Abstract
The degradation of 14C-orbencarb [S-(2-chlorobenzyl-ring-U-14C) N, N-diethylthiocarbamate], a herbicide for controlling weeds in upland crops, was studied under various soil conditions. Orbencarb was more rapidly degraded under upland conditions, than under flooded conditions. The degradation was retarded in sterile soils. Under upland conditions, 14CO2 evolved rapidly in soil, where the half-lives of orbencarb were 18 to 26 days. Orbencarb sulfoxide, monodesethyl-orbencarb, methyl 2-chlorobenzylsulfoxide, methyl 2-chlorobenzylsulfone and 2-chlorobenzylsulfonic acid were identified as orbencarb's major degradation products and N-ethyl-N-vinyl-orbencarb, N-ethyl-N-β-hydroxyethyl-orbencarb, 4-hydroxyorbencarb, 5-hydroxy-orbencarb, didesethyl-orbencarb, 2-chlorobenzyl alcohol, 2-chlorobenzoic acid and methyl 2-chlorobenzylsulfide as its minor. Soil bound residues derived from its 14C-U-benzene ring were found in humic acid, hulvic acid and humin fractions, and its benzene ring was finally degraded to 14CO2.
