title: Effect of fulvic acid surface coatings on plutonium sorption and desorption kinetics on goethite.
abstract: The rates and extent of plutonium (Pu) sorption and desorption onto mineral surfaces are important parameters for predicting Pu mobility in subsurface environments. The presence of natural organic matter, such as fulvic acid (FA), may influence these parameters. We investigated the effects of FA on Pu(IV) sorption/desorption onto goethite in two scenarios: when FA was (1) initially present in solution or (2) found as organic coatings on the mineral surface. A low pH was used to maximize FA coatings on goethite. Experiments were combined with kinetic modeling and speciation calculations to interpret variations in Pu sorption rates in the presence of FA. Our results indicate that FA can change the rates and extent of Pu sorption onto goethite at pH 4. Differences in the kinetics of Pu sorption were observed as a function of the concentration and initial form of FA. The fraction of desorbed Pu decreased in the presence of FA, indicating that organic matter can stabilize sorbed Pu on goethite. These results suggest that ternary Pu-FA-mineral complexes could enhance colloid-facilitated Pu transport. However, more representative natural conditions need to be investigated to quantify the relevance of these findings.
authors.affiliation: Glenn T. Seaborg Institute, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , P.O. Box 808, Livermore, California 94550, United States.
authors.forename: Ruth M
authors.initials: RM
authors.lastname: Tinnacher
authors.forename: James D
authors.initials: JD
authors.lastname: Begg
authors.forename: Harris
authors.initials: H
authors.lastname: Mason
authors.forename: James
authors.initials: J
authors.lastname: Ranville
authors.forename: Brian A
authors.initials: BA
authors.lastname: Powell
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Wong
authors.forename: Annie B
authors.initials: AB
authors.lastname: Kersting
authors.forename: Mavrik
authors.initials: M
authors.lastname: Zavarin
mesh_terms: D000327:Adsorption; D001578:Benzopyrans / Q000737:chemistry*; D004463:Ecology; D058085:Iron Compounds / Q000737:chemistry*; D007700:Kinetics; D008903:Minerals / Q000737:chemistry*; D011005:Plutonium / Q000737:chemistry*
chemical_list: D001578:Benzopyrans; D058085:Iron Compounds; D008903:Minerals; C094886:goethite; D011005:Plutonium; C005023:fulvic acid