Interactions between arsenic adsorption/desorption and indigenous bacterial activity in shallow high arsenic aquifer sediments from the Jianghan Plain, Central China.

Exposure to arsenic in the environment is hazardous to biota. Three types of sediments from a shallow, high arsenic aquifer were collected from Jianghan Plain, Central China to investigate interactions between indigenous bacterial activity and arsenic adsorption/desorption. For the same level of bacterial activity, the As(III) or As(V) adsorption rate in sediments decreased from clay loam to loamy sand to silty sand. However, the arsenic desorption rate from these sediments followed the reverse sequence. For the same arsenic speciation and content, bacterial activity decreased from clay loam to loamy sand to silty sand. Overall, arsenic adsorption/desorption rates were related to both bacterial activity and sediment texture. The bacteria present could reduce As(V) to As(III), thereby favoring its release from sediment into solution and increasing the ratio of As(III) to total arsenic. These results indicate indigenous bacteria strongly affect the adsorption/desorption and oxidation-reduction of arsenic, and are actively involved in the dynamic equilibrium of arsenic between sediment and groundwater in this shallow aquifer.