The degradation of diflubenzuron and its chief metabolites in soils. Part II: Fate of 4-chlorophenylurea

The fate of 4-chlorophenylurea in soils was studied with two preparations: one labelled with ¹⁴C in the phenyl ring and the other in the carbonyl group. The initial dose of 1 mg kg^?1 decreased to 50% in about 5 weeks in aerobic sandy clay and in about 16 weeks in anaerobic hydrosoil. Soil treatment with each of the preparations resulted in the release of ¹⁴C]carbon dioxide, pointing to decarbonylation and ring opening. The fraction of non-extractable (soil-bound) radioactivity increased during incubation. Quantities of ring-¹⁴C-labelled and carbonyl-¹⁴C-labelled bound residues differed strongly in the aerobic soil but only slightly in the anaerobic hydrosoil. It is assumed that two sorts of bound residues are formed from 4-chlorophenylurea: one is fairly stable and might consist of bound 4-chloroaniline or its transformation products, whereas the other is presumed to be a degradable derivative of 4-chlorophenylurea.