| Abstract
| - Knowledge of the kinetics and pathways of hydrolytic degradation is crucial to the prediction of thefate and transport mechanism of chemicals. This work first describes the kinetics of the chemicalhydrolysis of imazosulfuron, a new sulfonylurea herbicide, and evaluates the results to propose adegradation pathway. The hydrolysis of imazosulfuron has been studied in aqueous buffers bothwithin the pH range 1.9−12.3 at ambient temperature (thermostated at 25 ± 2 °C) and at pH 3.6within the temperature range of 15−55 °C. The hydrolysis rate of imazosulfuron was characterizedby a first-order kinetics, pH- and temperature-dependent, and accelerated by acidic conditions andhigher temperatures. The calculated half-lives at pH 4.5 and 5.9 were 36.5 and 578 days, respectively.At pH 6.6, 7.4, 9.2, and 12.3 no significant change in imazosulfuron concentration was observedafter 150 days. Half-lives were much lower at pH <4 (= imazosulfuron pKa), at which they rangedfrom 3.3 to 6.3 days. Moreover, a change in temperature from 15 to 25 °C in acidic conditions (pH3.6) decreased the half-life of imazosulfuron by a factor of ∼4.0; in any case, a 3−5-fold increase inthe rate of hydrolysis was found for each 10 °C increase in temperature. In acidic conditions theonly hydrolysis products were the two molecules resulting from the cleavage of the sulfonylureabridge. Keywords: Imazosulfuron; hydrolysis; half-life; pH; temperature
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