Genesis of the idea and definition of pedogeochemical barriers	of heavy metals migration
Authors: Savosko V. M. 
Published: February 2020

The aims of this study were to consider the genesis’s idea «geochemical barriers» and to invite a definition for «pedogeochemical barriers» by example of heavy metals’ migration. Object of this study – scientific publications that show the results of heavy metals’ content and distribution in soils. The concept of geochemical barriers was formulated by A. I. Perelman in 1961. At first ideas of this concept have been used for: 1) ordering of the geochemical conditions at hypergenesis zone, 2) justification the concept of geochemical field; 3) mathematical modeling of geochemical processes, 4) effective mineral exploration. With the passage of time, this concept has become successfully implemented in lithology, hydrogeology, soil science, geochemistry environment. In the XXI century geochemical barriers used in the development of rehabilitation technology of contaminated lands and limit the spread of pollutants. The concept of geochemical barriers began to be used in soil science, through the work of V. A. Kovda (1972), A. A. Rode (1975), M. A. Glazovskaj (1988). Later, the list of researchers who used this idea in their works has increased significantly. However, these researchers: 1) was performed a mechanical transfer this idea from geochemistry to soil science, 2) use this idea mainly for environmental protection, 3) used exclusively of the geochemistry methodology and of the geochemistry classification schemes. As for soil science the best analogue of «geochemical barriers» should recognize the term «pedogeochemical barriers». An essence pedogeochemical barrier, in our opinion, is as follows. In hypergenesis zone the geochemical barriers act as «situational and contrast» phenomenon. In soil profile the pedogeochemical barriers act as «substation and reaction» phenomenon. We are supposed to that the soil profile is a multiaspect complex of pedogeochemical barriers. At that some of them can be localized within several soil horizons. At the same time, several such barriers can be located in one soil horizon. Therefore, in the refined form, a pedogeochemical barrier should be understood as part of the soil profile, where, as a result of the formation of special conditions for substitution-reaction interactions, the accumulation of certain chemical elements occurs. Designed by A. I. Perelman's doctrine of geochemical barriers has found a varied and successful application in geochemistry, geology, lithology, mineralogy, and in other contiguous sciences. At present, the ideas of this exercise are very important for a fundamental understanding of the biogeochemical functions of the pedosphere as the theoretical basis for preserving the biosphere and improving the soil in conditions of modern technogenesis. In our understanding, the pedogeochemical barrier is part of the soil profile, where, as a result of the formation of special conditions for substitution-reaction interactions, the accumulation of certain chemical elements occurs. In further studies it is expedient to consider: mechanisms of action, typology, parameters of pedogeochemical barriers, and also to analyze these parameters on the example of heavy metals in chernozems of ordinary and southern.