HR: 15:25h
AN: H23H-07    [Abstracts]
TI: Colloid-Facilitated Transport of Plutonium, Pu(+V), in Saturated Alluvium
AU: * Abdel-Fattah, A I
EM: amr2450@lanl.gov
AF: Los Alamos National Lab, P.O. Box 1663, Mail Stop J514, Los Alamos, NM 87545 United States
AU: Reimus, P W
EM: preimus@lanl.gov
AF: Los Alamos National Lab, P.O. Box 1663, Mail Stop J514, Los Alamos, NM 87545 United States
AU: Ware, S
EM: dware@lanl.gov
AF: Los Alamos National Lab, P.O. Box 1663, Mail Stop J514, Los Alamos, NM 87545 United States
AU: Haga, M H
EM: march@lanl.gov
AF: Los Alamos National Lab, P.O. Box 1663, Mail Stop J514, Los Alamos, NM 87545 United States
AB: Natural groundwater colloids can facilitate the subsurface transport of strongly-sorbing radionuclides, such as plutonium (Pu). To evaluate this mechanism, packed-bed column experiments were conducted, comparing the simultaneous transport of dissolved plutonium (Pu-239) of an initial oxidation state (+V), Pu sorbed onto natural colloids, 190-nm and 500-nm diameter fluorescent Carboxylate Modified Latex (CML) microspheres, and tritium, as a conservative tracer, in saturated alluvium. The experiments were conducted in two columns having slightly different porosities at two flow rates, resulting in average linear velocities, v, of 0.6 to 3.65 cm/hr in one column and 0.57 to 2.85 cm/hr in the other. In all experiments, Pu associated with natural colloids transported through alluvium essentially unretarded, while dissolved Pu was entirely retained. These results were consistent with the strong sorption of Pu to alluvium and the negligible desorption from natural colloids, observed in separate batch experiments, over time scales exceeding those of the column experiments. The breakthrough of natural colloids preceded that of tritium in all experiments, indicating a slightly smaller effective pore volume for the colloids. The enhancement of colloids' transport over tritium decreased with v, implying ~40% enhancement at v = 0. The 500-nm CML microspheres were significantly attenuated in the column experiments compared to the 190-nm microspheres, which exhibited slightly more attenuation than natural colloids.
UR: http://pearl1.lanl.gov/external/INC/geochemistry/geochemistry.htm
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
DE: 1875 Unsaturated zone
DE: 1045 Low-temperature geochemistry
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting