Study On Digestion Dynamics And Risk Assessment Of Quizalofop-p-ethyl And Its Metabolites In Adzuki Bean

Quizalofop-p-ethyl is a selective herbicide with biological toxicity,and its application may pose a threat to ecological environment and human health.The European Union has banned the use of quizalofop-p-ethyl,but in our country is still widely used in beans and other crops.In order to further explore the safety of 10% cream of quizalofop-p-ethyl in adzuki bean,this paper conducted a field experiment of adzuki bean in Heilongjiang and Hunan in 2019.In this paper,the digestion rule of quizalofop-p-ethyl and its metabolites in adzuki bean plant and soil and the residue test of different application methods were studied,and the dietary risk was evaluated.The study mainly got the following results and conclusions:(1)In this paper,a method for the determination of quizalofop-p-ethyl and its metabolites in adzuki bean was established.The extractant of quizalofop-p-ethyl and its metabolites was acidized acetonitrile or acidified dichloromethane,and the adsorbent was Octadecyltrichlorosilane C18.The extracted substance was determined by HPLC.Method verification results show that the recovery was 88.7 ~ 116.2%,the relative standard deviation(RSDs)was 0.82 ~ 4.39%,and the method was reliable and stable.The limits of detection and limits of quantitation were 0.003 ~ 0.01 mg/kg and 0.01 ~ 0.03 mg/kg,which meets the detection requirements.(2)The field dissipation dynamic experiment of quizalofop-p-ethyl and its metabolites in adzuki bean was carried out.The results showed that the degradation law of quizalofop-p-ethyl in Heilongjiang and Hunan adzuki bean fields was in accordance with the first-order kinetic equation,and the half-life was between 3.4 and 6.7 days.Under different application methods and picking intervals,the residual amount of quizalofop-p-ethyl and its metabolites were between 0.03 ~ 1.20 mg/kg in adzuki bean and between 0.03 ~ 1.34 mg/kg in plant.In the final residue test results,the final residues of quizalofop-p-ethyl and its metabolites in seeds,plants and soil of Hunan and Heilongjiang during the harvest season were all < 0.01 mg/kg(limits of quantitation),which was lower than the maximum allowable residue limit of 0.1 mg/kg set by Chinese Ministry of Agriculture.This study shows that the herbicide is safe to use at the recommended dose.(4)The dietary risk assessment of quizalofop-p-ethyl and its metabolites in adzuki bean was carried out.The long-term dietary intake risk quotient(RQc)and short-term dietary intake risk quotient(RQa)were 2.0 ~ 19.7% and 0.5 ~ 1.3%,respectively.The risk of dietary intake is low.(5)The effects of temperature,humidity,organic matter and microorganism conditions on quizalofop-p-ethyl and its metabolites in the soil of Heilongjiang province were studied by single factor analysis.The results showed that the degradation rate of quizalofop-p-ethyl and its metabolite was the fastest in unsterilized soil with high organic matter content at 25°C and 35% water content.The microorganisms had the greatest influence on the degradation of quizalofop-p-ethyl and its metabolites.