Impact of mineral dust photochemistry on the atmosphere

The objective of this work is to study the heterogeneous processes of mineral dust surfacesunder UV-A radiation. It is know that mineral dust containing metal oxides which can absorbsolar radiation and therefore activate a different chemistry compared to that observed in thedark. In order to avoid m...

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Bibliographic Details
Main Author: Dupart, Yoan
Other Authors: Institut de recherches sur la catalyse et l'environnement de Lyon (IRCELYON), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie - CNRS Chimie (INC-CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard - Lyon I, Christian George, Barbara D'Anna
Format: Doctoral or Postdoctoral Thesis
Language:French
Published: HAL CCSD 2012
Subjects:
Dust photochemistry
Uptake coefficients
Aerosol flow tube
Nucleation
OH radicals desorption
Surface chemistry
Photocatalysis
Volcanic ashes
Photochimie des poussières
Coefficients de capture
Tube à écoulement d’aérosols
Nucléation
Désorption de radicaux OH
Chimie de surface
Photocatalyse
Cendres volcaniques
[CHIM.OTHE]Chemical Sciences/Other
Eyjafjallajökull
Iceland
Online Access:https://theses.hal.science/tel-00942848
https://theses.hal.science/tel-00942848/document
https://theses.hal.science/tel-00942848/file/TH2012DupartYoan.pdf
Description
Summary:The objective of this work is to study the heterogeneous processes of mineral dust surfacesunder UV-A radiation. It is know that mineral dust containing metal oxides which can absorbsolar radiation and therefore activate a different chemistry compared to that observed in thedark. In order to avoid measurement artifacts related to the nature of macroscopic films, anaerosol flow tube was developed during this work and applied to study the interactions ofSO2, NO2 and O3 with real mineral dust.An unexpected formation of new particles in the presence of SO2 was observed. In order toexplain this phenomenon, we suggest the desorption of OH radicals from the mineral dustsurface to the gas phase. This mechanism has also been supported by field campaigns.Using real samples of volcanic ash from the last eruption of Eyjafjallajökull in Iceland (2010)allowed us study capture of SO2 on macroscopic ashes films with uptake coefficient around10-7. Associated kinetic experiments combined with chemical analysis allowed us to propose areaction mechanism explaining the formation of iron sulfate on the surface of ashes.Finally, we investigated the photochemical interactions of O3 and NO2 with minerals dustaerosols in the flow tube reactor showing a good agreement with previous data obtained onmacroscopic surfaces. Les travaux de cette thèse reposent sur l’étude des processus hétérogènes à la surface desparticules minérales en présence d’irradiation UV-A. Nous savons que les poussièresminérales contiennent des oxydes métalliques pouvant absorber la radiation solaire et ainsiactiver une chimie très différente de celle observée à l’obscurité. Un réacteur à écoulementd’aérosols a été utilisé pour étudier les interactions des gaz (SO2, NO2 et O3) avec devéritables poussières minérales, évitant ainsi les artéfacts de mesure liés à la naturemacroscopique des films comme dans les études précédentes.La mise en suspension des poussières minérales a permis d’observer une formation inattenduede nouvelles particules ultrafines en présence de ...

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