Issues of uranium and radioactivity in natural mineral waters

Methodical investigations on uranium (U-238) concentrations were conducted on 15 selected mineral waters from European sources. The samples were selected according to their radioactivity deriving from Ra-226, which ranged from 3.7 to 1780 mBq l(-1). The determination of U-238 in mineral water by ICP-QMS showed to be an efficient replacement for the laborious radiochemical method. Results obtained by both methods were in reasonable good agreement. The U concentrations in the specimens ranged from less than the detection limit of ICP-QMS (15 ng l(-1) U-238) up to 8.6 mug l(-1) (corresponding to 218 mBq l(-1)). An extreme U concentration was found in a source from Moravia (Czech Republic) with 188 mug l(-1) U corresponding to 4747 mBq l(-1). On an average U contributed the same amount of radioactivity to a mineral water than Ra-226 (range: 0-87%). Although a daughter nuclide of the U-238 decay series, Ra-226 concentrations were not correlated. In multiple regression analysis the mineral components Ca2+, Mg2+, K+, Na+, Cl-, HCO3- and SO42- explained up to 99% of the summarized radioactivity (U + Ra-226) in the specimens. Chloride and potassium concentrations explained most of the variability and as a rough role of thumb it was found that twice the chloride concentration in mg l(-1) was equal the summarized radioactivity (U + Ra-226) in the investigated waters. The results of the investigation underline the need to communicate the content of radionuclides with the customer information of natural mineral waters.