This study was conducted to compare soil particle density (ρ_s), soil total porosity (TP), liquid limit (LL), plastic limit (PL), and plasticity index, and their relations with soil organic matter (SOM), of non-carbonate silty clay Fluvisols under different land uses. Three neighboring land uses were studied: native deciduous forest, arable land, and meadow, managed in the same way for more than 100 years. Soil was collected from 27 soil profiles and from three depths (0–15, 15–30 and 30–45 cm). Land use caused statistically significant but different impacts on soil properties, particularly in the topsoil. The forest topsoil measured the lowest ρ_s and bulk density (ρ_b) but the highest SOM and soil water content at PL, compared to meadow and arable soil. Statistically significant linear relationship was observed with the SOM content and ρ_s (− 0.851**), ρ_b (− 0.567**), calculated TP (0.567**) and measured TP (− 0.280**). There was a nonlinear relationship between SOM and LL (0.704**) and PL (0.845**) at the topsoil. The findings suggested that SOM content strongly affected ρ_s, ρ_b, TP, LL and LP. This regional study showed that the conversion of forestland into agricultural land without appropriate measures to conserve SOM leads to the degradation of physical and rheological soil properties.

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.