Ten years of continual monitoring of 222Rn concentration in Bratislava atmosphere

By the continual monitoring we obtained the extensive set of radon data in Bratislava atmosphere covering the time period of 1991 - 2000. The average annual radon activity concentrations varied from 4.1 to 7.2 Bq/m3. In the years 1996 - 1999 the decreasing of the average annual radon concentration was observed. The average daily courses of the radon activity concentration for individual months calculated on the basis of all data from 1991 - 2000 have a form of waves with the maximum in morning hours and with the minimum in the afternoon. The maximal amplitude of daily wave was found out in August (2.9 Bq/m3) and minimal in December (0.5 Bq/m3). The average daily wave obtained as the mean off all data from years 1991 - 2000 reaches the maximum between 4 and 6 a. m. and the minimum between 2 and 4 p. m. The Rn-222 activity concentration reaches its average daily value equal to 5.6 Bq/m3 at about 10 a. m and at 9 p. m. The amplitude of average daily wave is equal to 1.5 Bq/m3. The average annual radon course calculated on the basis of all the measured data reaches the minimum in April and the maximum in October with seasonal variation from 3.9 to 6.9 Bq/m3. The annual radon courses differ from each other for various periods of the day. (authors)