Natural Radioactivity In Certain Bulgarian Mineral Waters

Waters, as one of the most important components of the environment, are part of all food chains and a major route for the entry of radioactive substances into the human body. Therefore, regular and control studies of mineral water are necessary to guarantee that they have a low level of radioactivity. The objective of this study is to assess the Ra-226 activity and the concentration of natural uranium (nat. U) in mineral waters from certain most frequently used sources in Bulgaria by means of nuclear and analytical methods.Ra-226 is a naturally produced radioisotope with a period of half-life equal to 1600 years, whose specific activity in water was determined through analysis of the daughter product Rn-222. The measurements were carried out using a low-level liquid scintillation (LS) counting in a Packard Tri-Carb 2770 TR/SL LS spectrometer. The concentration of nat. U was determined with a luminescent method based on the ability of six-valent uranium melted with sodium fluoride to produce light under UV illumination.The results show that the Ra-226 activity is in the range 0.025-0.211 Bq/L and the concentration of nat. U varies from less than 0.003 mg/L to 0.86 mg/L. Due to differences in the geological structure of the aquifers, a large difference in values of the Ra-226 activity was observed, but no correlation with the nat. U concentration. The annual effective doses were calculated for all investigated waters for adult inhabitants assuming the yearly consumption of 730 L.The obtained new results are used to assess the radiation status of the investigated waters. They will support timely and adequate measures to reduce the harmful impact of ionizing radiation on the population in cases of increased radioactivity.