HR: 1340h
AN: B23B-1052    [Abstracts]
TI: Quantification of Iron Reoxidation in Microbially Reduced Sediments
AU: Komlos, J
EM: jkomlos@princeton.edu
AF: Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544 United States
AU: * Jaffe, P R
EM: jaffe@princeton.edu
AF: Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544 United States
AU: Kukkadapu, R K
EM: mailto:Ravi.Kukkadapu@pnl.gov
AF: Pacific Northwest National Laboratory, P.O. Box 999, K8-96, Richland, WA 99352 United States
AU: Zachara, J M
EM: john.zachara@pnl.gov
AF: Pacific Northwest National Laboratory, P.O. Box 999, K8-96, Richland, WA 99352 United States
AB: Microbial reduction of iron has been shown to be important in the transformation and remediation of contaminated sediments. Re-oxidation of microbially reduced iron may occur in sediments that experience cycles of oxidation and reduction and can thus impact the fate and extent of contaminant remediation, yet little research has been performed to quantitatively measure the rate of iron re-oxidation and changes in iron phases. The purpose of this research was to measure rates and extent of iron oxidation in a flow-through column filled with previously reduced sediment. In addition, the iron phases in the re-oxidized sediment were compared to the original sediment as well as the biologically reduced sediment. A unsaturated background sediment containing both Fe(III)-oxides and silicate Fe(II)/Fe(III) was biologically reduced in phosphate buffered (PB) medium at circumneutral pH utilizing the indigenous microbial population of the sediment in a long-term (500 day) column experiment in which acetate was supplied as the electron donor. Long-term iron reduction resulted in partial reduction of silicate Fe(III) and some goethite biotransformation, based on M”ssbauer spectroscopy study. There was no evidence of vivianite formation -- a ferrous phosphate. This reduced sediment was treated with an oxygenated PB solution in a flow-through column resulting in the re-oxidation of 38% of the biogenic Fe(II), mainly silicate Fe(II). Additional batch experiments show that the Fe(III) in the reoxidized sediment was more quickly reduced compared to the initial sediment, which was attributed to the higher Mn(VI) concentrations in the original sediment. This indicates that re-oxidation of sediment not only regenerated Fe(III) but also enhanced iron reduction compared to the initial sediment and may be a viable method to extend iron reducing conditions during in-situ bioremediation scenarios.
DE: 0409 Bioavailability: chemical speciation and complexation
DE: 0418 Bioremediation
DE: 0489 Trace element cycling (4875)
SC: Biogeosciences [B]
MN: Fall Meeting 2005