongly correlated with the variation of REDOX environment, the oxidation of organic matter bound iron minerals under weak oxidizing condition also played an important role in promoting the release of As and Fe.