It is now well established that heterogeneous chemistry has a drastic impact on the tropospheric composition. The complex physicochemical processes involved in this chemistry include : phase exchange, surface reactions, reactions in condensed phase followed by transfer to the gas phase have to be quantified in order to be able to develop reliable atmospheric models, and thus have a better understanding of the tropospheric chemistry.

Integrating heterogeneous physicochemical parameters (kinetics constants, accommodation coefficients, complexe refractive indexes, hygroscopicity parameter etc…) requires new tools allowing to perform experiments in conditions as close as possible to natural ones. This is the goal of the simulation chamber called CESAM (which means Multiphase Atmospheric Experimental Simulation Chamber).

This simulation chamber has been designed specifically to perform in realistic conditions experiments involving several phases like organic particule, water droplets, mineral dust, soot, salts and gas phase.

CESAM is an atmospheric simulation chamber dedicated to the study of multiphase atmospheric processes such as the formation of secondary aerosol or gaseous compounds in cloud-phase reactivity. This is a stainless steel reactor with a volume of 4.2 m³, equipped of pumping devices allowing to make a secondary vacuum, particularly to limit the potential memory effects which may persist to another experience.

The particular design of this chamber allows :

• to work at low enough levels of concentration to ensure that the studied processes are representative of those occurring in the natural atmospheres
• to ensure a lifetime of aerosol consistent with the study of its aging process. The body of the reactor is double-walled allowing the circulation of heat transfer fluids to regulate the temperature of the reaction mixture. This system is modular since it has twelve side plates supporting various equipment (optical spectrometry, lines of transfer, pump tubing, ports of introduction and sampling). The chamber is equipped with the most modern tools for metrology of aerosols and their precursors.

Being awarded "National Instrument of CNRS-INSU", CESAM is widely open to the international community. CESAM is part of the facilities of ACTRIS-FR and ACTRIS-EU.

------------------ News ------------------

CESAM news - Curated tweets by Prof_JF_Doussin

Octobre, 4, 2018
L'ANR PARAMOUNT is funded !

Great new ! The French National Research Agency project "PARAMOUNT" is funded. Aiming at better understanding the formation of secondary organic aerosol from droplet chemistry through the study of the multiphase chemistry of carbonyls it includes the Prof. Hartmut Herrmann team from TROPOS (Germany) and Prof. Anne Monod from Aix-Marseille Universiy. It is coordinated by LISA and will make a significant use of the unique possibilities of the CESAM chamber for the study the in-cloud photochemisty"

November, 16, 2017
The continuing story of our collaboration with Prof. Veronica Vaida (U. Colorado Boulder)

The sixth paper on the multiphase chemistry in CESAM chamber of multifunctional carbonyls is issued. Directed by Prof. Veronica Vaida this illustates well how fruitful can be the collaboration through physical access to CESAM. Entitled, "Atmospheric Simulation Chamber Studies of the Gas-Phase Photolysis of Pyruvic Acid" (https://pubs.acs.org/doi/10.1021/acs.jpca.7b05139)it takes advantages of many feature of the CESAM chamber : The combination of the long path length available in the chamber and its low surface area to volume ratio allows us to quantitatively examine the quantum yield and photochemical products of pyruvic acid. Such details are new to the literature for the low initial concentrations of pyruvic acid employed here. We determined photolysis quantum yields of ϕobsN2 = 0.84 ± 0.1 in nitrogen and ϕobsAir = 3.2 ± 0.5 in air, which are higher than those reported by previous studies that used higher partial pressures of pyruvic acid. The quantum yield greater than unity in air is due to secondary chemistry, driven by O2, that emerges under the conditions in these experiments. The low concentration of pyruvic acid and the resulting oxygen effect also alter the product distribution such that acetic acid, rather than acetaldehyde, is the primary product in air. These results indicate that tropospheric pyruvic acid may degrade in part via photoinduced mechanisms that are different than previously expected

Une bonne nouvelle ! L'ANR UNREAL visant à étudier le viellissement des émission aéronautiques est financée. Coordonée par Dr. Isamel Ortega de l'ONERA, elle implique des étude dans la chambre CESAM pour reproduire le vieillissement atmosphérique et etuider la formation d'aérosol secondaire.

November, 16, 2017
The continuing story of our collaboration with Prof. Veronica Vaida (U. Colorado Boulder)

The sixth paper on the multiphase chemistry in CESAM chamber of multifunctional carbonyls is issued. Directed by Prof. Veronica Vaida this illustates well how fruitful can be the collaboration through physical access to CESAM. Entitled, "Atmospheric Simulation Chamber Studies of the Gas-Phase Photolysis of Pyruvic Acid" (https://pubs.acs.org/doi/10.1021/acs.jpca.7b05139)it takes advantages of many feature of the CESAM chamber : The combination of the long path length available in the chamber and its low surface area to volume ratio allows us to quantitatively examine the quantum yield and photochemical products of pyruvic acid. Such details are new to the literature for the low initial concentrations of pyruvic acid employed here. We determined photolysis quantum yields of ϕobsN2 = 0.84 ± 0.1 in nitrogen and ϕobsAir = 3.2 ± 0.5 in air, which are higher than those reported by previous studies that used higher partial pressures of pyruvic acid. The quantum yield greater than unity in air is due to secondary chemistry, driven by O2, that emerges under the conditions in these experiments. The low concentration of pyruvic acid and the resulting oxygen effect also alter the product distribution such that acetic acid, rather than acetaldehyde, is the primary product in air. These results indicate that tropospheric pyruvic acid may degrade in part via photoinduced mechanisms that are different than previously expected

July, 27, 2018
Many visitors at CESAM this summer

Many good colleagues and highly respected scientists stop by CESAM to say "Hello" and better evaluate the potential of our facilities. In july : Dr. Bill Carter from UC Riverside and Prof. Barbara Finalyson-Pitts from AirUCI (UC Irvine) and in sepptember Prof. Manabu Shiraiwa from UCI too !

November, 16, 2017
The continuing story of our collaboration with Prof. Veronica Vaida (U. Colorado Boulder)

The sixth paper on the multiphase chemistry in CESAM chamber of multifunctional carbonyls is issued. Directed by Prof. Veronica Vaida this illustates well how fruitful can be the collaboration through physical access to CESAM. Entitled, "Atmospheric Simulation Chamber Studies of the Gas-Phase Photolysis of Pyruvic Acid" (https://pubs.acs.org/doi/10.1021/acs.jpca.7b05139)it takes advantages of many feature of the CESAM chamber : The combination of the long path length available in the chamber and its low surface area to volume ratio allows us to quantitatively examine the quantum yield and photochemical products of pyruvic acid. Such details are new to the literature for the low initial concentrations of pyruvic acid employed here. We determined photolysis quantum yields of ϕobsN2 = 0.84 ± 0.1 in nitrogen and ϕobsAir = 3.2 ± 0.5 in air, which are higher than those reported by previous studies that used higher partial pressures of pyruvic acid. The quantum yield greater than unity in air is due to secondary chemistry, driven by O2, that emerges under the conditions in these experiments. The low concentration of pyruvic acid and the resulting oxygen effect also alter the product distribution such that acetic acid, rather than acetaldehyde, is the primary product in air. These results indicate that tropospheric pyruvic acid may degrade in part via photoinduced mechanisms that are different than previously expected

February, 9, 2017
Publication d'un atlas de propriétés optiques dans l'infrarouge des poussière désertique !

C'est l'aboutissement de très nombreuses experiences réalisées dans la chambre CESAM, les propriétés optiques des poussières minérales formés par les deserts les plus emetteurs du monde sont publiées dans un article unique(https://www.atmos-chem-phys.net/17/1901/2017/). Ce set de données unique devrait permettre, à terme, d'améliorer la télédéction sattélitaire des nuages de poussières qui sont si important pour la modélisation climatique et même d'améliorer la restitution de l'ozone dont la signature spectrale interfère avec celle des poussières. Ces données devrait également ameliorer les calculs de transfère radiatif et donc la prise en compte de l'effet des poussière sur le rechauffement climatique.

January, 23, 2017
Lancement du réseau d’infrastructure des chambres de simulation atmosphérique : cap sur 2020 !

Plus de soixante scientifiques (physiciens, chimistes de l’atmosphère, biologistes) de 10 pays Européens se sont réunis à Paris la semaine dernière pour le colloque de lancement du réseau d’infrastructure EUROCHAMP-2020. Soutenu par le programme H-2020 de l’Union Européenne à hauteur de 9 millions d’euros et piloté par le CNRS (coord. J.-F. Doussin/LISA), ce projet vise à la coordination des chambres de simulation atmosphérique en une infrastructure distribuée ouverte à l’ensemble de la communauté scientifique. Il s’agit ni plus ni moins de développer, d’harmoniser et d’implémenter les protocoles qui permettent déjà (ou permettront dans l’avenir) l’étude en laboratoire de l’impact des transformations atmosphériques sur les déterminants du changement climatique, de la qualité de l’air, de leur effets sur la santé, ou sur la composition des masses d’air proches ou éloignées ou même des échanges océan-cryosphère-atmosphère. Riche de la diversité de ses plateformes qui lui permet d’aborder des thématiques très diverses, cette communauté poursuit un chemin commencé il y a plus de 10 ans et se rapproche encore d’autres infrastructures telles que celles dédiées à l’observation atmosphérique. Ces trois jours de réunion lui ont ainsi permis d’échanger sur ses stratégies expérimentales, de renouveler sa pratique d’ouverture aux utilisateurs de tous horizons, de réfléchir à son ouverture aux acteurs du monde socio-économique ou encore de se projeter sur le futur de son infrastructure dans la feuilles de route ESFRI. Cette initiative a également été l’occasion de définir leur tout nouveau centre de données dont la réalisation est confiée au pôle AERIS (www.aeris-data.fr).

Sept, 2016
Le projet REDDUST récompensé à l'EAC 2016

Lors de la dernière European Aerosol Conference tenue à Tours (France) le 4-9 Septembre 2016, le Best Poster Award à été decerné au travail intitulé «Global scale variability of the mineral dust longwave refractive index from new in situ chamber measurements » par C. Di Biagio et al..
Le poster propose de nouvelles déterminations d’indice de réfraction infrarouge des poussières désertiques obtenues à partir de mesures in situ dans la chambre de simulation CESAM.

January, 1, 2016
Experimental determination and theoretical framework of kinetic fractionation at the water vapour – ice interface at low temperature

Climate reconstruction from ice cores rely on good knowledge of equilibrium and kinetic isotopic fractionation at each step of the water cycle. One of the strongest limitations when interpreting water isotopes in remote Antarctic ice cores is the formulation of the isotopic fractionation at solid condensation (vapour to ice). The uncertainties associated with the coefficients for equilibrium fractionation and water vapour diffusion in air make the formulation of isotopic fractionation at solid condensation only empirical.

Here, using (1) recent development in the measurements of water isotopes in the water vapour through infra-red spectroscopy and (2) the possibility to measure accurately 17O-excess of water, we test the classical formulation and parameterization of isotopic fractionation at solid condensation. The spatial variability of water vapour isotopic composition differs from classical formulation from Jouzel and Merlivat (1984, figure b) but can be relatively well reproduced by the resolution of diffusion toward a cold plate. In addition, our experiments highlight the impact of kinetic fractionation at condensation on 17O-excess for the first time. This preliminary study opens new perspectives to revisit the classical formulation of water isotopic fractionation during solid condensation at very low temperature. Ref : http://dx.doi.org/10.1016/j.gca.2015.11.009

November, 10, 2015
"Irrespirable - Comment échapper à l’asphyxie" vient de paraître

Le livre sur la pollution de l'air "Irrespirable - Comment échapper à l’asphyxie" vient de paraître aux éditions Taillandier/Arte édition. Écrit par Delphine Prunault et Alice Bomboy. Décrivant, entre autre, la stratégie que nous mettons en oeuvre avec CESAM, cet ouvrage vient appuyer un long métrage documentaire prochainement diffusé (février 2016) dans le cadre des soirées thématiques d'ARTE.
Fruit d’une longue investigation, cet ouvrage fait l’état des lieux précis de l’ampleur de la menace, détaille les conséquences de la pollution sur la santé et tord le cou aux idées reçues. Cette enquête vous donne les clés pour vous protéger, le mieux possible, de ce fléau. Un document choc.
http://boutique.arte.tv/f10615-irrespirable_livre