Seasonal variations of 226Ra and 222Rn in mineral spring waters of Aguas da Prata, Brazil

In this paper the activity concentrations of 226Ra and 222Rn were assayed in the mineral spring waters of Aguas da Prata in order to evaluate the seasonal variations of such radionuclides. The results obtained were related to the chemical composition of the water as well as to the lithology of the aquifer and temperature. Higher activity concentrations up to 1.8 × 103 mBq L−1 for 226Ra and 1.2 × 102 Bq L−1 for 222Rn have been observed in waters with low levels of soluble salts. Waters which present high levels of carbonate and sulphate salts showed maximum values of 2.5 × 102 mBq L−1 for 226Ra and 2.7 × 101 Bq L−1 for 222Rn. This behaviour is mainly due to the physico-chemical properties of these radionuclides in water as well as to the lithologic structure of the aquifers.