Natural radionuclides in soil profiles and sediment cores from Jundiai reservoir, state of São Paulo

Abstract

The activity concentration of natural radionuclides in soils and sediments is dependent on many factors, such as the rock parental material, pedogenic and weathering processes, physical and chemical properties of the environment, anthropogenic sources, among other aspects. Naturally occurring radiation in the environment is mostly due to the decay of 238U and 232Th series; another important source of natural radiation is the radionuclide 40K. Reservoirs are artificial systems made in order to stock riverine and rainwater to supply water to the population. There are few studies about the levels of natural radionuclides in reservoirs in both, international and national, literature. The objective of this paper was to evaluate the activity concentration of 238U and 232Th by Instrumental Neutron Activation Analysis and 226Ra, 210Pb, 228Ra, 228Th and 40K by gamma spectrometry in two soil profiles and three sediment cores collected in the catchment area of Jundiai reservoir, located in the state of São Paulo, Brazil. Principal component analysis was applied to verify the correlation of the activity concentrations of the natural radionuclides with physical and chemical properties of soil and sediment samples. In the soil profiles, the radionuclides that showed higher activity concentration when compared to the UNSCEAR values were 232Th in the both profiles and 238U only in one; for the sediment cores, the activity concentrations of 238U and 232Th were higher than the UNSCEAR values in all the samples analyzed and also for the radionuclide 226Ra in two sediment cores.