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IMPACT OF REDOX DISEQUILIBRIA ON CONTAMINANT TRANSPORT AND REMEDIATION IN SUBSURFACE SYSTEMS
Citation:
Ford*, R AND R T. Wilkin*. IMPACT OF REDOX DISEQUILIBRIA ON CONTAMINANT TRANSPORT AND REMEDIATION IN SUBSURFACE SYSTEMS. Presented at Synchrotron Environmental Science Workshop, Argonne, IL, May 04, 2004.
Impact/Purpose:
To inform the public.
Description:
Partitioning to mineral surfaces exerts significant control on inorganic contaminant transport in subsurface systems. Remedial technologies for in-situ treatment of subsurface contamination are frequently designed to optimize the efficiency of contaminant partitioning to solid substrates either through emplacement of reactive solids or manipulation of subsurface chemistry to generate new reactive solid components from parent materials. Current research at the Ground Water and Ecosystems Restoration Division is focused towards developing a process-level understanding of the partitioning reactions that immobilize arsenic and chromium onto natural or engineered subsurface solids. Examples to be discussed include partitioning of arsenic to iron- and sulfur-bearing minerals in a contaminated shallow wetland aquifer system and immobilization of chromium during corrosion of zero valent iron materials installed in subsurface reactive barrier systems. The efficiency and stability of these partitioning processes is governed, in part, by reactions that take place across sharp redox chemical gradients. Coupling system scale chemical measurements with mineralogical characterization in space and time have been employed to better understand the salient reactions controlling contaminant uptake onto subsurface solids. Synchrotron-based X-ray absorption spectroscopy has recently been employed to better define observed heterogeneity in both trace and bulk element oxidation state and structural chemistry.