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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.
retrogradation, water migration and redistribution between crumb and crust and between starch and gluten) where molecular interactions occur at multiple temporal and spatial scales [ 2 – 4 ]. Mechanisms of bread staling are not yet completely understood and not
terms of fragility [ 23 ]. The different behavior of conductivity, on the one hand, and of dipolar relaxations, on the other hand, with respect to effects of silica, can be explained by considering the different spatial scale of the two types of
al., 2013. Detection of long-term landscape changes and trajectories in a Pannonian sand region: comparing land-cover and habitat-based approaches at two spatial scales. Community Ecology. 14 . (2) 219
Ekschmitt, K. et al., 2003. On the quality of soil biodiversity indicators: abiotic and biotic parameters as predictors of soil faunal richness at different spatial scales. Agriculture, Ecosystems and Environment. 98 . 273--283. On
ORVÁTH , F. , B AGI , I. & M OLNÁR , Zs. , 2013 . Detection of long-term landscape changes and trajectories in a Pannonian sand region: comparing land-cover and habitat-based approaches at two spatial scales . Community Ecology . 14 . ( 2 ) 219
