Effects of ultrasound combined with ozone on the degradation of organophosphorus pesticide residues on lettuce

Abstract

Methamidophos (MDP) and dichlorvos (DDVP) are organophosphorous pesticides which are commonly used for pest control in agriculture to obtain better yields. The occurrence of OPP residues in vegetables is known to cause serious health problems to consumers. In the present research, a laboratory-scale experiment was performed to investigate the effects of ultrasound (US)/ozone (O₃) combination on the degradation of the two pesticides on lettuce. Various parameters including ozone flow rate, water temperature, treatment time and initial concentration of OPPs were chosen to identify their effects on the degradation rate of MDP under US/O₃ treatment. The degradation rate could reach up to 82.16% under the optimal conditions of ozone flow rate 75 mg min⁻¹, time 60 min, initial concentration 0.1–0.2 mg kg⁻¹, and water temperature 8 °C. It was observed that the treatments with O₃, US and US/O₃ had no obvious impact on the quality of the lettuce. Subsequently, the reaction kinetics of DDVP degradation in water were studied, and the dynamical equation of US/O₃ treatment was obtained as: , which confirmed the practicability and applicability of the US/O₃ degradation process.