Figure 5: A conceptual diagram of different microbial processes involved in arsenic biochemistry in the As-contaminated aquifer. Four kinds of microbial population are considered, including (1) microbial community of groundwater, (2) reducing bacteria cultivated from groundwater, (3) microbial community of sediment, and (4) reducing bacteria cultivated from sediment. The solid and dash lines represent the major and minor mechanisms, respectively. The thick and thin circles represent the main and minor release components, respectively.