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Effects of Ionic Strength, Calcium, and Citrate on Orthophosphate Solubility in an Acidic, Montmorillonitic Soil
Author(s) -
Traina Samuel J.,
Sposito Garrison,
Hesterberg Dean,
Kafkafi U.
Publication year - 1986
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1986.03615995005000030016x
Subject(s) - solubility , citric acid , ionic strength , chemistry , inorganic chemistry , dissolution , metal , ionic bonding , nuclear chemistry , aqueous solution , ion , organic chemistry
A recent study by the authors of the effects of pH and organic acids on residual orthophosphate solubility in an acidic, montmorillonitic soil (Typic Chromoxererts) was extended to include variations of ionic strength (NaCl background) and Ca 2+ concentration at fixed ionic strength. The objective of the experiments was to elucidate further the mechanism of orthophosphate solubility in a montmorillonitic soil containing exchangeable Al(III) and added citric acid. At ionic strengths between 20 and 100 mol m −3 (NaCl) and Ca 2+ concentrations between 1 and 5 mol m −3 at 20 mol m −3 ionic strength (NaCl background), additions of citric acid at low concentrations (<0.1 mol m −3 ) reduced orthophosphate solubility. The solubility then gradually returned to its value in the absence of added organic acid as the citric acid concentration was increased to 0.6 mol m −3 . The only significant effect of increasing the ionic strength or the Ca 2+ concentration was to decrease orthophosphate solubility at any level of citric acid addition. Orthophosphate‐citric acid interactions in the soil were influenced only quantitatively, probably through the displacement of exchangeable Al(III) by Na + and/or Ca 2+ , by increasing the concentration of these two metal cations in the soil solution.