Digestion Dynamics Of Three Nicotine Pesticides On Cotton And Its Safety Evaluation On Apis Mellifera

Traditional nicotine pesticides,such as imidacloprid,thiophenazine,and acetamiprid,are toxic to pollinating insects in the soybean ecosystem,causing widespread concern.In this paper,the residual digestion dynamics of imidacloprid,thiamethoxam,and flupurone on cotton plants and soil under different application methods are studied.The acute toxicity and sub-lethality of three nicotine pesticides to Apis mellifera under different exposure routes are determined effect,providing a scientific basis for evaluating the safety of three nicotine pesticides in cotton areas in Xinjiang.(1)The Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry(UPLC-MS)residue analysis method of three kinds of nicotine pesticides in cotton plants and soil was established,using the fast and efficient QuEChERS method(Quick,Easy,Cheap,Effective,Rugged and Safe)as pre-processing.The method has a good linear relationship in the concentration range of 0.005～0.200 mg/L.The lowest detection concentration LOQ is 0.02 mg/kg.With the addition levels of 0.02 and 0.10 mg/kg,the recovery rates of the three nicotine pesticides in cotton leaves and soil were 84.94%～96.33%and 93.27%～101.63%.(2)The residue digestion dynamics of three kinds of nicotine pesticides on cotton plants under different application methods were clarified.After imidacloprid and thiamethoxam dressing,the residual amount could still be detected in different parts of cotton after 50 days of application.Imidacloprid concentration is 0.044～0.230 mg/kg and thiamethoxam concentration is 0.068～0.095 mg/kg.The relationship between the residues is:Soil>Root>Leaf.Imidacloprid,thiamethoxam,and fluopyrone were sprayed twice at the recommended dose,and the dynamic equations of the three nicotine pesticides on cotton leaves,flowers,and soil were in accordance with the first-order dynamic equation,the relationship between the residual amounts was:Leaf>Flower>Soil;After 2 times of application,the digestion half-lives of imidacloprid,thiamethoxam,and fluopyrone in cotton leaves were 1.3 d,1.2 d,and 1.9 d,and the digestion half-lives in flowers were 2.0 d,2.4 d,and 2.8 d,The digestion half-lives on the soil were 3.4 d,3.1 d and 3.1 d.(3)The dynamics of residual digestion of three nicotine pesticides in cotton plants in Changji,Korla and Aksu were studied.The dynamic equations of residual digestion of three nicotine pesticides on leaves,flowers and soil of cotton in three places conformed to the first-order kinetic equations.The dynamics of residual digestion in various parts of cotton showed negative exponential changes,and the relationship between the residual amounts was Upper leaves>Middle leaves≈Flowers>Lower leaves>Soil.Imidacloprid has the shortest digestion half-life in Aksu region,1.1 d;thiamethoxam has the shortest digestion half-life in Changji region,1.1 d;flupirone has the shortest digestion half-life in Changji region,1.4 d.(4)The acute toxicity and sub-lethal effects of three nicotine insecticides on Apis mellifera under both exposure and oral exposure routes were determined.The acute oral and acute contact LD50 of imidacloprid against Apis mellifera was 0.3214 μg a.i./bee and 0.0649 μg a.i./bee,and the toxicity level was highly toxic;the acute oral and acute contact LD50 of thiamethoxam against Apis mellifera was 0.0087 μg a.i./bee,0.0565μg a.i./bee,the toxicity level is high toxicity;the acute oral LD50 of flupranone to Apis melliferais 3.3070 μg a.i./bee,which is low toxicity,and its acute exposure is safe to the Apis mellifera.When three kinds of nicotine insecticides LD5,LD10 and LD20 were used as sub-lethal doses to treat Apis mellifera,the mortality rate was directly proportional to the amount of pesticide intake.Therefore,fluoropyrone can be used as a new alternative medicine in Xinjiang cotton area.