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The paper presents data on the vertical distribution of 137Cs of Chernobyl origin in arable and meadow soils to a depth of 40 cm in typical catenary junctions of predpolessie, predopolje, and opolje landscapes with a different density of 137Cs contamination 30 years after the accident at the Chernobyl nuclear power plant. Newly obtained data on the removal of 137Cs beyond the arable horizon presented in the paper indicate that this parameter varies depending on the landscape conditions: it varies in the range of 2.7–17.7% in predpolessie landscapes and in the range of 0.5 to 9% in opolje landscapes. In opolje landscapes, the coefficient of 137Cs removal from the arable horizon was proved to systematically decrease depending on the landscape catenary position: it amounts to 8.5% in the transit zone and is 1.4% in the accumulation zone. The vertical distribution of 137Cs and 210Pbex (excess) in the sod and floodplain soils in the basin of the Kostitsa River was studied to determine the sedimentation rate. Based on the analysis of the distribution of 137Cs in the soil, the sedimentation rate over the past 30 years in various parts of the floodplain was estimated at 0.42 ± 0.08 to 0.58 ± 0.11 cm/year. The average estimated sedimentation rate in the floodplain during approximately 50 past years was, according to the 210Pbex dating was equal to 0.7 ± 0.18 cm/year. The sedimentation rate in the bottom of a ravine was evaluated for sod soils based on the distribution of 210Pbex according to the CRS model for 1961–2016 y. It was revealed that the minimum sedimentation rate of 0.24 cm/year occurred in 1961–1988, and the maximal (0.7 cm/year) in 2000 to 2007. [ABSTRACT FROM AUTHOR]

Radioactive fallout, that entered the landscape, is strongly absorbed by soil particles and their further fate is the fate of the redistribution of many soil particles in the landscape. Therefore, Cs-137 is a unique tracer for studying soil erosion and sedimentation. Numerous studies of the behavior of Cs-137 by fallout from nuclear test have shown its uniqueness for investigation of soil erosion and sedimentation. Global Cs-137 fallout was successfully used to measure soil erosion rates and delineate patterns of soil erosion and deposition within landscape units. The accident at the Chernobyl Nuclear Power Plant, which occurred on April 26, 1986, provided a unique opportunity to use radioactive tracers in different landscapes of the Bryansk region, which were most affected by radioactive contamination. In 1993, the airborne gamma survey of the Bryansk region covered an area of 180x200 km in 100 m steps and embraced all contaminated areas with different soil types, including sod-podzolic, alluvial, gray forest, and peat bogs. The main radioactive contamination was formed by Cs-137, a well-tested tracer in soil studies. Air-gamma survey revealed significant spatial heterogeneity of Cs-137 contamination. The initial "spotting" of Cs-137 contamination, which in the spring of 1986 represented multi-scale complex patterns of contamination, was substantially transformed by 1993 due to erosion processes of various intensity.The objective of this study is to test various mathematical models actively used in pedometrics to evaluate the contribution of various landscape factors to the erosion and sedimentation processes that led to the formation of Cs-137 patterns at the time of the survey in 1993. Actually, this is a solution of the inverse problem when, according to the 1993 air-gamma measurement, it is necessary to restore the Cs-137 patterns that existed at the time of their formation in April-May 1986.Modeling the transformation of Cs-137 cesium-137 patterns is demonstrated using four plots as an example. Two remote sites (Kostitsa and Dubrovka) are located 280 km and 250 km away from the Chernobyl NPP, respectively, and characterise the transformation of cesium-137 patterns at levels slightly exceeding the global background: with regard to the Kostitsa site, the pollution is 8-21 kBq/m2, while for the Dubrovka site it is 3-16 kBq/m2. The two sites closest to the Chernobyl NPP (Vyshkov and Brakhlov), located at a distance of 175 km and 195 km from the Chernobyl NPP, respectively, have a contamination with cesium of 460-1570 kBq/m2 and 60-207 kBq/m2, respectively. To assess the relationship of Cs-137 with various landscape factors derived from DEM we used different statistical models, such as GLM, GAM. To analyze Cs-137 distribution depending on a number of parameters (Curvature, LS index, Slope) initial DEM and layer of Cs-137 was resampled to a grid 25 × 25 m using two methods: 1) spline approximation with optimal weights and 2) Bayesian interpolation methods. [ABSTRACT FROM AUTHOR]