Mossbauer Analysis of Microbial Redox Transformations of Fe-bearing Phyllosilicate and Oxide Minerals
EMSL Project ID
35207
Abstract
Microbial Fe redox transformations have a major impact on the aqueous and solid-phase geochemistry of subsurface environments, as well as on the behavior of various organic and inorganic contaminants. The objective of this project is to continue an ongoing collaboration with EMSL scientist Dr. Ravi Kukkadapu on experimental studies of microbial redox transformation of Fe-bearing phyllosilicate and oxide minerals in subsurface sediments. This collaboration has led to two peer-reviewed publications (Weber et al., Environ. Microbiol., 2006; Mohanty et al., Environ. Sci. Technol., 2008), and we are engaged now in several additional DOE/OBER-sponsored studies that will take place over the next three years. Dr. Kukkadapu is providing a critical ingredient to these studies, namely variable-temperature Mossbauer spectroscopic analysis of the identity, abundance, and redox speciation of solid-phase Fe-bearing minerals that have been subjected to microbial reduction and/or oxidation. In many instances, Mossbauer is the only suitable method for constraining the participation of phyllosilicates vs. oxides in microbially-driven Fe redox transformations. Although there are several Mossbauer specialists in the U.S. (and abroad) with whom we could potentially collaborate, our long-standing connection with Dr. Kukkadapu and other colleagues at PNNL (Roden and Shelobolina are participants in the PNNL Science Focus Area project led by John Zachara and Jim Fredrickson), and our mutual understanding of science questions and approaches relevant to the DOE mission, make the EMSL collaboration an ideal one.This user proposal consists of two related components that involve use of the variable-temperature Mossbauer to analyze solid-phase Fe redox speciation in sediments: (1) studies of microbial reduction of structural Fe(III) in phyllosilicate (e.g. smectite, illite) versus Fe(III) oxide (e.g. goethite) minerals in two different DOE-related subsurface sediment materials (weathered shale saprolite from Oak Ridge National Laboratory, TN, and Atlantic coastal plain sediment from Oyster, VA); and (2) studies of alternating reduction and oxidation of structural Fe(III) and Fe(II) in clay-rich subsurface sediments from the Hanford and Ringold formation in Richland, WA, and in a hydromorphic soil in Madison, WI. Although Mossbauer constitutes the major component of our ongoing utilization of EMSL facilities (ca. 1500 hours of instrument time), we also anticipate the need for modest amounts of electron microscopy, micro-XRD, and XPS (ca. 20-40 hours each) to confirm the composition, redox speciation, and localization of Fe mineral transformation products. The Fe redox transformation studies to be conducted have immediate relevance to controls on the subsurface speciation and migration of uranium and technetium, both priority radionuclide contaminants on DOE lands. In addition, these studies will make important contributions to our overall understanding of the pathways and quantitative significance of microbial phyllosilicate redox transformations in nature. We have recently discovered that lithotrophic microorganisms have the potential to directly oxidize structural Fe(II) in both primary and secondary phyllosilicate minerals. The role of this phenomenon in subsurface microbial Fe redox metabolism is almost completely unknown. This user proposal will provide world-class Mossbauer and other microscopic/spectroscopic data in support of OBER-funded studies that will make key contributions to this under-explored facet of sediment biogeochemistry.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2009-10-05
End Date
2012-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Shelobolina ES, H Xu, H Konishi, RK Kukkadapu, T Wu, M Blothe, and EE Roden. 2012. "Microbial Lithotrophic Oxidation of Structural Fe(II) in Biotite." Applied and Environmental Microbiology.