Mechanism and kinetic properties for OH-initiated atmospheric degradation of the organophosphorus pesticide diazinon

Abstract Diazinon is a member of the organophosphorus class of insecticides. It has been regarded as an important atmospheric pollutant because of its high detection-frequency in the air and potential adverse effects on humans and wildlife. In this paper, the reaction mechanism and possible degradation products for the OH-initiated atmospheric degradation of diazinon were investigated and the rate constants of crucial elementary steps over the temperature range of 180–370 K were predicted. Present results show that OH addition to C4 atom in the pyrimidyl ring, H abstraction from the –CH– moiety as well as OH addition to P atom are the dominant pathways for the reaction of diazinon with OH radicals. The dominant degradation products are diazoxon, SO 2 , P3, CH 3 CHO, P4, CH 3 CO, P14 as well as CH 3 CHCH 3 . This work provides a comprehensive investigation of the OH-initiated atmospheric degradation of diazinon and should help to clarify its potential risk to non-targets.