HR: 1330h
AN: H22A-0903    [PDF]
TI: Evaluating Cr(VI) Partitioning in the Vadose Zone Under Variably Saturated Conditions
AU: * Seaman, J C
EM: seaman@srel.edu
AF: SREL-Univ. of Georgia, Drawer E, Aiken, SC 29802 United States
AU: Hutchison, J
AF: SREL-Univ. of Georgia, Drawer E, Aiken, SC 29802 United States
AU: Singer, J
AF: SREL-Univ. of Georgia, Drawer E, Aiken, SC 29802 United States
AU: Aburime, S
AF: Clark Atlanta University, Department of Engineering 223 J.P. Brawley Drive, Atlanta, GA 30314 United StatesAB: A series of steady state solute transport experiments were conducted using the Unsaturated Flow Apparatus (UFA) and a vacuum-based column system using a coarse-textured, Fe-oxide coated soil material at various volumetric moisture contents ranging from 0.07-0.43. Once steady state flow was achieved with a surrogate groundwater solution, the columns were leached with a solution containing a common groundwater contaminant, hexavalent chromium, 0.1 or 0.5 mM Cr(VI), and tritium as a conservative tracer. At predetermined intervals, effluent samples were collected for Cr(VI) and tritium analysis. After full Cr(VI) breakthrough, the inlet solution was switched back to the groundwater surrogate and Cr(VI) was leached from the column. Experiment duration was much less and a greater range in water contents was achieved when using the UFA compared to the more traditional vacuum based system. Breakthrough curves were modeled using CXTFIT assuming equilibrium conditions since significant immobile water was not detected for the coarse material, based on the tritium data, regardless of the moisture content. As expected, Retardation (R) increased with decreasing water content, but water content had little effect on the calculated distribution coefficient. Despite the vast difference in residence times for the two column systems, similar levels of Cr(VI) sorption were observed, indicating that the retention mechanisms for Cr(VI) were not kinetically limited.
DE: 1832 Groundwater transport
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2003 Fall Meeting