Investigation for the degradation mechanism of avermectins exposed to non-thermal atmospheric plasma

In recent years, the application of non-thermal atmospheric plasma to pesticide residue treatment has attracted widespread attention, among which the analysis of degradation products is one of the key factors restricting the application of this technology in practice. Dielectric barrier discharge (DBD) is an ideal way to treat pesticides residues. In this paper, an experimental device of DBD is designed, and the electrical diagnosis and optical diagnosis of the device were made. The results of electrical diagnosis show that DBD discharge is resistance-capacitance discharge. The optical diagnosis results show that the discharge mode of the device is filament discharge, and the reactive oxygen components in the plasma produced are mainly $\cdot$OH and O. Based on the diagnosis of reactive oxygen species in plasma, molecular dynamics simulation of the reaction between reactive oxygen species and avermectin (AVM) was carried out using Material Studio. The simulation results show that O and $\cdot$OH destroy AVM molecules through hydrogen abstraction reaction and adsorption reaction, resulting in the breaking of C-O bond and the formation of C=O, C=C bond. When O acts alone, AVM would be degraded into two different products. When $\cdot$OH acted alone, AVM would be degraded into two different products. When O and $\cdot$OH react with avermectins together, AVM will be degraded into five different products.