Alkalinity of virgin solonetzes in Northern Kalmykia (the Arshan-Zel’men experimental station)статья
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Аннотация:The alkalinity of virgin solonetzes of the Ergeni Upland, Ergeni Plain, and Sarpinsk Lowland has been studied. These soils are characterized by the neutral salinization and the high alkalinity of the solonetzic and subsolonetzic horizons. The analysis of the soil water extracts demonstrated that the highest alkalinity is typical of the subsolonetzic horizons containing calcium carbonates (the B2 and BCca horizons). In the solonetzic horizons without CaCO3, the alkalinity is lower despite the high exchangeable sodium percentage (up to 42%). The alkalinity of the solonetzic and subsolonetzic horizons may be conditioned by two processes: (a) the hydrolysis of the exchange complex (EC) containing sodium (ECNa + H2O ECH + Na+ + OH–) and (b) the reaction of the ion exchange with the substitution of calcium for sodium in the exchange complex (EC2Na + CaCO3 ECCa + 2Na+ + Calculations performed on the basis of the thermodynamic equations of the physicochemical equilibria according to the LIBRA program indicate that soda is absent in the solonetzic horizons, whose alkalinity is related to the carbonate calcium equilibria. The high alkalinity of the calcareous subsolonetzic horizons is related to the presence of soda in combination with CaCO3. The formation of soda in these horizons is due to the reaction of ion exchange described by Gedroits.