Mechanistic and kinetic studies to reveal photodegradation behaviour of distinctive pesticides

Transformation of pesticides in the environment is a highly complex process affected by different factors. Both biological and physical-chemical factors may play a role in the degradation to variable extent. Our study is focused on revealing specific details of photolytic degradation of pesticides as photodecomposition might be regarded as one of the most crucial factors affecting the fate of pesticides. The toxicity of the examined pesticides is well known, however restricted information is available regarding their natural degradation processes. More detailed examinations are required in order to reveal the exact mechanism of the pesticide decomposition as well as the biological impacts of the degradates. Significance of this study is enhanced by the fact that decomposition of pesticides may result in the formation of toxic degradation products. The photolytic degradation of frequently applied pesticides (acetochlor, simazine, chlorpyrifos, carbendazim, EPTC) with different chemical structure was investigated. A special, immerseable UV-light source was applied in order to induce photodegradation. The degradation processes were followed by TLC and GC/MS techniques. EI mass spectrometry was used to identify the degradation species. Detailed mechanism of photolytic transformation was established by identification of each degradate. The photolytic degradation of pesticides of distinctive chemical character exhibited markedly different photodecomposition mechanisms. At least four degradation species were detected and identified in each case. Loss of alkyl, chloro and hydroxyl groups, as well as cleavage of alkyloxy, amide, amino-alkyl and ester bonds might be regarded as typical decomposition patterns. Deamination and ring opening might be observed at the very last stages of decomposition