In soils, cadmium (Cd) and its compounds, originating from industrial activities, differ both in mobility as well as in their ability to permeate the soil solution from naturally occurring cadmium compounds (native Cd). Therefore, the determination of the parameters of cadmium mobility in soils and its accumulation by plants in the soil–soil solution–plant system is very important from both scientific and practical viewpoints. ¹⁰⁹Cd was used as a radioactive tracer to study the processes of the transition of Cd into the aqueous phase and its uptake by plants over the course of a vegetative lysimeter experiment. Using sequential extraction according to the Tessier–Förstner procedure and modified BCR schemes, certain patterns were determined in the distribution of Cd/¹⁰⁹Cd among their forms in various compounds in the soil, along with the coefficients of the enrichment of native stable Cd with radioactive ¹⁰⁹Cd. It was shown that the labile pool of stable Cd compounds (29%) was significantly smaller than that of radioactive ¹⁰⁹Cd (69%). The key parameters characterizing the migration capacity of Cd in the soil–soil solution–plant system were determined. It was found that the distribution coefficient of native Cd between the soil and the quasi-equilibrium lysimeter solution exceeded the similar value for the ¹⁰⁹Cd radionuclide by 2.2 times, and the concentration coefficients of Cd and ¹⁰⁹Cd in the barley roots were 9 times higher than in its vegetative parts. During the experiment, the average removal of Cd (¹⁰⁹Cd) from the soil by each barley plant was insignificant: 0.002 (0.004)%. Based on the results of ¹³C nuclear magnetic resonance (NMR) spectroscopy of a lyophilized sample of the high-molecular-weight dissolved organic matter (HMWDOM) of the soil solution, its components were determined. It transpired that the isolated lyophilized samples of HMWDOM with different molecular weights had an identical structural and functional composition. The selective sorption parameters of the HMWDOM and humic acid (HA) with respect to Cd²⁺ ions were determined by the isotope dilution method.

The influence of soil characteristics on the lability and bioavailability of zinc at both background and phytotoxic concentrations in Albic Retisol soil (Loamic, Ochric) was studied using various methods. Ranges of insufficient, non-phytotoxic, and phytotoxic zinc concentrations in soil solutions were established in an experiment with an aqueous barley culture. It was experimentally revealed that for a wide range of non-toxic concentrations of Zn in the soil corresponding to the indicative type of plant response, there was constancy of the concentration ratio (CR) and concentration factor (CF) migration parameters. As a result, a new method for assessing the buffer capacity of soils with respect to Zn (PBC_Zn) is proposed. The transformation processes of the chemical forms and root uptake of native (natural) zinc contained in the Albic Retisol (Loamic, Ochric) through the aqueous culture of barley were studied using a cyclic lysimetric installation and radioactive ⁶⁵Zn tracer. The distribution patterns of Zn(⁶⁵Zn) between different forms (chemical fractions) in the soil were established using the sequential fractionation scheme of BCR. The coefficients of distribution and concentration factors of natural Zn and ⁶⁵Zn, as well as accumulation and removal of the metal by plants were estimated. The values of the enrichment factor of natural (stable) Zn contained in sequentially extracted chemical fractions with the ⁶⁵Zn radioisotope were determined and the amount of the pool of labile zinc compounds in the studied soil was calculated.

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...

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.