CONICET | Buscador de Institutos y Recursos Humanos

Soil is the most important source of natural radiation, containing trace quantities of radioactive elements, whose concentrations depend on the local geology of each region [1]. Moreover, the Southern Hemisphere was polluted by the debris originated in the South Pacific and middle Atlantic atmospheric nuclear weapon tests [2], being the 137Cs the most prominent fission product isotope in the Earth crust. The information about the presence and migration of radionuclides is crucial to fully understand the long-term behaviour in the environment, the uptake by flora and fauna including the human food chain, potential contribution to groundwater and to assessing the radiation dose to the population [1, 2]. In this context, a systematic compilation and analysis of radionuclide activity data of 40K, 226Ra and 137Cs in soils of Argentina, Brazil, Uruguay, Venezuela and Chile [3] is presented, together with the calculated absorbed dose rate at 1m above the ground, that depends on the concentration of radionuclides in the soil [1, 2]. The surface activity concentrations for 226Ra for Brazil are higher than the global mean values [1, 2]. The 232Th activity data of Argentina are closer to the worldwide values while the Brazilian ones are quite higher than these values [1,2]. In the case of Uruguay, it is not possible to extract conclusions yet due to the insufficiency and dispersion of data. The 40K data are higher than the UNSCEAR mean data in most of the cases, and fit into the worldwide range with some exceptions. The major absorbed dose rate is find in Brazil, whereas the values determined for Uruguay are lower than the mean value determined in Argentina. For adults, and analogous to the UNSCEAR reported value [1]. The calculated annual committed effective doses due to terrestrial external exposure resulted slightly higher that the UNSCEAR reported values. The analysis of the 137Cs inventories allows concluding that the experimental data do not follow the latitudinal band deposition predictions proposed by UNSCEAR [1,2]. It is worth to mention that the analysis of the whole set of information in South America allows to establish a correlation between the inventory and the annual precipitations. References 1. UNSCEAR, 2000. In: Sources and effects of ionizing radiation, Report of the General Assembly with Scientific Annexes, Vol. 1, New York 2. UNSCEAR, 2008. In: Sources and effects of ionizing radiation, Report of the General Assembly with Scientific Annexes, Vol. 1, New York 3. M. L. Montes, J. Desimoni, 2011. Radiological survey in soils of South America. Radioisotopes/Book 1, in Press, and the references therein.