Image de Christian George

Christian George

Sous-directeur

Numéro ORCID : 0000-0003-1578-7056


448 190 (Standard + 33 [0] 472 445 300)
C13.001

Mots clés

Atmospheric chemistry, surface reaction, heterogeneous chemistry, photochemistry, aerosols, ultrafine particles, pollution, air-sea interactions

Education

1999:    Research Habilitation Thesis (HDR) – Physical Chemisistry,   University Louis Pasteur - Strasbourg,      

             Thesis title: Atmospheric Chemistry : Study of the heterogeneous processes, Advisor: Ph. Mirabel.

1993:    Ph-D thesis - Physical Chemistry, University Louis Pasteur - Strasbourg

             Thesis title: Heterogeneous physical chemistry of the atmosphere : experimental and modelling studies of phase transfer, Advisor: Ph. Mirabel.

Professional Experience

2016-…               Deputy-director of the Research Institute on Catalysis and the Environment at Lyon – IRCELYON, CNRS-University Lyon 1, France.

2006-2015:        Senior Research Scientist at the "Centre National de la Recherche Scientifique" – CNRS- IRCELYON, University Lyon 1, France, Interdisciplinary Group Leader, in charge of ca. 43 persons.

1999-2006 :       Research Scientist at the "Centre National de la Recherche Scientifique" – CNRS, Laboratoire d'Application de la Chimie à l'Environnement, University Claude Bernard – Lyon.

1995-1999:        Research Scientist at the "Centre National de la Recherche Scientifique" – CNRS, Center for Surface Geochemistry, University Louis Pasteur – Strasbourg.

1994-1995:       Post-doctoral Fellow in Atmospheric Chemistry, Fraunhofer-Institut für Toxikologie und Aerosolforschung, Hanover.

Awards

2004 :                  EUREKA-Lillehammer Prize – EUROTRAC 2 2004.

2011 :                  Advanced Grant 2011 of the European Research Council (ERC).

Editorial boards

2015-…               Scientific Reports, published par Nature Journals.

2014-…               Environmental Science and Pollution Research.

2001-2008:        Atmospheric Chemistry and Physics (ACP), http://www.atmos-chem-phys.org

Guest Editor for a Special Issue of ChemPhysChem, Issue 18 (2010), for a Special Issue of Environmental Science and Technology (2011-2012) and for a Special Issue of Applied Catalysis B (2012).

Research interest

My current research portfolio is based on studies bringing together atmospheric chemistry, environmental chemistry, physical chemistry, chemical kinetics, Photochemistry… for a better understanding of the processes occurring in the troposphere. A central aspect of this work is the participation in collaborations across many disciplines.

Research in my group brings together techniques of physical chemistry to understand fundamental aspects of atmospheric and environmental chemistry. We use laser photolysis, mass spectrometry, infrared spectroscopy, combined with standard analytical methods to understand chemical interactions at interfaces of atmospheric importance.

The interfaces we are considering are those exposed by aerosols (mineral and organic), the ocean, indoor surfaces and also the built environment (urban grime).

Accordingly, the topics we are addressing are:

  • Atmospheric chemistry
  • Aerosol physical chemistry
  • Ocean atmosphere exchanges
  • Mineral dust photochemistry
  • Formation and ageing of organic aerosols

 

Recent research highlight

 

Unravelling chemistry is the Sea Surface Microlayer as a driving force for Air-Sea exchanges.

The surface of the oceans acts as a global sink and source for trace gases and aerosol particles. Recent studies suggest that photochemical reactions at this air/water interface produce organic vapors, enhancing particle formation in the atmosphere. However, current model calculations neglect this abiotic source of reactive compounds and account only for biological emissions. Here we show that interfacial photochemistry serves as a major abiotic source of volatile organic compounds (VOCs) on a global scale, capable to compete with emissions from marine biology. Our results indicate global emissions of 46.4–184 Tg C yr–1 of organic vapors from the oceans into the marine atmosphere and a potential contribution to organic aerosol mass of more than 60% over the remote ocean. Moreover, we provide global distributions of VOC formation potentials, which can be used as simple tools for field studies to estimate photochemical VOC emissions depending on location and season.

Associated publications

Bruggemann, M., N. Hayeck, and C. George (2018), Interfacial photochemistry at the ocean surface is a global source of organic vapors and aerosols, Nat. Commun., 9, 8, doi:10.1038/s41467-018-04528-7.

 

Discovering new photochemistry at the air-water interface.

Aerosols play many roles in the atmosphere, including seeding cloud formation and cooling the planet by scattering sunlight. We have found a potential new, unlikely source of precursors to atmospheric aerosols: fatty acids.

Although fatty acids exist in the environment, scientists long thought these molecules didn’t participate in atmospheric chemistry because they’re photochemically inactive at wavelengths beaming through the atmosphere.

We now showed that fatty acids are indeed photochemically active at environmentally relevant wavelengths—if the fatty acid is at a high enough concentration. Such concentrations can exist at the interface between water and air.

This routes leads to chemically active products with double bonds that are susceptible to reactions with ozone and hydroxyl radicals—reactions that can lead to aerosol formation.

Associated publication

Rossignol, S.; Tinel, L.; Bianco, A.; Passananti, M.; Brigante, M.; Donaldson, D. J.; George, C., Atmospheric photochemistry at a fatty acid-coated air-water interface, Science, 2016, 353 (6300), 699-702.

 

Unravelling New Processes at Interfaces: Photochemical Isoprene Production at the Sea Surface

Raluca Ciuraru, Ludovic Fine, Manuela van Pinxteren, Barbara D’Anna, Hartmut Herrmann, and Christian George

Publication Date (Web): September 10, 2015

ACS Editors’ Choice Date: October 4, 2015

DOI: 10.1021/acs.est.5b02388

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The oceans seem to produce significantly more isoprene, and consequently affect stronger the climate than previously thought. This emerges from a study by the Institute of Catalysis and Environment in Lyon (IRCELYON, CNRS / University Lyon 1) and the Leibniz Institute for Tropospheric Research (TROPOS), which had studied samples of the surface film in the laboratory. The results underline the global significance of the chemical processes at the border between ocean and atmosphere.

Isoprene is a gas that is formed by both the vegetation and the oceans. It is very important for the climate because this gas can form particles that can become clouds and then later affect temperature and precipitation. Previously it was assumed that isoprene is primarily caused by biological processes from plankton in the sea water. The atmospheric chemists from France and Germany, however, could now show that isoprene could also be formed without biological sources in surface film of the oceans by sunlight and so explain the large discrepancy between field measurements and models. The new identified photochemical reaction is therefore important to improve the climate models. 

The oceans not only take up heat and carbon dioxide from the atmosphere, they are also sources of various gaseous compounds, thereby affecting the global climate. A key role is played by the so-called surface microlayer (SML),  especially at low wind speed. In these few micrometers thin layer different organic substances such as dissolved organic matter, fat and amino acids, proteins, lipids are accumulating as well as trace metals, dust and microorganisms.

For the now published study, the research team took samples from the North Sea. The  surface film was collected in the Raunefjord near Bergen in Norway. For this purpose, a glass plate is immersed in water and then again carefully pulled from the water. The 200 micron thin film sticks to the glass and is then scraped off with a wiper. The sample thus obtained is analyzed in the laboratory later. At the Institute of Catalysis and Environment in Lyon (IRCELYON), which belongs to the French research organization CNRS and the University of Lyon 1, the team investigated its photochemical properties during which collected samples were irradiated with light and the gases were analyzed:  it became clear that isoprene was produced in magtnetudes that were previously attributed solely to plankton. "We were able for the first time trace back the production of this important aerosol precursor  to abiotic sources, so far  global calculations consider only biological sources," explains Dr. Christian George from IRCELYON.

Thus, it is now possible to estimate more closely the total amounts of isoprene, which are  emitted. So far, however, local measurements indicated levels of about 0.3 megatonnes per year, global simulations of around 1.9 megatons per year. But the team of Lyon and Leipzig estimates that the newly discovered photochemical pathway alone contribute 0.2 to 3.5 megatons per year additionally and could explain the recent disagreements. "The existence of the organic films at the ocean surface due to biological activities therefore influences the exchange processes between air and sea in a unexpected strong way. The photochemical processes at this interface could be a very significant source of isoprene", summarizes Prof. Hartmut Herrmann from TROPOS.

 

Photosensitized production of functionalized and unsaturated organic compounds at the air-sea interface

Raluca Ciuraru1, Ludovic Fine1, Manuela van Pinxteren2, Barbara D’Anna1, Hartmut Herrmann2, Christian George1*

  • Scientific Reports 5, Article number: 12741 (2015)
  • doi:10.1038/srep12741
  • http://www.nature.com/articles/srep12741

The sea-surface microlayer (SML) has different physical, chemical and biological properties compared to the subsurface water, with an enrichment of organic matter i.e., dissolved organic matter including UV absorbing humic substances, fatty acids and many others. Here we present experimental evidence that dissolved organic matter, such as humic acids, when exposed to sunlight, can photosensitize the chemical conversion of linear saturated fatty acids at the air-water interface into unsaturated functionalized gas phase products (i.e. saturated and unsaturated aldehydes and acids, alkenes and dienes,…) which are known precursors of secondary organic aerosols. These functionalised molecules have previously been thought to be of biological origin, but here we demonstrate that abiotic interfacial photochemistry has the potential to produce such molecules. As the ocean is widely covered by the SML, this new understanding will impact on our ability to describe atmospheric chemistry in the marine environment.

Production of Atmospherically Reactive Organic Compounds at the Air/Aqueous Interface

Hongbo Fu†‡§⊥, Raluca Ciuraru†‡, Yoan Dupart†‡, Monica Passananti†‡, Liselotte Tinel†‡,Stéphanie Rossignol†‡, Sebastien Perrier†‡, D. James Donaldson*∥, Jianmin Chen*§, and Christian George*†‡

J. Am. Chem. Soc., 2015137 (26), pp 8348–8351

DOI: 10.1021/jacs.5b04051

Abstract Image

We report on experiments that probe photosensitized chemistry at the air/water interface, a region that does not just connect the two phases but displays its own specific chemistry. Here, we follow reactions of octanol, a proxy for environmentally relevant soluble surfactants, initiated by an attack by triplet-state carbonyl compounds, which are themselves concentrated at the interface by the presence of this surfactant. Gas-phase products are determined using PTR-ToF-MS, and those remaining in the organic layer are determined by ATR-FTIR spectroscopy and HPLC-HRMS. We observe the photosensitized production of carboxylic acids as well as unsaturated and branched-chain oxygenated products, compounds that act as organic aerosol precursors and had been thought to be produced solely by biological activity. A mechanism that is consistent with the observations is detailed here, and the energetics of several key reactions are calculated using quantum chemical methods. The results suggest that the concentrating nature of the interface leads to its being a favorable venue for radical reactions yielding complex and functionalized products that themselves could initiate further secondary chemistry and new particle formation in the atmospheric environment.

 

 

Mineral dust photochemistry induces nucleation events in the presence of SO2

Yoan Dupart, Stephanie M. King, Bettina Nekat, Andreas Nowak, Alfred Wiedensohler, Hartmut Herrmann, Gregory David, Benjamin Thomas, Alain Miffre, Patrick Rairoux, Barbara D’Anna, Christian George

Proceedings of the National Academy of Sciences of The United States of America, DOI: 10.1073/pnas.1212297109, 109 no. 51 20842-20847, 2012

Highlighted in Chemical & Engineering News
 

Radicals released from the surface of airborne dust trigger formation of new aerosol particles in the atmosphere, according to a new study (Proc. Natl. Acad. Sci. USA, DOI:10.1073/pnas.1212297109). These aerosols play key roles in precipitation, climate, and air quality.

Scientists poorly understand how new aerosol particles nucleate in the air, despite aerosols’ importance in the
atmosphere: The particles may seed clouds, absorb or reflect sunlight, and cause respiratory and heart problems in people. An international team led by Christian George, a research scientist at the Institute for Research on Catalysis and Environment in Lyon, France, now report one possible mechanism based on chemistry at the surface of dust particles. Other researchers had previously determined that light-driven reactions on dust particles containing titanium dioxide or iron(III) oxide produce hydroxyl radicals from water.

These radicals can convert sulfur dioxide adsorbed onto the particles into sulfuric acid, which stays on the particles. Sulfuric acid is known to nucleate new aerosol particles, but only if it is not adsorbed on dust. George and his colleagues wondered if hydroxyl radicals could leave the dust particles and go on to initiate gas-phase chemistry with free sulfur dioxide.

To simulate such atmospheric conditions, the scientists shone light into a laboratory flow tube containing low concentrations of dust, along with water vapor and sulfur dioxide. As the team monitored particle concentrations inside the tube, they noticed levels increased over time instead of remaining constant. They also found that keeping the tube in the dark or removing the sulfur dioxide or water vapor led to no new particle formation.

Because new particles formed only in the light and with all of the ingredients present, the team thinks that the dust particles released hydroxyl radicals to the air. The radical species then conv

Professional service            

2013-… :       Board of trustees on behalf of the CNRS of the company PULSALYS (SATT Lyon Saint-Etienne).

2011-2015 : Regional vice coordinator of the academic community investigating environmental processes in Rhône-Alpes (ARC3).

2011-2012 : Vice President of the University of Lyon 1 – Claude Bernard.

2004-2009 : National vice coordinator (“chargé de mission”) of the Atmospheric division at INSU (Institut National des Sciences de l’Univers) of the CNRS.

Coordination of European projects INTROP, MOST, PHOTOPAQ

National and international panels 

2017-…         International Global Atmospheric Chemistry (IGAC).

2015, 2017, 2018: Academy of Finland - panel B on atmospheric sciences

2010-…         International Commission on Atmospheric Chemistry and Global Pollution (iCACGP).

2010-2016:  Panel of the Mediterranean Integrated Studies at Regional and Local Scales (MISTRALS).

2012-2015 : INERIS - Commission scientifique Risques Chroniques.

2013-… :       Advisory board (BEIRAT) of the Leibniz Institute für Troposphärenforschung à Leipzig (TROPOS).

2012-2016   Panel of the interdisciplinary program PRIMEQUAL-PREDIT. (Programme de Recherche Interorganisme pour une Meilleure Qualité de l'Air à l'Echelle).

1999-2004 : Panel of the French Program on Atmospheric Chemistry (Programme National de Chimie Atmosphérique du CNRS - PNCA)

2003-2007:   Secretary of the Atmospheric and Ocean Division at the European Geosciences Union (EGU).

2002-2010:   Chair of the programme on Atmospheric Chemistry INTROP at the European Science Foundation.

1998-2002 : Vice coordinator of the "Heterogeneous Chemistry" subgroup of the project "Chemical Mechanism Development" (CMD) funded within EUREKA - EUROTRAC-2.

Editorial boards      

2015-…               Scientific Reports, published par Nature Journals.

2014-…               Environmental Science and Pollution Research.

2001-2008:        Atmospheric Chemistry and Physics (ACP), http://www.atmos-chem-phys.org

Guest Editor for a Special Issue of ChemPhysChem, Issue 18 (2010), for a Special Issue of Environmental Science and Technology (2011-2012) and for a Special Issue of Applied Catalysis B (2012).

Teaching activities

 

2017-…                In charge of a Teaching Unit within the master “Sciences de l'Océan, de l'Atmosphère et du Climat (SOAC)” of the University Claude Bernard - Lyon 1.

2013-2019:        Co-organizer of the series of "Sino-European School on Atmospheric Chemistry (SESAC 1 - 4)", held in Shanghai.

2004-2010 :       Teaching within the Master “Caractérisation et Gestion de l'Atmosphère” of the University Claude Bernard - Lyon 1.