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

Heterogeneous degradation of pesticides by OH radicals in the atmosphere: Influence of humidity and particle type on the kinetics

“…calculated for OH radical concentration used for the calculation was 1.5 x 10 6 molecule cm -3 and the average exposure time was 12 hours Table 1 shows that available kinetic constants of pesticides in the heterogeneous phase toward OH radicals vary from -14 cm molecule -1 s -1 (i.e., half-life greater than 1000 days) to 10 -11 cm 3 molecule -1 s -1 (i.e., half-life of 1.3 days) with the majority of them being around 10 -13 cm 3 molecule -1 s -1 . Values obtained in our study for pesticides degraded by OH radicals are of the order of between 10 -13 cm 3 molecule -1 s -1 and 10 -12 cm 3 molecule -1 s -1 which is in accordance with kinetic constants available in the literature calculated for other pesticides of the same or different chemical families on hydrophobic silica (Pflieger et al, 2013), hydrophilic silica (Liu et al, 2005;Palm et al, 2011;Zetzsch, 1991), quartz surfaces (Bouya et al, 2015;Masri et al, 2014), and leaves (Lester et al, 2017). However, our values are of one to two orders of magnitude smaller than values determined by one research team for pesticides adsorbed on silicas (Palm et al, 1997(Palm et al, , 1998(Palm et al, , 1999.…”

“…The heterogeneous degradation of some pesticides with OH radicals has already been studied (Al Rashidi et al, 2011Bouya et al, 2015;Lester et al, 2017;Liu et al, 2005;Palm et al, 1997Palm et al, , 1998Palm et al, , 1999Palm et al, , 2011Pflieger et al, 2013;Zetzsch, 1991), but conditions employed to determine kinetic constants were very diverse in terms of surface (different silica particles, quartz surface, plant leaves) and humidity (<1% RH to 70% RH). To our knowledge, no study investigated the influence of relative humidity on the degradation kinetics of pesticides with OH radicals, although this factor has an influence on the heterogeneous degradation of organic compounds by ozone (Kaiser et al, 2011;Mattei et al, 2018;Pöschl et al, 2001).…”

Heterogeneous atmospheric degradation of pesticides by ozone: Influence of relative humidity and particle type

“…(cyprodinil, Arizona dust, 0% RH). The order of magnitude of these constants are in accordance with previous pesticide heterogeneous ozonolysis studies conducted on silica particles (Socorro et al, 2015 and reference therein), quartz surfaces (Al Rashidi et al, 2011Rashidi et al, , 2013El Masri et al, 2014;Bouya et al, 2015), ZnSe crystals (Segal-Rosenheimer and Dubowski, 2007), azelaic acid aerosols (Gan et al, 2010;Meng et al, 2010;Yang et al, 2010Yang et al, , 1012, and grape berries (Walse and Karaca, 2011).…”

“…The different reaction rate constants of heterogeneous ozonolysis and their associated atmospheric half-lives are summarized by chemical family of pesticides under study and compared to literature data (Meylan and Howard, 1993;Pflieger et al, 2009Pflieger et al, , 2011Yang et al, 2010Yang et al, , 2012Walse and Karaca, 2011;Bourgin et al, 2013;Bouya et al, 2015) in Table 1.…”

“…Several kinetic studies of heterogeneous ozonolysis of pesticides (Table 1; Meng et al, 2010;El Masri et al, 2014;Bouya et al, 2015;Socorro et al, 2015 and reference therein) were carried out under different experimental conditions as ozone mixing ratio (e.g., from 0.4 to 86 ppm), RH (e.g., from 0% to 80% RH and uncontrolled), temperature (e.g., from 19°C to 26°C), and type of particles (e.g., hydrophilic and hydrophobic silicas, quartz surfaces, ZnSe crystals, and azelaic acid aerosols). As a result, literature data is often difficult to compare.…”