Dissipation of pesticides residues during vegetable waste fermentation

The residue and dissipation of 50 pesticides such as carbendazim, imidacloprid, and pyridaben during cucumber vines fermentation were determined by gas chromatography and ultra high-performance liquid chromatography-tandem mass spectrometry in view of the pesticide residue conditions of vegetable waste. The effect of compost heights on pesticide degradation was evaluated. The results shows that: nine pesticides, including procymidone, carbendazim, azoxystrobin, difenoconazole, diemthomorph, chlorfenapyr, imidacloprid, acetamiprid and pyridaben, were detected in the waste of vegetable.  Carbendazim was found with highest average residue concentration of 11.2 mg/kg, and those of other pesticides ranged from 0.05 to 0.89 mg/kg. During the fermentation processes (24 days) under conditions with various compost heights, the concentrations of 9 pesticides degraded gradually and results of the dissipation of pesticides residues fitted to first-order kinetics. However, the half-lives varied between different pesticides. The longest half-life of 28.9 d was found in the case of imidacloprid. And the shortest half-life of 10.2 d  was found in the case of carbendazim. The degradation of pesticides also varied with different compost heights. In general, the highest degradation rate and the shortest half-life were obtained using 2.5 m compost height. The results of this study provide insights into the parameter optimization and quality control during the vegetable waste fermentation process and a new strategy for the high efficiency utilization of agricultural wastes for the fertilizer preparation in the organic vegetable production.