Heterogeneous Reaction of Suspended Phosmet Particles with NO₃ Radicals

Abstract

As an organophosphorous insecticide, phosmet is widely used for plant protection as well as against the ectoparasites on productive livestock. It emits into the atmosphere in both gas and particulate phases via spray drift from treatments and postapplication emissions, but its degradation in the atmosphere is not well-known up to now. In this study, the heterogeneous reaction of phosmet absorbed on the azelaic acid particles with NO(3) radicals is investigated in real-time using a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS). Two primary products and their nitro-substituted derivates are observed. The apparent reaction rate of phosmet particles with NO(3) radicals is also obtained by a relative rate method with isoprene and 1,4-cyclohexadiene as the reference compounds. The concentrations of the reference substance and phosmet particles are synchronously detected with an atmospheric gas analysis mass spectrometer and the VUV-ATOFMS. Under the experimental conditions, the average apparent reaction rate obtained is (1.92 ± 0.09) × 10(-12) cm(3) molecule(-1) s(-1), and the corresponding atmospheric lifetime toward NO(3) radicals is roughly estimated to be ~0.3 h.

Mass spectrometric approaches for chemical characterisation of atmospheric aerosols: critical review of the most recent advances

“…Measurements of the NO 3 uptake by mixed solid organics and liquid unsaturated fatty acids by Xiao and Bertram [230] confirmed that lifetimes of unsaturated organics should be short in liquid particles and increase when the unsaturated organics are embedded in a solid matrix. The kinetics of reactions of NO 3 with aerosolised insecticide (Phosmet) [231] and pesticide (Carbaryl) [232] was investigated using a VUV ATOFMS method. The results imply surprisingly short lifetimes of these compounds (0.3-1.3 h) with respect to oxidation by atmospheric NO 3 .…”

Heterogeneous reaction of particulate chlorpyrifos with NO 3 radicals: Products, pathways, and kinetics

“…Chemical transformations of pesticides in the atmosphere occur mainly through photolysis and reaction with atmospheric oxidants such as hydroxyl radicals (OH), ozone (O 3 ), and nitrate radicals (NO 3 ) [26][27][28]. NO 3 radicals are present in the atmosphere at a low concentration during the day because they are highly photolytic, but they can rapidly accumulate to an appreciable concentration at night.…”

Kinetic studies of heterogeneous reactions of particulate phosmet and parathion with NO3 radicals

“…Great efforts have been made into the studies on the two OPPs, but most of which focused on photolysis, toxic effects, and the metabolites in plants, waters and soils (Namba et al, 1971;Wauchope et al, 1992;Sinderhauf and Schwack, 2005;Wu and Linden, 2008;Slotkin et al, 2009;Fan et al, 2011). In our earlier studies, the reaction products and chemical mechanisms of heterogeneous reactions of particulate phosmet and parathion with NO 3 radicals have been reported (Liu et al, 2011(Liu et al, , 2012a. Additionally, the apparent reaction rate of phosmet and the decay rate of parathion have also been determined (Liu et al, 2011(Liu et al, , 2012a.…”

“…Considering its high concentration at night, NO 3 radicals may play an important role in controlling the lifetimes of atmospheric OPPs. However, few rate data for heterogeneous reactions of particulate OPPs with NO 3 radicals have hitherto been determined (Liu et al, 2011(Liu et al, , 2012aWang et al, 2012).…”

“…In our earlier studies, the reaction products and chemical mechanisms of heterogeneous reactions of particulate phosmet and parathion with NO 3 radicals have been reported (Liu et al, 2011(Liu et al, , 2012a. Additionally, the apparent reaction rate of phosmet and the decay rate of parathion have also been determined (Liu et al, 2011(Liu et al, , 2012a. However, as the key kinetic parameters of their heterogeneous reactions, effective rate constants and reactive uptake coefficients have not been determined yet.…”