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ARSENIC MOBILIZATION BY THE DISSIMILATORY FE(III)-REDUCING BACTERIUM SHEWANELLA ALGA BRY. (R825399)
Citation:
Cummings, D., F. Caccavo, S. Fendorf, AND R. F. Rosenzweig. ARSENIC MOBILIZATION BY THE DISSIMILATORY FE(III)-REDUCING BACTERIUM SHEWANELLA ALGA BRY. (R825399). ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 33:723-729, (1999).
Description:
The mobility of arsenic commonly increases as reducing conditions are
established within sediments or flooded soils. Although the reduction of arsenic
increases its solubility at circumneutral pH, hydrous ferric oxides (HFO)
strongly sorb both As(V) (arsenate) and As(III) (arsenite), the two primary
inorganic species. Thus, in the presence of excess HFO, reductive dissolution of
iron may be the dominant mechanism by which As is released into solution. In
this paper, we report that the dissimilatory iron-reducing bacterium
Shewanella alga strain BrY promoted As mobilization from a crystalline
ferric arsenate as well 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) spectroscopy revealed 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 sediments
from Lake Coeur d'Alene, ID, a mining-impacted environment enriched in both Fe
and As, was solubilized by the activity of S. alga BrY. In neither
experiment was As(III) detected. We conclude that arsenic mobility can be
enhanced by the activity of dissimilatory iron-reducing bacteria in the absence
of arsenic reduction.