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This study investigates the beryllium-7, lead-210 and caesium-137 activity concentrations in aerosol filter samples collected monthly along the 45°N zonal belt over 1991–2019. Sampling was performed in three locations, one in Serbia and two in Slovenia, and the Slovenian data records are published here for the first time. The activity concentrations were determined by standard gamma spectrometry. The obtained results are in general agreement with the literature data for Europe. The data sets at different sites display similarities in measurement ranges, overall means and seasonal cycles. Still, statistical tests show significant differences among the radionuclides’ concentrations across the locations. To investigate underlying processes that affect radioactivity in the surface air in this region, multivariate statistical concepts are applied to the radionuclides’ concentrations and local meteorological parameters. Discriminant analysis shows that all three sites are well separated from each other. Principal component analysis gives common pattern of interconnection between the observables: temperature has a stronger influence on the behaviour of beryllium-7 and lead-210 than that of caesium-137, but a negative correlation of the radionuclides’ concentrations with precipitation seems the strongest for caesium-137. Principal component analysis also shows local differences in the degree of relationship between the meteorological parameters and activity concentrations of the investigated radionuclides. This is an important finding for future atmospheric transport studies.

Specific activity of tritium (H-3) in precipitation and specific activity of Cs-137 in ground-level air were monitored at three locations in Belgrade (Meteorological Station of Belgrade at Zeleno Brdo (ZB), Meteorological Station Usek (USEK), and Vina Institute of Nuclear Sciences (VINS)). Data presented cover the period 1985-1997 for Cs-137 for all locations and 1985-2009 (ZB), 1988-1997 (USEK), and 1988-2009 (VINS) for H-3. Concentrations of H-3 in precipitation have been determined using electrolytic enrichment and liquid scintillation spectrometer LKB-Wallac 1219 RackBeta. The activity of Cs-137 in air was determined on an HPGe detector (Canberra, relative efficiency 23 %). H-3 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 Cs-137 in the atmosphere were observed after the nuclear plant accident at Chernobyl in April 1986. The concentrations obtained for Cs-137 in 1986 were compared with the integrated air concentrations of Cs-137 in the region. The increases of Cs-137 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 Cs-137 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 H-3 and Cs-137, seasonal indices, radionuclide loading indices, and linear correlation coefficients.

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 Cs-137 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 Cs-137 was also obtained for VINS, average monthly concentrations of Cs-137 in ground level air for this location were the lowest. The Cs-137 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.

Radioisotopes of uranium, thorium and plutonium in water, soil and fertilizer samples, have been chemically separated and determined by alpha-spectrometry method. Radiochemical Procedure involving ion-exchange, enabled to determine these isotopes in very tow concentrations (under 50 mu Bg/g). U-232, Th-229 and Pu-238 were used as a tracers for radiochemical yield recoveries (up to 90%). Thin layer sources have been obtained by electrodeposition. 6th International Conference on Separation of Ionic Solutes, May 15-19, 1995, Piest Any Spa, Slovakia