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Influence of Microscopic Mass Transfer on the Reactivity and Stability of Uranium


EMSL Project ID
4691a

Abstract

This proposed project will investigate microscopic U(VI) mass transfer under influence of biogeochemical reactions in representative Hanford U(VI)-contaminated sediments. Recent research by our group has revealed that solid phase U(VI) exists in complex, microscopic, intragrain domains in Hanford sediments. The fate and transport of in-ground U(VI) is expected to be controlled by the coupling of intragrain U(VI) desorption/dissolution with intergrain biogeochemical reactions through diffusive mass transfer that controls mass exchange between the intra- and inter- grain regions. The research strives to understand this coupled process under chemical/activity gradients as driven by three types of biogeochemical reactions that are relevant to engineered remediation and natural attenuation: 1) aqueous U(VI) complexation; 2) microbially induced reduction of U(VI) to U(IV); and 3) ligand-promoted U(VI) dissolution and reprecipitation. Batch and flow-through experiments will be performed to explore U(VI) mass transfer under influence of biogeochemical reactions. Microscopic and spectroscopic characterization will be used to provide insights on process mechanisms. The experiments and characterization will provide data to: 1) quantify the rates of microscopic U(VI) mass transfer and its coupling with biogeochemical reactions; 2) develop numerical models for description of individual and coupled processes; and 3) evaluate the stability and reactivity of in-ground U(VI).

Project Details

Project type
Exploratory Research
Start Date
2007-03-14
End Date
2008-03-23
Status
Closed

Team

Principal Investigator

Chongxuan Liu
Institution
Pacific Northwest National Laboratory

Team Members

Robert Ewing
Institution
Iowa State University

Zheming Wang
Institution
Pacific Northwest National Laboratory

John Zachara
Institution
Pacific Northwest National Laboratory

Related Publications

Ewing, R. P., Q. Hu, and C. Liu (2010), Scale dependence of intragranular porosity, tortuosity, and diffusivity, Water Resour. Res., 46, W06513, doi:10.1029/2009WR008183
Kerisit SN, and C Liu. 2010. "Molecular Simulation of the Diffusion of Uranyl Carbonate Species in Aqueous Solution." Geochimica et Cosmochimica Acta 74(17):4937-4952. doi:10.1016/j.gca.2010.06.007
Liu C, JM Zachara, L Zhong, SM Heald, Z Wang, BH Jeon, and JK Fredrickson. 2009. "Microbial Reduction of Intragrain U(VI) in Contaminated Sediment." Environmental Science & Technology 43(13):4928-4933. doi:10.1021/es8029208
Liu C, JM Zachara, N Qafoku, and Z Wang. 2008. "Scale-dependent desorption of uranium from contaminated subsurface sediments." Water Resources Research 44:W08413. doi:10.1029/2007WR006478
Wang Z, JM Zachara, C Liu, PL Gassman, AR Felmy, and SB Clark. 2008. "A cryogenic fluorescence spectroscopic study of uranyl carbonate, phosphate, and oxyhydroxide minerals." Radiochimica Acta 96(9-11):591-598. doi:10.1524/ract.2008.1541