A mechanistic and kinetic study of the heterogeneous degradation of chlorpyrifos and chlorpyrifos oxon under the influence of atmospheric oxidants: ozone and OH-radicals

Abstract

Chlorpyrifos in the heterogeneous phase of the atmosphere is quickly removed by reaction with OH radicals (∼2 day) whereas its degradation product, chlorpyrifos oxon is more persistent.

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.…”

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

“…The mass peak at m/z 197 is assigned as 3,5,6-trichloro-2-pyridinol (TCP, PII), a product observed previously in the hydrolysis of chlorpyrifos [19]. Chlorpyrifos oxon and TCP were identified as degradation products of both ozonolysis and OH-oxidation experiments of particulate chlorpyrifos [35]. The mass peak at m/z 170 may be O,O-diethyl O-hydrogen phosphorothioate (PIII) and/or O,O-diethyl ester thiophosphoric acid (PIV) in the TOF mass spectra.…”

“…The acquisition time for each mass spectrum was 10 s and each mass spectrum was normalized to its most intense mass peak. The mass peaks at m/z 349, 351, and 353 in Figure 2A are assigned to the molecular ions of chlorpyrifos with isotopic combinations of 35 [33], respectively. These peak intensities are consistent with the natural isotope abundances of the chlorine atom.…”

“…Chlorpyrifos oxon is a typical oxidation product of chlorpyrifos under atmospheric conditions [34]. The mass peak at m/z 298 is the daughter ion of PI after losing one 35 Cl atom during the VUV photoionization. The mass peak at m/z 197 is assigned as 3,5,6-trichloro-2-pyridinol (TCP, PII), a product observed previously in the hydrolysis of chlorpyrifos [19].…”