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 ( 226 Ra, 228 Ra), was found by radiometric analysis in the spring waters: Studenica ( 226 Ra: 289 mBq/L), Cibutkovica ( 226 Ra: 92, 4 mBq/L, 228 Ra: 610 mBq/L), and Crni Guber ( 226 Ra: 120 mBq/L, 228 Ra: 1170 mBq/L). On the other hand, the radiochemical results showed a higher concentration of 238 U in the bottled mineral water samples (dissolved uranium concentrations were from 0.21 mBq/L, for "Kopaonik" to 71.5 mBq/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: 238 U, 234 U, 232 Th, 230 Th, 225 Th, 228 Ra and 226 Ra were determined by alpha/gamma spectrometric analysis. The activity ratios 234 U/ 238 U, 226 Ra/ 230 Th and 228 Th/ 232 Th, 228 Ra/ 228 Th were calculated and are discussed as an indication of the radioactive disequilibrium in bothe the 238 U and 232 Th radioactive series. The high contents of radium isotopes with respect to the equilibrium values expected from the respective parents 232 Th/( 232 Th series) and 230 Th ( 238 U series) found in the spring water samples is the main evidence for the existence of significant radioactive disequilibrium in both the radioactive series.