Study On Residue Dynamics And Safety Evaluation Of Difenoconazole In Orange And Its Environment Behavior In Soil

In this essay, difenoconazole of triazole fungicides is regarded as object of study, field trials and trials of laboratory were conducted to study the residues dynamics and environment behavior, hoping to evaluate secure periode and the best using method of difenoconazole in the orange. The main idea and conclusion of the theis include to the next means:A method for determination of difenoconazole residue in oranges and soil by gas chromatography was reported. Samples were extracted with acetone, purified by liquid-liquid partition and alumininia chromatographic column, and washed by petroleum ether-acetic ether (1/1, V/V). The elution was evaporated and the residue was dissolved in petroleum ether, and analyzed by GC-ECD. The method was easy and fast. And the average recoveries ranged from 81.86% to 92.26%, and the related variation coefficient from 4.42% to 17.43%. The minimum detectable quantity of myclobutanil was 2.5×10¹¹g. The minim umdetectable concentration of myclobutanil in orange and soil sample was 0.002mg/kg.Degradation of difenoconazole in soils was influenced by such the factors as microorganisms, temperature , water-hold capacity and the consistency of pescide .The results indicate that microorganisms would accele rate the degradation difenoconazole. Degradation rate of difenoconazole increased with the enhancing temperature in soil,and achieved the high level when temperature increased to a certain. After that, degradation rate of difenoconazole had a decreasing tendency as temperature wenton .Degradation rate of difenoconazole increased with the increasing water-hold capacity of soils,and reached the high level when water-hold capacity increased to a certain. After that,degradation rate decreased with increasing water-hold capacity. Degradation of difenoconazole in soils speeded up with the increasing concentrations of difenoconazole, and then fell beyond the tolerant concentration.A field experiment was conducted to reveal residue dynamics of difenoconazole in orange and soil. The Result shows that difenoconazole degraded rapidly in the orange, but lowly in the soil relatively. The half-life of difenoconazole in the former was 7.95-12.65d and 8.16-12.16d, yet in the latter was 12.33-17.95d. Results of the two-year experiment shows, the last application was done 21 d before harvesting, the residue of difenoconazole in the harvested orange was lower than 0.2mg/kg, demonstrating that it is safe to apply difenoconazole to orange with the recommended rate.Determination and change during storage of difenoconazole residue levels in orange after a dip treatment, to study the indication of the efectiveness, residue uptake, and persistence of when stored at room temperature or at 0℃-4℃in the management of postharvest decay in orange. The residue levels showed less during storage at low temperature. The residue levels reduced slowly along with the storage time. In peel the residue levels were higher than that in pulp.