Effect of Sulfate on Ionic Transport and Balance in a Slightly Acidic Forest Soil1
- P. K. Khanna,
- G. T. Weaver and
- F. Beese2
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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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