Residual Degradation Law Of Kinds Pesticides On Leafy Green And Tomato Crops And The Study Of Residual Extrapolation

For the problem of applicating pesticides without registration on the crop,such as disorderly abuse and free expansion use, this paper was carried out the study of crop residue extrapolation.Two typical crops,leafy green vegatables and tomatoes were choosen in this study, and the field residue test under the good agricultural practices (GAP) condition was developed, then reasonable statistics, analysis and extrapolation were used with the obtained residual datas,in order to attest the feasibility of extrapolation and verify the representative commodities via the dietary intake of risk assessment.1. A residue analytical method was established to determinatin of trichlorfon, dimethoate, chlorpyrifos, chlorothalonil, beta cypermethrin, deltamethrin in cabbage, flower cabbage, lear mustard, leaf lettuce, water spinach and sweet potato leaves and chlorothalonil, beta cypermethrin, deltamethrin in tomato and cherry tamato based on the NY/T761-2008 method. After the oscillation extraction with 1%formic acid acetonitrile, a part of the extract supernatant cleaned up by activated carbon and diatomite(0.5:1) mixed chromatography column was using for the determination of trichlorfon, while the other part was directly used in the determination of chlorothalonil, Beta cypermethrin, deltamethrin.Besides, Some related studies were done to compensate the matrix effect of trichlorfon ect six pesticides in the analysis process.The results showed that it had no significant effects on the elimination of the matrix effect by improving the purification methods and instrument conditions. The six components couldn’t be analyzed simultaneously and the fortified recovery couldn’t achieve an ideal effect with the aid of three analyte protectants (propanediol, sorbitol and gulonic acid),but using the matrix-matched standard solution to correct the added recovery, at three spiked concentrations of 0.01,0.05 and 0.5 mg/kg, the average recoveries of trichlorfon ect six pesticides in six leafy green vegetables were at the range of 80 to 122%with relative standard deviations (RSD) between 2 to 14%, as well as the average recoveries of chlorothalonil ect three pesticides in two taomatoes were from 82 to 106%with RSD of 2-15%, achieved the reduction of the influence on matrix effect and the improvement of the peak profile and responsivity, according with recovery demands as well as good credibility and stability. The results indicated that the precisionsen and accuracy of the method accorded with requirements of residue analysis.2. In order to obtain residue datas, the field residual test of six pesticides (trichlorfon ect) on six leafy green vegetables and three pesticides(chlorothalonil ect) in two taomato vegetables were conducted. The results indicated that, the two kinds of the crops,lear mustard(or sweet potato leaves) and cherry tomato with a relatively high level of initial concentrations, maximum residue and final residue. The obtained residual regulations were calculated by the statistical analysis of the parameters of these pesticide residues, and lear mustard (or sweet potato leaves) was selected as the representative commodity of leafy green vegetables, while cherry tomato in tomatoes.3. Variance analysis about the maximal concentrations,initial concaitrations,half-life and final residue with pre-harvest intervals (PHI) of 7 days of six pesticides (trichlorfon ect) in six leafy green vegetables and three pesticides (chlorothalonil ect) in two taomato vegetables was carried out. The results showed that it had the similar characteristics in the same family, and lear mustard could be selected as the representative commodity of the three cruciferae (lear mustard, cabbage, flower cabbage) to realiz the residual extrapolation. The difference of 60%pesticides residues was significant on the two convolvulaceae(water spinach and sweet potato leaves),otherwise, every residual parameters of chlorothalonil, beta cypermethrin, deltamethrin on tomato and cherry tomato were of significant difference, thus further study of the possibility of residual extrapolation should be done.4. Dietary intake of risk assessment on the six pesticides (trichlorfon ect) in six leafy green vegetables and (three pesticideschlorothalonil ect) in two taomatoes were conducted, according to the final residue datas from the field residual test. Assessment results demonstrated that, the chronic assessment and the acute assessment of the six pesticides in lear mustard(or sweet potato leaves) were higher than other leafy green vegatables, which was consistent with the results of the final residual datas. And the two assessments of cherry tomato were higher than tomato.Therefore, selection of lear mustard(or sweet potato leaves) and cherry tomato as the representative commodities proved correct.5. Market monitoring of pesticide residues was carried out in three larger and more concentrated market of Nanning, Guangxi, according to the multiresidue determiantion method of six pesticides (trichlorfon ect) on six leafy green vegetables. The monitoring results showed that, the pesticide residues were found in flower cabbage, lear mustard, leaf lettuce and sweet potato leaves, and lear mustard was found in two monitored months. However, the dietary intake risk to residents were within the acceptable level, due to the RQc and RQa were lower than 5%, The monitoring results provided the realistic basis on the verification of field residual test results in this study.