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

Abstract

The specific activities of natural radionuclides (⁴⁰K, ²²⁶Ra and ²³²Th) and Chernobyl-derived ¹³⁷Cs 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 ⁴⁰K, ²²⁶Ra and ¹³⁷Cs with fine-grained soil fractions. Significant positive correlations were found between ¹³⁷Cs 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 ¹³⁷Cs. The strong positive correlations between ²²⁶Ra and ²³²Th specific activities and Fe and Mn indicate an association with oxides of these elements in soil. The correlations observed between ⁴⁰K and Cr, Ni, Pb and Zn and also between ¹³⁷Cs 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.