Abstract
Photodegradation of fenitrothion, fenitrothion microcapsule and chlordane in water was studied, using the corresponding 14C-labeled preparations. The half-life values under sunlight were 1.1-2.6 days for fenitrothion and 3.7-5.1 days for fenitrothion microcapsule, indicating that microencapsulation retarded the fenitrothion photolysis rate by 1.9-4.4 times. Chlordane was stable to photolysis, more than 78% of the applied 14C being recovered as unchanged parent compound after 14 days. The microscopic observation of the microcapsule and separate analysis of photodegradation products inside/outside the microcapsule indicated that fenitrothion was photodecomposed not only inside the microcapsule but also outside the microcapsule following destruction of the wall material with subsequent elution of fenitrothion into the surrounding water. Fenitrothion microcapsule was photodegraded in the same way as fenitrothion through oxidation of P=S to P=O, oxidation of the aryl methyl group to the carboxyl group, reduction of the nitro group to the amino group, coupling of the carboxyl group with the amino group leading to the formation of the dimeric compound, isomerization, cleavage of the P-O-aryl or P-O-methyl linkage, substitution of the nitro group by the hydroxyl group and photomineralization of the aromatic ring to carbon dioxide.
