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

This Article Figures Only Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Barrett, K. A. Articles by McBride, M.B. Search for Related Content PubMed Articles by Barrett, K. A. Articles by McBride, M.B. GeoRef GeoRef Citation Agricola Articles by Barrett, K. A. Articles by McBride, M.B. Related Collections Redox Processes Heavy Metals Soil Chemistry

Soil Chemistry

Trace Element Mobilization in Soils by Glyphosate

Dep. of Crop and Soil Sciences, Cornell Univ., Ithaca, NY 14853

^* Corresponding author (mbm7{at}cornell.edu)

Glyphosate, the most widely used herbicide in agriculture, has a strong tendency to sorb on minerals by bonding with surface metals through its metal-coordinating functional groups. However, this same chemical process can potentially mobilize sorbed trace metals by chelation and sorbed anions such as phosphate by displacement. The tendency for glyphosate to mobilize Cu and other elements was tested in soil leaching experiments by applying glyphosate alone or complexed with Cu to mineral and organic soil columns and measuring the concentrations of these elements in the leachates by inductively coupled plasma (ICP) spectrophotometry. Complexation with glyphosate inhibited Cu sorption on the soil columns, rendering this metal more mobile in both the mineral and organic soil. Glyphosate mobility was also enhanced when applied to the organic soil as the Cu complex, but this effect was not detected with the mineral soil. Glyphosate was adsorbed more completely on the organic soil than the mineral soil, suggesting a metal bridging mechanism to explain sorption of this anionic molecule. The application of a commercial Roundup spray to long-contaminated soils containing elevated concentrations of heavy metals and phosphate resulted in significant increases in the leaching of Cu, Zn, Al, Ni, P, Si, and As. No significant increases in elemental leaching were detected in mineral and organic soils with normal background concentrations of heavy metals and P. Batch equilibration studies confirmed the glyphosate-enhanced dissolution of Cu in Cu-contaminated soils, but reductions of free Cu²⁺ activity were measured only in uncontaminated soils. The results indicate that several elements, particularly Cu, Al, and P, could be mobilized within the thin surface layer of soils receiving a high effective rate of glyphosate during herbicide application.

Abbreviations: AMPA, aminomethylphosphonate • ANOVA, analysis of variance • CBD, citrate–bicarbonate–dithionite • CEC, cation exchange capacity • ICP, inductively coupled plasma spectrometry