In situ examination of uranium contaminated soil particles by micro-X-ray absorption and micro-fluorescence spectroscopies |
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Authors: | D B Hunter P M Bertsch |
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Institution: | (1) Advanced Analytical Center for Environmental Sciences, University of Georgia, Savannah River Ecology Laboratory, 29801 Aiken, SC, USA |
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Abstract: | Two complimentary spectroscopic techniques, X-ray absorption and fluorescence spectroscopy have been conducted at spatial
scales of 1 to 25 μm on uranium contaminated soil sediments collected from two former nuclear materials processing facilities
of the DOE: Fernald, OH and Savannah River Site, SC. A method of imbedding particles in a non-reactive Si polymer was developed
such that individual particles could be examined before and after extraction with a wide range of chemicals typically used
in sequential extraction techniques and others proposed forex situ chemical intervention technologies. Using both the micro-X-ray fluorescence (XRF) and micro-X-ray Absorption Near Edge Structure
(XANES) techniques, both elemental and oxidation state distribution maps were generated on individual particles before and
following chemical extraction. XANES can determine the relative proportion of U(VI) and U(IV) in phases comprising individual
particles before and after extraction and showed that greater than 85% of the uranium existed as hexavalent U(VI). Fluorescence
spectra of contaminated particles containing mainly U(VI) revealed populations of uranyl hydroxide phases and demonstrated
the relative efficacy and specificity of each extraction method. Correlation of XAS and fluorescence data at micron scales
provides information of U oxidation state as well as chemical form in heterogeneous samples. |
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