Comparative Measurements of Radon Content in Tap Water in Tbilisi and Rustavi Cities

Abstract

Results are presented of long-term periodic measurements of content of radioactive gas – radon ²²²Rn in drinking (tap) water from various districts in Tbilisi as a function of time during years 2009 and 2010. It is shown, that according to the level of radon content in tap water, the investigated districts can be divided conditionally into two groups: with rather high radon content – more than 1 Bq l⁻¹ (Vake, Saburtalo, Ortachala), and districts with rather low radon content – less than 1 Bq l⁻¹ (Digomi, Isani, Vazisubani). It is underlined that this circumstance can be connected with presence of two qualitatively distinguished sources of tap water supply in Tbilisi – underground (artesian wells near settlements Natakhtari, Bulachauri, Mukhrani) and surface (the Tbilisi reservoir filled with waters of the rivers Aragvi and Iori) in which conditions of aeration and degassing by radon have an essentially different character. Also some other features in the character of radon distribution are marked. Results of radon content researches in tap water in another large city in Georgia – Rustavi – are also given. Radon concentration varied in the range 0.06–16.5 Bq l⁻¹. Average values of radiological parameters have been estimated: in Tbilisi – committed effective dose (7.7·10⁻⁵ to 1.1·10⁻² mSv·year⁻¹) and dose equivalent to the stomach (2.2·10⁻³ to 3.3·10⁻¹ mSv·year⁻¹), and in Rustavi – committed effective dose (1.5·10⁻⁴ to 4.2·10⁻² mSv·year⁻¹) and dose equivalent to the stomach (4.4·10⁻³ to 1.2·mSv·year⁻¹).