Hydrolysis of triasulfuron, metsulfuron-methyl and chlorsulfuron in alkaline soil and aqueous solutions

Sarmah, Ajit K., Kookana, Rai S., Duffy, Michael J., Alston, Angus M., & Harch, Bronwyn (2000) Hydrolysis of triasulfuron, metsulfuron-methyl and chlorsulfuron in alkaline soil and aqueous solutions. Pest Management Science, 56(5), pp. 463-471.

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Abstract

The hydrolysis of triasulfuron, metsulfuron-methyl and chlorsulfuron in aqueous buffer solutions and in soil suspensions at pH values ranging from 5.2 to 11.2 was investigated. Hydrolysis of all three compounds in both aqueous buffer and soil suspensions was highly pH-sensitive. The rate of hydrolysis was much faster in the acidic pH range (5.2-6.2) than under neutral and moderately alkaline conditions (8.2-9.4), but it increased rapidly as the pH exceeded 10.2. All three compounds degraded faster at pH 5.2 than at pH 11.2. Hydrolysis rates of all three compounds could be described well with pseudo-first-order kinetics. There were no significant differences (P =0.05) in the rate constants (k, day-1) of the three compounds in soil suspensions from those in buffer solutions within the pH ranges studied. A functional relationship based on the propensity of nonionic and anionic species of the herbicides to hydrolyse was used to describe the dependence of the 'rate constant' on pH. The hydrolysis involving attack by neutral water was at least 100-fold faster when the sulfonylurea herbicides were undissociated (acidic conditions) than when they were present as the anion at near neutral pH. In aqueous buffer solution at pH > 11, a prominent degradation pathway involved O-demethylation of metsulfuron-methyl to yield a highly polar degradate, and hydrolytic opening of the triazine ring. It is concluded that these herbicides are not likely to degrade substantially through hydrolysis in most agricultural (C) 2000 Society of Chemical Industry.

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ID Code: 72745
Item Type: Journal Article
Refereed: Yes
Additional Information: Cited By (since 1996):41
Export Date: 26 May 2014
Source: Scopus
CODEN: PMSCF
Additional URLs:
Keywords: Acid hydrolysis, Alkaline soil, Base hydrolysis, Hydrolysis kinetics, Metabolites, Sulfonylureas, herbicide, sulfonylurea derivative, agriculture, article, high performance liquid chromatography, hydrolysis, kinetics, mass spectrometry, nonhuman, pest control, pH, soil
DOI: 10.1002/(SICI)1526-4998(200005)56:5<463::AID-PS138>3.0.CO;2-I
ISSN: 1526-498X
Divisions: Current > QUT Faculties and Divisions > Science & Engineering Faculty
Deposited On: 11 Jun 2014 22:45
Last Modified: 11 Jun 2014 22:45

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