Sorption of ionisable organic compounds by field soils. Part I: acids

A - Papers appearing in refereed journals

Nicholls, P. H. and Evans, A. A. 1991. Sorption of ionisable organic compounds by field soils. Part I: acids. Pesticide Science. 33 (3), pp. 319-330.

AuthorsNicholls, P. H. and Evans, A. A.

Sorption of different classes of weak organic acids was measured using soils with a range of pH values, taken from long-term field experiments that had received different amounts of lime. Non-ionisable compounds were used to demonstrate that the soils of different pH used in the experiments have similar sorptive properties. Values of the sorption coefficients for chloride ion were negative at all pHs except one. Sorption of moderately polar, monobasic, weak acids was weak in acidic soils and very weak in neutral and alkaline soils where they were predominantly dissociated. A lipophilic weak acid was strongly sorbed even at high pH. A model is presented which estimates soil/water distribution coefficients, at any soil pH, from lipophilicity and pK(a) of the acid and organic matter content of the soil. The model was derived using sorption measured for substituted phenoxyacetic acids. Sorption values calculated using the model were compared with values measured for chlorsulfuron and showed useful agreement. Dibasic acids were strongly sorbed, probably by the mechanism of ligand exchange, if they were chelating agents with potential to form 5- or 6-membered rings with an acceptor atom. Phenylphosphonic acid was strongly sorbed, being a strong monodentate ligand.

KeywordsAgronomy; Entomology
Year of Publication1991
JournalPesticide Science
Journal citation33 (3), pp. 319-330
Digital Object Identifier (DOI)doi:10.1002/ps.2780330306
Open accessPublished as non-open access
Funder project or code06
Project: 051213

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