Contributions of separate reactions to the acid–base buffering of soils in brook floodplains (Central Forest State Reserve)

Abstract

The acid–base buffering of gleyic gray-humus soils developed in brook floodplains and undisturbed southern-taiga landscapes has been characterized by the continuous potentiometric titration of soil water suspensions. During the interaction with an acid, the major amount of protons (>80%) is consumed for the displacement of exchangeable bases and the dissolution of Ca oxalates. In the O and AY horizons, Mn compounds make the major contribution (2–15%) to the acid buffering. The buffer reactions with the participation of Al compounds make up from 0.5 to 1–2% of the total buffering capacity, and the protonation of the surface OH groups of kaolinite consumes 2–3% of the total buffering capacity. The deprotonation of OH groups on the surface of Fe hydroxides (9–43%), the deprotonation of OH groups on the surface of illite crystals (3–19%), and the dissolution of unidentified aluminosilicates (9–14%) are the most significant buffer reactions whose contributions have been quantified during the interaction with a base. The contribution of the deprotonation of OH groups on the surface of kaolinite particles is lower (1–5%) because of the small specific surface area of this mineral, and that of the dissolution of Fe compounds is insignificant. In the AY horizon, the acid and base buffering of soil in the rhizosphere is higher than beyond the rhizosphere because of the higher contents of organic matter and nonsilicate Fe and Al compounds.