Study On Residues And Digestion Of Three Kinds Of Pesticides In Leafy Vegetables

Leafy vegetables are widely planted in China.It has a short growth cycle and common pests and diseases.It is usually treated with chemical control.However,the unreasonable and unscientific use of pesticides can easily lead to excessive residue and cause food safety problems.Imidacloprid,difenoconazole and chlorothalonil are several pesticides commonly used in the prevention and control of vegetable diseases and insect pests.These three pesticides are systematically carried out on different types of leafy vegetables,under different application times,in different parts of the same vegetables.Study on pesticide residues and digestion in upper and different planting environments.Provide a basis for scientific and rational use of pesticides to effectively avoid excessive pesticide residues.The main results are as follows:A method for the determination of imidacloprid,difenoconazole,and chlorothalonil on leafy vegetables was established.The pretreatment method of Qu ECh ERS was used,and acetonitrile was used for extraction.PSA was added according to the impurity characteristics of leafy vegetables.The bacteriological clear was detected by gas chromatography,and the difenoconazole and chlorothalonil were simultaneously detected by liquid chromatography-mass spectrometry.The correlation coefficient(R2)of the standard curve established by each method is greater than 0.99,the linearity is good,the precision is good,and the average recovery rate is between 80%and 120%,which is in line with the relevant standards for pesticide residue detection.The initial deposition of imidacloprid on three leafy vegetables was lettuce>small green vegetables>cabbage,half-life lettuce<small green cabbage<cabbage,and the final residue in small green vegetables,lettuce and cabbage was 0.09 after 7 days of safe interval.Mg/kg,0.04 mg/kg and 0.06 mg/kg.The initial deposition of difenoconazole on three leafy vegetables was lettuce>small green vegetables>cabbage,and the half-life was small green vegetables<lettuce<cabbage,which was found in small green vegetables,lettuce and cabbage after 7 days of recommended safe interval.The final residues were 0.75 mg/kg,0.82 mg/kg,and 0.18 mg/kg,respectively.The initial deposition of chlorothalonil on three leafy vegetables was lettuce>small green vegetables>cabbage,half-life small green vegetables<lettuce<cabbage,and the final residues in small green vegetables,lettuce and cabbage were 7 days after the safety interval.20.08 mg/kg,33.64 mg/kg,and 3.32 mg/kg.The three kinds of pesticides have a large residual amount on the small green vegetables and lettuce,and the digestion is faster,and the residual amount on the cabbage is small,and the digestion is slow.In the autumn,the highest recommended dose is applied and harvested according to the recommended safe interval.Imidacloprid and difenoconazole will not cause excessive residue,while chlorothalonil residue is serious.In autumn,the dosage of chlorothalonil should be strictly controlled.It is safety interval to avoid contamination of pesticides on leafy vegetables and improve the quality and safety of agricultural products.3.The residues of diclofenac,chlorothalonil and imidacloprid on the outer leaves of cabbage were significantly higher than those inside the cabbage and the outside of the cabbage,and the residues of difenoconazole and imidacloprid in the interior of the cabbage sphere were extremely high.The chlorothalonil inside the cabbage ball is not detected,and the initial deposition amount of the three pesticides on the outer leaves of cabbage is 2-6 times of the outside of the cabbage.The application times of the three pesticides have a great influence on their residues in leafy vegetables.After the second application,the accumulation of imidacloprid,difenoconazole and chlorothalonil on three kinds of leafy vegetables basically increased.After the third application,difenoconazole and chlorothalonil were in the third application.The accumulation of the three leafy vegetables increased,and the residues of imidacloprid and difenoconazole increased with the increase of the number of applications,but the increase was small.The final residual amount of imidacloprid and difenoconazole after 7 days of recommended safe interval was lower than the maximum residue limit specified on vegetables.The digestion rate of chlorothalonil was slow,and the residual amount of chlorothalonil applied for the first time in the second application was still high.The initial deposition amount of the two application was higher,and the cumulative amount was the third time.The initial deposition amount is higher than the deposition amount of the secondary application,so the chlorothalonil is appropriately extended after the multiple application.The residual amounts of the three pesticides in different parts of cabbage were different.It is all outside the cabbage leaf>the outside of the cabbage ball>the inside of the cabbage ball.The residual amount of imidacloprid and difenoconazole in the cabbage sphere was extremely low,and the initial deposition amount was<0.05 mg/kg.After the application of chlorothalonil,it was not detected inside the cabbage sphere.The residues of three pesticides on the outer leaves of cabbage were significantly higher than those outside the cabbage,and the initial residues of the three pesticides on the outer leaves of cabbage were 2-6 times that of the outside of the cabbage.Under the two planting conditions of protected land and open field,the initial deposition of chlorothalonil and difenoconazole on the protected green cabbage and lettuce was greater than that of open field.The digestion rate of chlorothalonil and difenoconazole on the protected land was also slower than that of open field.The half-lives of chlorothalonil in the protected field were 2.83 days and 2.94 days,respectively,and the corresponding half-life in the underground was 2.41 days.And 2.44 days;the half-lives of difenophyrin and lettuce on the protected ground were 2.02 days and 2.18 days,respectively,while the corresponding half-lives in the exposed ground were 1.76 d and 1.91 d.It is safe to administer difenoconazole on both vegetables in the open field and on the protected ground in strict accordance with the recommended dosage for 7 days after the recommended safety interval.At the recommended safety interval,the residual amount of chlorothalonil in the protected area is 2 to 3 times that of open field.When applying the recommended dosage in autumn,the recommended interval between chlorothalonil and open field may not be suitable for the vegetable.The actual production requires a proper extension of the safety interval for the protection of the above-ground vegetables,thus avoiding safety problems.