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 2018-2019), une thèse de doctorat (à partir d'Octobre 2019), 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

Measurement of carbonaceous particles in the exhaust line of a combustion system using scanning mobility particle sizing and laser induced incandescence

This subject concerns the control of soot particles emission at the exhausts of gasoline engines. Today, emission standards are limited to particles greater than 23 nm. The next emission standards will be more restrictive in number of particles and will be extended to smaller particles down to 10 nm. The measurement of such small particles can be performed in principle using commercial scanning mobility particle sizers (SMPS) or using laser diagnostic such as laser induced incandescence (LII). However, measuring such small particle size remains a challenging task.

The objective of the internship is to perform a comparative study of the above mentioned techniques for different experimental conditions. SMPS requires that particles are sampled from the exhausts, while LII can be applied in-situ. The sensitivity and accuracy of the techniques will be evaluated for different size classes of the particles which will be generated either by a carbon nanoparticle generator or by a sooting flame. Then, the penetration function of the particles in the exhaust line will be analyzed to assess the effect of thermophoresis and sedimentation, possibly by class of the primary particle and aggregate size, and compared to theoretical models.

 

The master student will be in charge to install and to operate the overall setup under appropriate support from his/her supervisors.

 

This internship takes part of the European contract PEMS4nano. http://www.pems4nano.eu/

Keywords: soot, SMPS, laser diagnostics, environmental regulation

Linked to the workpackage of the Labex CaPPA : WP 5

Supervisor(s): Pascale DESGROUX and Alessandro FACCINETTO

Study of the reactivity of radical species in atmospheric chemistry

In the atmosphere, organic pollutants such as Volatile Organic Compounds (VOCs) from biogenic and anthropogenic sources are photochemically oxidized to form peroxy radicals such as hydroperoxy HO2 and alkylperoxy RO2 radicals, which play a major role in tropospheric chemistry. The reactivity of these radicals controls the oxidative capacity of the atmosphere and the formation of tropospheric ozone and secondary pollutants. However, the reactivity of HOx (OH and HO2) and RO2 radicals is still poorly understood and controversial in the literature, particularly in “clean” environments containing low NOx concentrations (remote regions: marine boundary layer or tropical forest).

 

The objective of this project is the study of the reactions between RO2 and HOx radicals for a better understanding of atmospheric chemistry. For that, a new and unique experimental set-up has been developed at the PC2A, it consists of a fast flow reactor coupled to three complementary techniques:

-Laser Induced Fluorescence (LIF) for in-situ OH radicals measurements

-continuous wave Cavity Ring-Down Spectroscopy (cw-CRDS) for HO2 radicals measurements

-Mass Spectrometry with Molecular Beam sampling (MB/MS) for the measurement of stable reaction products and radical species.

Rate constants and branching ratios measurements of the reactions RO2 + HOx will be performed.

 

This project is addressed to candidates interested in the experimental aspects of research and having knowledge in atmospheric chemistry.

Keywords: atmospheric chemistry, radicals reactivity, laser techniques, mass spectrometry

Linked to the workpackage of the Labex CaPPA : WP 1

Supervisors: Laure Pillier

Kinetic study of reactions with interest to atmospheric and combustion chemistry by simultaneous detection of OH and RO2 radicals coupled to laser photolysis

OH radicals as well as peroxy radicals (HO2 and RO2) are key species not only in the atmospheric chemistry reaction mechanism, but also in combustion processes, two research domains that are developed in the laboratory PC2A. In this frame, we have set-up an experimental technique able to determine the concentrations of these radicals in a time resolved manner with the goal of studying kinetics of elementary reactions involving these radicals. The set-up is composed of a photolysis laser, initiating the reaction by a pulsed photolysis of an appropriate precursor in the reaction (i.e. H2O2 for generating OH radicals), coupled to two detection techniques:

- OH radicals by Laser Induced Fluorescence (LIF) at high repetition rate (10 kHz)

- Peroxy radicals by continuous wave Cavity Ring Down Spectroscopy (cw-CRDS) in the near IR

In the frame of the proposed PhD work, this experimental set-up will be used to study different reaction systems of atmospheric or combustion interest, for example:

- the degradation of isoprene, a biogenic volatile organic compound (VOC)emitted in large quantities by vegetation

- the cross reactions between HO2 and other RO2 radicals, a very important class of reaction in remote environment, only poorly understood. The simultaneous measurement of OH and HO2 / RO2 radicals will allow determining the branching ratios of such reactions.

Keywords: Peroxy radicals, OH radicals, laser photolysis, laser spectroscopy

Linked to the workpackage of the Labex CaPPA : WP 1

Supervisors: Christa Fittschen / Coralie Schoemaecker

 

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., pure water droplets, water droplets containing bioaerosols or silica particles with water adsorbed on their surface. 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 physicist or chemist 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

Supervisors: Denis Petitprez (PC2A) - Hervé Herbin (LOA) - Olivier Pujol (LOA)

Modelling iodine interactions with atmospheric aerosols

 

Following a severe nuclear power reactor accident, radionuclides like caesium and iodine are released into the atmosphere. Models could predict health impact and organize population evacuation if the need arises. The computer codes used by the IRSN in case of accidental release of radioactive products do not consider the dispersion and drawdown effects; the source term is chemically inert. However, the reactivity of iodine in the atmosphere is well known, and this hypothesis has to be reassessed.

During the Fukushima accident, the simulations have defined quantities of caesium relatively close to those measured in the field, this is not the case for iodine. This discrepancy could be explained by the chemical reactivity of iodine in the atmosphere, which is not implemented in the codes. Indeed, parameters like deposition velocity or the dose-effect factor depends on Iodine chemical speciation and physical form (gas, particle, liquid, solid). Therefore, heterogeneous reactions are important to evaluate the radiologic impact.

The purpose of this internship is to make a critical review of the literature to complete the iodine chemical mechanism with the heterogeneous reactions. 0D modelling studies will be conducted to evaluate the iodine species speciation under various atmospheric conditions (temperature, photolysis, gas and aerosols concentration, ...). The iodine reactivity will be added in heterogeneous phase to the chemical transport models (Chimere and Polair3D in our case) to have a better understanding of the Fukushima accident.

This project will be performed in the framework of the Laboratoire de Recherche Commun C3R (Cinétique Chimique, Combustion, Réactivité) IRSN/CNRS/Lille1 and the Labex CaPPA – WP6 (Chemical and Physical Properties of the Atmosphere).

 

Keywords:  Iodine, Chemistry-transport, Heterogeneous Reactivity, Fukushima

Linked to the workpackage of the Labex CaPPA : WP6

Supervisors: Valérie FEVRE-NOLLET / Patrick LEBEGUE

Biomarkers of Air Pollution on Pollen

Pollen grain has a brief atmospheric airborne life ranging from hours to days during pollination period. Pollen grain is modified by gaseous and particulate pollution during its transport in the atmosphere.

     The modifications of pollen grains by atmospheric pollution induce an inhibition of the germinative capability of the pollen, an increase of its allergenic potential and facilitate the dispersion of allergens in the fine fraction of atmospheric aerosols (1).

     Pollen lipidic fraction can be modified in laboratory conditions by air pollutants, particularly by ozone (2). With this internship, pollen will be exposed to oudoor atmospheric pollution in situ. The candidate will have to design suitable exposure conditions of pollen to outdoor pollution. The lipidic fraction of pollen will be used as a marker of pollution. Lidids will be extracted and analyzed by chromatographic techniques (GC-MS, GC-FID and HPLC).

     Rupture of pollen will also be studied by measuring size distributions with an Aerodynamic Particle Spectrometer (APS).

(1) Sénéchal, H. et al. A Review of the Effects of Major Atmospheric Pollutants on Pollen Grains, Pollen Content and Allergenicity. The Scientific World Journal 2015, ID 940243 (2015).

(2) Naas, O. et al. Chemical modification of coating of Pinus halepensis pollen by ozone exposure. Environmental Pollution 214, 816–821 (2016).

 

Keywords: Heterogeneous Chemistry, Analytical Chemistry, Allergy

Linked to the workpackage of the Labex CaPPA: WP 2

Supervisor: Nicolas Visez

Gas phase reactivity of iodine-containing species of atmospheric interest

The goal of this internship is to improve the understanding of the homogeneous reactivity of iodine-containing species with major photo-oxidants, to better address the lack of data in the field of atmospheric chemistry and nuclear safety, and to provide a set of reliable kinetic and mechanistic data on gas-phase iodine reactivity. These data will improve the relevance and accuracy of iodine dispersion models.

 

Quantum chemistry is more and more used to determine rate constants for gas-phase elementary reactions because the power of the current generation of computers allows to obtain reliable kinetic parameters. It permits to understand the mechanism of global and elementary reactions. It allows to calculate the molecular properties (geometrical data, molecular mass, vibrational frequencies, inertia moments) of reactants, products, transition states, and molecular complexes for an elementary reaction. Then, the macroscopic quantities such as the thermodynamical functions (internal energy, enthalpy, and Gibbs free energy) are calculated from molecular properties using statistical thermodynamics. Finally, temperature and pressure dependencies of rate constants are determined using kinetic theories from thermodynamical functions.

 

This project will be performed in the framework of the Laboratoire de Recherche Commun C3R (Cinétique Chimique, Combustion, Réactivité) IRSN/CNRS/Lille1 and the Labex CaPPA – WP6 (Chemical and Physical Properties of the Atmosphere). The subject of this research project can be pursued through a Ph-D.

 

Keywords: Iodine, theoretical chemistry, reactivity, kinetics, atmospheric chemistry, nuclear safety

Linked to the workpackage of the Labex CaPPA : WP6

Supervisor(s): Florent LOUIS / Marc RIBAUCOUR

Soil spreading of organic waste products: source of secondary organic aerosols?

Agricultural lands occupy about 40-50% of the Earth’s land surface. In order to assess the potential of agricultural ecosystems to act as a source or sink for ozone and volatile organic compounds (VOC), it is necessary to determine the emissions and deposition within the interface soil-atmosphere.

The valorisation of different types of organic waste products (OWP) from farms (cattle, pigs...), urban origin (sewage sludge, green waste) or industrial (sweets, etc.) is currently promoted as a substitute for mineral fertilizers. OWPs have a wide variety of characteristics due to their origin and the treatments that they may undergo before spreading and this diversity of characteristics could have a significant impact on gaseous emissions following soil application.

The agricultural soils emit volatile organic compound (VOC) that contribute to the formation of secondary pollutants such as ozone but also to the formation of secondary organic aerosols (SOA), both pollutants being under regulation.

The present project is focused in the study of SOA formation and ozone deposition and reactivity at the soil-atmosphere interface. Laboratory based measurements will investigate the related emissions of VOC from OWPs and their subsequent reaction with ozone to form aerosols. The experiments will be performed in an aerosol flow tube where the VOC will react with the ozone. An high panel of scientific equipment will be deployed and allow the physical and chemical characterisation of the VOCs and freshly formed aerosols (proton transfer mass spectrometer, scanning mobility particle sizer,…). Filter measurements of aerosols will allow their chemical and molecular characterisation by off-line analysis (gas chromatography, time of flight secondary ions mass spectrometry).The interested candidate will participate at the development of the experimental set-up and will perform experiments.

    

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

 

Labs: PC2A and INRA

Period: from February 1st 2017 to June 30 2017

Gratification: €554.40 per month

Keywords: volatile organic compounds, organic waste products, aerosols, mass spectrometry

Supervisors: RalucaCiuraru (INRA) and Denis Petitprez (PC2A)

 

 

 

Thèses

Mise au point d’une technique de mesure par absorption UV de particules dans un environnement gazeux complexe en vue d’une application dans la ligne d’échappement d’un moteur à combustion interne.

La mesure et le contrôle en temps réel des polluants issus de la combustion est un enjeu majeur pour des raisons désormais évidentes de santé publique. Pour des raisons de simplicité et de coût, disposer d’un unique capteur permettant de mesurer la totalité des polluants (gaz et particules) est un challenge qui est maintenant envisageable.

En particulier, des travaux initiés récemment sur la mise au point d’un capteur multigaz (BTX, H2S, SO2, NO, NO2, NH3…) embarquable sont en voie de finalisation et la preuve de concept est en cours de validation sur véhicule léger. Des travaux récents ont mis en évidence que la technique de mesure utilisée –absorption UV- peut également répondre à la présence particules.

L’objectif de la thèse est donc d’étudier et d’analyser le signal d’absorption du système multigaz en fonction des caractéristiques des particules présentes dans la zone de mesure et cela en présence ou non de gaz interférents dans l’ultra-violet (ex NH3, NO…). De nombreux paramètres devront être étudiés permettant une compréhension précise des phénomènes physiques en jeu. Une part importante de cette caractérisation portera sur l’impact des propriétés des suies sur le signal d’absorption obtenu. En effet, la littérature corrèle les propriétés optiques des particules à leur composition chimique et leur microstructure. En plus de ces paramètres, les paramètres de taille de particule et de nombre de particule seront étudiés.

Programmes de recherche en lien avec le sujet :  CLIMIBIO – Labex CaPPA

Mots clés :          particules, suie, émission, moteur, polluant

Responsables et coordonnées :

PC2A :                   Pascale Desgroux              pascale.desgroux@univ-lille.fr         Tel : 0320434930

                                Alessandro Faccinetto       alessandro.faccinetto@univ-lille.fr   Tel :0320434485

IFPEN :                  Matthieu Lecompte         matthieu.lecompte@ifpen.fr        Tel : 0437702168

                               

Financement  : 100 % IFPEN

Effets de la pollution atmosphérique sur le pollen allergisant – Comparaison entre l’exposition réelle des habitants de la région Hauts-de-France et les études de laboratoire

La littérature sur la pollution du pollen est abondante (Sénéchal et al., 2015)* et il est désormais acquis que les grains de pollen sont modifiés par la pollution atmosphérique. L’importance du rôle de la pollution atmosphérique sur l’allergie n’est pourtant toujours pas clairement définie ; il est en effet délicat de faire le lien entre les études de laboratoire fondamentales sur la pollution artificielle du grain et les études de terrain prélevant les pollens en atmosphère réelle.

L’objectif principal de ce travail de thèse est d’analyser finement l’état de pollution de pollens allergisants respirés par les habitants de la région Hauts-de-France.

Ce travail s’articulera en deux volets. Dans le premier volet, du pollen sera exposé en laboratoire aux deux polluants gazeux principalement observés en atmosphère urbaine : NO2 et O3 à différentes humidités relatives. Ce pollen artificiellement exposé sera analysé avec détails en multipliant les approches expérimentales : microscopie et cryomicroscopie électronique à balayage couplée à la spectrométrie d’émission de rayons X (MEB/EDX), techniques spectroscopiques vibrationnelles (Raman et infrarouge), microscopie à force atomique et chromatographie liquide et gazeuse. L’effet du gaz polluant et de l’humidité sur le pollen à l’échelle du grain individuel sera étudié in-situ par techniques de microspectrométrie Raman et infrarouge couplées à des cellules environnementales (LinkamTM et lévitation acoustique). L’influence des polluants sur la rupture du grain de pollen par exposition à l’humidité sera aussi considérée. Ces analyses doivent permettre de déterminer des indicateurs de la pollution à l’ozone et au dioxyde d’azote à l’échelle du  grain de pollen.

Dans le second volet, des collecteurs de pollen seront portés par quelques volontaires. Les pollens ainsi collectés pendant les périodes de pollinisation seront analysés selon les mêmes techniques que le premier volet pour rechercher les indicateurs de la pollution qui auront été mis en évidence. Cette comparaison nous permettra de déterminer l’état de pollution du pollen respiré en conditions réelles, ce qui d’après notre connaissance de la littérature n’a jamais été étudié avec notre protocole original.

Cette étude sera focalisée sur deux des pollens parmi les plus problématiques pour les habitants de notre région Hauts-de-France : le bouleau, l’un des arbres dont le pollen est le plus allergisant et la phléole des prés, une graminée également avérée comme extrêmement allergisante. Ce travail sera effectué en partenariat avec l’Association de Prévention de la Pollution Atmosphérique APPA qui est un acteur reconnu dans notre région sur la prévention des allergies et la surveillance des concentrations en pollens.

*(Sénéchal et al. 2015, doi.org/10.1155/2015/940243)

Programmes de recherche en lien avec le CPER CLIMIBIO

Mots clés :         Bioaérosols, pollens, pollution atmosphérique, allergie

Responsables et coordonnées : Nicolas Visez (PC2A), Tel : 03 20 43 65 62, Marie Choël (LASIR), Tel : 03 20 43 47 48

 

 

 

Post-docs

Metrology and kinetic studies of HOx radicals for atmospheric applications

Context:

This post-doctoral position is proposed in the frame of the CPER CLIMIBIO project and will focus on the understanding of the gas phase chemical oxidation processes taking place in the atmosphere through a twofold approach: experiments in laboratory to study kinetics of reactions involving the radicals OH, HO2 and RO2 and field deployment to quantify these radicals as well as the OH reactivity in the atmosphere. The experiments will be carried out with a FAGE instrument developed in our laboratory and under improvement to be able to measure simultaneously all these parameters.

Post-doc tasks:

For the kinetic studies, the recruited post-doc will have to carry out measurements on reactions of interest with the FAGE instrument in the reactivity mode, under controlled and variable conditions to study the influence of parameters such as the humidity and pressure on rate constants.

For the quantification studies, the recruited post-doc will have in charge to optimize the conditions of use of the instrument for field deployment and in particular for RO2 quantification. A participation to a field campaign in July 2019 is probable.

Profile:

The applicant should hold a PhD in the field of atmospheric chemistry and experimental development. Knowledge in optical spectroscopy (in particular Laser Induced Fluorescence), with experimental skills in the kinetic studies will be appreciated. The research involves improving and using a FAGE instrument set-up as well as data collection and analysis. Skills in data analysis and computer programming (LabView or equivalent) will be also appreciated.

 

Funding: This post-doctoral position is proposed in the frame of a regional project (CPER CLIMIBIO) involving 16 laboratories on the understanding of the climate change and its impact. Month salary depends on candidate experience.

Duration: 12 months.

Starting date: February 2019

Working place: University of Lille- Sciences and Technologies

PC2A laboratory- UMR CNRS 8522

To apply: send by e-mail to the contacts a detailed CV, including the list of publications, a covering letter detailing your motivation for the position and your expertise in regard of the profile, 2 reference letters and a list of people to contact for complementary references

Contacts:

Coralie Schoemaecker: coralie.schoemaecker@univ-lille.fr

Christa Fittschen: christa.fittschen@univ-lille.fr

PC2A laboratory- PhysicoChimie des Processus de Combustion et de l'Atmosphère