PhD in Sciences de la Terre et de l'Univers
Thesis defended on 6th November 2017
Departement Sciences de l’Atmosphère et Génie de l’Environnement, IMT Lille Douai


Title and thesis summary

Atmospheric degradation of multifunctional organic compounds : hydroxy ketones and unsaturated aldehydes

This work was carried out with the objective of providing relevant information on the atmospheric fate of two families of multifunctional oxygenated volatile organic compounds (OVOCs), hydroxyketones and unsaturated aldehydes, to complement atmospheric models for air quality forecasts and for the drafting of regulations. The reactivity of the selected compounds was carried out in a flexible atmospheric simulation chamber equipped with various analytical techniques. The present work provides the first kinetic and mechanistic study of 4-hydroxy-4-methyl-2-pentanone (4H4M2P) photolysis and the first determination of the relative rate coefficient for the reaction of Cl atoms with 4H4M2P. The photolysis frequencies of 4-hydroxy-3-hexanone (4H3H) and 5-hydroxy-2-pentanone (5H2P) were also determined. These measurements enable estimating the atmospheric lifetimes of the three compounds by photolysis which ranged from 7 to 28 days. The main photolysis products of 4H4M2P were acetone (121±4)% and formaldehyde (20±1)%. These results allowed us to propose a mechanistic scheme for photolysis including a Norrish II intramolecular rearrangement process. In a second part, the preliminary study of photolysis kinetics of two unsaturated aldehydes, trans-2-hexenal (T2H) and trans-2-pentenal (T2P) was carried out. The estimated rate constant for photolysis of T2H ((1.2±0.6)´10-3 h-1) indicates that the photodissociation of T2H is negligible in the atmosphere. All the data obtained show that the photolytic reactivity of OVOCs is strongly linked to their structure.

Referees :
Wahid MELLOUKI, Directeur de recherche CNRS, ICARE, Orléans
Marie-Thérèse RAYEZ, Directrice de recherche émérite CNRS, ISM, Bordeaux

Examiners :
Aline GRATIEN, Maitre de Conférences, LISA, Créteil
Iustinian G. BEJAN, Chercheur, CERNESIM, Iasi (Roumanie)

Thesis co-supervisor :
Christa FITTSCHEN, Directrice de recherche, PC2A, Lille

Thesis supervisor :
Alexandre TOMAS, Professeur, IMT Lille Douai

Laboratories :
Département Sciences de l’Atmosphère et Génie de l’Environnement, IMT Lille Douai
et  PhysicoChimie des Processus de Combustion et de l'Atmosphère

Financing : Labex CaPPA and Region Hauts-de-France