HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Norvell, W. A. Articles by Lindsay, W. L. Search for Related Content PubMed Articles by Norvell, W. A. Articles by Lindsay, W. L. Agricola Articles by Norvell, W. A. Articles by Lindsay, W. L.

Reactions of EDTA Complexes of Fe, Zn, Mn, and Cu with Soils¹

ABSTRACT

The Fe, Zn, Cu, and Mn complexes and the Na salt of EDTA (ethylenediaminetetraacetic acid) were reacted with suspensions of acid, neutral, and calcareous soils. The initial concentration of chelate was 1 x 10^-4M or on a soil weight basis, 11.2, 13.1, 12.7, and 11.0 ppm of Fe, Zn, Cu, and Mn, respectively. Suspensions were aerated and shaken continuously for periods of 2 hours to 30 days. At the termination of each reaction period the pH of the suspensions was measured; following centrifugation, the supernatant solutions were analyzed for Fe, Zn, Cu, Mn, Ca, and Mg by atomic absorption spectrophotometry. The concentration of ¹⁴C-labeled EDTA was determined by liquid scintillation.

FeEDTA was stable in soil suspensions of pH 5.7 and 6.1, moderately stable at pH 6.75, and unstable at pH 7.3 and 7.85. This behavior was satisfactorily predicted using formation constants to describe equilibria of EDTA with Fe³⁺, Ca²⁺, and H⁺, with the assumption that the Fe³⁺ concentration was controlled by the solubility of amorphous iron(III) oxides. ZnEDTA and CuEDTA were most stable in suspensions near neutrality. In acid soils Cu and Zn were increasingly displaced by Fe as pH decreased while in calcareous soils these metals were displaced by Ca as pH increased. The loss of Mn from MnEDTA was very rapid in all soils and was essentially complete in less than one day from suspensions of pH 6.1 to 7.85.

Contribution from the Department of Agronomy, Colorado State Univ., Fort Collins. Published with the approval of the Director of the Colorado Agr. Exp. Sta. as Scientific Series Paper no. 1326. This work was supported in part by the Geigy Agricultural Chem. Div. of Geigy Chemical Corp., Ardsley, N.Y. Presented at a symposium — Metal Chelation in Soils — Div. S-2, Soil Science Society of America, Nov. 8, 1967, in Washington, D.C.

² Graduate Research Assistant and Professor of Soil Science, respectively, Colorado State University.

Received for publication June 17, 1968. Accepted for publication July 16, 1968.