Heterogeneous kinetics of the OH-initiated degradation of fenthion and parathion

Wei Tao , Yuanhong Shang , Yongchun Liu , Jinfeng Tian , Changgeng Liu , Xuejun Zhu , Jun Wang , Dandan Chen


Received March 24, 2022,Revised , Accepted May 24, 2022, Available online June 01, 2022

Volume 35,2023,Pages 161-170

Fenthion and parathion are two representative kinds of organophosphorus pesticides and widely used in agriculture. They are directly or indirectly released into the atmosphere by spraying or volatilization processes. However, their heterogeneous reactivity toward OH radicals has not yet been well understood. Therefore, this work investigated the heterogeneous kinetics of the OH-initiated degradation of surface-bound fenthion and parathion using a flow reactor. The results showed that OH radicals played an important role in the atmospheric degradation of fenthion and parathion. Their average rate constants were (7.20 ± 0.77) × 10−12 and (10.40 ± 0.60) × 10−12 cm3/(mol· sec) at a relative humidity (RH) and temperature of 35% and 20 °C, respectively, suggesting that they have relatively short lifetimes in the atmosphere. In addition, a negative RH dependence and a positive temperature dependence of the rate constants were observed. The Arrhenius expressions of fenthion and parathion were k2 = (1.34 ± 0.48) × 10−9exp[−(1432.59 ± 105.29)/T] and k2 = (1.96 ± 1.38) × 10−9exp[−(1619.98 ± 222.02)/T], respectively, and their overall activation energy was estimated to be (11.88 ± 0.87) and (13.48 ± 1.83) kJ/mol. The experimental results will update the kinetic data of fenthion and parathion in the atmosphere and be helpful to further understand their atmospheric transportation processes.

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