Residual Degradation Behaviors of Chlorpyrifos in Apple

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.