Competitive Reduction of Pertechnetate (⁹⁹TcO₄^- ) by Dissimilatory Metal Reducing Bacteria and Biogenic Fe(II)

Journal Article · Thu Jan 06 04:00:00 EST 2011 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es1027647· OSTI ID:1009729

Plymale, Andrew E.; Fredrickson, James K.; Zachara, John M.; Dohnalkova, Alice C.; Heald, Steve M.; Moore, Dean A.; Kennedy, David W.; Marshall, Matthew J.; Wang, Chongmin; Resch, Charles T.; Nachimuthu, Ponnusamy

The fate of pertechnetate (⁹⁹Tc(VII)O₄^-) during bioreduction was investigated in the presence of 2-line ferrihydrite (Fh) and various dissimilatory metal reducing bacteria (DMRB) (Geobacter, Anaeromyxobacter, Shewanella) in comparison with TcO₄^- bioreduction in the absence of Fh. In the presence of Fh, Tc was present primarily as a fine-grained Tc(IV)/Fe precipitate that was distinct from the Tc(IV)O₂·nH₂O solids produced by direct biological Tc(VII) reduction. Aqueous Tc concentrations (<0.2 μm) in the bioreduced Fh suspensions (1.7 to 3.2 × 10^-9 mol L^-1) were over 1 order of magnitude lower than when TcO₄^- was biologically reduced in the absence of Fh (4.0 × 10^-8 to 1.0 × 10^-7 mol L^-1). EXAFS analyses of the bioreduced Fh-Tc products were consistent with variable chain length Tc-O octahedra bonded to Fe-O octahedra associated with the surface of the residual or secondary Fe(III) oxide. In contrast, biogenic TcO₂·nH₂O had significantly more Tc-Tc second neighbors and a distinct long-range order consistent with small particle polymers of TcO₂. In Fe-rich subsurface sediments, the reduction of Tc(VII) by Fe(II) may predominate over direct microbial pathways, potentially leading to lower concentrations of aqueous ⁹⁹Tc(IV).

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1009729
• Report Number(s): PNNL-SA-77182; 42318; KP1702030
• Journal Information: Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 3 Vol. 45; ISSN 0013-936X
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
BACTERIA
BIODEGRADATION
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
ELECTRON-DONOR
Environmental Molecular Sciences Laboratory
FE(III)-REDUCING BACTERIUM
FERRIHYDRITE
GEOCHEMISTRY
GREEN RUST
HYDROUS FERRIC-OXIDE
IRON COMPOUNDS
IRON REDUCTION
MINERALIZATION PATHWAYS
PERTECHNETATES
REDUCTION
SEDIMENTS
TC(VII)
TECHNETIUM 99
TECHNETIUM REDUCTION