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

Abstract

In this study, the specific activity of ¹³⁷Cs 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 ¹³⁷Cs 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 ¹³⁷Cs in soil was estimated through Pearson correlations. The specific activity of ¹³⁷Cs 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 ¹³⁷Cs in the soil was calculated to be 1.96 nSv h⁻¹. Geographic mapping of the external effective gamma dose rates originating from ¹³⁷Cs 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 ¹³⁷Cs specific activity in surface soil. There were positive correlations between organic matter and ¹³⁷Cs specific activity in surface soil; and between specific electrical conductivity, organic matter, silt content and ¹³⁷Cs specific activity in soil profiles.