Examining the Relationships Between the Activities of 3H in Precipitation and 137Cs in Ground-Level Air in Belgrade City Area

Abstract

Specific activity of tritium (3H) in precipitation and specific activity of 137Cs in ground-level air were monitored at three locations in Belgrade (Meteorological Station of Belgrade at Zeleno Brdo (ZB), Meteorological Station Usek (USEK), and Vinca Institute of Nuclear Sciences (VINS)). Data presented cover the period 1985–1997 for 137Cs for all locations and 1985–2009 (ZB), 1988–1997 (USEK), and 1988–2009 (VINS) for 3H. Concentrations of 3H in precipitation have been determined using electrolytic enrichment and liquid scintillation spectrometer LKB-Wallac 1219 RackBeta. The activity of 137Cs in air was determined on an HPGe detector (Canberra, relative efficiency 23 %). 3H concentrations in precipitation ranged from 0.40 ± 0.08 to 74.6 ± 5.2 Bq l−1 decreasing with distance from the nuclear facilities. Significantly higher tritium levels were measured in samples in VINS compared with those from an off-site location. The observed seasonal variations of tritium concentration indicate the stratospheric source of tritium. Increases in activity concentration of 137Cs in the atmosphere were observed after the nuclear plant accident at Chernobyl in April 1986. The concentrations obtained for 137Cs in 1986 were compared with the integrated air concentrations of 137Cs in the region. The increases of 137Cs air concentrations in 1987 and 1988 were attributed to local resuspensions from the ground. Since 1989, the activity level before the accident has been obtained. The average monthly concentrations of 137Cs in ground-level air were shown spread maximum in spring–summer period and pronounced maximum during winter. The obtained results were statistically analyzed, i.e., the following parameters were determined: tritium deposition, monthly activities of 3H and 137Cs, seasonal indices, radionuclide loading indices, and linear correlation coefficients.