In a vegetation experiment on sod-podzolic sandy loam soil with Cd2+ addition at doses of 25 and 45 mg/kg, we studied how the response of barley plants to the toxic effects of cadmium changes if various amounts of heavy metals (HM) with the functions of trace elements were introduced together with it, using the example of zinc and copper. In addition, several variants were laid, in which copper and zinc were also introduced along with cadmium. Thus, doses and combinations of metals were used in the experiment: Cd45, Cd25Cu50, Cd25Cu100, Cd25Cu100, Cd25Cu200, Cd45Cu50, Cd45Cu100, Cd45Cu200, Cd45Zn50, Cd45Zn100, Cd45Zn150. Morphometric parameters (appearance, height of plants, their biomass and leaf area), biochemical parameters (accumulation of MDA, total antioxidants and crude protein), crop structure (straw weight, grain weight, 1000 grain weight) were evaluated in experimental plants. In addition, the gross content of HM and other elements in the soil and their transition to the soil solution were analyzed. It is shown that the introduction of cadmium alone led to a significant inhibition of the growth and development of barley plants. At the same time, the combined addition of HM trace elements with cadmium significantly modified the effect of cadmium. Zinc contributed to a decrease in the toxic effects of cadmium, and the intensity of this effect increased as the concentration of zinc increased, and the toxic effects of this HM at the doses considered had not yet manifested themselves. Copper, as a more toxic element, showed its stimulating effect at lower doses than zinc, and at higher doses, the development of acute stress caused by the combined toxic effects of 2 HM was observed. This is true for a dose of cadmium of 45 mg/kg, with a lower dose of cadmium (25 mg/kg), copper had a greater stimulating effect. The considered effects were primarily noted when evaluating morphometric indicators and productivity. Based on the biochemical parameters, it was not possible to draw clear conclusions about how the addition of zinc and copper changed the effects of cadmium. Apparently, it was more appropriate to use other biochemical parameters to assess stress effects. It was noted that the introduction of trace elements generally contributed to a reduction in the accumulation of cadmium in the aboveground biomass of barley plants, however, the addition of zinc led to an increased transition of cadmium into straw, but not into grain.

In the vegetation experiment, with the introduction of Cd2+ into sod-podzolic soil at concentrations of 25 and 50 mg/kg, barley of 4 varieties was grown, which, according to the results of a laboratory experiment with seedlings, turned out to be contrasting in resistance to the action of Cd2+. The aim of the work is to find out whether these varieties retain their properties as resistant or sensitive to cadmium not only as a seedling model, but also during the entire plant ontogenesis. The appearance of plants, plant height, biomass, leaf area, enzyme activity associated with plant protection from environmental stress factors, phytohormone content in aboveground biomass, grain weight, straw and 1000 grains, cadmium accumulation in aboveground plant biomass (straw and grain) were evaluated. Significant differences between groups of cadmium-resistant and cadmium-sensitive varieties were revealed in the experimental conditions. In terms of morphometric parameters and productivity when grown on cadmium-contaminated soil, resistant varieties significantly outperformed sensitive ones. These effects were most noticeable at a cadmium dose of 50 mg/kg, and a dose of 25 mg/kg was insufficient for confident differentiation of varieties into sensitive and resistant ones. It was noted that on the 50th day of the experiment, the concentration of stress hormones increased, and growth hormones decreased when 50 mg/kg cadmium was introduced into the soil of. At the same time, the concentration of stress hormones in resistant varieties increased already on the 30th day, and in growth varieties – both on the 30th and on the 50th day, it did not decrease as much as in sensitive ones. There was a high activity of antioxidant enzymes in resistant varieties compared with sensitive ones. Resistant varieties showed generally high productivity when a cadmium dose of 50 mg/kg was applied to the soil. Sensitive varieties accumulated cadmium in aboveground biomass in greater quantities than resistant ones, while the differences became clear when a dose of cadmium of 50 mg/kg was applied. The results of the study confirmed that the differentiation of barley varieties in terms of resistance found during the assessment of the effects of cadmium on seedlings persists throughout the entire plant life cycle and affects yield and other economically valuable characteristics. The data obtained are useful for assessing the consequences of anthropogenic pollution of agrocenoses, the tasks of breeding varieties of main crops with high resistance to cadmium. In addition, the research materials can be used in the development of a methodology for assessing the state of soils contaminated with heavy metals and for environmental rationing tasks.

The transfer of zinc (natural stable Zn and radioactive tracer 65Zn) to aqueous phase and its uptake by barley have been studied using a specially designed vegetation testbench comprising a lysimeter unit filled with coarse-textured soil and drainage and the vegetation vessels with aqueous barley culture. Although the zinc migration to soil aqueous phase and its uptake by plants are spatially separated, they are sequentially coupled. The patterns of Zn(65Zn) distribution among different compounds (chemical fractions) in soil were determined using parallel and sequential fractionation procedures. The relative content of native (stable) Zn in labile and conventionally labile forms is 2.1–6.5-fold lower as compared with the relative content of radionuclide 65Zn and, vice versa, 2.8–3.0-fold higher for conservative (fixed) fractions of the metal in soil. The dynamics of the following parameters were assessed: Zn concentration, 65Zn specific activity, distribution and concentration factors of natural Zn and 65Zn, and uptake and removal of the metal by plants. The enrichment factors of stable Zn, contained in sequentially extracted chemical fractions, with radioisotope 65Zn, were determined, and the pool of the labile zinc compounds in the studied soil was evaluated.

The influence of humidity of typical Chernozem on the acidity and cationic composition of various energy fractions of the equilibrium soil solution was studied. As the object of research, we used soil solutions extracted by pressure (PSS) from the samples of the arable horizon of typical Chernozem contaminated with Zn, after the completion of the growing experiment with the test culture – barley. The studies of the cationic composition and acidity of quasi-equilibrium soil solutions dependence on the humidity of Chernozem were carried out in the humidity range of 11–40%, i.e., in the range of productive moisture available to plants (pF: 2.17–4.45). For the PSS of variants "bare fallow" and "barley" (Zn0, Zn250 and Zn500), with a decrease in the residual humidity of the sample in the studied range, the concentration of the studied metals in the sequentially extracted PPR fractions also decreased. The acidity of the quasi-equilibrium PSS with increasing humidity (with dilution) decreased. The changes reached 2 pH units. For all the energy fractions of PSS, there was a decrease in acidity for the "barley" variants (Zn0, Zn250, Zn500) compared to the "bare fallow" variants.

The mobility and migration capacity of Zn in the soil-plant system were studied in a series of pot experiments with barley as a test plant. The parameters of Zn accumulation depending on the metal concentrations in soils and soil solutions were estimated by soil and water culture methods. Experiments with barley in water culture were performed on a nutrient (soil) solution extracted from soddy-podzolic soil (Albic Retisol (Loamic, Ochric)) to which Zn 2+ was added to reach working concentrations increasing from 0.07 to 430 μM. Different responses of barley plants to changes in the concentration of Zn in the studied soil were identified. Ranges of the corresponding concentrations in the soil and aboveground barley biomass were determined. Parameters of Zn accumulation by test plants were determined depending on the metal content in soddypodzolic soil and the soil solution. A new method was proposed for evaluating the buffer capacity of soils with respect to a heavy metal (Zn) using test plants (BCS(P) Zn ). The method was used to evaluate the buffering capacity of loamy sandy soddy-podzolic soil. The considered methodological approach offers opportunities for using data obtained during the agroecological monitoring of agricultural lands with heavy metals (HMs), including the contents of exchangeable HMs and macroelements (C and Mg) in soils and concentrations of HMs and (Ca + Mg) in plants, in the calculation of the buffering capacity of the surveyed soils for HMs.

The relationship between the main physicochemical properties of soils and the accumulation of natural Zn and 65 Zn radionuclide has been studied, and the capacity of soils to limit the mobility of the element in the soil–plant system has been assessed. The contribution of each of the selected soil state parameters to the accumulation of zinc by barley has been determined, and the soil state parameters have been ranked. It has been found that the largest contributions to the variation of the resulting parameter ( 65 Zn accumulation coefficient, K a ) are made by mobile Fe (25%), free carbonates (21%), and acid-soluble Zn (18%). The largest contributions to the Zn ac K a are made by free carbonates (13%) and mobile Fe (8%). The contributions of physical clay and organic carbon in soils and qualitative composition of humic substances are almost similar (4% for each). No differences in the inactivating capacity of different soils (soddy-podzolic soils, gray forest soils, and chernozems) for 65 Zn are observed. This is related to the fact that the transfer of 65 Zn to plants is statistically significantly controlled by the contents of free carbonates, mobile iron, and potentially plantavailable forms of stable natural Zn (carrier of 65 Zn) rather than the quantitative and qualitative composition of organic matter and the degree of dispersion of mineral particles. The analysis of the Zn ac K a / 65 Zn K a ratios has shown that the share of plant-available Zn in the acid-soluble form of the metal (1 M HCl) is 0.61 on the average for the studied soils, and its share in the total Zn content in the soils is only 0.14.

The forecasting model of the concentration ratio (CR) of 137Cs in the plants taking into consideration organic carbon, pH, mobile and total content of potassium in soil has been developed on the basis of the radioecological investigations in the valleys of the Resseta and Vytebet rivers. The type of functional dependence of CR from soil characteristics can be used for an estimation of the content of radionuclides in various species and productive parts of plants.