In-situ reduction of Fe(Ⅲ) (hydr)oxides-adsorbed As(Ⅴ) via electron shuttling in the presence of organic matter

OM can promote microbial As(V) reduction in high As groundwater systems. As a result, we explored how As(V) adsorbed on FeOOH minerals could be in-situ reduced via electron shuttling between AsRB and different OM. Our findings showed that AQDS was more effective than other two natural organic matter (NOM, i.e., SRHA and SRFA) in reducing both As(V) and Fe(III), due to its high content of quinone moieties. The results of kinetic analysis demonstrated in-situ reduction of As(V), and As(V) bound to ferrihydrite was more readily reduced than As(V) bound to goethite. In addition, the transcriptional activities of three As metabolic genes initially increased but later declined due to high As concentrations, which further slowed the As(V) reduction process. Therefore, we studied As and Fe species at four locations in our designed anaerobic agar electron shuttle device, and changes in relative expression levels of three As metabolic genes (arsC, arrA and arsB).