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).

有机物（OM）能够在高砷地下水系统中促进微生物对砷(V)的还原。因此，我们探讨了砷(V)吸附在FeOOH矿物上的情况下，如何通过AsRB与不同的OM之间的电子转移实现原位还原。我们的研究发现，由于其高含量的醌基团，AQDS在还原砷(V)和Fe(III)方面比其他两种天然有机物（NOM，即SRHA和SRFA）更为有效。动力学分析的结果表明，原位还原砷(V)，并且与赤铁矿结合的砷(V)比与针铁矿结合的砷(V)更容易被还原。此外，由于高砷浓度，三个砷代谢基因（arsC、arrA和arsB）的转录活性最初增加但随后下降，这进一步减缓了砷(V)的还原过程。因此，我们在设计的厌氧琼脂电子穿梭装置的四个位置研究了砷和铁物种，并观察了三个砷代谢基因（arsC、arrA和arsB）的相对表达水平的变化。