Thorium and uranium rapid quantification in soil with portable X-ray fluorescence

This study aims to evaluate the thorium (Th) and uranium (U) quantification in soil employing a commercial routine in a portable X-ray fluorescence (pXRF) spectrometer. Certified reference materials (CRMs), as well as a soil sample set, were measured by pXRF and gamma-ray spectrometry. The pXRF results showed that the thorium average detection and quantification limits (in mg kg-1) were 3.3 +/- 0.5 and 11.0 +/- 1.7, respectively. The uranium values were 3.0 +/- 0.4 and 9.9 +/- 1.3. Quantitative pXRF results for Th were in accordance with the reference reported for most CRMs analyzed, and the same accordance was obtained in the comparison with gamma-ray spectrometry results for the soil sample set. However, U results were overestimated by pXRF when compared both with the CRM-reported values and the gamma-ray spectrometry results. In conclusion, the tested pXRF commercial routine may be a viable technique to identify variations in natural Th levels in soil but needs to be used with caution to identify and quantify U. Th and U quantification in soil with portable X-ray fluorescence (pXRF) was tested against reference materials and gamma spectrometric analysis. The tested pXRF commercial routine proved to be a viable and rapid technique to quantify Th natural levels in soil. pXRF commercial routine needs to be used with precaution to identify U natural levels in soil.