Effect of Dissolution of Aluminosilicates and Carbonates on Ionic Activity Products of Calcium Carbonate in Soil Extracts
1981
Levy, Rachel
Monosilicic acid, bicarbonate, calcium, magnesium, sodium, and chloride released in six sequential deionized water extracts by a noncalcareous and a calcareous soil at 1:10 and 1:1 soil/water ratios were measured. It was found that the concentrations of all soluble species released by the two soils increased and their amounts decreased with the increase in soil/water ratio. Such a dissolution pattern could be due to the presence of minerals with an intermediate solubility, i.e., higher than that of sparingly soluble minerals and lower than that of very soluble salts. These minerals could be either metastable soluble aluminosilicates, soluble carbonate surfaces, or both. It was found that both soils contained minerals of intermediate solubility. When the amounts of these minerals were small, at 1:10 soil/water ratio, the extracts of the noncalcareous soil were undersaturated in respect to any well-crystallized carbonate, whereas those of the calcareous soil were in equilibrium with calcite. When the amounts of these minerals increased at a 1:1 soil/water ratio, they released enough calcium and carbonate to oversaturate the extracts of the two soils in respect to calcite. The pIAP (ionic activity product) of the 1:1 extracts of the noncalcareous soil was 7.99 and that of the calcareous soil was 7.76.
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