INTERFACIAL REDUCTION-OXIDATION MECHANISMS GOVERNING FATE AND TRANSPORT OF CONTAMINANTS IN THE VADOSE ZONE
Immobilization of toxic and radioactive metals (e.g., Cr, Tc, and U) in the vadose zone by In Situ Gaseous Reduction (ISGR) using hydrogen sulfide (H2S) is a promising technology for soil remediation. Earlier laboratory and field studies have shown that Cr(VI) can be effectively immobilized by treatment with dilute gaseous H2S. The objective of this project is to characterize the interactions among H2S, the metal contaminants, and soil components. Understanding these interactions is needed to assess the long-term effectiveness of the technology and to optimize the remediation system. Proposed research tasks include: (A) Evaluation of the potential catalytic effect of mineral surfaces on the rate of Cr(VI) reduction by H2S and the rate of H2S oxidation by air; (B) Identification of the reactions of soil minerals with H2S and determination of associated reaction rates; (C) Evaluation of the role of soil water chemistry on the reduction of Cr(VI) by H2S; (D) Assessment of the reductive buffering capacity of H2S reduced soil and the potential for emplacement of long-term vadose zone reactive barriers; (E) Evaluation of the potential for immobilization of Tc and U in the vadose zone by reduction and an assessment of the potential for remobilization by subsequent reoxidation. Through a collaborative effort in the last three years, Tasks A, B, C, and E have been completed, resulting in a much improved understanding of reaction kinetics and mechanisms involved in the Cr(VI)-H2S-O2-Soil System and the treatability for Tc and U. Research on Task C will continue in the one-year period of no-cost extension granted to this project. The result will be submitted to the Department of Energy by October 2003 as a supplement to this report.
- Research Organization:
- University of Missouri-Columbia; Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE Office of Environmental Management (EM) (US)
- DOE Contract Number:
- FG07-99ER15011
- OSTI ID:
- 833523
- Report Number(s):
- EMSP-2002-70088; R&D Project: EMSP 70088; TRN: US200430%%1600
- Resource Relation:
- Other Information: PBD: 1 Jun 2002
- Country of Publication:
- United States
- Language:
- English
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