Natural radioactivity of some spring and bottled mineral waters from several Central Balkan sites, as a way of their characterization

In this work, a study of the radioactive content of some spring and bottled mineral waters originating from metamorphic rock areas was carried out. A high content of radium isotopes (226Ra, 228Ra), was found by radiometric analysis in the spring waters: Studenica (226Ra: 289 mBq/L), Cibutkovica (226Ra: 92, 4 mBq/L, 228Ra: 610 mBq/L), and Crni Guber (226Ra: 120 mBq/L, 228Ra: 1170 mBq/L). On the other hand, the radiochemical results showed a higher concentration of 238U in the bottled mineral water samples (dissolved uranium concentrations were from 0.21 mBq/L, for "Kopaonik" to 71.5mBq/L fo "Skadarska") than in the spring water samples (dissolved uranium concentrations were very low ?10 mBq/L). The concentrations of all the present naturally occuring radionuclides: 238U, 234U, 232Th, 230Th, 228Th, 228Ra and 226Ra were determined by alpha/gamma spectrometric analysis. The activity ratios 234U/238U, 226Ra/230Th and 228Th/232Th, 228Ra/228Th were calculated and are discussed as an indication of the radioactive disequilibrium in bothe the 238U and 232Th radioactive series. The high contents of radium isotopes with respect to the equilibrium values expected from the respective parents 232Th/(232Th series) and 230Th (238U series) found in the spring water samples is the main evidence for the existence of significant radioactive disequilibrium in both the radioactive series. .