SEASONAL-VARIATIONS OF RA-226 AND RN-222 IN MINERAL SPRING WATERS OF AGUAS DA PRATA, BRAZIL

In this paper the activity concentrations of Ra-226 and Rn-222 were as sayed in the mineral spring waters of Aguas da Prata in order to evalu ate the seasonal variations of such radionuclides. The results obtaine d were related to the chemical composition of the water as well as to the lithology of the aquifer and temperature. Higher activity concentr ations up to 1.8 x 10(3) mBq L-1 for Ra-226 and 1.2 x 10(2) Bq L-1 for Rn-222 have been observed in waters with low levels of soluble salts. Waters which present high levels of carbonate and sulphate salts show ed maximum values of 2.5 x 10(2) mBq L( )for Ra-226 and 2.7 x 10(1) Bq L-1 for Rn-222. This behaviour is mainly due to the physico-chemical properties of these radionuclides in water as well as to the lithologi c structure of the aquifers. (C) 1998 Elsevier Science Ltd. All rights reserved.