Acid buffer capacity of mineral horizons of podzolic and bog-podzolic soils of the Komi Republic

摘要

The acid buffer capacity of water suspensions and KCl extracts from the main genetic horizons of podzolic and bog-podzolic soils of the Komi Republic was studied by continuous potentiometric titration. Acid titration of eluvial horizons involves the following buffer reactions: displacement of exchangeable bases by protons. dissolution of finely dispersed AI hydroxides, and protonation of pH-dependent exchange positions on Fe and A1 hydroxides. When the degree of hydromorphism increases, the acid buffer capacity of the water suspensions decreases because of the decrease in the pH of the initial titration point and in the content of exchangeable bases and amorphous A1 compounds. In the acid titration of water suspensions from the B and C horizons of the soils studied, the main buffer reaction is the displacement of exchangeable Ca and Mg by protons. A decrease in the basicity of the extracted aluminum hydroxo and aluminum-organic complexes and the protonation of anions of the strongest dissolved organic acids can be the main buffer reactions proceeding during the acid titration of KCl extracts from eluvial horizons of podzolic and bog-podzolic soils. The buffer role of the protonation of organic anions increases with the increasing degree of hydromorphism.