Assessment of Natural Radioactivity and Radiological Risks in River Sediments from Calabria (Southern Italy)

This study was developed to carry out a comprehensive radiological assessment of natural radioactivity for river sediment samples from Calabria, southern Italy, and to define a baseline background for the area on a radiation map. In the studied area, elevated levels of natural radionuclides are expected, due to the outcropping acidic intrusive and metamorphic rocks from which the radioactive elements derive. To identify and quantify the natural radioisotopes, ninety river sediment samples from nine selected coastal sampling points (ten samples for each point) were collected as representative of the Ionian and the Tyrrhenian coastline of Calabria. The samples were analyzed using a gamma ray spectrometer equipped with a high-purity germanium (HPGe) detector. The values of mean activity concentrations of Ra-226, Th-232 and K-40 measured for the studied samples are (21.3 +/- 6.3) Bq kg(-1), (30.3 +/- 4.5) Bq kg(-1) and (849 +/- 79) Bq kg(-1), respectively. The calculated radiological hazard indices showed average values of 63 nGy h(-1) (absorbed dose rate), 0.078 mSv y(-1) (effective dose outdoors), 0.111 mSv y(-1) (effective dose indoors), 63 Bq kg(-1) (radium equivalent), 0.35 (H-ex), 0.41 (H-in), 0.50 (activity concentration index) and 458 mu Sv y(-1) (Annual Gonadal Equivalent Dose, AGED). In order to delineate the spatial distribution of natural radionuclides on the radiological map and to identify the areas with low, medium and high radioactivity values, the Surfer 10 software was employed. Finally, the multivariate statistical analysis was performed to deduce the interdependency and any existing relationships between the radiological indices and the concentrations of the radionuclides. The results of this study, also compared with values of other locations of the Italian Peninsula characterized by similar local geological conditions, can be used as a baseline for future investigations about radioactivity background in the investigated area.