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Ozonation of isoproturon adsorbed on silica particles under atmospheric conditions
Abstract The results on heterogeneous ozonation of a phenylurea pesticide, isoproturon, under atmospheric conditions are presented for the first time in the present study. The study was carried out using an experimental device previously adopted and validated for the heterogeneous reactivity of organics toward ozone (Pflieger et al., 2011). Isoproturon was adsorbed on silica particles via a liquid-to-solid equilibrium with a load far below a monolayer (0.02% by weight/surface coverage of 0.5%). The rate constants were estimated by measuring the consumption of the organic (dark, T = 26 °C, RH < 1%). The experimental data were fitted by both the modified Langmuir–Hinshelwood and the Eley–Rideal patterns, resulting in atmospheric lifetimes of heterogeneous ozonation of 4 and 6 days, respectively (for 40 ppb of O3). Parameters, such as the number and the quantity of pesticides adsorbed on the solid support, which can significantly influence the heterogeneous kinetics, were investigated as well. The results obtained suggest that the organic compound is adsorbed in multilayer aggregates on the aerosol even though submonolayer coverage is assumed. The presence of a second herbicide, trifluralin, together with isoproturon on the aerosol surface does not affect the kinetics of ozonation, indicating that both compounds are adsorbed on different surface sites of silica particles.
Highlights ► Little is known about the atmospheric heterogeneous processes of pesticides. ► Heterogeneous ozonation kinetics is faster for lower surface coverage. ► Isoproturon very likely adsorbs on the solid support in isolated aggregates. ► Trifluralin is about 20–25-times less reactive to ozone than isoproturon. ► The lifetime of isoproturon in particulate phase is ca. one week regarding ozone.
Ozonation of isoproturon adsorbed on silica particles under atmospheric conditions
Abstract The results on heterogeneous ozonation of a phenylurea pesticide, isoproturon, under atmospheric conditions are presented for the first time in the present study. The study was carried out using an experimental device previously adopted and validated for the heterogeneous reactivity of organics toward ozone (Pflieger et al., 2011). Isoproturon was adsorbed on silica particles via a liquid-to-solid equilibrium with a load far below a monolayer (0.02% by weight/surface coverage of 0.5%). The rate constants were estimated by measuring the consumption of the organic (dark, T = 26 °C, RH < 1%). The experimental data were fitted by both the modified Langmuir–Hinshelwood and the Eley–Rideal patterns, resulting in atmospheric lifetimes of heterogeneous ozonation of 4 and 6 days, respectively (for 40 ppb of O3). Parameters, such as the number and the quantity of pesticides adsorbed on the solid support, which can significantly influence the heterogeneous kinetics, were investigated as well. The results obtained suggest that the organic compound is adsorbed in multilayer aggregates on the aerosol even though submonolayer coverage is assumed. The presence of a second herbicide, trifluralin, together with isoproturon on the aerosol surface does not affect the kinetics of ozonation, indicating that both compounds are adsorbed on different surface sites of silica particles.
Highlights ► Little is known about the atmospheric heterogeneous processes of pesticides. ► Heterogeneous ozonation kinetics is faster for lower surface coverage. ► Isoproturon very likely adsorbs on the solid support in isolated aggregates. ► Trifluralin is about 20–25-times less reactive to ozone than isoproturon. ► The lifetime of isoproturon in particulate phase is ca. one week regarding ozone.
Ozonation of isoproturon adsorbed on silica particles under atmospheric conditions
Pflieger, Maryline (author) / Grgić, Irena (author) / Kitanovski, Zoran (author)
Atmospheric Environment ; 61 ; 40-47
2012-07-10
8 pages
Article (Journal)
Electronic Resource
English
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