【摘 要】
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The redox state of arsenic controls its toxicity and mobility in the subsurface environment.Understanding the redox reactions of arsenic is particularly important for addressing its en-vironmental behavior.Clay minerals are commonly found in soils and sed
【机 构】
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Key Laboratory of Drinking Water Science and Technology,Research Center for Eco-Environmental Scienc
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The redox state of arsenic controls its toxicity and mobility in the subsurface environment.Understanding the redox reactions of arsenic is particularly important for addressing its en-vironmental behavior.Clay minerals are commonly found in soils and sediments,which are an important host for arsenic.However,limited information is known about the redox reac-tions between arsenic and structural Fe in clay minerals.In this study,the redox reactions between As(Ⅲ)/As(Ⅴ) and structural Fe in nontronite NAu-2 were investigated in anaerobic batch experiments.No oxidation of As(Ⅲ) was observed by the native Fe(Ⅲ)-NAu-2.Interest-ingly,anaerobic oxidation of As(Ⅲ) to As(Ⅴ) occurred after Fe(Ⅲ)-NAu-2 was bioreduced.Fur-thermore,anaerobic oxidization of As(Ⅲ) by bioreduced NAu-2 was significantly promoted by increasing Fe(Ⅲ)-NAu-2 reduction extent and initial As(Ⅲ) concentrations.Bioreduction of Fe(Ⅲ)-NAu-2 generated reactive Fe(Ⅲ)-O-Fe(Ⅱ) moieties at clay mineral edge sites.Anaer-obic oxidation of As(Ⅲ) was attributed to the strong oxidation activity of the structural Fe(Ⅲ)within the Fe(Ⅲ)-O-Fe(Ⅱ) moieties.Our results provide a potential explanation for the pres-ence of As(Ⅴ) in the anaerobic subsurface environment.Our findings also highlight that clay minerals can play an important role in controlling the redox state of arsenic in the natural environment.
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