苹果中毒死蜱残留降解动态研究

Residual Degradation Behaviors of Chlorpyrifos in Apple

为了解苹果生产过程中毒死蜱的残留污染情况和其在苹果中的降解规律，为指导苹果的安全生产和建立苹果安全综合指标体系提供科学依据，通过田间试验对喷布不同浓度和不同次数的苹果中毒死蜱残留进行了GC—NPD动态分析。结果表明，毒死蜱不同处理在苹果中的残留量顺序为：1080g·hm^-2喷施3次〉1080g·hm^-2喷施2次〉1080g·hm^-2喷施1次〉540g·hm^-2喷施3次〉540g·hm^-2喷施2次，喷药浓度是影响农药残留量的主要因素；苹果中毒死蜱主要残留于果皮，果皮残留量是果肉的30—85倍；苹果中毒死蜱的降解规律符合一级动力学模型，其半衰期为10．7～13．1d，其降解过程主要是酶解、水解和光解；苹果果肉降解速率（T1/2=9．2d）比果皮（T1/2=12．7d）快，是由于果肉内含有丰富的有机物质、酶和水分。施药30d后，苹果中毒死蜱残留量可降低到0．05mg·kg^-1以下，远低于我国和欧盟等国家对苹果中毒死蜱最大残留限量要求。一方面说明毒死蜱是对果品安全的农药，可以在生产上长期应用，另一方面说明，苹果中毒死蜱的残留最大限量完全可由现在的1mg·kg^-1降低到0．05mg·kg^-1，供修订相关苹果安全质量标准时参考。

Chlorpyrifos is one of a few organophosphorous pesticides which are permitted to be used in apple production. The pesticide residue is an important control data for apple. In order to know clear residue pollution and degradation trends of chlorpyrifos in apple, and provide scientific data for instructing secure production and constructing integrated security guide system, chlorpyrifos residues in apple which were treated with different concentration and different times were determined by GC-NPD method. The results indicated that the chlorpyrifos residues order for different treatments were as follows： spraying thrice at 1 080 g·hm^-2 〉 twice at 1 080 g·hm^-2 〉 once at 1 080 g·hm^-2 〉 thrice at 540 g·hm^-2 〉 twice at 540 g ·hm^-2 . The spraying concentration of chlorpyrifos was the main factor for residues in apple. The residues mainly remained in pericarp. The residues of pericarp were about 30-85 times than that of pulp. The degradation behaviors of chlorpyrifos in apple accorded with first order kinetics with half life from 10.7 d to 13.1 d. Its degradation process was mainly the actions of enzyme, water and light. The degradation speed of residual chlorpyrifos in pulp was faster than that of in pericarp. The main reason was that there were more organic compounds, enzymes and water in pulp. Chlorpyrifos residues in apple were lower than 0.05 mg·kg^-1 after spraying 30 d, which was far under MRL of China, European union and other countries. This means that chlorpyrifos is a safety organophosphorous pesticide for apple, which can be used in apple production perpetually. The MRL of chlorpyrifos in apple security standards could be debase to 0.05 mg·kg^-1 from present 1 mg·kg^-1.