Metal
extractability from contaminated SRS sediments: comparison of column and
batch results
J. C. Seaman1, V. M. Vulava2, A. G. Sowder3, B. P. Jackson4, S. A. Aburime5 and P. M. Bertsch6
1
Savannah River Ecology Laboratory, University of Georgia, PO Drawer E,
Aiken, South Carolina 29802; seaman@srel.edu
2
Savannah River Ecology Laboratory, University of Georgia, PO Drawer E,
Aiken, South Carolina 29802
3 Savannah River Ecology Laboratory, University of Georgia,
PO Drawer E, Aiken, South Carolina 29802
4 Department of Earth Sciences and Department of Chemistry,
HB6105, Dartmouth College, Hanover, NH 03755
5 Savannah River Ecology Laboratory, University of Georgia,
PO Drawer E, Aiken, South Carolina 29802
6 Savannah River Ecology Laboratory, University of Georgia,
PO Drawer E, Aiken, South Carolina 29802
Abstract
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, solidphase metal redistribution
was evaluated using the toxicity characteristic leaching procedure and
sequential extraction methods. For comparison, batch extractions were
conducted using a solid-tosolution 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.
SREL
Reprint #2910
Seaman, J. C., V. M. Vulava, A. G. Sowder, B. P. Jackson, S. A. Aburime and P. M. Bertsch 2005. Metal extractability from contaminated SRS sediments: comparison of column and batch results. Environmental Geosciences 12:235-242.
