Study On Residual Degradation Of Chlorpyrifos And Emamectin Benzoate In Cabbage, Soil And Relative Photodegradation

Chlorpyrifos and emamectin benzoate as the main subjects were studied in this paper.The degradation and residues of them were studied both in room and filed experiment. In order to supply more reasonable consultation, degradation and residues of chlorpyrifos·emamectin benzoate EW in soil and cabbage in summer and autumn were studied due to the affection of seasons. Chlorpyrifos microemulsion, emamectin benzoate emulsifiable concentrates and the mixture of them were selected to compare the difference of their degradation rate in soil and cabbage, which demonstrated that they could affect the degradation rate of pesticide when they were mixed.This phenomenon was also found in photodegradation experiment. And the limit dosage ratio that could affect degradation rate of pesticide was also confirmed. The threat of TCP to environment could not be ingnored due to its high polarity and great water solubility, so it was very necessary to study the formation of TCP in aqueous solution.The main results were summarized as follows:1. A method that samples were extracted with ethylacetate, detected by GC-FPD was developed to detect chlorpyrifos residue in soil and cabbage, which was simple, fast and economic.2. A method that samples were detected by HPLC-FLD after chemical derivatization was developed to detect emamectin benzoate residue in cabbage and soil, which was more sensitive compared to the traditional methods without derivatization.3. The degradation rate of chlorpyrifos and emamectin benzoate in cabbage was faster in summer than in autumn, while not significant in soil.4. The degradation rate of emamectin benzoate in cabbage was slow in the form of emamectin benzoate emulsifiable concentrates than in the form of mixture of chlorpyrifos microemulsion and emamectin benzoate emulsifiable concentrates.The half-life of them was 3.81 d and 2.84 d respectively.5. The photodegradation rate of chlorpyrifos and emamectin benzoate on slide glass related to its initial concentration and luminous intensity. Half-life would be longer with increasing concentration while it would be shorter with higher luminous intensity under high pressure mercury Lamp.6. Emamectin benzoate accelerated the degradation of chlorpyrifos apparently with a dosage ratio of emamectin benzoate to chlorpyrifos 10:1, positive correlations between efficiency and dosage ratio. When a dosage ratio of chlorpyrifos to emamectin benzoate was 3: 1, chlorpyrifos accelerated the degradation of emamectin benzoate apparently. Affects would not get stronger with the increase of dosage ratio. It was high enough to accelerate the degradation of emamectin benzoate with the dosage ratio of chlorpyrifos to emamectin benzoate 5: 1.7. The initial dosage ratio of chlorpyrifos to emametin benzoate was about 168:1 in cabbage after pesticide applied, which proved that excessive chlorpyrifos accelerated the degradation of emamectin benzoate in cabbage apparently, while low dosage of emamectin benzoate had little affect to the degradation of chlorpyrifos in cabbage.8. The formation of TCP, metabolism of chlorpyrifos in aqueous solution followed the trend that its concentration increased, then decressed.