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Etude du processus d'activation des gouttelettes de nuage : implications en chimie multiphases

Abstract : Understanding the activation processes of particles to cloud droplets and the incorporation of gases into the formed liquid phase was the main goal of this study. A classification of the different air masses encountered on the Puy de Dôme site was performed, on the basis of the chemical composition of the aerosol phase. Air masses encountered on the site show an anthropogenic influence mostly associated to an increase in inorganic species. Segregation of different chemical families allows the observation of external mixture between inorganic and carbonaceous species. This observation has important consequences on the comportment of particles when a cloud is forming. A complex experimental set up (Counterflow Virtual Impactor, Round Jet Impacteur, Whole Air Inlet) allows the observation of, for a given size of particles, inorganic soluble species are significantly better scavenged than carbonaceous species. An alteration of the particle surface is further modifying their hygroscopic behavior. Contrarily to several studies, we found that carbonaceous aerosol particles were not efficient cloud condensation nuclei. The use of a microphysical model for particulate activation processes showed that modeled scavenging efficiencies are fitting the measured scavenging efficiencies, only in case of an external mixture of surface-modified aerosols. At last, none of the phases (gas or particulate) can be neglected in considering the final droplet concentration. After the droplet evaporated, the solid residue is enriched with nitrate rather than with sulfate by cloud processing.
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Submitted on : Friday, June 15, 2012 - 11:28:51 AM
Last modification on : Friday, March 25, 2022 - 11:10:23 AM
Long-term archiving on: : Thursday, December 15, 2016 - 2:58:25 PM


  • HAL Id : tel-00708514, version 1



Karine Sellegri. Etude du processus d'activation des gouttelettes de nuage : implications en chimie multiphases. Milieux et Changements globaux. Université Joseph-Fourier - Grenoble I, 2002. Français. ⟨NNT : ⟩. ⟨tel-00708514⟩



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