Degradation of thiobencarb in anaerobic soils

The rate and products of degradation of thiobencarb in three types of Californian soils under anaerobic conditions were examined. Dechlorination of the herbicide in the soils was also investigated. A laboratory study using 14 C-thiobencarb in a soil-water aquatic ecosystem showed a slow rate of dissipation of the herbicide in anaerobic soils. Much (37–44%) of the applied thiobencarb remained in the water 45 days after treatment. A steady build-up of the herbicide concentration in the soils was observed, suggesting a slow rate of degradation. Major degradation products were 4-chlorobenzyl alcohol, 4-chlorobenzoic acid and desethylthiobencarb. The formation of dechlorinated thiobencarb, reported to be phytotoxic to rice plants, was not evident in the soils, with or without augmentation with rice straw. Kadar dan hasilan degradasi thiobencarb di dalam tiga jenis tanah California telah dikaji. Penyahklorinan racun herba di dalam tanah juga diselidiki. Kajian makmal dengan menggunakan 14 C-thiobencarb dalam ekosistem akuatik tanah-air menunjukkan bahawa kadar penguraian racun herba yang perlahan dalam keadaan anaerob. Kebanyakan (37–44%) thiobencarb yang digunakan berada di dalam air sehingga 45 hari selepas perlakuan. Racun herba yang didapati sekata pengumpulannya di dalam tanah menunjukan kadar degradasi yang perlahan. Hasilan degradasi utama ialah 4-klorobenzil alkohol, 4-asid klorobenzoik dan desethylthiobencarb. Pembentukan thiobencarb nyahklorin yang dilaporkan bersifat fitotoksik kepada pokok padi tidak ditemui di dalam tanah dengan atau tanpa penambahan jerami padi. Keywords: thiobencarb; degradation; anaerobic soils