Anaerobic aquatic degradation of flumetsulam [N-(2,6-difluorophenyl)-5-methyl[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonamide]

The herbicide flumetsulam [N-(2,6-difluorophenyl)-5-methyl[1, 2,4]triazolo[1,5-a]pyrimidine-2-sulfonamide] was investigated in sediment-water systems to ascertain anaerobic aquatic degradation as a potential route for dissipation. In a strongly anaerobic test system (sulfate-reducing or methanogenic) flumetsulam degraded to a dominant product which preferentially partitioned to the water phase; flumetsulam half-life (t1/2) Was 183 days. The anaerobic degradation product was identified as reduced flumetsulam hydrate [N-(2,6-difluorophenyl)-4,5, 6,7-tetrahydro-5-hydroxy-5-methyl[1,2,4]triazolo[1, 5-a]pyrimidine-2-sulfonamide]. Reduced flumetsulam hydrate distributed among several products in an equilibrium mixture and reverted to flumetsulam upon aeration. Thus, the anaerobic degradation product never accumulated in a weakly anaerobic test system (initially denitrifying). When applied to aerobic soil, the anaerobic degradation product exhibited a t1/2 of 2 days compared to a t1/2 of 40 days for flumetsulam. Aerobic degradation yielded parent flumetsulam and the primary aerobic degradation product of flumetsulam metabolism. Flumetsulam anaerobic aquatic degradation is viewed as a principally abiotic process occurring only in strongly anaerobic, static environments isolated from the atmosphere. The likelihood of reduced flumetsulam hydrate occurrence and accumulation in the environment is minimal when flumetsulam is used for terrestrial food crops