RESUMO
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.
RESUMO
The direct estimation of the value of the diffusion component of mass transfer of pollutants in arable soil horizons is an important task of scientific and applied importance. The values of effective diffusion coefficients of 60Co radionuclide (Deff) in water-saturated samples of different soils with disturbed structure and the same initial bulk density were obtained during the laboratory experiment. Of particular interest is the assessment of the contribution of individual specific characteristics of soils that have undergone the gleying process to the regulation of Deff60Co.There was noted a significant variability of Deff60Co for investigated soils due to different soil characteristics. To assess this, influence a statistical approach has been used, where edaphic factors representing the most important characteristics of the soils acted as independent variables (predictors), and the dependent (resulting) variable was Deff60Co. The contributions of each of the selected indicators of soils state (independent variables) in varying of Deff60Co were also identified. During the experiments, there was revealed a particularly strong increase in the Deff60Co for soils with a high Eh, ΣFr.<0.01 mm and decrease in the absolute value of the dependent variable with two predictors: pHH2O and P2O5mobile in conditions of excessive moisture. Based on the study of the dependence between the main physicochemical soil properties and the magnitude of effective diffusion coefficients (Deff60Co), the selected physicochemical characteristics of soils were ranked by the degree of influence on the value of the dependent variable: pHH2O > Eh > ΣFr.<0.01 mm > P2O5mobile > Corg.At the same time, the multiple linear regression analysis of the obtained data showed statistical significance for two independent predictors of the model (pHH2O and ΣFr.<0.01 mm). As a result, semi-partial determination coefficients responsible for the share of the total variation of the dependent variable due to the statistically significant corresponding independent variables (pHH2O and ΣFr.<0.01 mm) were calculated based on the data presented.
