Radionuclides of Natural Origin in Environmental Samples Collected in the Catchment Area of Ponte Nova Reservoir, São Paulo, Brazil

Natural radiation is generally classified as terrestrial primordial radiation or cosmogenic radiation. Primordial radiation is mostly due to the decay series of ²³⁸U and ²³²Th and is present in soil, sediments and water; another important source of natural radiation is ⁴⁰K. Reservoirs are a very dynamic system with several phenomena to study, due to their huge impact on ecosystems and river flow. Ponte Nova reservoir (23°34'43.23^S, 45°56'56.76^W) is the first reservoir in a cascade system that was built in the 1970s to control the Upper Tietê River basin water flow. In the present work, the activity concentrations of ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²³²Th, ²²⁸Th, ²²⁸Ra and ⁴⁰K were determined using instrumental neutron activation analysis and gamma spectrometry in soil profiles collected in the catchment area of Ponte Nova Reservoir and sediment cores collected close to the soil samples. The highest concentration obtained in the soil samples was for ⁴⁰K that varied from 49 to 2410 Bq/kg and ²¹⁰Pb in the sediment samples, which varied from 20 to 774 Bq/kg. Cluster analysis and principal component analysis were applied to all the results obtained to verify a probable correlation between the radionuclides determined in the soil and sediment samples. (author)