Fluctuation of radiocaesium concentrations in the near-surface atmospheric layer in Bialystok in the period 1992-1999

Air samples were collected at an early-warning sampling and monitoring radioactive contamination station ASS-500. The results of the measurements are presented for radioactive aerosols collected on filters each week between 1992 and 1999. The large variations in activity concentration were observed in annual cycles. The maximum values exceeded the mean annual values by a factor of 2.8 to 7.3. Over the period of eight years the mean values of activity in air was found to decrease from 5.3 muBq m(-3) in 1992 to 2.2 muBq m(-3) in 1999. A good correlation between the Cs-137 activity and dust content in the air indicates that in the observed period the main source of Cs-137 activity is the dust with soil and vegetation particles. The effect of radiation from inhalation is negligible (626 pSv).