Arsenic Mobilization by the Dissimilatory Fe(III)-Reducing Bacterium Shewanella alga BrY

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• 作者：David E. Cummings ; Frank Caccavo ; Jr. ; Scott Fendorf ; and R. Frank Rosenzweig
• 刊名：Environmental Science & Technology
• 出版年：1999
• 出版时间：March 1, 1999
• 年：1999
• 卷：33
• 期：5
• 页码：723 - 729
• 全文大小：103K
• 年卷期：v.33,no.5(March 1, 1999)
• ISSN：1520-5851

文摘

The mobility of arsenic commonly increases as reducingconditions are established within sediments or flooded soils.Although the reduction of arsenic increases its solubilityat circumneutral pH, hydrous ferric oxides (HFO) stronglysorb both As(V) (arsenate) and As(III) (arsenite), the twoprimary inorganic species. Thus, in the presence ofexcess HFO, reductive dissolution of iron may be thedominant mechanism by which As is released into solution.In this paper, we report that the dissimilatory iron-reducing bacterium Shewanella alga strain BrY promotedAs mobilization from a crystalline ferric arsenate aswell as from sorption sites within whole sediments. S.alga cells released arsenate from the mineral scorodite(FeAsO₄·2H₂O) as a result of dissimilatory (i.e., respiratory)reduction of Fe(III) to Fe(II). Solid-phase analysis with SEM-EDS and XAFS (X-ray absorption fine structure) spectroscopyrevealed that the valence states of Fe and As in the solid-phase product were identical to those in solution, i.e.,Fe(II) and As(V). Additionally, As(V) sorbed to sedimentsfrom Lake Coeur d'Alene, ID, a mining-impacted environmentenriched in both Fe and As, was solubilized by theactivity of S. alga BrY. In neither experiment was As(III)detected. We conclude that arsenic mobility can be enhancedby the activity of dissimilatory iron-reducing bacteria inthe absence of arsenic reduction.