Occurrence of Reductive Dechlorination Products in the Paddy Field Soil Treated with CNP (Chlornitrofen)

Abstract

Dwarf symptom of rice plants was generated with dechlorinated thiobencarb formed in soil, when a herbicide thiobencarb (benthiocarb, S-4-chlorobenzyl N, N-diethylthiocarbamate) was applied at a high rate to the paddy field which have been incorporated with a high rate of rice straws and grains. In order to compare the reductive dechlorination of CNP (chlornitrofen, 4-nitrophenyl 2, 4, 6-trichlorophenyl ether) which was applied to the field in combination with thiobencarb, CNP-amino (4-aminophenyl 2, 4, 6-trichlorophenyl ether) and its dechlorinated analogs were extracted from the soil samples which were treated with hot alkaline solution, trifluoroacetylated, identified and determined by GC and GC-MS, wherefore, a group of compounds including CNP are comprehensively dealt in the lump of the amino analogs, in this study. By these methods, 4-aminophenyl 2, 6-dichlorophenyl ether was detected in the soils since 34 days after the application of CNP, and the maximum content was 1.50ppm/dry soil. Subsequently, 4-aminophenyl 2-chlorophenyl ether and 4-aminophenyl phenyl ether were detected to lesser extents. However, 2, 4-dichlorophenyl and 4-chlorophenyl analogs were not detected more than a trace amount in the soils. The results reveal that the reductive dechlorination pathways, preceded by the replacement of the para-chlorine of the trichlorophenyl group, took place in the soils. It is suggested that the dechlorination of CNP in soil was rather slower and the products were more stable than that of thiobencarb.