Colloid-Facilitated Transport of Radioactive Cations in the Vadose Zone: .....

Colloid-facilitated transport of radioactive cations in the vadose zone: Field experiments at Oak Ridge National Laboratory The overall objective of this research is to provide an improved fundamental understanding and predictive capability of colloid-facilitated transport of radioactive cations from the column-scale to the field. Column and field experimental investigations on the vadose-zone transport of colloids, organic matter, and associated DOE contaminants (90Sr and 137Cs) will utilize soils and facilities at the Oak Ridge National Laboratory. Specifically, laboratory and field experiments will be coupled with transport modeling to pursue the following detailed objectives; (1)evaluation of the impact of inorganic colloids and organic matter to the facilitation of radioactive cation transport in the vadose zone, (2)assessment of the role of adsorption and desorption kinetics in the facilitated transport of radioactive cations, (3)examination of the effects of rainfall and infiltration dynamics and in the facilitated transport of radioactive cations, (4)exploration of the role of soil heterogeneity and preferential flow paths (e.g., macropores) on the facilitated transport of radioactive cations, and (5)development of a mathematical model of facilitated transport of contaminants in the vadose zone that accurately incorporates pore-scale and column-scale processes with the practicality of predicting transport with readily available parameters. This research will contribute significantly to better understanding of facilitated transport of radioactive cations in the vadose zone, and that better understanding of the process will lead to better predictions of the importance of facilitated transport in assessing the risk of contaminants of interest to DOE. (see hardcopy for complete abstract)