The Influence of different Fe(III) Phases and the Effect of Sulfate Reduction on the Simultaneous Bioreduction of Iron and Uranium
EMSL Project ID
30465
Abstract
Biostimulation of Fe(III) and/or sulfate reducing microorganisms by addition of acetate can effectively reduce U(VI). However, U(VI) removal from groundwater was hindered in field trials at the Rifle IFC when the system changed from Fe(III)- to sulfate reduction. Column experiments, using Rifle-site sediment have not seen a decrease of U(VI) reduction after the onset of sulfate reduction. To gain new insights into these processes, and provide feedback to the Rifle IFC project (funded by DOE-OBERs ERSP program), we propose to conduct a rigorous study of the biogeochemical dynamics during the transition of iron- to sulfate reduction, its effect on the U(VI) bioreduction and the stability of U(IV). We have divided this 3-year effort into three tasks/objectives. Objective 1 (year1). Determine the effect of sulfate reduction on iron and uranium reduction rates. This will be done by analyzing via Mössbauer spectroscopy changes in Fe-57 goethite that was amended to eight columns with Rifle sediment. Columns were sacrificed at 10-day intervals bracketing the onset of sulfate reduction at day 35. Due to the sensitivity Mössbauer to Fe-57, these experiments will yield precise measurements of Fe phase-change before and after the onset of sulfate reduction and provide new insights on how sulfate reduction affects iron reduction. Objective 2 (year 2). Gain predictive capabilities of the rate and sequence at which different iron phases present at Rifle are reduced, the phases that are formed, and determine if the bulk iron reduction rate can be predicted based on the kinetics of the reduction of the individual Fe(III) phases. We will conduct a batch kinetic experiments to study the reduction of individual Fe(III) phases (Al-goethite, magnetite, hematite, silicate Fe(III)) identified for the Rifle sediments, as well as identifying the new Fe(III)/Fe(II) phases formed via Mössbauer and X-Ray diffraction. Objective 3 (year 3). Spatially map the reduced uranium, iron, and sulfur, identify the individual phases formed as well as their stability as the system is reoxidized. Seven sediment columns with Rifle sediment will be biostimulated past sulfate reduction. One column will be sacrificed and Rifle groundwater (DO ~ 0.2 mg/l) will be supplied to the other six, which will be sacrificed at two week intervals. Sediments will be collected and analyzed for extractable Fe(III)/Fe(II) and AVS. Sediment samples will then be shipped to EMSL for SEM analyses and Mössbauer spectroscopy to determine how Fe(III) phases are changing during the reoxidation phase, and to determine with what phases (specially Fe and S) U is associated with, and how this association changes with time of reoxidation.
This study is a collaborative effort between Dr. Peter Jaffe at Princeton University and Dr. Ravi Kukkadapu from EMSL. The work conducted at EMSL will be the collection of Mössbauer spectra of the Fe-57 phases, microscopy (SEM-FIB and TEM), and ICP-MS. Column operation, batch experiments, analytical methods for the effluent/extract analysis, X-ray diffraction will be conducted at Princeton University. A graduate student or postdoctoral fellow from Dr. Jaffes laboratory will travel to EMSL to assist Dr. Kukkadapu with the analysis on site.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2008-09-30
End Date
2009-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Moon HS, L McGuinness, RK Kukkadapu, AD Peacock, J Komlos, Jr., L Kerkhoff, PE Long, and PR Jaffe. 2010. "Microbial Reduction of Uranium under Iron- and Sulfate-reducing Conditions: Effect of Amended Goethite on Microbial Community Composition and Dynamics." Water Research 44(14):4015-4028.