Natural radioactivity measurements and radiological risk evaluation along the Calabrian coast (South Italy)

The knowledge of the natural radioactivity levels and the consequent assessment of public health hazard continues is still an environmental and public concern. Natural radioactivity due to the radioactive families 238U and 232Th and 40K provides the largest contribution to the dose received by the population. Radionuclides concentrations and their decay products are determined by both the rock types and the formation processes. Many pocket beach placers outcrop along the Calabria coastline (South Italy) and are popular as tourist destination for summer holidays. Those sands conatin heavy-mineral with significant concentrations of radioactive elements thus representing a potential danger for the human health due to radiogenic exposure. This study aims to calculate the gamma dose rate, crucial to estimate the radiological risk from external irradiation, and the annual effective dose equivalent (AEDE) received from a three months stay (e.g. summer period) in the investigated beach. The study area is the Pizzo-S. Eufemia beach, produced by the slow dismantling process of the granitoid rocks belong to the Serre Massif that represents the linkage between the southern (Aspromonte Massif and Peloritani Mts) and the northern (Sila Massif and Coastal Chain) sectors of the Calabria-Peloritani Arc. The radioactivity investigation was performed by a high resolution HPGe gamma-ray spectrometer. From the measured gamma-spectra, the average activity concentrations were determined for 226Ra (in secular equilibrium with 238U), 228Ac (in secular equilibrium with 232Th) and 40K. In particular, for 226Ra values ranged from 199.9 ± 19.3 Bq/kg to 266.1 ± 31.3 Bq/kg; for 228Ac, from 1559.9 ± 96.1 Bq/kg to 1832.5 ± 112.7 Bq/kg and for 40K from 238.6 ± 47.5 Bq/kg to 276.6 ± 45.6 Bq/kg. The absorbed dose rate and the effective dose rate outdoor were found to be in the range of 1045 -1240 nGy/h and 0.32 - 0.37 mSv/y, respectively. To provide a full characterization of the heavy-mineral sand a multidisciplinary approach including Scanning Electron Microscopy (SEM-EDX), X-ray powder Diffraction (XRPD) and X Ray Fluorescence (XRF) has been used. The heavy mineral phases identified are magnetite, ilmenite, garnet, rutile and monazite. Bulk chemistry data put in evidence very high amount of Th in the range of 409 - 464 ppm. The results of this study, also compared with values of other locations around the world, can be used as a baseline for future investigations about radioactivity background levels along the Calabria coastline and coupled with epidemiological studies to better evaluate possible health effects on the population.