Difference Of Uptake,Distribution And Accumulation Of Imidacloprid In Several Vegetables Growth In Water

Leaf vegetables have short growth cycle,and are vulnerable to a variety of plantdiseases and pests.The large use of pesticides on vegetables have caused a serious problem of pesticide residues.In this paper,Imidacloprid was chose as the test pesticide.Based on a hydroponic experiment under laboratory condition,the uptake,translocation and accumulation regularity of Imidacloprid in seven different leaf vegetables were studied.Meanwhile,the dynamic accumulation of Imidacloprid in different parts of the lettuce was also studied.The main findings are as follows:Simple and fast methods for extraction and detection of Imidacloprid in roots,shoots and nutrient solution were established.The residues of Imidacloprid were detected and quantified by HPLC equipped with a UV detector.The mobile phase was 30%aqueous acetonitrile and Imidacloprid was detected at 270 nm.The root and shoot samples were extracted by acetonitrile and the average recoveries of root and shoot samples in three levels from 0.1 mg/kg to 5 mg/kg were 78.09?103.54%,79.09?92.21%with the RSDs in the range of 1.46?4.31%,1.44?5.43%,respectively.The Imidacloprid in nutrient solution were extracted by dichloromethane and the average recoveries were 87.23?90.94%with RSDs2.68?7.71%.The uptake,translocation and accumulation regularity of Imidacloprid in seven specie leaf vegetables,including Xiadi cabbage(XDQ),Huaguan cabbage(HGQ),Gaogengbai(GGB),Guanyi cabbage(GYQ),Shanghaiqing(SHHQ),Kangresijiqing(KRQ),Zijinxiangfei(ZJXF),were studied.The results showed that Imidacloprid could be detected in all tested vegetables,and the Imidacloprid residues in vegetables inereased with the increase of the solution concentration.However,the distributions of Imidacloprid in different vegetable parts differed among different specie vegetables.Accumulation of Imidacloprid in different parts of the seven specie vegetables were quite different.The vegetable species with the highest and lowest concentrations of Imidacloprid in shoots were GGB and ZJXF,respectively,while in roots were KRQ and GGB..Imidacloprid could be transferred from nutrient solution to roots for all tested vegetables,but the transferration was affected by the initial solution concentration.For the higher concentration trearrment,ZJXF demonstrated the highest capacity to transfer Imidacloprid from nutrient solution to roots,while KRQ showed the highest capacity at the lower trearrment.GGB always showed the weakest capacity to transfer Imidacloprid from nutrient solution to roots.Imidacloprid also could be translocated from roots to shoots for all tested vegetables.The capacity of GGB to translocate Imidacloprid from roots to shoots was the strongest,while ZJXF was the weakest.The dynamic accumulation of Imidacloprid in diffrent parts of the lettuce was studied.The results showed that Imidacloprid could be absorbed by the lettuce roots and then translocated to the stems,growth points,old leaves and new leaves.The residues of Imidacloprid in different parts of the lettuce differed.Imidacloprid was gradually translocated to the leaves,which resulted in the higher concentrations in leaves than other parts of the lettuce.Meanwhile,the concentration of Imidacloprid in old leaves were higher than the new leaves.