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

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.