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| Titel |
Uranium in surface soils: an easy-and-quick assay combining X-ray diffraction and fluorescence qualitative data |
| VerfasserIn |
M. O. Figueiredo, T. P. Silva, M. J. Batista, J. Leote, M. L. Ferreira, V. Limpo |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250023762
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| Zusammenfassung |
| Portugal has been a uranium-producer since the beginning of the last century. The
uranium-rich area of Alto Alentejo, East-central Portugal, was identified more than fifty years
ago [1]. Almost all the uranium-bearing mineralization occurs in schistose rocks of the
contact metamorphic aureole produced by intrusion of the Hercynian monzonitic granite of
Alto Alentejo into the pre-Ordovitian schist-greywacke complex forming deposits of vein and
dissemination type.
The Nisa uranium-reservoir, situated at the sharp border of a large and arch shaped granite
pluton, was identified in 1957 [2] but its exploitation was considered economically
impracticable until recently. However, its existence and the accumulated detritus of these
prospect efforts are a concern for local populations [3].
A study of the near-surface soils close to the Nisa reservoir was therefore undertaken to
assess the uranium retention by adsorption on clay components under the form of uranyl ions,
[UO2]2+ [4-6] and its eventual release into the aquifer groundwater.
As an attempt to very quickly appraise the presence of uranium in as-collected near-surface
sediment samples a combination of laboratory X-ray techniques was designed: X-ray
diffraction (XRD) to identify the mineral phases and roughly estimate its relative proportion
plus X-ray fluorescence spectrometry in wavelength dispersive mode (XRF-WDS) to
ascertain the presence of uranium and tentatively evaluate its content by comparison with
selected chemical components of the soil.
A description of the experimental methodology adopted for the implemented easy-and-quick
uranium assay is presented. Obtained results compare quite well to the data of certified
time-consuming analytical tests of uranium in those soil samples.
[1] L. Pilar (1966) Conditions of formation of Nisa uranium deposit (in Portuguese).
Comunic. Serv. Geol. Portugal, tomo L, 50-85.
[2] C. Gonçalves & J.V. Teixeira Lopes (1971) Uranium deposit of Nisa: geological
aspects of its discovery and valorisation (in Portuguese). Internal Rept., JEN, 20
pp.
[3] http://www.naturtejo.com
[4] J.A. Davis et al. (2006) Processes affecting transport of uranium in a suboxic aquifer.
Phys. Chem. of the Earth 31, 548-555.
[5] Y. Arai et al. (2007) Spectroscopic evidence for uranium bearing precipitates in
Vadose zone sediments at the Hanford 300-Area site. Environ. Sci. Technol. 41,
4633-4639.
[6] A. Kremleva, S. Krüger & N. Rösch (2008) Density functional model studies of uranyl
adsorption on (001) surfaces of kaolinite. Langmuir 24, 9515-9524. |
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