Radiological assessment, mineralogy and geochemistry of the heavy-mineral placers from the Calabrian coast (South Italy)

Abstract

The presence of heavy minerals, including radionuclides such as 238U and 232Th, in the beach placers outcropping along the western Calabrian coast (South Italy) has been investigated in order to single out the contribution from natural sources to the total radiation level. Assessing the human health radiation risk for these areas is of great importance due to their main touristic destination. With the aim of characterizing the natural radionuclides contents of the Calabrian sands, the correlations existing between their mineralogical and geochemical features and those of the parent rocks have been studied by measuring the sand radionuclides concentrations and decay products and by calculating the outdoor effective dose rate. The radioactivity in the Calabrian beach sediments is for the most part attributed to monazite and, in turn, to the high amount of Th (in the 409–464 ppm range), and is a function of the rock types and of the formation processes. The outdoor dose and effective dose rates for an exposure period of three months are in the range 1045–1240 nGy/h and 0.32–0.37 mSv/y, respectively. Although these values are remarkably higher than the corresponding average world values, they fall within the limits fixed by the Italian legislation, assuming individuals that spend three summer months on the beach. The results obtained for this area of the Southern Italy coastlines can be used as a baseline for future investigations concerning radioactivity background levels, also in other regions. Moreover, the coupling of the present findings with those of epidemiological studies will allow gaining a better evaluation of possible health effects on the population.