Residue Dynamics of Chlorpyrifos in Spinach

The degradation dynamics of chlorpyrifos residues in spinaches grown in winter-greenhouse, spring-greenhouse, and open-field was investigated. Residues of chlorpyrifos in spinach were determined with gas chromatography (GC3800, NPD). Based on the recommended dose and double dose, the half-life of chlorpyrifos residue decomposition in spinach varied with its growing conditions tested, being 13.46, 2.75 and 2.64 days under the conditions of winter-greenhouse, spring-greenhouse, and spring-field, respectively. The decomposition rate of chlorpyrifos residue in spinach grown in winter-greenhouse was significantly slower than that in spring-greenhouse and open-filed, while it was similar in spring-greenhouse and open-filed. It was concluded that the safe-times for chlorpyrifos were 62, 11 and 8 days under the conditions of winter-greenhouse, spring-greenhouse and spring-field, respectively, being referred to the MRL(1mg·kg-1)of Chinese Standards; while to the MRL(0.01mg·kg-1)of Japanese Standards, it was 150, 29 and 25 days, respectively. It is better not to use chlorpyrifos for killing insects in spinach in winter-greenhouse. It is important to pay more attention to the differences in growing conditions, seasons of pesticide used and MRL for the safety use of pesticides in vegetable production.