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 using hydrogen sulfide (H2S) is a promising technology the U.S. Department of Energy (DOE) is developing for soil remediation. Earlier laboratory studies have shown that Cr(VI) in a number of soil samples can be effectively immobilized by treatment with dilute gaseous H2S. A field test has also been completed that resulted in 70% immobilization of Cr(VI). 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