title: U(VI) bioreduction with emulsified vegetable oil as the electron donor--model application to a field test.
abstract: We amended a shallow fast-flowing uranium (U) contaminated aquifer with emulsified vegetable oil (EVO) and subsequently monitored the biogeochemical responses for over a year. Using a biogeochemical model developed in a companion article (Tang et al., Environ. Sci. Technol.2013, doi: 10.1021/es304641b) based on microcosm tests, we simulated geochemical and microbial dynamics in the field test during and after the 2-h EVO injection. When the lab-determined parameters were applied in the field-scale simulation, the estimated rate coefficient for EVO hydrolysis in the field was about 1 order of magnitude greater than that in the microcosms. Model results suggested that precipitation of long-chain fatty acids, produced from EVO hydrolysis, with Ca in the aquifer created a secondary long-term electron donor source. The model predicted substantial accumulation of denitrifying and sulfate-reducing bacteria, and U(IV) precipitates. The accumulation was greatest near the injection wells and along the lateral boundaries of the treatment zone where electron donors mixed with electron acceptors in the groundwater. While electron acceptors such as sulfate were generally considered to compete with U(VI) for electrons, this work highlighted their role in providing electron acceptors for microorganisms to degrade complex substrates thereby enhancing U(VI) reduction and immobilization.
authors: Environmental Sciences Division, Oak Ridge National Laboratory, PO Box 2008, MS-6038, Oak Ridge, Tennessee 37831-6038, United States. tangg@ornl.gov
authors: Guoping
authors: G
authors: Tang
authors: David B
authors: DB
authors: Watson
authors: Wei-Min
authors: WM
authors: Wu
authors: Christopher W
authors: CW
authors: Schadt
authors: Jack C
authors: JC
authors: Parker
authors: Scott C
authors: SC
authors: Brooks
mesh_terms: D000085:Acetates / Q000378:metabolism; D001419:Bacteria / Q000378:metabolism; D001673:Biodegradation, Environmental; D018533:Biomass; D004583:Electrons; D004655:Emulsions / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D005285:Fermentation; D005990:Glycerol / Q000378:metabolism; D006868:Hydrolysis; D007501:Iron / Q000378:metabolism; D008697:Methane / Q000096:biosynthesis; D008954:Models, Biological; D009566:Nitrates / Q000378:metabolism; D010084:Oxidation-Reduction; D010938:Plant Oils / Q000378:metabolism*; D013431:Sulfates / Q000378:metabolism; D014501:Uranium / Q000302:isolation & purification*
chemical_list: D000085:Acetates; D004655:Emulsions; D005227:Fatty Acids; D009566:Nitrates; D010938:Plant Oils; D013431:Sulfates; D014501:Uranium; D007501:Iron; D008697:Methane; D005990:Glycerol