Actions for Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone [electronic resource].

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Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone [electronic resource].

Published
Washington, D.C. : United States. Dept. of Energy. Office of Science, 2008.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Additional Creators
University of Missouri--Columbia, United States. Department of Energy. Office of Science, and United States. Department of Energy. Office of Scientific and Technical Information
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Summary
There are many soil contamination sites at the Department of Energy (DOE) installations that contain radionuclides and toxic metals such as uranium (U), technetium (Tc), and chromium (Cr). Since these contaminants are the main 'risk drivers' at the Hanford site (WA) and some of them also pose significant risk at other DOE facilities (e.g., Oak Ridge Reservation - TN; Rocky Flats - CO), development of technologies for cost effective site remediation is needed. Current assessment indicates that complete removal of these contaminants for ex-situ disposal is infeasible, thus in-situ stabilization through reduction to insoluble species is considered one of the most important approaches for site remediation. In Situ Gaseous Reduction (ISGR) is a technology developed by Pacific Northwest National Laboratory (PNNL) for vadose zone soil remediation. The ISGR approach uses hydrogen sulfide (H₂S) for reductive immobilization of contaminants that show substantially lower mobility in their reduced forms (e.g., Tc, U, and Cr). The technology can be applied in two ways: (i) to immobilize or stabilize pre-existing contaminants in the vadose zone soils by direct H₂S treatment, or (ii) to create a permeable reactive barrier (PRB) that prevents the migration of contaminants. Direct treatment involves reduction of the contaminants by H₂S to less mobile species. Formation of a PRB is accomplished through reduction of ferric iron species in the vadose zone soils by H₂S to iron sulfides (e.g., FeS), which provides a means for capturing the contaminants entering the treated zone. Potential future releases may occur during tank closure activities. Thus, the placement of a permeable reactive barrier by ISGR treatment can be part of the leak mitigation program. Deployment of these ISGR approaches, however, requires a better understanding of the immobilization kinetics and mechanisms, and a better assessment of the long-term effectiveness of treatment. The primary objective of this project was to understand the complex interactions among the contaminants (i.e., Cr, Tc, and U), H₂S, and various soil constituents. The reaction with iron sulfide is also the focus of the research, which could be formed from iron oxide reduction by hydrogen sulfide. Factors controlling the reductive immobilization of these contaminants were identified and quantified. The results and fundamental knowledge obtained from this project shall help better evaluate the potential of in situ gaseous treatment to immobilize toxic and radioactive metals examined.
Report Numbers
E 1.99:951276
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Note
Published through SciTech Connect.
05/12/2008.
"MU Project #00000975/00003626"
Principal Investigator: Baolin Deng, Uni; Co-Principal Investigator: Silvia Sabine; Co-Principal Investigator: Edward C. Tho; Co-Principal Investigator: Jeff Terry, I.
Type of Report and Period Covered Note
Final; 09/01/2003 - 12/17/2007
Funding Information
FG02-03ER63616
View MARC record | catkey: 14131857