Search Results - "Bargar, J R"

Mechanisms of Uranium Interactions with Hydroxyapatite:  Implications for Groundwater Remediation by Fuller, C. C, Bargar, J. R, Davis, J. A, Piana, M. J

“…The speciation of U(VI) sorbed to synthetic hydroxyapatite was investigated using a combination of U LIII-edge XAS, synchrotron XRD, batch uptake measurements,…”
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Determination of Uranyl Incorporation into Biogenic Manganese Oxides Using X-ray Absorption Spectroscopy and Scattering by Webb, S. M, Fuller, C. C, Tebo, B. M, Bargar, J. R

“…Βiogenic manganese oxides are common and an important source of reactive mineral surfaces in the environment that may be potentially enhanced in bioremediation…”
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Molecular-Scale Characterization of Uranium Sorption by Bone Apatite Materials for a Permeable Reactive Barrier Demonstration by Fuller, C. C, Bargar, J. R, Davis, J. A

“…Uranium binding to bone charcoal and bone meal apatite materials was investigated using U LIII-edge EXAFS spectroscopy and synchrotron source XRD measurements…”
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Local and Global Sensitivity Analysis of a Reactive Transport Model Simulating Floodplain Redox Cycling by Perzan, Z., Babey, T., Caers, J., Bargar, J. R., Maher, K.

“…Reactive transport models (RTMs) are essential tools that simulate the coupling of advective, diffusive, and reactive processes in the subsurface, but their…”
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Geochemical, mineralogical and microbiological characteristics of sediment from a naturally reduced zone in a uranium-contaminated aquifer by Campbell, K.M., Kukkadapu, R.K., Qafoku, N.P., Peacock, A.D., Lesher, E., Williams, K.H., Bargar, J.R., Wilkins, M.J., Figueroa, L., Ranville, J., Davis, J.A., Long, P.E.

“…► U, sulfate, and Fe reduction has occurred in a zone of naturally reduced sediment. ► Reduced U has accumulated in the naturally reduced sediment. ► Reduction…”
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A New Modeling Framework for Multi-Scale Simulation of Hydraulic Fracturing and Production from Unconventional Reservoirs by Birkholzer, J. T., Morris, J., Bargar, J. R., Brondolo, F., Cihan, A., Crandall, D., Deng, H., Fan, W., Fu, W., Fu, P., Hakala, A., Hao, Y., Huang, J., Jew, A. D., Kneafsey, T., Li, Z., Lopano, C., Moore, J., Moridis, G., Nakagawa, S., Noël, V., Reagan, M., Sherman, C. S., Settgast, R., Steefel, C., Voltolini, M., Xiong, W., Ciezobka, J.

“…This paper describes a new modeling framework for microscopic to reservoir-scale simulations of hydraulic fracturing and production. The approach builds upon a…”
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XAFS and Bond-Valence Determination of the Structures and Compositions of Surface Functional Groups and Pb(II) and Co(II) Sorption Products on Single-Crystal α-Al2O3 by Bargar, J.R., Towle, S.N., Brown, G.E., Parks, G.A.

“…The structures and compositions of Pb(II) adsorption complexes and surface binding sites on α-Al2O3(0001) and (1&1macr;02) surfaces were investigated in the…”
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Uranyl adsorption and surface speciation at the imogolite–water interface: Self-consistent spectroscopic and surface complexation models by Arai, Yuji, McBeath, M., Bargar, J.R., Joye, J., Davis, J.A.

“…Macro- and molecular-scale knowledge of uranyl (U(VI)) partitioning reactions with soil/sediment mineral components is important in predicting U(VI) transport…”
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In situ characterization of Mn(II) oxidation by spores of the marine Bacillus sp. strain SG-1 by Bargar, J.R, Tebo, B.M, Villinski, J.E

“…Microbial oxidation of Mn(II) and subsequent precipitation of insoluble, reactive Mn(IV) oxides are primary sources of these solid phases in the environment…”
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Surface Precipitation of Co(II)(aq) on Al2O3 by Towle, Steven N., Bargar, John R., Brown, Gordon E., Parks, George A.

“…Surface precipitation is an important process in many areas of science and technology, including modeling contaminant segregation from groundwater to solid…”
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Local and Global Sensitivity Analysis of a Reactive Transport Model Simulating Floodplain Redox Cycling by Perzan, Z., Babey, T., Caers, J., Bargar, J. R., Maher, K.

“…Abstract Reactive transport models (RTMs) are essential tools that simulate the coupling of advective, diffusive, and reactive processes in the subsurface, but…”
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EXAFS, XANES and in-situ SR-XRD characterization of biogenic manganese oxides produced in sea water by Bargar, J R, Webb, S M, Tebo, B M

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Uranium redox transition pathways in acetate-amended sediments by Bargar, John R., Williams, Kenneth H., Campbell, Kate M., Long, Philip E., Stubbs, Joanne E., Suvorova, Elenal I., Lezama-Pacheco, Juan S., Alessi, Daniel S., Stylo, Malgorzata, Webb, Samuel M., Davis, James A., Giammar, Daniel E., Blue, Lisa Y., Bernier-Latmani, Rizlan

“…Redox transitions of uranium [from U(VI) to U(IV)] in low-temperature sediments govern the mobility of uranium in the environment and the accumulation of…”
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Determination of uranyl incorporation into biogenic manganese oxides using x-ray absorption spectroscopy and scattering by Webb, S M, Bargar, J R, Tebo, B M

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Structural dependence of Mn complexation by siderophores: Donor group dependence on complex stability and reactivity by Harrington, James M., Parker, Dorothy L., Bargar, John R., Jarzecki, Andrzej A., Tebo, Bradley M., Sposito, Garrison, Duckworth, Owen W.

“…Siderophores traditionally have been viewed as solely being involved in the biogeochemical cycling of Fe(III). This paradigm, however, ignores the diverse…”
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Structural characterization of terrestrial microbial Mn oxides from Pinal Creek, AZ by Bargar, John R., Fuller, Christopher C., Marcus, Matthew A., Brearley, Adrian J., Perez De la Rosa, M., Webb, Samuel M., Caldwell, Wendel A.

“…The microbial catalysis of Mn(II) oxidation is believed to be a dominant source of abundant sorption- and redox-active Mn oxides in marine, freshwater, and…”
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Mononuclear U(IV) complexes and ningyoite as major uranium species in lake sediments by Morin, G., Mangeret, A., Othmane, G., Stetten, L., Seder-Colomina, M., Brest, J., Ona-Nguema, G., Bassot, S., Courbet, C., Guillevic, J., Thouvenot, A., Mathon, O., Proux, O., Bargar, J.R.

“…Natural attenuation of uranium in subsurface environments is usually assigned to immobilisation processes due to microbially mediated reduction of U(VI)…”
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The exceptionally stable cobalt(III)–desferrioxamine B complex by Duckworth, Owen W., Bargar, John R., Jarzecki, Andrzej A., Oyerinde, Oyeyemi, Spiro, Thomas G., Sposito, Garrison

“…The biogeochemistry of trivalent iron, manganese, and cobalt in the oceans is dominated by soluble complexes formed with high-affinity organic ligands that are…”
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Surface complexation of Pb(II) at oxide-water interfaces: II. XAFS and bond-valence determination of mononuclear Pb(II) sorption products and surface functional groups on iron oxides by Bargar, J.R., Brown, G.E., Parks, G.A.

“…Pb(II) sorption on goethite and hematite powders was studied at room temperature as a function of pH (6–8), sorption density (2–10 μmoles/m 2), and [Pb] eq…”
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Spectroscopic Confirmation of Uranium(VI)−Carbonato Adsorption Complexes on Hematite by Bargar, John R, Reitmeyer, Rebecca, Davis, James A

“…Evaluating societal risks posed by uranium contamination from waste management facilities, mining sites, and heavy industry requires knowledge about uranium…”
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