A radiometric and petrographic interpretation of discrepancies on uranium content in samples collected at Alte Madonie Mounts region (Sicily, Italy)

The main goal of this work is to evaluate a correlation between anomalous Uranium (U) content and petrographic features of some soil and rock samples collected at Alte Madonie Mounts region (Northcentral Sicily, Italy). A total of 41 samples of selected soils and rocks were collected, powdered, dried and sealed in“Marinelli”beakers for 20 days before the measurement to ensure that radioactive equilibrium between 226Ra and 214Bi was reached. Gamma-ray spectrometric analysis was used to quantify radioactivity concentrations. Mineralogical and chemical features of the samples were determined by X-ray Fluorescence (XRF), X-ray Diffractometry (XRD), Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) and Scanning Electron MicroscopeeEnergy Dispersive Spectrometry (SEM-EDS) analyses. The average values of concentrations of 226Ra, 228Ac and 40K were respectively 30, 17 and 227 Bq kg-1 while the greatest values were 134, 59 and 748 Bq kg- 1. Linear relationships were observed between 226Ra, 228Ac and 40K concentrations: the activities of 226Ra and 228Ac were comparable, while those of 40K were about 10 times greater. An exception was highlighted for a group of samples where 226Ra activities were much higher than expectations. Chemical compositions and mineralogical features of the samples have made it possible to justify these anomalies.