Degradation of 3-(3-chloro-4-chlorodifluoromethylthiophenyl)-1,1-dimethylurea (Clearcide) in paddy soils

The degradation of 3-(3-chloro-4-chlorodifluoromethylthiophenyl)-1, 1-dimethylurea (Clearcide®) in paddy soils on which rice plants were planted under flooded conditions was investigated in accordance with growth stages of rice plants by using 14C-Clearcide labeled at 1, 1-dimethyl and unlabeled Clearcide. At the end of the growth stage periods of rice plants, the soil was sampled and extracted with 80% acetonitrile and partitioned into organic, aqueous and unextracted fractions. Each fraction was subjected to radioactivity assay, tlc and glc. More than 50% of radioactivity was detected in the chloroform soluble fraction even after the lapse of time and the activity in the water soluble fraction was negligible (maximum detected value was 2.7%). Detected compounds from the acetonitrile extracts were mainly parent Clearcide and small amounts of degradation products. Desmethyl Clearcide and Clearcide sulfoxide and its sulfone were identified as major degradation products, and desmethyl Clearcide sulfoxide, its sulfone and aniline derivatives were also identified. Small amounts of three unknown degradation products were found with the lapse of time. Half life period of Clearcide in paddy soils was about 30 to 40 days.