Mineralogical analysis of substrates and end-products of microbial Fe redox transformations
EMSL Project ID
2461a
Abstract
Current DOE-funded (EMSP and NABIR programs) research at The University of Alabama (UA) is directed toward understanding the influence of microbially-catalyzed redox transformations of Fe-bearing minerals on the mobility and speciation of metal-radionuclide contaminants in subsurface sedimentary environments. This research includes studies of (i) the distribution of bacterial Fe(III) oxide reduction potential in shallow coastal plain aquifer sediments in relation to sediment physiochemical properties; (ii) bacterial dissimilatory reduction of Fe(III) oxides and the interaction of this process with reductive immobilization of uranium(VI) in laboratory reactor systems; and (iii) microbially-catalyzed nitrate-dependent oxidation of soluble and solid-phase Fe(II) compounds and the potential impact of such processes on contaminant metal mobility in subsurface sediments. Research at UA is focused on process-level analysis of the kinetics of various reaction pathways and their dynamic interactions. We do not possess advanced instrumentation for mineralogical analysis of the substrates and end-product of microbial Fe redox transformations. However, understanding the mineralogical nature of such compounds has the potential to provide important insight into factors controlling the outcome of process-level experiments, and to define the reactive phases that are likely to play a key roles in governing the impact of microbial Fe redox transformations on contaminant fate and transport. Through collaboration with Dr. John Zachara and other scientists at PNNL/EMSL, I propose to examine various aspects of the mineralogy of Fe-bearing phases which are either used as substrates for microbial activity, or which are produced during microbial Fe redox transformation, using the following analytical technologies available at the EMSL facility: X-ray diffraction spectroscopy; M?ssbauer spectroscopy; scanning electron microscopy; transmission electron microscopy. Initial studies will focus on (i) characterization of Fe(III) oxides phases generated by nitrate-dependent oxidation of soluble Fe(II) under different aqueous geochemical conditions; and (ii) characterization of Fe(III) oxide mineralogy in shallow coastal plain aquifer sediments, and changes in Fe(III) oxide abundance/speciation and production of Fe(II)-bearing solid-phases which result from bacterial Fe(III) oxide reduction activity.
Project Details
Project type
Exploratory Research
Start Date
2005-07-20
End Date
2007-03-22
Status
Closed
Released Data Link
Team
Principal Investigator