Hydrolysis and adsorption of cyhalofop-butyl and cyhalofop-acid on soil colloids |
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| Authors: | Pinna Maria Vittoria Braschi Ilaria Blasioli Sonia Gessa Carlo E Pusino Alba |
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| Institution: | Dipartimento di Scienze Ambientali Agrarie e Biotecnologie Agro-Alimentari, Università di Sassari, Viale Italia 39, 07100 Sassari, Italy. pusino@uniss.it |
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| Abstract: | A study was undertaken to investigate the stability of cyhalofop-butyl (2 R)-2-4-(4-cyano-2-fluorophenoxy)phenoxy]butylpropanoate (CyB), an aryloxyphenoxy-propionic herbicide, at different pH values. The hydrolysis of CyB was faster in nonsterile than in sterile water. In sterile medium, CyB degraded only to (2 R)-2-4-(4-cyano-2-fluorophenoxy)phenoxy]propanoic acid (CyA), whereas in nonsterile water, also the metabolites (2 R)-2-4-(4-carbamoyl-2-fluorophenoxy)phenoxy]propanoic acid (CyAA) and (2 R)-2-4-(4-carboxyl-2-fluorophenoxy)phenoxy]propanoic acid (CyD) were detected. The adsorption of CyB onto clays, iron oxide, and dissolved organic matter (DOM), using a batch equilibrium method, was also studied. A lipophilic bond is responsible for CyB adsorption on DOM. CyB was adsorbed on Fe(III)- and Ca-clays through hydrogen bonding between the carbonyl oxygen and water surrounding the exchangeable cations. In the interlayer of K-clay, CyB was hydrolyzed to CyA, which remained adsorbed therein as a monomer. The acid CyA was adsorbed only by the Fe-oxide through complexation. The CyA-Fe-oxide complex was stable and did not undergo degradation. |
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