Аннотация:The aim of this study was to summarize the data available in the scientific literature on the values of the 137Cs/133Cs isotopic ratio in soils and plant cover of forest ecosystems in radioactively contaminated and background territories. The values of the specific activity of 137Cs and the concentration of 133Cs presented in radioecological studies were unified by calculating the molar ratio of these isotopes. Based on generalized literature data, it was shown that the 137Cs/133Cs values in soils, forest litter, and vegetation increase in radioactivelycontaminated areas. In background regions exposed only to global radioactive fallout, the 137Cs/133Cs isotopic ratio was about 0.1–1.0 (×10–8), whereas it increased by 1000–100000 times in the Chernobyl fallout zone. The 137Cs/133Cs isotopic ratio decreased down the soil profiles in various forest ecosystems. Spatial variationof the 137Cs/133Cs ratio in litter is associated with the diversity of ecotopes in forest biogeocenoses. A comparison of the values of the 137Cs/133Cs ratio in the plant cover and upper soil horizons indicated the achieved equilibrium of technogenic 137Cs with natural stable 133Cs in the biogeochemical turnover of this element.A comparative study revealed that the 137Cs/133Cs isotopic ratio increased in the following series of plant cover representatives: Bryophyta < Sorbus aucuparia < Lichenes < Russula vesca < Frangula alnus < Polypodiophyta. For fungi, interspecific differences were noted in the following ascending series in the 137Cs/133Cs isotopic ratio: Lactarius deliciosus < Sarcodon scabrosus < Suillus bovinus < Tricholoma saponaceum < Lepistanuda < Russula delica < Macrolepiota excoriata. For the reference species of coniferous trees Pinus sylvestris, the 137Cs/133Cs isotopic ratio in the forest area of Bryansk oblast polluted by Chernobyl fallout increased in the following series of components: roots < large branches < trunk wood < needles < small branches < cones.
