Using gamma-ray spectrometry and geostatistics for assessing geochemical behaviour of radioactive elements in the Lese catchment (southern Italy)

Gamma-rays emitted from the ground surface relate to the primary mineralogy and geochemistry of the bedrock, and the secondary weathered materials. This information can contribute significantly to an understanding of the geochemical and pedogenetic history of a region. The main aim of this paper was to study the relationship between ground gamma-ray data and basement geochemistry in the Lese catchment (Calabria, southern Italy) and to map them, using geostatistics, from in-situ gamma-ray spectrometry. The activities of naturally occurring radionuclides were measured at 179 locations by in situ measurements of 40K, 238U, 232Th and total radioactivity and by using gamma-ray spectrometry. Then a multi-Gaussian approach was used to explore and map the activity of naturally occurring radionuclides (40K, 238U, 232Th) and total radioactivity. Locations and lithological compositions of bedrock appear to be responsible for variations in radioelement activity. From radiometric investigations it has emerged that the natural activity of radionuclides in rocks and soils is not equally distributed, but rather influenced by the different geologic conformations of the various examined areas. As expected, high values of 40K, 232Th and total radioactivity were found in rocks of plutonic origin and low values in sedimentary rocks. Uranium radioactivity behaved in a constant manner in these lithologies, albeit with some differences in clayey sites particularly rich in Uranium.