Migration of <sup>137</sup>Cs in Soils of Erosive Agricultural Landscapes of the Northern Part of the Forest-Steppe Zone

The results of a study of 137Cs migration in leached chernozems at slopes and soils in hollows of erosive agricultural landscapes of the Tula region are presented. A study has revealed that there was an active redistribution and differentiation of 137Cs fluxes entering erosive agricultural landscapes due to the Chernobyl accident. The distribution of 137Cs in soils across various parts of slope landscapes is influenced by factors such as the exposure, length, steepness, and shape of the slopes, along with the presence of microrelief features. Radionuclide removal zones are at the top of slopes, transit zones are in the middle, and the main accumulation occurs at the bottom of the slopes. A notable feature of the distribution of 137Cs in diluvial deposits at the toes and bottoms of slopes is the increase in 137Cs reserves with depth. This increase reaches a peak at a depth of 10–40 cm, depending on the thickness of the deposits. Following this, depending on the presence of geochemical barriers, there is a sharp or moderately gradual decrease in 137Cs reserves in the lower layers of the soil profile. The contamination density of 137Cs increases moving from the upper part to the lower line of the greatest slope and, conversely, decreases closer to the watershed. The ratio of 137Cs contamination densities between the watershed sections and gulch bottoms is typically 1.0:(1.2–1.5), and between the upper and lower sections relative to the bottoms, it is 1.0:(2.0–1.5). The maximum differences between these indicators are typical for the steep, longitudinally straight southern slopes, as well as longitudinally concave southwestern slopes. The minimum values were observed in the gentler slopes of the eastern and western exposures. The highest 137Cs densities were recorded at feet and bottoms of short slopes. On slopes of medium length, there has been a notable increase in soil surface contamination by 137Cs, primarily concentrated in the central areas of these slopes. The extent of soil contamination by 137Cs is affected by the steepness of the slopes. Steeper slopes have a 1.3 times higher contamination density compared to the upper parts of the slopes. On gentler slopes, the contamination density decreases to 1.1 times. Understanding these factors and the migration patterns of 137Cs is important for accurately predicting how radionuclides will spread in different types of land. This knowledge helps in developing effective measures to enhance soil fertility and reduce the build-up of radionuclides in agricultural products.