Degradation of isoxaben in soils and an aqueous system

The degradation of isoxaben {N-[3-(1-ethyl-1-methylpropyl)-5-isoxazolyl]-2, 6-dimethoxybenzamide} was studied in soil and in an aqueous system. Soil st udies were conducted in Erlenmeyer flasks (treated with 1 mug/g isoxaben) a nd mineralization studies in Biometer flasks (treated with 1 mug/g unlabele d and C-14-isoxaben) incubated at 23 C. Degradation in the aqueous system w as performed in Erlenmeyer flasks under aerobic and anaerobic conditions in cubated at 23 degreesC. Incubation mixtures were extracted at selected time s and analyzed for isoxaben and degradation products by HPLC with product i dentification confirmed by GC-MS. After 8 weeks, 78% and 23% of the total i soxaben disappeared in nonsterile and sterile soils, respectively. After 12 weeks, approximately 1% of the labeled isoxaben was recovered as CO2 in th e Biometer flask experiments; no volatile products were detected, and 5% an d 33% of the total radioactivity was recovered from the nonsterile and ster ile soils, respectively. In the aquatic system after 8 weeks, isoxaben had decreased from 1 mug/g to 0. 1 and 0.004 mug/g under aerobic and anaerobic conditions, respectively. Degradation products detected from the soil studi es were 3-nitrophthalic acid and 4-methoxyphenol, and 3-nitrophthalic acid in the aqueous system studies. Microbial activity was considered to be a ma jor factor in the degradation of isoxaben in this study.