Spodosol cation release and buffering of acidic inputs

The release and leaching of base cations and aluminum by acid additions to O and B soil horizons was examined using both batch and column experimental methods. Solution and soil contact time was a significant factor in the amount of cation release and leaching from the B horizon. Increased acidity resulted in greater levels of base cations and aluminum being released or leached from all soils. The type of acid anion, NO₃⁻or SO₄²⁻strongly influenced the amount of soil base cation released; Ca²⁺was much lower in the H₂SO₄extracted solutions (maximum 20.0 versus 110 μeq. g⁻¹from the 0 horizon and 0.40 versus 2.0 μeq·g⁻¹from the B horizon for H₂SO₄and HNO₃solutions, respectively). Gypsum formation was suggested as a possible explanation for the decreased Ca²⁺levels; however, SO₄²⁻adsorption was also believed to contribute to the reduction in base cation release. Proton buffering was due to three soil processes which included: Cation exchange reactions, protonation of organic constituents, and SO₄²⁻adsorption. Differences in contact time and solution composition were deemed to be important factors in cation release from these soils.