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.