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Christian George

Chercheur

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

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).

 

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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

Atmospheric photosensitization: a new pathway for sulfate formation

Northern China is regularly subjected to intense wintertime “haze events”, with high levels of fine particles that threaten millions of inhabitants. While sulfate is a known major component of these fine haze particles, its formation remains unclear especially under highly polluted conditions, with state-of-the-art air quality models unable to reproduce or predict field observations. These haze conditions are generally characterized by simultaneous high emissions of SO2 and photosensitizing materials. We found that the excited triplet states of photosensitizers could induce a direct photosensitized oxidation of hydrated SO2 and bisulfite into sulfate S(+VI) through energy transfer or electron transfer. This photosensitized pathway appears to be a new and ubiquitous chemical route for atmospheric sulfate production. Comparing to other aqueous-phase sulfate formation pathways with ozone, hydrogen peroxide, nitrogen dioxide, or transition metal ions, the results also show that this photosensitized oxidation of S(IV) could make an important contribution to aerosol sulfate formation in Asian countries, particularly in China.

Associated publication

Wang X, R. Gemayel, N.Hayeck†, S. Perrier, N. Charbonnel†, C. X‡, H. Chen, C. Zhu, Liwu Zhang, Lin Wang, Sergey A. Nizkorodov, X. Wang, Z Wang, T. Wang, A. Mellouki, M. Riva, J. Chen, C. George, Atmospheric photosensitization: a new pathway for sulfate formation, Environ Sci Technol. 2020 Mar 17;54(6):3114-3120.  doi: 10.1021/acs.est.9b06347.

 

 

 

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

The sea-surface microlayer (SML), defined as the uppermost tens to hundreds of μm of the surface of the ocean, covers more than 70% of the Earth’s surface. The SML is known to concentrate organic matter i.e., dissolved organic matter including UV absorbing humic substances, amino acids, proteins, lipids, phenolic compounds, as well as surfactants i.e., fatty acids. This interface, having different chemical, physical and biological properties compared to subsurface waters, plays a significant role in biogeochemical processes on a global scale i.e., air-sea gas exchange, trace gas deposition to the ocean and secondary organic aerosol formation. Now, our group provided evidences that a rich photochemistry is taking place in the SML which drives the emission of a large range of functionalized volatile compounds (acting as aerosol precursors, such as isoprene), which were through to be solely emitted by biological activities. Our studies suggest that, in fact, surface chemistry may also play a significant role, leading to a significant abiotic production of VOCs.

Associated publications

R. Ciuraru, L. Fine, M. van Pinxteren, B. D’Anna, H. Herrmann, C. George, Photosensitized production of functionalized and unsaturated organic compounds at the air-sea interface, Scientific Reports (A Nature Journal), 5, Article number: 12741, doi:10.1038/srep12741, 2015, http://www.nature.com/articles/srep12741

Bruggemann, M., N. Hayeck, C. Bonnineau, S. Pesce, P. A. Alpert, S. Perrier, C. Zuth, T. Hoffmann, J. Chen, and C. George (2017), Interfacial photochemistry of biogenic surfactants: a major source of abiotic volatile organic compounds, Faraday Discussions, doi:10.1039/C7FD00022G.

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.

 

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.

 

 

Photocatalytical nature of atmospheric mineral dust – introducing a new renoxification process of the troposphere and nucleation events in the troposphere.

Mineral dust represents a major fraction of atmospheric aerosols, with a composition related to the crustal elements from which they originate. As a consequence, they do carry titanium and iron oxides, which are semiconductors, having the potential to give to atmospheric dust photocatalytic properties, entirely changing day time chemistry of dust. The George group has suggested such properties and studied them by means of laboratory based experiments. They also suggested that hydroxyl radicals, produced by the photocatalytic activities of dust, could desorb and interact with sulphur dioxide, producing sulfuric acid and atmospheric nucleation events. A recent study published in 2014 (in a Nature journal) has now provided direct field evidences for such processes.

Associated publication

Y. Dupart, S.M. King, B. Nekat, A. Nowak, A. Wiedensohler, H. Herrmann, G. David, B. Thomas, A. Miffre, P. Rairoux, B. D’Anna, C. George, Mineral dust photochemistry induces nucleation events in the presence of SOProceedings of the National Academy of Sciences of the United States of America, 109(51), 20842-20847, 2012

 

 

Photosensitization: a new pathway for secondary organic aerosol growth in the troposphere.

Atmospheric aerosols affect precipitation and climate, and they are also associated with adverse health effects. While primary aerosols are emitted directly into the air, secondary aerosols form in the atmosphere. Traditionally, scientists believed that secondary organic aerosols grew through a mechanism in which volatile organic compounds reacted with atmospheric oxidants, making the compounds less volatile and able to condense onto particles. Now, the George group provided evidences for aerosol growth through heterogeneous photosensitized reactions at rates comparable to those observed in the field.

Associated publication

M.E. Monge, T. Rosenørn, O. Favez, M. Müller, G. Adler, A. Abo Riziq, Y. Rudich, C. George, B. D’Anna, Alternative pathway for atmospheric particles growth, Proceedings of the National Academy of Sciences of the United States of America, 2012, 109, 6840-6844, 2012.

 

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”)
                     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.

2013-2021:  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
                    European Geosciences Union (EGU).

2002-2010:  Chair of the programme on Atmospheric Chemistry INTROP
                     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      

2019-               Journal of Geophysical Research –Atmosphere

2015-2021      Scientific Reports, published par Nature Journals.

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).

2017-…           In charge of a Teaching Unit on atmospheric chemistry
                        Master “Sciences de l'Océan, de l'Atmosphère et du Climat SOAC)”
                        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.