Study On Degradation Of Carbendazim Pesticide Residues By Gamma Irradiation

Nowadays,people pay more and more attention to food safety.Due to the widespread use of pesticides,many fruits and vegetables have pesticide residues.It will harm human health and often lead to various diseases when people eat too much food with pesticide residues.Therefore,it is imperative for us to take high-tech measures to solve this food problem.Through Gamma radiation,an advanced oxidation technology of high efficiency and non-pollution,taking carbendazim,a kind of pesticide in fruits,as a research object,this paper discusses the irradiation degradation and degradation mechanism of carbendazim,especially how to apply the irradiation technology to the degradation of carbendazim in apple juice and the feasibility of applying the irradiation technology to the degradation of pesticide residues through toxicity test.The main study results of this paper are as follows:（1）Gamma irradiation can effectively degrade carbendazim in aqueous solution and apple juice solution.The lower the initial concentration of carbendazim was,the higher the absorbed dose of carbendazim and acidic pH value of the solution were,the higher the degradation rate of carbendazim would be.The contribution to carbendazim degradation by the radicals is in the order of ·OH>·H>e_aq^-.As apple’s ingredients contain free radical scavenging,the degradation efficiency of carbendazim in the apple juice is slower than that in aqueous solution.（2）The degradation products of carbendazim were analyzed.Three degradation products were detected through LC-MS with m/z of 119,134 and 208 respectively.The other three degradation products were detected by GC-MS and m/z were all 106.Through mass spectrometry the possible structure of the six products was deduced,which include benzimidazole,2-aminobenzimidazole,5-hydroxy carbendazim and three isomers of xylene.（3）Quantum chemical information as bond length,bond level and NBO charge of carbendazim can explain the degradation products detected through the experimental method.Combined with the detection results from LC-MS and GC-MS and analysis of quantum chemistry,the pathway of carbendazim degradation was figured out.5-hydroxycarbendazim and benzimidazole were degraded from carbendazim when they reacted with ·OH radicals,2-aminobenzimidazole was produced by carbendazim when they reacted with ·H ande_aq^-,and benzimidazole was produced by 2-aminobenzimidazole when they reacted with ·OH radicals.Benzimidazole continued to degrade to ortho-xylene after the attack of free radicals.O-xylene can generate m-xylene and p-xylene through structural rearrangement and electron transfer.（4）Toxicity test showed that the toxicity of carbendazim aqueous solution would become less after irradiation while that in apple juice would decrease firstly after irradiation and rose and then decreased again,which was same as the changing regulation of apple juice.But the toxicity after irradiation was both less than that before the irradiation,which indicated that the irradiation technology was effective to degrade pesticide residues in apple and to reduce the toxicity.