The heterogeneous photo-oxidation of difenoconazole in the atmosphere

Heterogeneous reactions of ozone with commonly used pesticides adsorbed on silica particles

“…We assumed, that the pesticides that do not degrade in presence of ozone have a lifetime > than 33 days. For difenoconazole, our results are consistent with those found by Al Rashidi et al (2011), >33 days and 264 days respectively. Concerning pyrethroids, 36 and 23 days are observed by SegalRosenheimer and Dubowski (2007) and Segal-Rosenheimer et al (2011), respectively, for cypermethrin compared to 12 and 17 days in this study for deltamethrin and permethrin, respectively, although the supports are different.…”

“…Although, the kinetic experiments were performed at very low relative humidity ( 1%) and quite high ozone mixing ratios (ranging between 500 ppb and 41 ppm; Pflieger et al, , 2011Pflieger et al, , 2012Yang et al, 2012), the observed second-order rate constants with respect to the LeR mechanism span in a range between 0.5 and 20.9 $ 10 À19 cm 3 molecules À1 s À1 which is in good agreement with the observed kinetic data set in this study. Even if the supports are different, similar results are observed for the same pesticide, difenoconazole, between Al Rashidi et al (2011), who observed a rate constant of 0.26 $ 10 À19 cm 3 molecules À1 s À1 and the present study (<3.4 $ 10 À19 cm 3 molecules À1 s À1 ). Moreover, the same chemical class of dinitroaniline was studied by Pflieger et al ( , 2011 and Yang et al (2012) and their data are very similar to the observed rate constant in this study concerning pendimethalin ((3.4 ± 0.1) $ 10 À19 cm 3 molecules À1 s À1 ) which belongs to the dinitroaniline class.…”

“…Obviously there is a discrepancy with the experimental kinetic data set in this study considering that our k (max) was ranging between 0.4 and 1.7 $ 10 À4 s À1 and K ðO3Þ spanned between 21 and 358 $ 10 À16 cm 3 molecules À1 . The same applies to the kinetic data fitted with the LeH mechanism by Al Rashidi et al (2011Rashidi et al ( , 2013. The K ðO3Þ constant corresponds to the partitioning of the ozone molecules between the gas phase and the surface; hence, it depends on the nature of the adsorption sites on the particles.…”

Kinetics of the heterogeneous photo oxidation of the pesticide bupirimate by OH-radicals and ozone under atmospheric conditions

“…The experimental procedure has been presented in detailed in previous publications (Al Rashidi et al, 2011Rashidi et al, , 2013El Masri et al, 2014). Briefly, the experimental device was a l m long and 5 cm in diameter cylindrical photochemical reactor equipped with quartz windows at both extremities.…”

“…In fact little heterogeneous kinetics between pesticides and atmospheric oxidant has been investigated (Palm et al, 1997;Segal-Rosenheimer and Dubowski, 2007;Meng et al, 2010;Al Rashidi et al, 2011Pflieger et al, 2013;Wang et al, 2013;El Masri et al, 2014;Li et al, 2014). The vast diversity of phytosanitary products, as well as the numerous parameters influencing their particle/atmosphere degradation (physical and chemical properties of the pesticide, nature of the solid support, etc.…”