| Abstract
| - The degradation of penoxsulam {2-(2,2-difluoroethoxy)-N-5,8-dimethoxy[1,2,4]triazolo[1,5-C]pyrimidin-2-yl-6-(trifluoromethyl)benzene-sulfonamide} was studied in flasks simulating flooded rice fieldconditions using four representative rice field soils from the Sacramento Valley. Degradation half-lives (t1/2 values) ranged between 2 and 13 days. Increased degradation rates were observed inflask systems with steeper redox gradients between the flooded soil layer and the overlaying water.Two transient metabolites were identified that were temporarily formed in amounts exceeding 5% ofthe total initial mass of penoxsulam. The results of high-performance liquid chromatography/14Cradiodetection studies indicate that the degradation of the triazolopyrimidine system and its substituentsis the main pathway of microbial transformation processes. Microbial activity, as measured bydehydrogenase activity, was not affected by penoxsulam concentrations corresponding to the proposedmaximum annual use rate of 40 g active ingredient/ha. Keywords: Anaerobic transformation; paddy incubation conditions; environmental fate; Granite;triazolopyrimidine sulfonamide; acetolactate synthase inhibitor; metabolic activity
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