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Micronutrient Cation Complexes in Soil Solution: III. Characterization of Soil Solution Ligands and their Complexes with Zn 2+ and Cu 2+
Author(s) -
Geering H. R.,
Hodgson J. F.
Publication year - 1969
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/sssaj1969.03615995003300010018x
Subject(s) - chemistry , metal , loam , chelation , inorganic chemistry , ligand (biochemistry) , dissociation constant , zinc , acid dissociation constant , dissociation (chemistry) , nuclear chemistry , soil water , organic chemistry , aqueous solution , biochemistry , environmental science , receptor , soil science
At least three groups of compounds were found to complex Zn 2+ and Cu 2+ in soil solution from the A horizon of a Williamson silt loam. A nondialyzable fraction of soil solution ligands had a poorly defined acid dissociation, pKa, ranging from 3 to 4.7. The dialyzable fraction had acid dissociation constants of 4.5 and 9.5, which were attributed to aliphatic and amino acids, respectively. The equivalent concentration of the nondialyzable acid fraction was only 1/40 that of the dialyzable fraction, but was more effective in complexing Zn and Cu in the soil solution. The average metal/ligand ratio was equal to unity in complexes of both the dialyzable and nondialyzable fractions with Zn 2+ and Cu 2+ . Estimated, log 10 (average formation constants) of the nondialyzable‐metal complexes were calculated on the basis of titratable acidity as 4.3 ± 0.1 and 5.5 ± 0.1 for Zn 2+ and Cu 2+ , respectively.