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Tims Branch, a stream on the U.S. Department of Energy's Savannah River Site located near Aiken, South Carolina, received significant amounts U and Ni as a result of nuclear materials production and refinement. Batch and column experiments were used to evaluate potential remediation scenarios and the migration hazard of U and Ni from flood-plain sediments collected along Tims Branch. Treatment solutions included a low-ionic-strength groundwater surrogate (artificial groundwater), 1 mM ethylenediaminetetraacetic acid (EDTA), 1 mM CaCl2 (pH 3.0), 1 mM Na-phytate (Na12C6H6O24P6), and 1 mM Ca-phytate (CaC6H16O24P6). The two organic phosphate compounds were included in the study because of their potential to serve as in-situ immobilizing agents through the formation of insoluble precipitates in association with the contaminant metals. Repacked columns were leached with a specific treatment solution for 30 pore volumes (PV) at a constant seepage velocity of 8 m day−1 (26 ft day−1). After leaching, solid-phase metal redistribution was evaluated using the toxicity characteristic leaching procedure and sequential extraction methods. For comparison, batch extractions were conducted using a solid-to-solution ratio (1:20) that mimicked the total leaching volume. Despite differences in reaction time, batch and column results were generally consistent. The CaCl2 and EDTA column treatments removed substantial Ni from the labile fractions, i.e., water soluble and exchangeable, as indicted by subsequent extractions for the residual sediments. The effectiveness of the treatments in removing U and Ni was not evident from digestion of the residual column sediments. Ca-phytate significantly reduced U mobility in columns, with evidence for solid-phase redistribution to more recalcitrant fractions. Na-phytate extracted the most U in batch and columns despite inducing colloid dispersion that clogged the column and precluded further leaching after 8–10 PV.
John C. Seaman is an associate research professor with the Savannah River Ecology Laboratory, located on the Savannah River Site and operated for the Department of Energy by the University of Georgia. Seaman received his B.S. (1987) and M.S. (1990) degrees from Texas A&M University in agronomy and soil science, respectively, and his Ph.D. (1994) in environmental soil science from the University of Georgia.Vijay M. Vulava is a research associate with the Department of Earth and Planetary Sciences at the University of Tennessee. He has a B. Tech. degree (1992) and an M.S. degree (1994) in civil and environmental engineering from J.N. Technological University, India, and University of Maryland, United States, respectively, and a Ph.D. (1998) in environmental soil chemistry from the Federal Institute of Technology, Switzerland.
Andrew G. Sowder is a physical scientist with the Office of the Senior Coordinator for Nuclear Safety at the U.S. Department of State. Sowder received his B.S. degree (1990) in optics from the University of Rochester and his Ph.D. (1998) in environmental engineering and science from Clemson University.
Brian Jackson is Director of the Trace Element Analysis Laboratory in the Center for Environmental Sciences at Dartmouth College, Hanover, New Hampshire. Jackson received his B.S. degree (1989) in chemistry from Oxford University and his Ph.D. (1998) in environmental soil science from the University of Georgia.
Sunnie A. Aburime is an associate professor in the Department of Engineering at Clark Atlanta University, Atlanta, Georgia. Aburime received both his B.S. (1978) and M.S. (1982) degrees in chemistry from Jackson State University and his Ph.D. (1986) in environmental engineering from Cornell University.
Paul M. Bertsch is a professor of environmental soil science and director of Savannah River Ecology Laboratory of the University of Georgia. Bertsch received his B.S. degree in plant and soil science from the University of Connecticut, his M.S. degree in soil chemistry from Virginia Tech, and his Ph.D. (1994) in soil physical chemistry and mineralogy from the University of Kentucky.