SREL Reprint #2880




Sorption and transport of iodine species in sediments from the Savannah River and Hanford Sites

Qinhong Hu1, Pihong Zhao1, Jean E. Moran1, and John C. Seaman2

1Chemical Biology and Nuclear Science Division, Lawrence Livermore National Laboratory,
7000 East Avenue, MS L-231, Livermore, CA 94550 USA
2Advanced Analytical Center for Environmental Sciences, Savannah River Ecology Laboratory,
University of Georgia, Aiken, SC 29802 USA

Abstract: Iodine is an important element in studies of environmental protection and human health, global-scale hydrologic processes and nuclear nonproliferation. Biogeochemical cycling of iodine is complex, because iodine occurs in multiple oxidation states and as inorganic and organic species that may be hydrophilic, atmophilic, and biophilic. In this study, we applied new analytical techniques to study the sorption and transport behavior of iodine species (iodide, iodate, and 4-iodoaniline) in sediments collected at the Savannah River and Hanford Sites, where anthropogenic 129I from prior nuclear fuel processing activities poses an environmental risk. We conducted integrated column and batch experiments to investigate the interconversion, sorption and transport of iodine species, and the sediments we examined exhibit a wide range in organic matter, clay mineralogy, soil pH, and texture.
The results of our experiments illustrate complex behavior with various processes occurring, including iodate reduction, irreversible retention or mass loss of iodide, and rate-limited and nonlinear sorption. There was an appreciable iodate reduction to iodide, presumably mediated by the structural Fe(II) in some clay minerals; therefore, careful attention must be given to potential interconversion among species when interpreting the biogeochemical behavior of iodine in the environment. The different iodine species exhibited dramatically different sorption and transport behavior in three sediment samples, possessing different physico-chemical properties, collected from different depths at the Savannah River Site. Our study yielded additional insight into processes and mechanisms affecting the geochemical cycling of iodine in the environment, and provided quantitives estimates of key parameters (e.g., extent and rate of sorption) for risk assessment at these sites.

Keywords: Iodine, Sorption, Transport, Sediment

SREL Reprint #2880

Hu, Qinhong, P. Zhao, J. E. Moran, and J. Seaman. 2005. Sorption and transport of iodine species in sediments from the Savannah River and Hanford sites. Journal of Contaminant Hydrology 78:185-205.

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