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A model of solid‐solution interactions in acid organic soils, based on the complexation properties of humic substances
Author(s) -
TIPPING E.,
HURLEY M. A.
Publication year - 1988
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1988.tb01235.x
Subject(s) - chemistry , humic acid , soil water , titration , ionic strength , organic matter , inorganic chemistry , dissolved organic carbon , ion exchange , environmental chemistry , ion , aqueous solution , soil science , organic chemistry , fertilizer , environmental science
SUMMARY CHAOS (Complexation by Humic Acids in Organic Soils) is a quantitative chemical model of organic soils that incorporates complexation by the functional groups of humic substances and non‐specific ion‐exchange reactions. The two types of interaction are linked by the net humic charge, Z, which depends on the extents of proton and metal complexation, and which in turn determines ionic concentrations in the diffuse part of the electrical double layer, by a Donnan equilibrium. CHAOS was found to account satisfactorily for the results of acid‐base titration experiments (pH range 3–5) with soil samples, giving reasonable simultaneous predictions of solution pH and concentration of A1 3+ . Predictive calculations with CHAOS suggest that organic soils acidified by acid rain would respond on a time‐scale of years‐to‐decades to reductions in rain acidity. An associated effect might be an increase in the concentration of dissolved organic matter in the soil solution.