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Partitioning and Availability of Uranium and Nickel in Contaminated Riparian Sediments
Author(s) -
Sowder Andrew G.,
Bertsch Paul M.,
Morris Pamela J.
Publication year - 2003
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2003.8850
Subject(s) - environmental chemistry , lability , chemistry , sediment , total organic carbon , dissolved organic carbon , organic matter , riparian zone , nickel , contamination , solubility , carbon fibers , microcosm , uranium , aqueous solution , fraction (chemistry) , geology , ecology , metallurgy , paleontology , biochemistry , materials science , organic chemistry , habitat , composite number , composite material , biology
ABSTRACT The effects of iron oxides and organic matter on the partitioning and chemical lability of U and Ni were examined for contaminated riparian sediments from the U.S. Department of Energy's Savannah River Site. In sequential extractions of four sediments that ranged from 12.7 to 82.2 g kg −1 in organic carbon, U was found almost exclusively in moderately labile fractions (93% in acid‐soluble + organically bound). Nickel was distributed across all operationally defined fractions, including substantial amounts in the very labile fractions (4–15% in water‐soluble + exchangeable), noncrystalline and crystalline iron oxides (38–49%), and in the nonlabile residual fraction (25–34%). Aqueous U concentrations in 1:1 sediment–water extracts were highly correlated to dissolved organic carbon (DOC) ( R 2 = 0.96; p < 0.0001) and ranged from 29 to 410 μg L −1 Aqueous concentrations of Ni exceeded U by two to three orders of magnitude (124–2227 μg L −1 ) but were not correlated with DOC ( R 2 = 0.04; p = 0.53). Partitioning and solubility trends suggest that Ni availability is controlled primarily by iron‐oxide phases, whereas U availability is dominated by naturally occurring organic carbon. Discrete mineral phases were also identified as nonlabile reservoirs of anthropogenic metals. In spite of comparably high sediment concentrations, Ni appears to be significantly more available than U in riparian sediments and therefore warrants greater consideration in terms of environmental consequences (i.e., transport, biological uptake, and toxicity).