The natural radioactivity of selected sources of drinking water in Southern Bulgaria was investigated using U-238, U-234 and Po-210 activity measurements and dose calculation, respectively. The activities of U-238, U-234 and Po-210 varied from 226 to 826 mBq/L, 274 to 1623 mBq/L and < 0.6 to 25.5 mBq/L, respectively, being lower than derived concentrations for radioactivity in water intended for human consumption of the considered radionuclides, given in EC Directive 2013/51/EURATOM. In some drinking waters, the mass concentration of natural uranium exceeded the set maximum chemical concentration level of 0.030 mg/L. A radioactive disequilibrium between U-234 and U-238 in water was detected.
Based on the radionuclide activity concentrations total annual effective ingestion doses for adults, as well as contribution of each particular radionuclide to the total doses, were assessed and discussed. Тhe lowest contribution to the annual effective doses was found for Po-210 and the highest for U-234. The results show that the annual effective doses of residents are below the reference level of 100 µSv/y according to the recommendations of the World Health Organization. The obtained new results are used to assess the radiation status of the investigated water.
The research has been supported by Bulgarian Science Fund under Contract No. KP-06-N44/1, 27.11.2020. The results were published online in Natural Science and Advanced Technology Education.