Residue Behavior Of Imidacloprid In Potato And Peanut Cultivation System And Its Dietary Risk Assessment

Imidacloprid is an effective and widely used neonicotinoid insecticide.In recent years,the residue of imidacloprid in vegetables has attracted more attention.Field experiments were conducted to explore the dissipation dynamics and residue behavior of imidacloprid in potato and peanut fields to provide data support for dietary and environmental risk assessment and scientific use of imidacloprid.This paper established an efficient analytical method for determining imidacloprid and its metabolite 6-chloronicotinic acid in potato,potato plants,peanuts,peanut plants,and soil based on the Qu ECh ERS extraction method and ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS)detection techniques.The dissipation dynamics and final residue of imidacloprid in potato and peanut planting systems were investigated through supervised field trials,and the dietary risk assessment was conducted according to dietary consumption and residue data obtained from field experiments.The main results are as follows:(1)Analytical methods for the residue analysis of imidacloprid and its metabolite 6-chloronicotinic acid in potato,potato plants,peanuts,peanut plants,and soil were established by UPLC-MS/MS.The results showed that the LOQs of imidacloprid and 6-chloronicotinic acid in potato and soil were 0.01mg/kg and 0.1 mg/kg,respectively.The average recoveries of imidacloprid and 6-chloronicotinic acid in potato and field soil were 70.78～95.62% and 70.58～104.90%,and the relative standard deviations(RSDs)were 2.13 ～ 17.41% and 1.62 ～ 8.95% respectively;The LOQs of imidacloprid and 6-chloronicotinic acid in peanut and soil were 0.05 mg/kg and 0.1 mg/kg,and the average recoveries of imidacloprid and 6-chloronicotinic acid were 76.96～102.32% and 78.58 ～ 98.50%,with the RSDs in the range of 2.20 ～ 10.60% and 4.12 ～ 14.40% respectively.The results showed that the established method has good sensitivity,accuracy,and precision,which can meet the residue detection requirements of imidacloprid and its metabolite 6-chloronicotinic acid.(2)The dissipation dynamics and residue behavior of imidacloprid in the potato planting system were investigated by field experiments in Shandong and Jilin Provinces in China.In the dissipation dynamics experiment,imidacloprid flowable seed coating agent was applied once at a high dose(1.5 times of the recommended dose),and samples were collected at different time points for detection.The results showed that the first-order degradation kinetic model well described the dissipation dynamics of imidacloprid in potato plants and soil.The half-life of imidacloprid in potato plants and soil was 6.9 ～ 26.7 days and 19.8 ～28.9 days respectively.In the final residue experiment,imidacloprid was applied once at low dose(recommended dose)and high dose(1.5 times of recommended dose)respectively.Potato and soil samples were collected to detect the final residues at harvest time.The highest average residues of imidacloprid and6-chloronicotinic acid in potato were 0.778 mg/kg and 0.491 mg/kg,respectively,while the highest average residues in potato field soil were 0.149 mg/kg and 0.181 mg/kg,respectively.(3)Field experiment was carried out in Shandong,Henan,and Anhui Provinces in China to study the dissipation kinetics of imidacloprid in peanut plants and soil and detect the final residues.In the dissipation dynamics experiment,imidacloprid flowable seed coating agent was applied once at a high dose(1.5 times of the recommended dose),and samples were collected at different time points for detection.The results showed that the degradation of imidacloprid in peanut plants and soil was in accordance with the firstorder kinetic model.The half-life of imidacloprid in peanut plants and soil was 21.0 ～ 46.2 days and 10.3to 30.1 days respectively.In the final residue experiment,low dose(recommended dose)and high dose(1.5 times recommended dose)were applied for one time respectively.Peanut and soil samples were collected at harvest time to detect the final residues.The results showed that the average residue of imidacloprid in peanuts was less than 0.05 mg/kg,and the highest average residue of 6-chloronicotinic acid in peanuts was 0.344 mg/kg.Furthermore,the maximum average imidacloprid and 6-chloronicotinic acid residue in peanut field soil were 0.370 mg/kg and 0.716 mg/kg,respectively.(4)Potato and peanut were treated with 600 g/L of imidacloprid flowable seed coating agent at the recommended dose and 1.5 times of the recommended dose.Samples were collected and tested during the harvest period for the residue data for dietary and ecological risk assessment.The results of the dietary risk assessment showed that the chronic risk quotient(RQ)of imidacloprid to the general population in potato and peanut was 39.73% and 39.82% respectively,and both of them were less than 100%,indicating that imidacloprid would not pose an unacceptable risk to human health.Ecological risk quotient(RQ)and toxicological exposure ratio(TER)were used to evaluate the ecological risk of imidacloprid,which showed the toxicity of imidacloprid to earthworms was low to medium.However,it was very toxic to springtails in potato and peanut fields.In addition,the results of the ecotoxicity exposure ratio(TER)showed that imidacloprid had a moderate risk to earthworms in the soil of potato and peanut fields but a serious chronic risk to springtails.Therefore,special care should be taken when using imidacloprid in soil because it is vulnerable to non-target soil organisms.