HR: 0800h
AN: H31D-0433    [Abstracts]
TI: Unraveling the Fate and Transport of SrEDTA-2 and Sr+2 in Hanford Sediments
AU: * Pace, M N
EM: pacem@ornl.gov
AF: Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6038 United States
AU: Mayes, M A
EM: mayesma@ornl.gov
AF: Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6038 United States
AU: Jardine, P M
EM: jardinepm@ornl.gov
AF: Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6038 United States
AU: Mehlhorn, T L
EM: mehlhorntl@ornl.gov
AF: Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6038 United States
AU: Liu, Q G
EM: q-liu@northwestern.edu
AF: Northwestern University, 633 Clark Street, Evanston, IL 60208 United States
AU: Yin, X L
EM: yinx@ornl.gov
AF: Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6038 United States
AB: Accelerated migration of strontium-90 has been observed in the vadose zone beneath the Hanford tank farm. The goal of this paper is to provide an improved understanding of the hydrogeochemical processes that contribute to strontium transport in the far-field Hanford vadose zone. Laboratory scale batch, saturated packed column experiments, and an unsaturated transport experiment in an undisturbed core were conducted to quantify geochemical and hydrological processes controlling Sr+2 and SrEDTA-2 sorption to Hanford flood deposits. After experimentation, the undisturbed core was disassembled and samples were collected from different bedding units as a function of depth. Sequential extractions were then performed on the samples. It has been suggested that organic chelates such as EDTA may be responsible for the accelerated transport of strontium due to the formation of stable anionic complexes. Duplicate batch and column experiments performed with Sr+2 and SrEDTA-2 suggested that the SrEDTA-2 complex was not stable in the presence of soil and rapid dissociation allowed strontium to be transported as a divalent cation. Batch experiments indicated a decrease in sorption with increasing rock:water ratios, whereas saturated packed column experiments indicated equal retardation in columns of different lengths. This difference between the batch and column experiments is primarily due to the difference between equilibrium conditions where dissolution of cations may compete for sorption sites versus flowing conditions where any dissolved cations are flushed through the system minimizing competition for sorption sites. Unsaturated transport in the undisturbed core resulted in significant Sr+2 retardation despite the presence of physical nonequilibrium. Core disassembly and sequential extractions revealed the mass wetness distribution and reactive mineral phases associated with strontium in the core. Overall, results indicated that strontium will most likely be transported through the Hanford far-field vadose zone as a divalent cation.
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting