A study was conducted to determine the influence of organic matter on the solubility of Al in organic soil horizons from different geographic regions. Results showed that the equilibrium solubility of Al was dependent on solution pH and the degree to which the soil organic matter was saturated with Al. Plots of Al solubility showed that, as solution pH decreased, soluble Al increased, and that, for a given pH, soluble Al increased with increasing surface‐bound Al. In addition, Al solubility was always less than that predicted from the solubility of natural gibbsite or kaolinite. Temperature dependence and rate studies suggested that Al solubility was governed by an ion‐exchange reaction between H + and Al and the organic matter. Aluminum solubility was similar in Oi and Oa horizon soils at the same bound aluminum ratio (BAR) and pH. No differences were noted when the soils were compared on a regional basis, suggesting that prediction of aqueous Al concentrations in organic horizons and peaty hydrologic areas could be accomplished with a simple model.
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Walker et al. (1990) studied this question.