Element fluxes and buffer reactions in acidified soils from a humid-temperate region of southern europe

摘要

The present study aimed to assess the buffering reactions and identify the sources of ion replenishment by carrying out a laboratory leaching experiment using some soils from a humid, temperate region of Northern Spain. The experiment consisted of the addition of a solution of H2SO4 to five soils developed on various types of parent materials (granulite, serpentinite, schist, granite and sandy sediments) and differing markedly in their mineralogy and chemical properties. Although the treatment considerably intensified the leaching of base cations, the exchangeable fraction increased or was not affected, which indicated significant mobilization of these elements from non exchangeable fractions. The soils differed markedly in the amounts of SO42- retained, however only a small part of the amount retained in the upper horizons was adsorbed. Acid load was mainly produced by free deposited H+ and nitrification of internal organic N. Sulphate retention was the dominant buffering mechanism in the soils developed on serpentinite and schist. Proton consumption linked to Al mobilization occurred in the surface horizons of all soils, but especially in the most acidic soils, those on granite and schist. In the soil on sandy sediments, the dissolution of CaCO3 constituted the only buffering mechanism. References: 23