Study On Degradation Behavior Of Dinotefuran In Soil Of Jujube Orchard

Neonicotinoids insecticides have the characteristics of high insecticidal activity,wide insecticidal spectrum,good internal absorption and environmental safety,and are known as the new generation of"green"insecticides.Dinotefuran is the third generation of nicotinic insecticide,which has the characteristics of high efficiency,low toxicity and environmental protection,and will develop rapidly in the next 5~10 years.Although pesticide auxiliaries do not kill target organisms,they are harmful to the environment.Therefore,it is of great significance to study the degradation behavior of dinotefuran and its commonly used pesticide additives in soil environment to guide the use of dinotefuran and its additives.In this paper,the degradation trend of dinotefuran in water and soil environment of jujube garden was studied by using surfactant(SDS,AEO,CMN,organosilicone)and non-surfactant(humic acid)in combination with dinotefuran.At the same time,the effects of application of dinotefuran and pesticide auxiliaries on soil microorganism in jujube orchard were analyzed.The change of soil microbial community was analyzed by high-throughput sequencing to reveal the degradation mechanism of dinotefuran.In order to provide reference for the rational use of dinotefuran and pesticide auxiliaries and environmental safety assessment.The main conclusions are summarized as follows:(1)HPLC method for detection of dinotefuran and its isomers in water and soil was established.The quantitative results show that in 0.50,1.00,2.00 mg·L~-11 under the adding level of dinotefuran in the substrate,the dinotefuran and its isomer results conform to the pesticide residue analysis method to the requirement of precision,accuracy and sensitivity,can be used in subsequent research.(2)The effects of auxiliaries(SDS,CMN,AEO,organosilicone,humic acid)on the degradation dynamics of dinotefuran in different buffer and distilled water under dark and light conditions were studied under laboratory simulation conditions.The results showed that the half-life of the degradation of dinotefuran isomers in the buffer solution with pH=4 was4.51 and 4.38 days under the condition of avoiding light.Under the light condition,the addition of auxiliaries reduced the degradation rate of dinotefuran isomers,but the effect of different auxiliaries on dinotefuran isomers was different.Among them,SDS has quenching effect on the photolysis of dinotefuran,while the other four auxiliaries have photosensitization effect on the photolysis of dinotefuran.(3)The effects of additives(CMN,AEO,organosilicone)on the degradation dynamics of dinotefuran in soil of jujube orchard were studied under the laboratory conditions.The results showed that the degradation half-life of dinotefuran in the soil of jujube orchard was15d,and the degradation characteristic was that it was easy to degrade pesticide.The addition of additives effectively promoted the degradation of dinotefuran.Among them,the degradation effect of non-ionic surfactant siloxane on dinotefuran was the strongest,while the degradation effect of anionic surfactant CMN on dinotefuran was the weakest.The degradation half-life of dinotefuran in the soil with organosilicone was 6.8d.(4)Under laboratory conditions,soil was adopted to study the effect of the addition of auxiliaries on soil microorganisms and enzyme activities with dinotefuran.Dinotefuran was mixed with different pesticide auxiliaries(CMN,AEO,organosilicon)and then exposed to the soil of jujube garden for culture.The effects of dinotefuran and its auxiliaries on soil microbial and enzyme activities were evaluated by studying the quantity of microorganisms(bacteria,fungi,actinomycetes)and soil enzyme activities(urease,sucrase,catalase).The results showed that the addition of different auxiliaries and dinotefuran had no significant effect on the quantity of microorganisms in the soil of jujube garden,but the addition of auxiliaries could promote the quantity of bacteria to some extent,and the promotion intensity was different.The addition of dinotefuran and auxiliary agents had an obvious activation effect on soil urease,and the activation effect of adding fatty alcohol polyoxyethylene ether on soil urease was up to 106%.The effects of adding dinotefuran and additives on soil sucrase were as follows:inhibition-recovery-activation;In a certain period of time,the effects of the addition of non-surfactant organosilicone on soil catalase were significantly different.(5)In order to explore the influence of the addition of non-ionic surfactant AEO on the composition of soil microbial community in jujube garden,high-throughput sequencing technology was used to analyze the bacterial and fungal communities in soil.The results showed that the addition of AEO had a certain effect on the number of soil bacteria.The Shannon index value of soil samples with additives was 8.18~8.89,indicating the highest diversity of bacterial species.However,the addition of AEO reduced the fungus richness in soil samples.The addition of AEO affected the microbial community distribution in the soil,and the addition of additives changed the dominant bacteria in the soil:the richness of proteobacteria increased,the richness of Proteobacteria decreased,and the richness of Acaulium and Ascomycetes decreased.