Acid-Induced Aluminum Mobilization in Finnish Mineral Soils

Summary

The release of aluminum following acid additions to soil samples representing the common forest site types in Finland was followed in the laboratory. The surface mineral soil layers of Finnish soils contain appreciable amounts of organic matter. The role of organic matter in the release of Al was found to be decisive in the Ao and A layers, Al only being released when the pH fell below 3.5–3.0. Organic matter in the B horizon also appears to decrease somewhat the pH at which Al dissolution occurs. Al release in the Ao horizon was primarily based on cation exchange reactions and not directly on pH. The affinity of the major metallic cations for exchange sites in the Ao horizon followed the order: K < Mg < Mn < Ca < Al < Fe.