Reductive dissolution and sequestration of arsenic by microbial iron and thiosulfate reduction

Abstract

Iron oxide and oxy-hydroxide are commonly used for remediation and rehabilitation of arsenic (As)-contaminated soil and water. However, the stability of As sequestered by iron oxide and oxyhydroxide under anaerobic conditions is still uncertain. Geochemical properties influence the behavior of As

in addition, microbial activities affect the mobility of sequestered As in soil and water. Microbialmediated iron reduction can increase the mobility of As by reductive dissolution of Fe oxide

however, microbial-mediated sulfate reduction can decrease the mobility of As by sulfide mineral precipitation. This study investigated the geomicrobial impact on the behavior of As and stability of sequestered As in ironrich sediment under anaerobic conditions. Increase in Fe(II) concentrations in water was evidence of microbial-mediated iron reduction. Arsenic concentrations increased with Fe(II) concentration

however, the thiosulfate reduction process also induced immobilization of As through the precipitation of AsFeS. Therefore, microbial-mediated iron reduction and thiosulfate reduction have opposite influences on the mobility of As under anaerobic condition.