Proposition de stages, thèses et post-docs

Laboratoire de Physicochimie des Processus de Combustion et de l'Atmosphère
PC2A - UMR 8522 CNRS/Lille1
Université Lille 1 Sciences et Technologies
Cité scientifique, Bâtiment C11/C5
59655 Villeneuve d'Ascq Cedex, France

Le Laboratoire de Physicochimie des Processus de Combustion et de l'Atmosphère de l'Université Lille1 Sciences et Technologies cherche des physico-chimistes, chimistes ou physiciens de formation, pour préparer un stage de recherche Master (Année universitaire 2019-2020), une thèse de doctorat (à partir d'Octobre 2020), ou un Post-Doc dans le domaine de l'énergétique et de l'environnement.

Les sujets de recherche proposés concernent les domaines de la combustion, de la sûreté nucléaire et de l'environnement. Ils s'inscrivent dans des axes de recherche soutenus par le Ministère de l'Enseignement Supérieur et de la Recherche, le CNRS-INSIS, l'Institut de Radioprotection et de Sûreté Nucléaire (IRSN) et le Contrat de Projet Etat-Région Hauts de France.

Les candidatures, comportant un CV et une lettre de motivation, doivent être soumises auprès des chercheurs responsables des sujets proposés.

Master 2

Role of the resonantly stabilized radicals in the inception of soot particles

Fossil fuel combustion constitutes the principal source of our energy needs. This combustion is unfortunately also the main source of the air pollution. Among the pollutants emitted by fuel combustion, there are polycyclic aromatic hydrocarbons (PAHs) of which we have a solid conviction that some of them are strongly harmful for health: there are indeed toxicological studies, which show their cancerogenic character. In addition, many studies carried out on the comprehension of the processes involving during PAHs and soot formation, agree on the implication of PAHs as precursors of soot particles. Soot particles are also very harmful for human being, more particularly the small particle sizes, which have a strong capacity of penetration in the lungs.

 

This training course lies within the scope of the continuation of the development and the validation of a detailed kinetic mechanism of hydrocarbon oxidation under rich fuel conditions producing soot particles. It aims to identify the impact of the resonantly stabilized radicals in the formation of the first aromatic rings. A particular attention will be paid to small PAHs (up 4-5 rings) as pyrene and its isomers, which are considered as direct precursors of nucleation soot process. It is expected to carry out quantum chemistry calculations by using chemical tools as Gaussian16. This work should confirm/cancel certain literature thermokinetic data, or to generate new data.

 

Keywords: PAHs, soot, combustion, detailed kinetic reaction mechanism, Flames, Quantum Calculations.

Linked to the workpackage of the Labex CaPPA : WP2

Supervisor(s): Abderrahman El Bakali / Sonia Taamalli

 

Optical properties of aerosols measured in the Optical properties of aerosols measured in the IR and UV range

Because of their ability to absorb and to scatter radiations, airborne particles play an important role in the energy budget of the earth-atmosphere system. It is assumed that aerosols are one of the atmospheric constituents participating to the cooling effect, but estimates are highly uncertain owing to the large spatial and temporal variability of aerosol concentration and physical properties.

The measurements from space-borne instruments are the only means for observing aerosol distributions from local to global scale. However, to fully exploit the instruments capabilities it is essential to have reference optical properties of various particles and mainly their complex refractive indices.

The aim of this work is to measure transmittance spectra of model airborne particles in the infrared and the UV-vis spectral region using a dedicated experimental setup developed in PC2A. The extinction spectra of the aerosol are measured by Fourier Transform InfraRed (FTIR) spectrometer and UV-vis spectrometer and the corresponding size distributions are recorded using optical counters. The whole methodology has been validated using model silica particles and volcanic ashes. The team wants to extend this methodology to other particles of atmospheric interest, e.g. water droplets containing bioaerosols or silica particles with water adsorbed on their surface. Reactivity with OH radicals will be also considered in order to estimate the role of atmospheric aging on the optical properties of the aerosols. Thus the objective of the internship is to transform the set-up in order to generate such particles and to measure their optical properties in parallel with chemical composition and some physical properties such as the size and the concentration of the particles. The experimental data are then processed in order to retrieve the complex refractive indexes of these aerosols (collaboration with LOA).

                 

This project is addressed to chemist or physicist candidates, interested in the experimental aspects of the research and motivated by the atmospheric impact of aerosols.

                 

Keywords: atmospheric particles, metrology of the aerosol, FTIR and UV-vis spectroscopy.

Workpackage of the Labex CaPPA: WP2

Supervisor: Denis Petitprez (PC2A) – Co-supervisor : Hervé Herbin (LOA)

 

 

Low-cost aerosol counters in a volcanic environment

 

The populations of aerosols are more and more studied because they present a very great diversity of chemical compositions, origins and distributions in sizes (oceanic, industrial, biogenic, volcanic, etc.). This wealth leads to multiple effects, that can be negative or positive, on the evolution of the Earth system and its biosphere: impact on climate, chemical balance (desert and marine aerosols) and imbalance (anthropogenic pollution) of ecosystems, pollen and human health problems, for instance. These impacts can be revealed at different scales (from indoor pollution to climate impact). It results in an interest in a wide range of instrumentation for the study and monitoring of aerosol populations at different scales from satellites to local in situ measurements.

Low-cost particle counters are now available and pave the way for in situ real-time mapping of aerosol populations. These sensors can easily be integrated, embedded and deployed in a network to probe hostile environments like a volcano, or an area with complicated topography such as a subway network. These small instruments are however much less efficient than the research instruments used in the laboratories, and characterization of their response to a given environment is necessary. In the framework of anemerging collaboration between LACy (University of La Reunion), LASIR (University of Lille) and PC2A (University of Lille), we propose an internship on the conditions of use of this instrumentation for the study of aerosols in the volcanic and oceanic environment of La Réunion island: the Optical Particle Counter OPCN3 (Alphasense company) counts particles in the range 350 nm - 40 µm in 24 channels and weights 100g. The Grimm MiniWRAS 1371 countsparticles in the range 10 nm - 35 µm in 41 channels and weights 7 kg. Thus, they allow to probe the kinetic of the Aitken and coagulation/accumulation modes. The internship will consist in working in the PC2A laboratory on the response of these sensors in a controlled atmosphere and then deploying the sensors during a campaign on the Piton de la Fournaise. The data will then be analyzed by combining routine aerosol measurements at the Reunion Island Atmosphere Physics Observatory (OPAR) located a few tens of kilometers from the volcano.

 

Keywords: Low-cost particle counter, sensor answer, natural aerosols, volcano, data science

Laboratories:LACy (Laboratoire de l’Atmosphère et des Cyclones) ; PC2A (laboratoire de Physicochimie des Processus de Combustion et de l'Atmosphère) ; LASIR (Laboratoire de Spectrochimie Infra-rouge et Raman) ; LOA (Laboratoire d’optique Atmosphérique)

Linked to the workpackage of the LabexCaPPA:WP 3

Supervisor(s): Guillaume Guimbretière (LACy) et Nicolas Visez (PC2A)

 

 

 

 

Thèses

Identification de seuils universels de concentrations de composés aromatiques à l’origine de la formations des premières particules de suies dans les flammes

La formation des particules fines dans les flammes constitue un problème majeur dans les procédés utilisant la combustion pour la conversion de l’énergie. L’identification des facteurs déterminants la genèse de ces premières particules est une question fondamentale qui pose de nombreuses difficultés expérimentales et théoriques. Très récemment, en s’appuyant sur des études expérimentales utilisant l’hydrogène moléculaire dans les systèmes réactifs initiaux, il a été mis en évidence la possibilité d’existence de « concentrations seuils universels » de composés aromatiques à l’origine de l’apparition des particules fines. Ces études menées sur des flammes de méthane dans des conditions particulières, montrent en effet l’invariabilité de ces seuils vis à vis de la pression, le taux de dilution et de la manière dont l’hydrogène est introduit dans la flamme (ajout ou substitution) de méthane. Ces observations, s’elles venaient à être confirmées, peuvent avoir des retombées pratiques majeures en termes d’applications industrielles notamment dans le secteur de
transport. L’identification d’un « seuil universel » signifierait en effet la possibilité d’identifier les conditions optimales permettant son évitement. Cependant, ces hypothèses nécessitent une validation expérimentale bien plus large. En plus de l’effet de la pression, la dilution et de la composition initiale, le contrôle de la nature du fuel sur ces supposés seuils universels de concentration de composés aromatiques est absolument nécessaire. Ce projet propose donc d’étudier l’impact de ce paramètre en examinant l’effet des structures de différentes familles chimiques qui sont les alcanes (linéaires et ramifiés), les cyclo-alcanes, les alcynes, les alcènes et les structures aromatiques. Ce travail expérimental très conséquent s’appuiera sur des dispositifs optiques et analytiques performants et hautement sensibles pour l’analyse de la phase gazeuse et
particulaire dans des flammes particulières ces différents composés.

Programmes de recherche en lien avec le sujet : Labex CAPPA

Responsables et coordonnées :

Abderrahman El Bakali  abderrahman.elbakali@unv-lille.fr          Tél : 03 20 43 48 04
Xavier Mercier               xavier.mercier@univ-lille.fr                     Tél : 03 20 43 48 04

 

Combustion de nouveaux biocarburants : étude du mécanisme de formation des Hydrocarbures Aromatiques Polycycliques Oxygénés (HAPOs) et des petites particules de suie (<10 nm)

Les biocarburants cellulosiques (BCC) contiennent dans leur structure un ou plusieurs atomes d’oxygène, et sont considérés comme une source prometteuse d'énergie alternative. Un de leurs intérêts est que leur combustion produit moins de particules de suie de grande taille (>10nm) comparé aux carburants conventionnels. Pour ces raisons, l’utilisation des BCC est en constante augmentation ces dernières années. Cependant, leur combustion peut générer un grand nombre de particules de suie de petite taille (<10 nm). Celles-ci contiennent également une proportion importante d’Hydrocarbures Aromatiques Polycycliques Oxygénés (HAPOs) rendant potentiellement les suies plus nocives. Comprendre et maitriser les mécanismes de formation des HAPOs, ainsi que leur responsabilité dans la formation des petites particules de suie est l’une des conditions préalables indispensables à l’utilisation des BCC comme énergie alternative, propre et sûre. Dans ce contexte, le projet de thèse proposé a pour objectif de contribuer à une meilleure compréhension des phénomènes physico-chimiques impliqués. Sa réalisation s’appuiera sur les compétences du laboratoire PC2A qui sont reconnues au niveau international dans le domaine. Le laboratoire PC2A dispose de bancs expérimentaux de haute technicité permettant de réaliser les travaux envisagés dans le cadre de ce projet. Ainsi, l’équipe a récemment fait l’acquisition de deux nouveaux dispositifs (notamment dans le cadre du CPER CLIMIBIO) qui seront mis en œuvre dans cette étude :

- un dispositif GC (chromatographie en phase gazeuse) permettant l’analyse quantitative d’espèces chimiques d’intérêt, équipé d’un système spécial dédié au piégeage des HAPs/HAPOs ;

- un dispositif SMPS (granulomètre de type Scanning mobility particle sizer) de toute nouvelle génération permettant la caractérisation de particules de l’ordre du nanomètre (1nm).

La haute sensibilité de ces dispositifs expérimentaux sera mise à profit pour l’analyse qualitative et quantitative des espèces chimiques clés impliquées dans la formation des particules de suie dans des flammes de BCC. L’obtention de cette base de données expérimentales, couplée avec le développement d’un modèle chimique détaillé, permettra une analyse fine de la cinétique de combustion des BCC et de formation des HAPOs/suie.

Programmes de recherche en lien avec le sujet : CPER Climibio / Labex CAPPA

 

Mots clés :   Biofuels, combustion, HAPs oxygénés, nucléation de suies, nanoparticules de suies (<10 nm)

 

Responsables et coordonnées :

Luc-Sy Tran                           luc-sy.tran@univ-lille.fr                      Tel: 03 20 43 49 78

Laurent Gasnot                      laurent.gasnot@univ-lille.fr                       03 20 43  48 02

 

Financement envisagé :  Bourse Région Hauts-de-France/ADEME/Labex CaPPA

 

Modelling studies of the chlorine atmospheric chemistry

The importance of gas-phase halogenated compounds (chlorine, bromine, and iodine) in the atmosphere has been established since the 1970s with the discovery of ozone hole over the Antarctic. These gases generate radicals with a broad range of applications for tropospheric and stratospheric chemistry: ozone budget, atmospheric concentrations (OH, NOx, volatile organic compounds), aerosol formation in the marine boundary layer, halogen interactions, climate change.

 

Numerous studies have been already performed with halogen chemistry using global models. Most of them have focused on bromine and iodine, which are more active than chlorine because of the higher chemical stability of HCl by comparison to other HX acids (X = Br, I). In the chemistry-transport models, there are limited numbers of reactions especially dealing with the organic halogenated compounds. To date, the atmospheric gas phase reactivity and gas–aerosol interactions data sets remain incomplete and poorly understood. Quantum chemistry tools will be employed to gain a more profound insight into the observed reactivity trends and predict thermokinetic parameters for the experimental data that are difficult or impossible to obtain. A recent work performed by our group has demonstrated that the addition of the iodinated organic scheme to the atmospheric model strongly influences its chemical speciation (Fortin et al, Atm. Env., 2019, 214, 116838).

 

The objectives of the thesis are the following: (i) update the chlorine reaction mechanism using an exhaustive literature review, (ii) integrate the new reaction mechanism in the atmospheric models, (iii) perform kinetic analysis with a 0D model to establish the major reaction pathways and to identify the lack of data, (iv) complete the status of knowledge by molecular modelling (v) evaluate with the chemistry-transport model MOCAGE the impact of the updated mechanism on stratospheric and tropospheric air composition at the global scale, in particular on the ozone layer..

 

The new obtained data will help and orient the risk management community and government health and policy makers to better protect and serve the public interest.

 

Research program linked to the subject : Labex CaPPA

 

Keywords : Chlorine, atmosphere, molecular simulations, 0D/3D modelling

 

Advisors :

PC2A

                        Florent Louis                 florent.louis@univ-lille.fr             Tel : 03 20 33 63 32

                        Valérie Fèvre-Nollet       valerie.fevre-nollet@univ-lille.fr   Tel : 03 20 43 67 22

CNRM (Météo-France/CNRS)

Virginie Marécal            virginie.marecal@meteo.fr         Tel : 05 61 07 93 61

 

Funding : Labex CaPPA with MétéoFrance

 

FILLED, POURVU, Atmospheric Chemistry of Silicon Compounds and their Role in Indoor Air Quality

This position is now filled

Indoor air quality and chemistry has been a subject of increasing interest in recent years. Indeed, we spend more than 80% of our time indoors, but the chemistry and health impacts of indoor air have attracted far less interest than that of outdoor air. Trace gas species are generally much higher indoors than outdoors, and this can be further enhanced in low energy buildings, where air exchange is reduced to a minimum in order to minimize energy consumption for heating (mostly in France) or cooling (mostly in Australia).

Volatile silicon compounds are present in a wide range of household items, particularly in personal care products such as cosmetics and deodorants. Of particular interest are the cyclic polysiloxanes, which are emerging persistent chemicals of concern. The atmospheric chemistry of silicon compounds remains relatively unstudied. However, in indoor environments volatile siloxanes can be present at significant concentrations. For example, it was recently shown that D4 (cyclic polysiloxane made of 4 Si- and 4 O-atoms) was the most abundant volatile compound in a university classroom. Even in outdoor environments silicon compounds can be found at high levels.

To understand potential health effects of indoor air we need to know the rate at which siloxanes are removed by reaction with free radical oxidants, which will control their airborne lifetimes. Moreover, we need to understand the chemical products that these compounds are ultimately transformed into, so that we can assess their impacts on human health and the environment.

This project is focused on verifying and then expanding our understanding of this chemistry, through a suite of combined experiments (in France) and theoretical simulations (in Australia) in order to characterize the rate at which volatile silicon compounds react with the OH radical, and identify the products that result from subsequent oxidation of the products.

The candidate will mostly carry out experiments in Lille using two different laser-based experimental set-ups: a laser photolysis system coupled to a detection by FAGE (fluorescence assay by gas expansion) and another laser photolysis system coupled to a detection by LIF (laser induced fluorescence) or cw-CRDS (cavity ring down spectroscopy). The PhD project also includes extended stays at the University Melbourne to get formation in theoretical chemistry and participate in the quantum chemical calculations. A counterpart PhD student at the University Melbourne will mostly do quantum chemical calculations and will participate in experiments during extended stays in Lille.

 

Programmes de recherche en lien avec le sujet :  PRC CNRS – University Melbourne

Mots clés : Indoor Air Quality, reaction kinetic, laser spectroscopy

Responsables et coordonnées :

PC2A                     Christa Fittschen                christa.fittschen@univ-lille.fr              Tel: 03 20 33 72 66

                                Coralie Schoemaecker      Coralie.schoemaecker@univ-lille.fr   Tel: 03 20 33 72 66

U Melbourne        Gabriel da Silva                   gdasilva@unimelb.eduau

Financement envisage : PhD grant secured in the frame of the PRC CNRS-Melbourne

 

FILLED, POURVU, Pollution sensors and building ventilation strategies

This position is now filled

Since 2014 PC2A laboratory has been investigating the use of miniature gas and particle sensors to characterize the pollution levels inside buildings as well as the individual exposure of people to air pollutants. Recent results also pointed out the potential of miniature sensors to understand the behavior of the buildings themselves and of the people inside the buildings.

 

To further delve into these aspects, PC2A laboratory, in partnership with the Building Physics group at the University of Gent, is looking for a motivated student willing to undertake a PhD at the intersection of two fields with strong scientific, social and economic impacts : energy and public health. We propose to investigate, using the miniature air quality sensor systems developed at ULille, the mechanisms responsible for the outdoor to indoor transfer of pollutants, and the respective importance of particulate pollution from indoor and from outdoor origin. We will eventually be able to integrate the particles sensors into demand controlled ventilation systems, in order to renew the air in buildings while simultaneously considering the energy preservation objective prescribed for new buildings and ensuring a healthy indoor air for the occupants. The project therefore joins the expertise in atmospheric chemistry and physics and in individual exposure of the partners in ULille, with the expertise in building physics and ventilation of the UGent partner. The project relies on academic research that can be in a near future transferred to the economic world.

Due to the multidisciplinary nature of the envisioned project, candidates from various background may apply: atmospheric chemistry and physics, analytical chemistry, building science, architecture, public health…

 

Keywords: air quality, miniature sensors, building physics, ventilation schemes

 

Contacts :        Benjamin Hanoune           Benjamin.hanoune@univ-lille.fr   (PC2A, Lille)

                        Jelle Laverge                    Jelle.laverge@ugent.be             (Gent)

                               

 

Funding : I-SITE funding (not secured yet, main criterium is the candidate) : http://www.isite-ulne.fr/index.php/fr/app/co-tutelles-de-theses-2020-universite-de-gand/

Deadline for application: April 29, 2020.

 

Post-docs