RADIOACTIVITY OF TAP WATER OF TBILISI CITY (GEORGIA) AND ESTIMATION OF RADIOLOGICAL RISK FOR POPULATION

10th International Multidisciplinary Scientific GeoConference - SGEM2010, www.sgem.org, SGEM2010 Conference Proceedings/ ISBN 10: 954-91818-1-2, June 20-26, 2010, Vol. 2, 39-46 pp

ABSTRACT

Long-term periodic measurements of content of radioactive gas – radon Rn-222 in tap
water for different districts of Tbilisi city depending on time (during the period from
January, 2009 till December, 2009) were carried out. It is shown, that according to the
level of radon content in tap water the investigated districts can be divided conditionally
into 2 groups: with rather big radon content – more than 1 Bq L-1 (ranged in the interval
2.15 ± 1.17 Bq L-1, districts Vake, Saburtalo, Ortachala), and districts with rather small
radon content - less than 1 Bq L-1 (ranged in the interval 0.36 ± 0.35 Bq L-1, districts
Digomi, Isani, Vazisubani). It is underlined, that this radon distribution can be
connected with presence of two qualitatively distinguished sources of tap water supply
of Tbilisi - underground (artesian wells near settlements Natakhtari, Bulachauri,
Mukhrani) and surface (the Tbilisi reservoir filled with waters of the rivers Aragvi and
Iori) for which conditions of aeration and degassing by radon have essentially different
character. There are marked also some other features in character of radon distribution.
Estimates of radiological risk for population were made: estimated values of the
committed effective dose and dose equivalent to stomach are: 0.0060 ± 0.0033 mSv y-1
and 0.16 ± 0.09 mSv y-1 for 1st group of districts, and 0.0010 ± 0.0009 mSv y-1 and
0.026 ± 0.025 mSv y-1 for 2nd group of districts.

Key words: Concentration of radon, Water quality, Drinking water