Etude de la dégradation photochimique des pesticides adsorbés à la surface de particules atmosphériques

Abstract : The atmosphere is an important vector for pesticides dissemination in local to global environment since 30 to 50% of these compounds enter the atmosphere especially during agricultural treatments. A comprehensive knowledge of the behaviour of these compounds in the atmosphere is necessary in order to understand their environmental fate. Although pesticides can be associated to particles, their atmospheric life times are calculated from their homogeneous reactivity in the gaseous phase (structure-activity relation). Moreover, it is sometime suggested that pesticides may react slower in the particulate phase than in the homogeneous gaseous phase. This assumption could explain the obvious discrepancy between the long range transport revealed by field measurement and the short atmospheric lifetimes currently estimated. The aim of this work was precisely to aboard this problematic by investigating the reactivity of three herbicides (alachlor, terbuthylazine and trifluralin) adsorbed on silica particles under simulated atmospheric conditions in a flow reactor. Experimental protocols have been specially developed to observe the presumed low kinetics of these herbicides with ozone and hydroxyl radicals. The obtained results suggest that the pesticides' atmospheric lifetimes currently used are under-estimated, at least for the less volatile compounds. It seems therefore essential to pursue the investigation of pesticides' heterogeneous reactivity to draw a more complete picture of their atmospheric degradation. This information is necessary to calculate more realistic atmospheric lifetime.
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Maryline Pflieger. Etude de la dégradation photochimique des pesticides adsorbés à la surface de particules atmosphériques. Océan, Atmosphère. Université de Provence - Aix-Marseille I, 2009. Français. ⟨tel-00414758⟩

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