Related Experiment Videos
Microbially catalyzed nitrate-dependent oxidation of biogenic solid-phase Fe(II) compounds.
K A Weber1, F W Picardal, E E Roden
1Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama 35487-0206, USA.
Environmental Science & Technology
|May 2, 2001
Summary
Microbial nitrate reduction drives the oxidation of solid iron(II) compounds, impacting contaminant metal and radionuclide migration in subsurface environments.
Area of Science:
- Geochemistry
- Environmental Microbiology
- Biogeochemistry
Background:
- Microbial processes significantly influence the fate of iron (Fe) in subsurface environments.
- Nitrate (NO3-) is a common electron acceptor in anoxic environments, and its reduction can be coupled to various oxidation reactions.
- Understanding the microbial oxidation of solid-phase Fe(II) by nitrate is crucial for predicting contaminant transport.
Purpose of the Study:
- To investigate the potential for microbially catalyzed nitrate-dependent oxidation of various solid-phase Fe(II) compounds.
- To assess the influence of mineralogy and microbial activity on the efficiency of this oxidation process.
- To evaluate the implications for the mobility of metals and radionuclides in the subsurface.
Main Methods:
- Utilized an established autotrophic, denitrifying, Fe(II)-oxidizing enrichment culture.
- Tested the oxidation of microbially reduced goethite, biogenic Fe3O4, biogenic FeCO3, chemically precipitated FeCO3, and two iron(III) oxide-rich subsoils.
- Compared reaction rates and molar ratios of nitrate reduced to Fe(II) oxidized with theoretical stoichiometry.
- Used pasteurized cultures to confirm the biological nature of the observed reactions.
Main Results:
- Microbial nitrate-dependent Fe(II) oxidation rapidly occurred with microbially reduced goethite, subsoils, and chemically precipitated FeCO3.
- Significant oxidation was observed for biogenic Fe3O4, while biogenic FeCO3 showed minimal oxidation.
- Pasteurized controls confirmed the requirement for active microbial catalysis.
- Molar ratios deviated from theoretical stoichiometry in several cases, potentially due to coupled heterotrophic nitrate reduction.
Conclusions:
- Microbial nitrate-dependent Fe(II) oxidation can significantly accelerate the transformation of solid-phase Fe(II) compounds.
- This process has important implications for the environmental fate and transport of contaminant metals and radionuclides.
- The efficiency of oxidation is dependent on the specific Fe(II) mineralogy and microbial community composition.