Experimental Study on the Degradation of Acaricides on the Surface of Kumquat Cuimi by Nonthermal Air Plasma

Nonthermal air plasma, which can be generated by air discharge, contains large amounts of reactive oxygen species (ROS), reactive nitrogen species (RNS) and high-energy particles. The ROS and RNS have strong oxidizing properties, and the high-energy particles can break chemical bonds in organic compounds, a process which can be used to degrade organic matter such as pesticides. In the present study, the effects of nonthermal air plasma on the degradation of several pesticides were investigated. An air plasma processing system was designed and constructed to produce nonthermal air plasma and to degrade five commonly used acaricides, namely, avermectin, bifenazate, spirodiclofen, etoxazole, and lufenuron, during the production of kumquat cuimi. The experimental results showed that nonthermal air plasma could degrade all the acaricides on the surface of the kumquat cuimi effectively. After 20 min of plasma treatment, the residues of avermectin, bifenazate, spirodiclofen, etoxazole and lufenuron on the surface of the kumquat cuimi were reduced by 80.67%, 79.52%, 62.40%, 48.93% and 23.11%, respectively. Further analysis indicated that the primary chemical bonds, hydrophobicity, and the pH value of the plasma-activated water can all affect the efficiency of pesticide degradation.