Uranium in surface soils: An easy-and-quick assay combining X-ray diffraction and X-ray fluorescence qualitative data

An environmental concern for uranium-producing countries is the possible dissemination of this radionuclide in soils nearby mineral deposits, even non-exploited ones. This is the case of the Nisa uranium deposit in Alto-Alentejo, East-central Portugal, considered economically impracticable after prospecting efforts that left behind masses of accumulated debris. A first step towards the assessment of uranium retention through adsorption by soil clay minerals was a test study of a topsoils profile close to the Nisa deposit. With the aim of quickly appraising the presence of this element in a large set of as-collected soil samples, a combination of laboratory X-ray techniques was applied: X-ray diffraction to identify the main mineral phases and X-ray fluorescence spectrometry in wavelength dispersive mode to certify the presence of uranium and roughly estimate its comparative content. A description of the so-implemented easy-and-quick uranium assay is presented and critically evaluated. Obtained results compare well to the chemical data from certified analytical tests of uranium performed over a set of eleven test soil samples. (C) 2010 Elsevier B.V. All rights reserved.