Characterization of a typical urban soil in terms of natural radionuclide content. The case study of a university campus

A first comprehensive survey was carried out in a university campus in Italy in order to investigate in terms of natural elements an area where medium-high values of natural radiation are expected because of its peculiar geological features. The content of terrestrial radionuclides in 20 topsoil samples from the campus was determined with the aim to provide an important database of the soil characteristics. ²²⁶Ra, ²³²Th, and ⁴⁰K concentrations were analysed by High Purity Germanium (HPGe) gamma-ray spectrometer in order to determine the background levels of natural radionuclides characteristics of the original area. The mean concentrations of radionuclides in the investigated soil samples ranged from 58.95 ± 4.20 to 158.05 ± 19.95 Bq kg^-1 for ²²⁶Ra, from 72.28 ± 7.61 to 146.00 ± 22.27 Bq kg^-1 for ²³²Th and, for ⁴⁰K, from 550.76 ± 33.24 to 1367.50 ± 18.73 Bq kg^-1. The radiological hazard indices, including radium equivalent activity, external hazard index, annual effective dose, absorbed dose rate, lifetime excess cancer risk, were also evaluated and compared with global averages, revealing values above the worldwide ones. Finally, a spatial modelling methodology of the site-specific radionuclides levels as graphical tool for the monitoring of the potential land redevelopment of urban soils was proposed.