| Abstract
| - The fate of prosulfuron, primisulfuron methyl, rimsulfuron, andthifensulfuron methyl in aqueoussolutions was investigated, using capillary electrophoresis (CE) forherbicide detection. Thehydrolysis of the four sulfonylureas followed first-order kinetics andwas pH dependent andaccelerated at higher temperature. Rimsulfuron and thifensulfuronmethyl showed fast degradationin water, with half-lives from 12 to 0.06 days in the pH range from 2to 8.5 at 25 °C. The degradationrate of prosulfuron and primisulfuron methyl resulted relatively slow,with half-lives from 49 to399 days in the pH range from 5 to 7.5, at 25 °C. The hydrolysisof the four sulfonylureas as afunction of temperature and pH was mathematically combined. Theresulting complex equationsrepresent simple and useful models to predict the hydrolyticdissipation of these sulfonylureas.The complex equations of prosulfuron and primisulfuron methylsuggest that once these herbicidesreach the groundwater, they would tend to persist, due to their slowdegradation at neutral andsubalkaline pHs and low temperatures. On the contrary, rimsulfuronand thifensulfuron methylwould not create problems of aquifer pollution, due to their fasthydrolysis in a wide range of pHand temperature combinations. Keywords: Prosulfuron; primisulfuron methyl; rimsulfuron; thifensulfuronmethyl; half-life in water
|
