{"title":"In Situ Reduction of Fe(III) (Hydr)oxides-Bound As(V) via Electron Shuttling in the Presence of Organic Matter","authors":"Zhengqi Su, Huaming Guo, Zhipeng Gao, Tiantian Ke, Xiaojun Feng, Lingzhi Zhang","doi":"10.1029/2024JG008675","DOIUrl":null,"url":null,"abstract":"<p>Although the reduction of pentavalent arsenic (As(V)) bound to Fe(III) (hydr)oxides (As(V)-containing FeOOH) coupled with organic matter (OM) degradation has received extensive attention, little is known about in situ reduction of FeOOH mineral-bound As(V) (As(V)<sub>(s)</sub>) via electron shuttling in the presence of As(V)-reducing bacteria (AsRB). Here, anthraquinone-2,6-disulfonate (AQDS), Suwannee River humic acid (SRHA), and fulvic acid (SRFA) were used to establish an agar electron shuttle system with ferrihydrite-As(V)/goethite-As(V) and AsRB, which was isolated from high-As groundwater as the candidate strain (RA-1). We found that AQDS was more efficient in shuttling electrons to reduce As(V)<sub>(s)</sub> and Fe(III) than SRHA and SRFA. High contents of quinone moieties in AQDS indicated that quinone moieties were conducive to As(V)<sub>(s)</sub> and Fe(III) reduction. The reduction kinetic rates (<i>K</i><sub>red</sub>) of As(V)<sub>(s)</sub> were higher than those of Fe(III), indicating the occurrence of in situ As(V)<sub>(s)</sub> reduction via electron shuttling. Furthermore, <i>K</i><sub>red</sub> of As(V)<sub>(s)</sub> for ferrihydrite-As(V) systems was greater than that of goethite-As(V) systems, demonstrating that As(V) bound to ferrihydrite via monodentate was more easily reduced than that bound to goethite via bidentate. The relative expression levels of As metabolic genes (<i>ars</i>C, <i>arr</i>A, and <i>ars</i>B) initially increased and then decreased in the late stage of experiments. High As concentrations in suspension inhibited the transcriptional activity of As metabolic genes in the late stage, reducing the electron production efficiency of RA-1 and subsequently slowing in situ reduction of As(V)<sub>(s)</sub>. This study highlights the importance of OM electron shuttling in the reduction of As(V)<sub>(s)</sub>, offering new perspectives in As enrichment in groundwater.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 3","pages":""},"PeriodicalIF":3.7000,"publicationDate":"2025-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Geophysical Research: Biogeosciences","FirstCategoryId":"93","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1029/2024JG008675","RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENVIRONMENTAL SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Although the reduction of pentavalent arsenic (As(V)) bound to Fe(III) (hydr)oxides (As(V)-containing FeOOH) coupled with organic matter (OM) degradation has received extensive attention, little is known about in situ reduction of FeOOH mineral-bound As(V) (As(V)(s)) via electron shuttling in the presence of As(V)-reducing bacteria (AsRB). Here, anthraquinone-2,6-disulfonate (AQDS), Suwannee River humic acid (SRHA), and fulvic acid (SRFA) were used to establish an agar electron shuttle system with ferrihydrite-As(V)/goethite-As(V) and AsRB, which was isolated from high-As groundwater as the candidate strain (RA-1). We found that AQDS was more efficient in shuttling electrons to reduce As(V)(s) and Fe(III) than SRHA and SRFA. High contents of quinone moieties in AQDS indicated that quinone moieties were conducive to As(V)(s) and Fe(III) reduction. The reduction kinetic rates (Kred) of As(V)(s) were higher than those of Fe(III), indicating the occurrence of in situ As(V)(s) reduction via electron shuttling. Furthermore, Kred of As(V)(s) for ferrihydrite-As(V) systems was greater than that of goethite-As(V) systems, demonstrating that As(V) bound to ferrihydrite via monodentate was more easily reduced than that bound to goethite via bidentate. The relative expression levels of As metabolic genes (arsC, arrA, and arsB) initially increased and then decreased in the late stage of experiments. High As concentrations in suspension inhibited the transcriptional activity of As metabolic genes in the late stage, reducing the electron production efficiency of RA-1 and subsequently slowing in situ reduction of As(V)(s). This study highlights the importance of OM electron shuttling in the reduction of As(V)(s), offering new perspectives in As enrichment in groundwater.
期刊介绍：
JGR-Biogeosciences focuses on biogeosciences of the Earth system in the past, present, and future and the extension of this research to planetary studies. The emerging field of biogeosciences spans the intellectual interface between biology and the geosciences and attempts to understand the functions of the Earth system across multiple spatial and temporal scales. Studies in biogeosciences may use multiple lines of evidence drawn from diverse fields to gain a holistic understanding of terrestrial, freshwater, and marine ecosystems and extreme environments. Specific topics within the scope of the section include process-based theoretical, experimental, and field studies of biogeochemistry, biogeophysics, atmosphere-, land-, and ocean-ecosystem interactions, biomineralization, life in extreme environments, astrobiology, microbial processes, geomicrobiology, and evolutionary geobiology
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