Confocal micrometer-scale X-ray fluorescence and X-ray absorption fine structure studies of uranium speciation in a tertiary sediment from a waste disposal natural analogue site.
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Publication Details
Output type: Journal article
Author list: Denecke MA, Janssens K, Proost K, Rothe J, Noseck U.
Publisher: American Chemical Society
Publication year: 2005
Journal: Environmental Science and Technology (0013-936X)
Volume number: 39
Issue number: 7
Start page: 2049
End page: 2058
Number of pages: 10
ISSN: 0013-936X
eISSN: 1520-5851
URL: http://dx.doi.org/10.1021/es048644k
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Open access status: closed
Abstract
Investigations by micrometer-scale X-ray fluorescence and X-ray absorption fine structure (micro-XRF and micro-XAFS) recorded in a confocal geometry on a bore core section of a uranium-rich tertiary sediment are performed in order to assess mechanisms leading to immobilization of the uranium during diagenesis. Results show uranium to be present as a tetravalent phosphate and that U(IV) is associated with As(V). Arsenic present is either As(V) or As(O); we found no evidence for As(III). The As(O) is observed to be intimately associated with the surface of Fe(II) nodules and likely arsenopyrite. A hypothesis for the mechanism of uranium immobilization is proposed, where arsenopyrite acted as reductant of groundwater-dissolved U(VI), leading to precipitation of less soluble U(IV) and thereby forming As(V).
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