2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 8
Presentation Time: 9:45 AM

Attenuation of Hexavalent Chromium in the Vadose Zone and Regional Aquifer, Los Almaos, New Mexico

DING, Mei1, LONGMIRE, Patrick A.2, VANIMAN, David T.3, BROXTON, David E.3, KATZMAN, Danny4, REARICK, Michael5, SPALL, Brian N.6, BARGAR, John R.7 and WEBB, Samuel M.8, (1)EES-6 Group, Earth and Environmental Science Division, Los Alamos National Lab, Los Alamos, NM 87545, (2)Hydrology, Geochemistry, and Geology Group, Los Alamos National Laboratory, Mail Stop D469, Los Alamos, NM 87545, (3)Earth Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM 87545, (4)Water Stewardship Program, Los Alamos National Laboratory, MS M992, Los Alamos, NM 87545, (5)Earth and Environmental Sciences Division, Los Alamos National Laboratory, Mail Stop D469, Los Alamos National Laboratory, Los Alamos, NM 87545, (6)School of Earth and Environmental Sciences, Washington State University, Webster Physical Science Building 1228, Pullman, WA 99164-2812, (7)Stanford Synchrotron Radiation Lightsource, 2575 Sand Hill Rd, Menlo Park, CA 94025, (8)Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Ctr, Building 137, MS 69, 2575 Sand Hill Road, Menlo Park, CA 94025, mding@lanl.gov

Adsorption coefficients of Cr(VI) in vadose zone and aquifer materials were measured as part of ongoing environmental investigations that address fate and transport of chromium(VI) originating in Sandia Canyon, Los Alamos, NM. Here, we present our initial findings of the characterization of vadose zone and regional aquifer materials with regard to their Cr(VI) retention capacity. We also present an assessment of the role of naturally occurring adsorbents present in the subsurface media such as clay minerals, ferric (oxy)hydroxide, and calcium carbonate on the adsorption of Cr(VI) under relevant field conditions. The results of our studies (1) directly assess the relation between mineralogical and geochemical characterization and transport behavior of Cr(VI) in the hydrogeological setting of interest, (2) provide site-specific adsorption and precipitation parameters obtained through experiments to refine the fate and transport modeling of chromium in the vadose zone and regional aquifer, and (3) reveal the mechanisms of chromate retention processes within the geomedia of interest.