QUANTITATIVE AND QUALITATIVE STUDY OF RADON CONTENT IN BULGARIAN MINERAL WATERS.

This study presents the results of 222Rn in 24 sources of mineral water, 54 samples from different captured natural springs and drillings. 222Rn determination was performed by direct measurement using Alpha Guard with Aqua Kit. The results for the TDS, anions (F-, Cl-, SO42-), cations (Na+, Ca2+, Mg2+), pH and temperature of the investigated mineral waters were correlated with radon content by statistical software tool IBM SPSS. In the paper are shown the results of investigated correlations between the 222Rn content and gross alpha activity, gross beta activity and specific activity of 226Ra. The received results show that the 222Rn activities range from 0.40 to 476 Bq/l with a median value of 16 Bq/l. The Spearman's rho coefficients demonstrate a strong positive correlation between SO42- and F- anions and 222Rn (r, 0.731 and r, 0.784 respectively). Correlations between226Ra/222Rn, gross alpha activity/222Rn, gross beta activity/222Rn were investigated but not observed.

Radionuclides Content in Pasteurized Cow Milk: Dose Estimation.

Results from the radiological monitoring of 46 pasteurized cow milks for the period of 2011-2015 are presented. The activity of 137Cs, 90Sr, 226Ra, 40K, 210Pb, 232Th and natural U was determined by gamma spectrometry for gamma emitters and by radiochemical separation for 90Sr. The maximum obtained results are 0.449 ± 0.016 Bq/l (137Cs), 0.105 ± 0.020 Bq/l (90Sr), 1.63 ± 0.16 Bq/l (226Ra), 53.1 ± 1.6 Bq/l (40K), 1.01 ± 0.30 Bq/l (210Pb), 0.05 ± 0.07 Bq/l (232Th) and 0.14 ± 0.12 mg/l (natural U). Annual Effective Dose from the ingestion of above-mentioned radionuclides was estimated on the basis of the consumption for adults and children (1-2 y) applying two models-realistic and conservative. The values for the Ingestion Dose vary from 0.02 mSv/y to 0.05 mSv/y (adults, realistic model) and from 0.06 to 0.15 mSv/y (adults) and from 0.15 to 0.87 mSv/y (children 1-2 y old) from conservative model. For bought models, the main contribution to the Ingestion Dose, instead of 40K, is due to the 210Pb and 226Ra. Three hypotheses are given for the 226Ra content in pasteurized cow milk. The received results demonstrate the need of determination of artificial and natural radionuclides in cow milk.

Natural radioactivity content in Bulgarian drinking waters and consequent dose estimation.

Natural radioactivity in drinking water from Bulgaria was determined in 994 samples. Nine hundred and seventeen of them are from the Southwestern part of the country. The measured activity of natural uranium, (226)Ra, gross alpha and gross beta activity varied from 20 (5) ng l(-1) to 0.11 (3) mg l(-1), MDA to 0.39 (6) Bq l(-1), MDA to 6.23 (39) Bq l(-1) and 0.030 (7) Bq l(-1) to 0.98 (22) Bq l(-1), respectively. Approximately 33% of the investigated waters exceeded a gross alpha activity of 0.1 Bq l(-1), 1.8% a natural uranium concentration of 0.03 mg l(-1) and 1% an (226)Ra concentration of 0.15 Bq l(-1). Annual effective dose from natural radionuclides ranges from 0.0175 (43) µSv to 95.5 (2.6) µSv. Median values of the contribution of the (226)Ra and uranium to the indicative dose are 10.22 and 0.21 µSv y(-1), respectively. Poor relationships between (226)Ra/nat.U (r, 0.12) and for gross beta activity/natural uranium (nat.U) (r, 0.29) were observed. The relationships between nat.U/gross alpha activity (r, 0.50) and for gross alpha activity/gross beta activity (r, 0.52) concentration distributions were stronger.