Hydrolysis and adsorption of cyhalofop-butyl and cyhalofop-acid on soil colloids.
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.
Dipartimento di Scienze Ambientali Agrarie e Biotecnologie Agro-Alimentari, Università di Sassari, Viale Italia 39, 07100 Sassari, Italy. pusino@uniss.it
Maria Vittoria
MV
Pinna
Ilaria
I
Braschi
Sonia
S
Blasioli
Carlo E
CE
Gessa
Alba
A
Pusino
D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry; D002073:Butanes / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D000077215:Clay; D003102:Colloids / Q000737:chemistry; D052918:Environmental Restoration and Remediation / Q000379:methods*; D006540:Herbicides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D009570:Nitriles / Q000737:chemistry*; D012987:Soil / Q000032:analysis*; D017550:Spectroscopy, Fourier Transform Infrared
D000538:Aluminum Silicates; D002073:Butanes; D003102:Colloids; D006540:Herbicides; D009570:Nitriles; D012987:Soil; C501583:cyhalofop-butyl; D000077215:Clay