The Residue Dynamics Of Imidaclopride In Honey And Bee Pollen From Tea(Longjing 43) And Their Risk To Bees

Tea trees were suffered from the smaller green leafhopper,tea aphids,thrips,spiny black whitefly during the whole growth period.The imidacloprid Wettable Powder was allowed to protect tea trees.In this work,the 10%imidacloprid Wettable Powder were used to spray tea trees during the flowering period.After the pesticide treatment,bees collect bee-products(honey,pollen)on a regular basis.This study developed the rapid detection method and dynamic residual degradation rules of imidacloprid and its metabolites imidacloprid olefin,imidacloprid urea and 6-chloronicotinic acid in honey and bee pollen.Fianlly through the existing toxicology data and risk assessment model,evaluate the risk of bees.The main results are presented as follows:1.A method was developed for the determination of imidacloprid and its metabolites imidacloprid olefin,imidacloprid urea and 6-chloronicotinic acid in honey and bee pollen by liquid chromatography tandem mass spectrometry(LC-MS/MS).Basing on the typical QuEChERS method,the pH and times of solvent extraction,sorbents were optimized to ensure the extraction efficiency and the purification of extraction.Finally,the method was developed as follows:matrix was extracted with 5%formic acid-acetonitrile twice,extraction was cleaned with EMR,detected with LC-MS/MS and quantified with external matrix standards.The results indicated that:in bee-products,imidacloprid,imidacloprid olefin,imidacloprid urea and 6-chloronicotinic acid' s linear correlation coefficient(R)of standard curve were 0.9996?1.0000;the limit of detections(LODs)were 0.2,3.5,0.4,14.0 ?g/kg;the limit of quantifications(LOQs)were 0.6,11.6,1.2,45.0 ?g/kg,respectively;the recoveries were 85.9%-111.5%(under the spiked concentration of LOQ,5×LOQ,10×LOQ),with the relative standard deviations(RSD,n=5)were 1.7%?9.6%.The method was rapid and simple with high sensitivity and good reproducibility,and suitable for the determination of imidacloprid and its three metabolites residues in honey and bee pollen.2.Studied the residues degradation dynamics of imidacloprid in honey and bee pollen.In honey,the highest residue of imidacloprid is 1.7 ?g/kg;the residues of imidacloprid olefin,imidacloprid urea and 6-chloronicotinic acid are not checked out.The residue degradation equation of imidacloprid is y=1.9612e-0.102x,R=0.9431;with the half-life period is 6.8 day.In bee pollen,the highest residues of imidacloprid and its metabolites imidacloprid olefin,imidacloprid urea and 6-chloronicotinic acid are 529.2,4.8,39.8,149.8 ?g/kg,respectively.The residue degradation equation of imidacloprid is y=2131.8e-0 434x,R=0.9371;with the half-life period is 1.6 day.The residues of imidacloprid and its metabolites imidacloprid olefin,imidacloprid urea and 6-chloronicotinic acid in bee pollen is much more than in honey.3.The influence of imidacloprid residue in honey and bee pollen of tea flowers to bees was studied,including the toxicity evaluation and exposure assessment.(1).The hazard quotient(HQ)was used as the theory risk evaluation index.The evaluation result showed that:the HQ of imidacloprid is 476.2?975.6,so the imidacloprid that applied on the nectar plant tea trees has moderate risk to bees.(2).The toxicity exposure ratio(TER,toxic/exposure levels)was used as the actual exposure risk assessment index.The assessment result showed that:under this experiment conditions,after the pesticide treatment 1 to 18 days,the residuals in bee pollen have unacceptable actual exposure risk to bees.(3).The ratio values of NOEC(no observed effect concentration)to residual was used as the chronic toxicity risk assessment index.The assessment result showed that:under this experiment conditions,after the pesticide treatment 1 to 8 days,the residuals in bee pollen have unacceptable chronic toxicity risk to bees.