GEOC 55 |
| Pihong Zhao1, Yunwei Sun2, Qinhong Hu1, and Jean E. Moran1. (1) Chemical Biology and Nuclear Science Division, Lawrence Livermore National Laboratory, 7000 East Avenue, L-231, Livermore, CA 94550, (2) Environmental Science Division, Lawrence Livermore National Laboratory, 7000 East Avenue, L-646, Livermore, CA 94550 |
| The fission product iodine-129, a long-lived and presumably mobile element with a potentially large role in long-term dose assessment, is a radioactive contaminant that exhibits complex transport behavior in nature. Negatively charged iodide species are reportedly highly mobile in water-mediated natural systems. On the other hand, iodide also reacts with many natural substances under various conditions, resulting in its partitioning among solid, liquid, and gaseous phases in the geologic environment. We studied the reactive transport of iodide in clay minerals by conducting sorption experiments using columns and reactive stir-cells. Tritium was used as a conservative tracer in solutions of stable iodine spiked with radioactive iodine-125, so that we were able to examine changes in the partitioning coefficients of iodide onto kaolinite and illite in iodide concentrations ranging from 10-13 to 10-5 M. Both kaolinite and illite showed a measurable sorption of iodide at low concentrations. To better understand the iodide sorption mechanism, reactive-transport models coupled with chemical reactions were used to describe our experimental systems. Thermodynamic parameters, including partitioning coefficients and reaction rate constants, were derived from our analytical solutions. |
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Colloid-Facilitated Transport of Contaminants in the Subsurface: The Life and Death of a Colloid
1:00 PM-5:20 PM, Monday, March 29, 2004 Marriott -- Marquis NW, Oral
Division of Geochemistry |