Determination of Symmetrical Index for 3H in Precipitation and 137Cs in Ground Level Air

Abstract

The paper presents results of a long-term investigations of tritium activity concentrations in precipitation and radiocesium activity concentrations in ground level air in Belgrade, Serbia. Samples were collected at three locations in Belgrade (Meteorological Station of Belgrade MS at Zeleno Brdo (ZB), Meteorological Station MS Usek (USEK), and Vinca Institute of Nuclear Sciences (VINS)). Presented data cover the period 1985–1997. Significantly higher tritium levels were measured in samples in VINS compared with off-site location, while the impact of research reactor for 137Cs was not detected. It was found that the value of the symmetrical index n is higher for VINS in case of tritium, compared to other locations, which is in accordance with the fact that the highest average monthly concentrations of tritium were obtained in the samples from the cited place. Although the highest value of index n in case of 137Cs was also obtained for VINS, average monthly concentrations of 137Cs in ground level air for this location were the lowest. The 137Cs concentration in the ground level air is described by a kinetic equation of the first order and provides a good description of the time changes in these concentrations.