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Title: Retention and chemical speciation of uranium in an oxidized wetland sediment from the Savannah River Site

Uranium speciation and retention mechanism onto Savannah River Site (SRS) wetland sediments was studied using batch (ad)sorption experiments, sequential extraction desorption tests and U L{sub 3}-edge X-ray absorption near-edge structure (XANES) spectroscopy of contaminated wetland sediments. U was highly retained by the SRS wetland sediments. In contrast to other similar but much lower natural organic matter (NOM) sediments, significant sorption of U onto the SRS sediments was observed at pH <4 and pH >8. Sequential extraction tests indicated that the U(VI) species were primarily associated with the acid soluble fraction (weak acetic acid extractable) and NOM fraction (Na-pyrophosphate extractable). Uranium L3- edge XANES spectra of the U-retained sediments were nearly identical to that of uranyl acetate. The primary oxidation state of U in these sediments was as U(VI), and there was little evidence that the high sorptive capacity of the sediments could be ascribed to abiotic or biotic reduction to the less soluble U(IV) species. The molecular mechanism responsible for the high U retention in the SRS wetland sediments is likely related to the chemical bonding of U to organic carbon.
Authors:
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Publication Date:
OSTI Identifier:
1108731
Report Number(s):
SRNL-MS-2013-00093
Journal ID: ISSN 0265-931X
DOE Contract Number:
DE-AC09-08SR22470
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Environmental Radioactivity; Journal Volume: 131
Publisher:
Elsevier
Research Org:
SRS
Sponsoring Org:
DOE
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES Wetland sediments, uranium, chemical speciation, retention