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 226Ra, 232Th and 40K 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 (Hex), 0.41 (Hin), 0.50 (activity concentration index) and 458 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.