Effect of Sulfate on Ionic Transport and Balance in a Slightly Acidic Forest Soil
1986
Khanna, P. K. | Weaver, G. T. | Beese, F.
Sulfate (CaSO₄) was percolated at low (1.4 mg S L⁻¹) and high (60.8 mg S L⁻¹) concentrations, in a solution of composition equivalent to that of the canopy drip under beech (Fagus sylvatica L.) forests, through undisturbed columns of a slightly acid soil (Terra Fusca Rendzina or Lithic Rendoll). Concentrations of Ca²⁺, Mg²⁺, NO⁻₃, and probably HCO⁻₃ increased and of K decreased in the percolates. Decomposition of soil organic matter caused a significant production and subsequent leaching loss of 1.0 mmolc m² of NO⁻₃ during the experimental period of 156 d. Sulfate was released by the soil during the phase of low SO²⁻₄ addition but was retained during the phase of high SO²⁻₄ addition. Production of NO⁻₃ and probably HCO⁻₃, retention and release of SO²⁻₄, and the release of cations involved a significant amount of production/consumption of protons in the soil. Calcium (II) and Mg²⁺ were leached from the soil but K⁺ was retained. Breakthrough curves showed peaks, usually wide, for cations when about two pore volumes of solutions had been replaced. Sulfate behaved as a reactive ion in this soil and its transport could be described by a solute transport model using suitable parameters (adsorption isotherms, apparent diffusion coefficients, bulk density, and water content), which were obtained from independent studies.
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