title: In situ bioremediation of uranium with emulsified vegetable oil as the electron donor.
abstract: A field test with a one-time emulsified vegetable oil (EVO) injection was conducted to assess the capacity of EVO to sustain uranium bioreduction in a high-permeability gravel layer with groundwater concentrations of (mM) U, 0.0055; Ca, 2.98; NO3(-), 0.11; HCO3(-), 5.07; and SO4(2-), 1.23. Comparison of bromide and EVO migration and distribution indicated that a majority of the injected EVO was retained in the subsurface from the injection wells to 50 m downgradient. Nitrate, uranium, and sulfate were sequentially removed from the groundwater within 1-2 weeks, accompanied by an increase in acetate, Mn, Fe, and methane concentrations. Due to the slow release and degradation of EVO with time, reducing conditions were sustained for approximately one year, and daily U discharge to a creek, located approximately 50 m from the injection wells, decreased by 80% within 100 days. Total U discharge was reduced by 50% over the one-year period. Reduction of U(VI) to U(IV) was confirmed by synchrotron analysis of recovered aquifer solids. Oxidants (e.g., dissolved oxygen, nitrate) flowing in from upgradient appeared to reoxidize and remobilize uranium after the EVO was exhausted as evidenced by a transient increase of U concentration above ambient values. Occasional (e.g., annual) EVO injection into a permeable Ca and bicarbonate-containing aquifer can sustain uranium bioreduction/immobilization and decrease U migration/discharge.
authors.affiliation: Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6038, United States. watsondb@ornl.gov
authors.forename: David B
authors.initials: DB
authors.lastname: Watson
authors.forename: Wei-Min
authors.initials: WM
authors.lastname: Wu
authors.forename: Tonia
authors.initials: T
authors.lastname: Mehlhorn
authors.forename: Guoping
authors.initials: G
authors.lastname: Tang
authors.forename: Jennifer
authors.initials: J
authors.lastname: Earles
authors.forename: Kenneth
authors.initials: K
authors.lastname: Lowe
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Gihring
authors.forename: Gengxin
authors.initials: G
authors.lastname: Zhang
authors.forename: Jana
authors.initials: J
authors.lastname: Phillips
authors.forename: Maxim I
authors.initials: MI
authors.lastname: Boyanov
authors.forename: Brian P
authors.initials: BP
authors.lastname: Spalding
authors.forename: Christopher
authors.initials: C
authors.lastname: Schadt
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Kemner
authors.forename: Craig S
authors.initials: CS
authors.lastname: Criddle
authors.forename: Philip M
authors.initials: PM
authors.lastname: Jardine
authors.forename: Scott C
authors.initials: SC
authors.lastname: Brooks
mesh_terms: D001673:Biodegradation, Environmental; D004583:Electrons; D007501:Iron / Q000737:chemistry; D008345:Manganese / Q000737:chemistry; D008697:Methane / Q000737:chemistry; D010938:Plant Oils / Q000737:chemistry*; D014501:Uranium / Q000737:chemistry*; D014675:Vegetables / Q000737:chemistry*
chemical_list: D010938:Plant Oils; D008345:Manganese; D014501:Uranium; D007501:Iron; D008697:Methane