HR: 0830h
AN: H51C-1050    [PDF]
TI: Uranium Transport in Subsurface Materials: An Experimental Analysis of the Effects of pH and Inorganic Carbonate Concentration
AU: * Harrington, S
EM: harrinst@engr.oregonstate.edu
AF: Environmental Engineering Oregon State University, 202 Apperson Hall, Corvallis, OR 97331 United States
AU: Wood, B
EM: brian.wood@oregonstate.edu
AF: Environmental Engineering Oregon State University, 202 Apperson Hall, Corvallis, OR 97331 United States
AB: Uranium is a long-lived radionuclide, and has been found in high concentrations in various groundwater systems leading to human health concerns. Uranium in the (VI) valence state forms many mobile hydroxide and carbonate complexes. Immobilization of uranium by reduction to U(IV), either by direct biological enzymatic processes or by the production of a reducing ``biobarrier'', has been proposed as one possible mechanism for remediating uranium contamination. In this preliminary work, we have examined U(VI) transport and sorption in natural sediments (on iron oxide mineral phases) under various inorganic carbon and pH conditions. To determine the dependence of U(VI) transport on these variables, a series of six experiments were conducted in a closed one-dimensional column system utilizing three pH (high, neutral, and low) and two carbonate concentrations (high and low). Pulses of U(VI) were introduced into the column at a fixed pore velocitiy, and samples were collected using an auto sampler to develop breakthrough curves. Effective transport and kinetic sorption parameters were determined by inverse fitting the data using the code CXTFIT. Speciation of uranium for each experiment was determined utilizing the code MINEQL+. The dependence of U(VI) adsorption on pH and carbonate concentration have been quantified under conditions of flow and transport, and it appears that at groundwater-relevant pore water velocities, an equilibrium model may not accurately describe the sorption process.
DE: 1010 Chemical evolution
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2003 Fall Meeting