HR: 1340h
AN: B13A-1036    [Abstracts]
TI: Anaerobic, Nitrate-Dependent Fe(II) Oxidation Under Advective Flow
AU: * Weber, K A
EM: kweber@nature.berkeley.edu
AF: University of California, 271 Koshland Hall, Berkeley, CA 94806
AU: Coates, J D
EM: jcoates@nature.berkeley.edu
AF: University of California, 271 Koshland Hall, Berkeley, CA 94806
AB: Microbially-catalyzed nitrate-dependent Fe(II) oxidation has been identified as a ubiquitous biogeochemical process contributing to anaerobic iron redox cycling in sedimentary environments. Most probable number enumeration revealed nitrate-dependent Fe(II) oxidizing microbial communities in groundwater and subsurface sediments in the order of 0 - 2.04 x 10³ cells mL^-1 and 2.39 x 10² - 1.17 x 10³ cells (g wet sediment)^-1, respectively. The efficacy of nitrate-dependent Fe(II) oxidation under advective flow was evaluated in a meso-scale column reactor packed with sterile low iron sand amended with subsurface sediments collected from the NABIR FRC background field site (10% mass/mass). Continuous flow of minimal medium mimicked the natural groundwater. Periodic FeCl₂ and nitrate injections over a period of 49 days resulted in the retention of 95% of the iron (290 mmol). Extraction of solid-phase Fe revealed a net increase in Fe(III) of 160 mmol above background Fe(III) content indicating that 55% of the injected Fe(II) was oxidized. Differential solubility analysis of 0.5M HCl-extractable Fe and 3M HCl-extractable Fe indicated that the oxidation product was crystalline in nature as only 20% was soluble in 0.5M HCl. This formation of crystalline biogenic Fe(III) oxides is consistent with previous studies. Periodic injections of nitrate and acetate did not result in significant changes in Fe(II) or Fe(III) throughout a control column. Together these results demonstrate that native subsurface sediments harbor microbial communities capable of nitrate-dependent Fe(II) oxidation under advective flow. The biogenic formation of reactive Fe(III) oxide minerals capable of immobilizing heavy metals and radionuclides presents a plausible bioremediative strategy for contaminated subsurface environments.
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0418 Bioremediation
DE: 0461 Metals
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
SC: Biogeosciences [B]
MN: Fall Meeting 2005