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Title: Microscopic Controls on the Desorption/Dissolution of Sorbed U(VI) and Their Influence on Reactive Transport

Abstract

A sizable groundwater U plume exists in Hanford's 300 A resulting from the disposal of fuel rod dissolution wastes containing Al, Cu, and U to the vadose zone. This project is studying U-contaminated samples collected along a flow path from the waste source to the Columbia River. Three primary objectives are being pursued: (1) To develop microscopic models for U desorption/adsorption in sediments along the flow path including both geochemical reaction and diffusive mass transport processes. (2) To parameterize the microscopic models with appropriate laboratory measurements and data within context of a dual continuum, reactive transport model (DCM). (3) To apply the parameterized DCM to laboratory columns of different size and sediment texture for testing of scaling hypotheses.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA; Stanford University, Stanford, CA; US Geological Survey, Menlo Park, CA; Los Alamos National Laboratory (LANL), Los Alamos, NM; Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
895617
Report Number(s):
ERSD-86748-2006
R&D Project: ERSD 86748; TRN: US0700509
DOE Contract Number:
FG07-02ER63498; FG07-02ER63495
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 54 ENVIRONMENTAL SCIENCES; 38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; COLUMBIA RIVER; DISSOLUTION; FUEL RODS; PLUMES; SEDIMENTS; TESTING; TEXTURE; TRANSPORT; WASTES

Citation Formats

Zachara, John m., Brown, Gordon E., Davis, James A., Lichtner, Peter C., and Steefel, C.I. Microscopic Controls on the Desorption/Dissolution of Sorbed U(VI) and Their Influence on Reactive Transport. United States: N. p., 2006. Web. doi:10.2172/895617.
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Zachara, John m., Brown, Gordon E., Davis, James A., Lichtner, Peter C., & Steefel, C.I. Microscopic Controls on the Desorption/Dissolution of Sorbed U(VI) and Their Influence on Reactive Transport. United States. doi:10.2172/895617.
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Zachara, John m., Brown, Gordon E., Davis, James A., Lichtner, Peter C., and Steefel, C.I. Thu . "Microscopic Controls on the Desorption/Dissolution of Sorbed U(VI) and Their Influence on Reactive Transport". United States. doi:10.2172/895617. https://www.osti.gov/servlets/purl/895617.
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@article{osti_895617,
title = {Microscopic Controls on the Desorption/Dissolution of Sorbed U(VI) and Their Influence on Reactive Transport},
author = {Zachara, John m. and Brown, Gordon E. and Davis, James A. and Lichtner, Peter C. and Steefel, C.I.},
abstractNote = {A sizable groundwater U plume exists in Hanford's 300 A resulting from the disposal of fuel rod dissolution wastes containing Al, Cu, and U to the vadose zone. This project is studying U-contaminated samples collected along a flow path from the waste source to the Columbia River. Three primary objectives are being pursued: (1) To develop microscopic models for U desorption/adsorption in sediments along the flow path including both geochemical reaction and diffusive mass transport processes. (2) To parameterize the microscopic models with appropriate laboratory measurements and data within context of a dual continuum, reactive transport model (DCM). (3) To apply the parameterized DCM to laboratory columns of different size and sediment texture for testing of scaling hypotheses.},
doi = {10.2172/895617},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 2006},
month = {Thu Jun 01 00:00:00 EDT 2006}
}
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DOI:  10.2172/895617
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  • ; ; ; ...
    A number of published studies have sought to understand geochemical kinetic process of uranium (U) that are relevant to nuclear waste sites and repositories by studying the weathering of U ore bodies and downgradient transport of weathering products. Such studies have provided important insights on processes operative over many thousand to millions of years. This project also seeks knowledge on the geochemical kinetics of U, but for shorter in-ground time periods (e.g., 20-50 years) relevant to DOE legacy waste sites. Several representative field sites were selected for intense study at Hanford as part of EMSP research to provide: (1) fundamentalmore » insights on intermediate duration geochemical events of U controlling fate and transport, and (2) key scientific information needed for remedial action assessment and informed decision making. The site discussed in this poster is the 300 A uranium plume. This plume is located at the south end of Hanford and discharges directly to the Columbia River. The plume resulted from the discharge of fuels fabrication wastes (nitric acid solutions containing U and Cu) and cladding dissolution wastes (basic sodium aluminate) to the North and South Process Ponds between 1943 and 1975 near the Columbia River. A Kd-based remedial action assessment fifteen years ago predicted that the plume would dissipate to concentrations below the DWS within 10 y. As a result of this assessment, an interim, MNA remedial decision was agreed to by DOE and state/federal regulators. It has been 15 y since the above assessment, and groundwater concentrations have not decreased (attenuated) as projected. Stakeholders are now demanding remedial intervention, and DOE seeks science-based conceptual and numeric models for more accurate future projections. The objectives are: (1) Identify the chemical speciation (e.g., adsorption complexes precipitates), mineral residence, and physical location of contaminant U in a depth sequence of sediments from the disposal source to groundwater. (2) Measure desorption/dissolution rates of sorbed U(VI), quantify controlling factors, and develop descriptive kinetic models to provide a scientific basis to forecast U(VI) fluxes to groundwater, future plume dynamics, and long-term contaminant attenuation. (3) Establish reaction networks and determine geochemically/ physically realistic reaction parameters to drive state-of-the-art reactive transport modeling of U in vadose zone pore fluids and groundwater.« less

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  • The research in FY04 was focused in five specific topics: (1) U(VI) sorption on microbially and abiotically reduced sediments, (2) oxidation of biogenic U(IV) in presence of Fe(II), (3) U(VI) reduction by reduced sediments, (4) kinetics of U(VI) sorption on natural sediments under conditions of flow, and (5) NMR imaging of S. onidensis biofilms in porous media. Two manuscripts are currently in review, and another five (or four?) manuscripts are currently in preparation for submission.

  • The research in Y02 was focused on the design and execution of experiments in the abiotic reduction of U(VI) by simulated biogenic Fe(II) in porous medium under conditions of flow, and on the development of appropriate descriptive theory. Because the project started only in February of this year, we are reporting some work in progress.

  • Subsurface contamination by metals and radionuclides represent some of the most challenging remediation problems confronting the Department of Energy (DOE) complex. In situ remediation of these contaminants by dissimilatory metal reducing bacteria (DMRB) has been proposed as a potential cost effective remediation strategy. The primary focus of this research is to determine the mechanisms by which the fluxes of electron acceptors, electron donors, and other species can be controlled to maximize the transfer of reductive equivalents to the aqueous and solid phases. The proposed research is unique in the NABIR portfolio in that it focuses on (i) the role ofmore » flow and transport in the initiation of biostimulation and the successful sequestration of metals and radionuclides [specifically U(VI)], (ii) the subsequent reductive capacity and stability of the reduced sediments produced by the biostimulation process, and (iii) the potential for altering the growth of biomass in the subsurface by the addition of specific metabolic uncoupling compounds. A scientifically-based understanding of these phenomena are critical to the ability to design successful bioremediation schemes. The laboratory research will employ Shewanella putrefaciens (CN32), a facultative DMRB that can use Fe(III) oxides as a terminal electron acceptor. Sediment-packed columns will be inoculated with this organism, and the reduction of U(VI) by the DMRB will be stimulated by the addition of a carbon and energy source in the presence of Fe(III). Separate column experiments will be conducted to independently examine: (1) the importance of the abiotic reduction of U(VI) by biogenic Fe(II); (2) the influence of the transport process on Fe(III) reduction and U(VI) immobilization, with emphasis on methods for controlling the fluxes of aqueous species to maximize uranium reduction; (3) the reductive capacity of biologically-reduced sediments (with respect to re-oxidation by convective fluxes of O2 and NO3-) and the long-term stability of immobilized uranium mineral phases after bioremediation processes are complete, and (4) the ability for metabolic uncoupling compounds to maintain microbial growth while limiting biomass production. The results of the laboratory experiments will be used to develop mathematical descriptive models for the coupled transport and reduction processes.« less