Search Results - "Bargar, J."

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…”
Get full text

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,…”
Get full text

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…”
Get full text

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…”
Get full text

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…”
Get full text

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…”
Get full text

Surface complexation studied via combined grazing-incidence EXAFS and surface diffraction: arsenate on hematite (0001) and (10-12) by Waychunas, G, Trainor, T, Eng, P, Catalano, J, Brown, G, Davis, J, Rogers, J, Bargar, J

“…X-ray diffraction [crystal-truncation-rod (CTR)] studies of the surface structure of moisture-equilibrated hematite reveal sites for complexation not present…”
Get full text

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…”
Get full text

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…”
Get full text

Composition, stability, and measurement of reduced uranium phases for groundwater bioremediation at Old Rifle, CO by Campbell, K.M., Davis, J.A., Bargar, J., Giammar, D., Bernier-Latmani, R., Kukkadapu, R., Williams, K.H., Veramani, H., Ulrich, K.-U., Stubbs, J., Yabusaki, S., Figueroa, L., Lesher, E., Wilkins, M.J., Peacock, A., Long, P.E.

“…► Diffusion, biomass and groundwater solutes retard in-well oxidative dissolution of biogenic UO 2. ► Kinetic limitations and redox buffering may extend the…”
Get full text

Quantitative charge state analysis of manganese biominerals in aqueous suspension using scanning transmission X-ray microscopy (STXM) by Pecher, K., McCubbery, D., Kneedler, E., Rothe, J., Bargar, J., Meigs, G., Cox, L., Nealson, K., Tonner, B.

“…We have applied Scanning Transmission Soft X-ray Microscopy (STXM) to investigate the charge state distribution of Mn in two kinds of Mn-biominerals, Mn…”
Get full text

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…”
Get full text

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…”
Get full text

Surface complexation studied via combined grazing-incidence EXAFS and surface diffraction: arsenate on hematite (0001) and (10–12) by Waychunas, G., Trainor, T., Eng, P., Catalano, J., Brown, G., Davis, J., Rogers, J., Bargar, J.

Get full text

Archeological applications of XAFS: prehistorical paintings and medieval glasses by Farges, F, Chalmin, E, Vignaud, C, Pallot-Frossard, I, Susini, J, Bargar, J, Brown, G E, Menu, M

Get full text

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…”
Get full text

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

Get full text

Characterization of the manganese oxide produced by pseudomonas putida strain MnB1 by Villalobos, Mario, Toner, Brandy, Bargar, John, Sposito, Garrison

“…Manganese oxides form typically in natural aqueous environments via Mn(II) oxidation catalyzed by microorganisms, primarily bacteria, but little is known about…”
Get full text

Mechanisms of Pb(II) Sorption on a Biogenic Manganese Oxide by Villalobos, Mario, Bargar, John, Sposito, Garrison

“…Macroscopic Pb(II) uptake experiments and Pb L3-edge extended X-ray absorption fine structure (EXAFS) spectroscopy were combined to examine the mechanisms of…”
Get full text

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

Get full text