Edaphic factors affecting the vertical distribution of radionuclides in the different soil types of Belgrade, Serbia

The specific activities of natural radionuclides (K-40, Ra-226 and Th-232) and Chernobyl-derived Cs-137 were measured in soil profiles representing typical soil types of Belgrade (Serbia): chernozems, fluvisols, humic gleysols, eutric cambisols, vertisols and gleyic fluvisols. The influence of soil properties and content of stable elements on radionuclide distribution down the soil profiles (at 5 cm intervals up to 50 cm depth) was analysed. Correlation analysis identified associations of K-40, Ra-226 and Cs-137 with fine-grained soil fractions. Significant positive correlations were found between Cs-137 specific activity and both organic matter content and cation exchange capacity. Saturated hydraulic conductivity and specific electrical conductivity were also positively correlated with the specific activity of Cs-137. The strong positive correlations between Ra-226 and Th-232 specific activities and Fe and Mn indicate an association with oxides of these elements in soil. The correlations observed between K-40 and Cr, Ni, Pb and Zn and also between Cs-137 and Cd, Cr, Pb and Zn could be attributed to their common affinity for clay minerals. These results provide insight into the main factors that affect radionuclide migration in the soil, which contributes to knowledge about radionuclide behaviour in the environment and factors governing their mobility within terrestrial ecosystems