Articles

The aim of the work is to summarize the data available in the scientific literature on the values of the ¹³⁷Cs/¹³³Cs isotope ratio in soils and vegetation 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 are unified by calculating the molar ratio of these isotopes. Based on the generalized literature data, it is shown that the values of ¹³⁷Cs/¹³³Cs in soils, forest litter and vegetation increase in radioactively contaminated areas. In background regions exposed only to global radioactive fallout, the isotopic ratio of ¹³⁷Cs/¹³³Cs is about 0,1–1,0 (× 10^-8), whereas in the Chernobyl fallout zone it increases by 1000–100 000 times. The isotopic ratio of ¹³⁷Cs/¹³³Cs decreases down the soil profiles in various forest ecosystems. Spatial variation of the ¹³⁷Cs/¹³³Cs ratio in litter is associated with the diversity of ecotopes in forest biogeocenoses. The alignment of the values of the ¹³⁷Cs/¹³³Cs ratio in the vegetation cover and upper soil horizons indicates the achieved equilibrium of technogenic ¹³⁷Cs with natural stable ¹³³Cs in the biogeochemical cycle of this element. A comparative study revealed that the isotopic ratio of ¹³⁷Cs/¹³³Cs increases in the following range of plant cover representatives: Bryophyta < Sorbus aucuparia < Lichenes < Russula vesca < Frangula alnus < Polypodiophyta. For fungi, interspecific differences were noted in the following increasing series in the isotopic ratio ¹³⁷Cs/¹³³Cs: Lactarius deliciosus < Sarcodon scabrosus < Suillus bovinus < Tricholoma saponaceum < Lepista nuda < Russula delica < Macrolepiota excoriata. For the reference species of coniferous trees — Pinus sylvestris - the isotopic ratio of ¹³⁷Cs/¹³³Cs in the forest area of the Bryansk region polluted by Chernobyl fallout increases in the following number of components: roots < large branches < trunk wood < needles < small branches < cones.

The article provides an overview of the results of long-term studies of the migration of radionuclides in the composition of lysimetric waters. The features of lysimetric studies at various stages of radioecology development are considered. It is noted that the use of lysimeters for a long time was limited to low levels of radionuclides in soil solutions, and large-scale studies began after the Chernobyl fallout (1986). It is shown that the greatest output of radionuclides in lysimetric waters occurs in forest, especially coniferous phytocenoses, the least — in meadow and agrophytocenoses. In the long-term dynamics, the maximum intensity of radionuclide migration in the lysimetric waters is observed in the initial period after aerial precipitation, in the seasonal period — in the summer. A small amount of radionuclides migrates with downward water flow. Annual outflow with vertical subsurface runoff varies depending on soil-climatic conditions, the period after precipitation, the thickness and depth of the layer. Annual outflow from the forest litter layer varies from tenths to units of percentage, from the layer 0–20 cm — from hundredths to tenths of a percentage from the total radionuclide supply in these layers. The relative output of ⁹⁰Sr is much bigger than ¹³⁷Cs. In soil solution from 70% to 90% radionuclides [¹⁴⁴Ce, ²³⁹Pu ¹⁰⁶Ru ,¹³⁷Cs and ⁹⁰Sr] are in the form of radionuclide-organic compounds of various molecular weights. 

We studied the ecological state of the soils of the seven most visited recreational areas located throughout Moscow: Losinyi Ostrov, Park Pobedy, Ostankino, Sokolniki, Izmailovo, Kuzminki-Lublino, and Tsaritsyno. Soil samples were collected in summer of 2018 at three sites in each park. The concentrations of 38 chemical elements (Na, Si, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, As, Br, Rb, Sr, Mo, Sb , Cs, Ba, La, Ce, Nd, Sm, Eu, Tb, Tm, Yb, Hf, W, Au, Th, U, Cd, Pb and Cu) in soil samples were determined using neutron activation analysis and atomic absorption  spectrometry. We made the sanitary-hygienic and ecological-geochemical assessment of soils samples and identified slight exceedances of approximate permissible concentration by elements belonging to the first hazard class (As, Cd, Zn). Also, we calculated the total pollution index. The moderately soil pollution by elements belonging first and third danger class was found in the territory of the following parks: Sokolniki, Izmailovo and Park Pobedy. The total pollution index calculated using all trace elements indicated that 50% of the sites belonged to the dangerous pollutionies. Sb, Th, Tb, Cs, and Hf significantly contributed to the total pollution. The highest pollution indices were found in soils samples collected on the territory of the Eastern administrative district in Sokolniki and Izmailovo parks.

In Russia, the lands with oil contaminated soils exceed tens of thousands hectares. However, to date, there were no unified approaches to the rationing of oil and petroleum hydrocarbons (PH) in soils, a guideline to choose optimal evaluation indicators. The response of plants in the pot experiment could provide significant results for assessing and rationing of PH content in soils and their use in agriculture after land remediation. In this work we assessed the response of higher plants as a marker of the direction and intensity of biological processes in soils in the pot experiment under oil contamination to justify the standards of permissible residual content of PH in soils of agricultural lands. The composition and properties of Luvic Chernozems, Calcic Chernozems, Voronic Chernozems (WRB, 2015) used in the pot experiment, which was carried out in a month after the soil contamination with crude sulfur-containing oil, were investigated. The effect of different oil doses on the bioproductivity of wheat and peas was evaluated. Wheat in terms of dry biomass showed higher sensitivity to PH, containing medium and heavy fractions, than peas. Rationing the PH content in chernozems, a nonlinear regression model described by a logistic curve was applied. The quality standard values found for wheat biomass was 0,9; 0,4; 1,0 g * kg^-1 for Luvic Сhernozems (humus content ~ 9,8%, sandyloam texture); Calcic Chernozems (humus content ~7,6%, clay loam texture), Voronic Chernozems (humus content ~12.8%, loam texture), respectively. The residual PH contents, found as 30% of soil functioning change, which corresponded to the risk level of soil degradation, estimated by the soil fertility parameter — dry wheat biomass were 1,2 g·kg^-1 for Voronic Chernozems; 0,5 g·kg^-1 — Calcic Chernozems; 1,1 g·kg^-1 in Luvic Chernozems.

New indicators of lanthanide affinity for carrier phases in the soil, based on the rationing of lanthanide concentrations by their soil clarks, are proposed. This made it possible to obtain an original indicator of the affinity of lanthanide A_LN to carrier phases in soils. The indicator of affinity of lanthanide A_LN showed its advantage over the accepted pC_Ln index in the analysis of Russian and Swedish soils.

Salt neoformations in sandy and silty loam soils of the Aral Sea dried bottom in the south-western part were studied by X-ray fluorescence, electron microscopic, sedimentation methods of analysis and laser diffractometry. The surface layers of soils are significantly saline and enriched with CaCO₃. The distribution of CaCO₃ over the area is quite uniform, which indicates relatively close conditions of its formation during desiccation. The salt content varies from 0.4 to 1.2% in sands and from 3.1 to 5.8% in silty loam. The latter are characterized by the highest salinity, when, in addition to gypsum and halite, readily soluble salts are formed: eugsterite (2Na₂SO₄^.CaSO₄.2H₂O), astrakhanite (Na₂SO₄^.MgSO₄^.4H₂O), and mirabilite (Na₂SO₄^.10H₂O). Precipitation of calcite upon drying leads to the formation of CaCO₃-ooids in sands and CaCO₃- microaggregates from clay and silty particle in silty loam. The reason for the increased activity of easily soluble salts in the processes of aeolian transport has been established. This transport and, correspondingly, the salinization of adjacent territories are facilitated by the blocking of adsorption centers in clays by calcite, which prevents the binding of easily soluble salts in clay-salt microaggregates.