Spatial distribution and vertical migration of 137Cs in soils of Belgrade (Serbia) 25 years after the Chernobyl accident

In this study, the specific activity of Cs-137 was determined by gamma-ray spectrometry in 72 surface soil samples and 11 soil profiles collected from the territory of Belgrade 25 years after the Chernobyl accident. Based on the data obtained the external effective gamma dose rates due to Cs-137 were assessed and geographically mapped. The influence of pedogenic factors (pH, specific electrical conductivity, cation exchange capacity, organic matter content, soil particle size and carbonate content) on the spatial and vertical distribution of Cs-137 in soil was estimated through Pearson correlations. The specific activity of Cs-137 in surface soil samples ranged from 1.00 to 180 Bq kg(-1), with a mean value of 29.9 Bq kg(-1), while in soil profiles they ranged from 0.90 to 58.0 Bq kg(-1), with a mean value of 15.3 Bq kg(-1). The mean external effective gamma dose at 1 m above the ground due to Cs-137 in the soil was calculated to be 1.96 nSv h(-1). Geographic mapping of the external effective gamma dose rates originating from Cs-137 revealed much higher dose rates in southern parts of Belgrade city and around the confluence of the Sava and Danube. Negative Pearson correlation coefficients were found between pH, cation exchange capacity and Cs-137 specific activity in surface soil. There were positive correlations between organic matter and Cs-137 specific activity in surface soil; and between specific electrical conductivity, organic matter, silt content and Cs-137 specific activity in soil profiles.