Geochemical Features of Alluvial Soils of the Middle Reaches of the Bolshaya Kokshaga River

The article presents the results of the identification of the paragenesis of chemical elements and radial geochemical barriers in alluvial soils (Fluvisols) of the middle reaches of the Bolshaya Kokshaga River (Republic of Mari El). It has been established that Fe is the leading (typomorphic) element, and Mn, Ba, P, Zn, and Ni are associated with it. Al forms a geochemical family with K, Mg, Ti, and Cr. The content of Ca, S, Sr, and Cu is related to the amount of loss on ignition, and Na and Zr are related to Si. Particular elements are fixed on radial geochemical barriers: Si and Zr on the mechanical one; Ca, S, Sr, and Cu on the biogeochemical one; Al, K, Mg, Ti, and Cr on the sorption on; Fe on the oxygen one; and Mn, Ba, P, Zn, and Ni on the chemisorption one. The peak concentrations of Si and Zr are determined on the mechanical barrier in the profile of all soil types. Ca, S, Cu, and Sr are fixed on the biogeochemical barrier in soddy and swamp soils. Increased concentrations of Al, K, Mg, Ti, and Cr are found on the sorption barrier in all types of soils. The effect of oxygen and chemisorption barriers is manifested in meadow and mucky-gley soils.