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

摘要

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 (North-central 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 ~(226)Ra and ~(214)Bi 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 Microscope - Energy Dispersive Spectrometry (SEM-EDS) analyses. The average values of concentrations of ~(226)Ra, ~(228)Ac and ~(40)K 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 ~(226)Ra, ~(228)Ac and ~(40)K concentrations: the activities of ~(226)Ra and ~(228)Ac were comparable, while those of ~(40)K were about 10 times greater. An exception was highlighted for a group of samples where ~(226)Ra activities were much higher than expectations. Chemical compositions and mineralogical features of the samples have made it possible to justify these anomalies.