Yuanfu Zang

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.

With the development of plasma-activated water (PAW) technology, its applications in the fields of food, agriculture, and biomedicine are becoming increasingly widespread. PAW has sterilization, pesticide residue reduction, anti-cancer, and blood clotting functions. Traditional methods for pesticide degradation include home processing, baking and freeze-drying, and UV treatment; however, they generally suffer from poor degradation efficiency and adverse effects on fruit quality. This study found that PAW treatment is a green and efficient environmental technology with the advantages of simple operation, good treatment effect, and no secondary pollution. This paper investigated the efficiency of PAW on the reduction of two acaricides, namely, bifenazate and spirodiclofen, and the effect of PAW treatment on the quality of Cuimi kumquat. The results showed that after PAW treatment, the residual amounts of bifenazate and spirodiclofen were reduced to a minimum of 1.19 mg·kg⁻¹ and 0.23 mg·kg⁻¹, with a reduction of 74.35% and 59.37% respectively compared to the control. Moreover, PAW treatment did not have any negative effects on the storage quality of Cuimi kumquat.

Growing attention has been paid to nonthermal plasma treatment technology and its effects on the degradation of organic matter, especially for antibiotics. However, the majority of the conducted research has focused on the experimental results. Rare attempts were made to analyze the reaction mechanism at the microscopic level. In this paper, molecular dynamics simulation and reactive forcefields were used to investigate the reaction mechanism of different plasma particle interactions with azithromycin molecules. The simulation results indicated that the degradation of azithromycin was caused by the destruction of C-H and C-C bonds, followed by the formation of C=C and C=O bonds when reacted with the active particles. It was also found that the ability of degrading azithromycin varied among the different types of active particles. The oxygen atoms had the strongest ability to decompose the azithromycin molecule, with 38.61% of the C-H bonds broken as compared with other oxygenated species. The findings from this computational simulation could provide theoretical support and guidance for subsequent practical experiments.