Degradation and leaching behavior of the pyrethroid insecticide cypermethrin in soils

• Published in: Journal of Pesticide Science 1986/02/20, Vol.11(1), pp.71-79
• Main Authors: Sakata, S, Mikami, N, Matsuda, T, Miyamoto, J
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Chemical control; Control; degradation; Ecotoxicology, biological effects of pollution; Fundamental and applied biological sciences. Psychology; leaching; Phytopathology. Animal pests. Plant and forest protection; Protozoa. Invertebrates; pyrethrins; soil; Terrestrial environment, soil, air
• ISSN: 0385-1559; 1348-589X; 1349-0923
• DOI: 10.1584/jpestics.11.71

The degradation of (1R, cis)- and (1R, trans)-isomers of cypermethrin [(RS)-α-cyano-3-phenoxybenzyl (1RS)-cis, trans-3-(2, 2-dichlorovinyl)-2, 2-dimethylcyclopropanecarboxylate] in two soils was studied under laboratory conditions, using 14C preparations labeled separately in the cyclopropyl and benzyl rings. The half-life of disappearance was 4.1 to 17.6 days for the trans-isomer and 12.5 to 56.4 days for the cis-isomer. The insecticide was degraded via pathways including cleavage of the ester or diphenyl ether bond, hydroxylation at the 4-position of the phenoxy ring, and hydrolysis of the cyano group to the amide and carboxyl groups. The main degradation route was hydrolysis of the ester linkage. The resultant products underwent further degradation to form 14CO2 and bound residues. A larger amount of 14CO2 was evolved in soils treated with the less persistent trans-isomer and with the benzyl-14C preparation. In contrast, a larger amount of bound 14C was formed in soils treated with the cis-isomer and with the cyclopropyl-14C preparation. Although a trace amount of cypermethrin appeared in the effluent from sand containing less than 0.1% organic matter, there was no leaching of cypermethrin with water through other three types of soil columns, when leaching was started immediately after treatment or after a 30-day preincubation of the treated soil columns.