Application of the radiocesium method and morphometric relief indicators to the calculation of soil loss intensity on plowed slopes in the Sukhaya Orlitsa river basin
Authors: Trofimetz Lyubov , Panidi Evgeny , Chaadaeva Natalia , Sankova Elena , Ivaneha Taras , Tyapkina Angela , Saraeva Anna , Alexandrova Angelica , Barkalov Aleksandr , Stepanpva Vera , Lavrusevich Andrey 
Published: November 2021

Based on the authors’ data, the paper describes a methodology for assessing the spatial distribution of soil losses on the plowed slopes of the experimental site. The site is located in the basin of the Sukhaya Orlitsa River in the Orel District, Orel Region. The introduction of the principles of precision farming into land use practice requires a point estimate of soil losses, which is possible when using morphometric relief indicators. Geomorphometry methods in combination with GIS and the radiocaesium method made it possible to develop a method for calculating the specific activity of cesium-137 (as an indicator of soil losses) based on the morphometric parameters of the relief. The article presents the dependencies developed for depressions with a catchment area of ≤ 23,000 m2 and ≤ 50,000 m2. The development of a method for calculating soil losses in the elements of a depression complex on a plowed slope was carried out in two stages. At the first (field) stage, soil samples in the arable layer were taken in thalweg of depressions of different sizes. Sampling points were recorded during GPS survey. Gamma-spectrometric analysis of soil samples and their application to a digital elevation model (DEM) allowed to obtain a spatially distributed model of the specific activity of cesium-137 of Chernobyl origin on a scale of 1:10,000. To recognize the depressions, ultra-high resolution satellite images published in Google Earth were used. On the basis of the DEM, using the SAGA GIS tools, the authors built the fields of the collection area (calculated by the DEMON algorithm) and the profile curvature of the relief. The method was based on a system of dependences of the specific activity of cesium-137 on the collection area and the sign of the profile curvature. The specific activity of cesium-137 for inter-depression spaces was calculated using the equations developed for depressions with a collection area of up to 23,000 m2. To calculate soil losses, it was proposed to establish the reference value of cesium-137 individually for each of the three studied fields, which is due to the presence of the trend of Chernobyl fallout. In conditions of a polygonal block microrelief of paleocryogenic origin (which is widespread in the analyzed territory), the authors recommended determining the reference value of the specific activity of cesium-137 within block increases on the watershed surface of the plowed slopes. The trend was established on the results of the analysis of the layer-by-layer distribution of cesium-137 in depth in the thalweg of the depressions and in the balka, “receiving” overburdens from the fields under the study. Taking into account the results of the calculations, a map of the intensity of soil losses was constructed for the experimental site as of from 1986 to 2016.