Estimation of substance distribution in the soil-plant system (on the example of crop species)

Assessment of the distribution of nutrients and pollutants in the soil-plant system is a relevant theoretical and applied task in biogeochemistry, agrochemistry and environmental biotechnology. Pointwise, average and extreme values of the concentration of the studied substance in the plant (Cp) and in the soil (Cs), as well as biological absorption coefficients (Kab=Cp /Cs), do not characterize the distribution of the studied substance in the system. This work investigates the effect of substance concentration in a soil on its distribution between the plant and the soil. The use of the Cp=f(Cs) and Kab=f(Cs) functions for describing the substance content in the plant depending on its concentration in the soil, allowed us to propose approaches to quantitative assessment of the distribution process. The first approach consists in the approximation of dependences by Freundlich and Langmuir linear or adsorption power functions Cp=f(Cs), on which basis the concentration parameters of а, 1Кр, Кр, С∞are determined. These parameters are used to study the mechanism and intensity of substance accumulation by a plant. The second approach includes obtaining a power function Kab=f(Cs) or its linear representation lgKab=f(lgCs) and calculating standardized coefficients Kab. These coefficients are sensitive at low (1, 10) and limiting at high (100, 1000) concentrations of the studied substance in the soil. The example of benz(a)pyrene, fluorine and zinc, i.e., substances different in terms of their physical, chemical and biological properties, was applied to demonstrate the process of determining the absolute and relative accumulation of the substances by different crop species. A comparison of different plants was conducted; possible mechanisms of the distribution of the studied substances and their intensity are considered.