Postdoc - Contribution of traffic to the formation of organic aerosols in urban areas

Présentation

Durée : 2 years

Context:
Transport pollution is a major societal and regulatory issue. Particulate transport emissions and
secondary aerosols produced after emissions have considerable consequences on climate (IPCC,
2011), building, agriculture, visibility, and especially public health.
In France, particulate pollution levels have not decreased significantly since 2007 despite various
source reduction measures (Ministry 2013), the dominant fraction being composed of secondary
aerosols, formed through various atmospheric processes (Tsigaridis et al, 2014). Road transport
contributes to secondary organic aerosols through oxidation processes of volatile organic
compounds (VOCs) and semi-volatiles (SVOCs) into less volatile species that condense on
pre-existing particles.
The contribution of road transport to atmospheric aerosols is clearly poorly quantified, due to
metrological and methodological difficulties in characterizing emissions (Kim et al., 2016), and
difficulties in estimating secondary organic aerosol formation (AOS).
These uncertainties affect air quality models, which systematically underestimate the fraction of
secondary organic aerosol, especially in urban areas (Tisgaridis et al., 2014, Bergström et al., 2012,
Hallquist 2009). This underestimation can be linked on the one hand to the lack of knowledge of the
emissions of gaseous precursors, volatile organic compounds (VOCs) and semi-volatiles (SVOC)
(Sartelet et al., 2018, Couvidat et al., 2012), and of on the other hand, to a limited or incomplete
representation of the mechanisms of aerosol formation and aging in the atmosphere in the models
(Tsigaridis et al, 2014).
In order to reduce the uncertainties on particle concentrations related to road traffic, experiments are
carried out on a 2-axle roller bank (measurement of emissions) and coupled to a simulation
chamber of atmospheric evolution of pollutants under controlled conditions.
Innovative complementary gas and particle phase AOS formation measurements have also been
conducted in an aerosol flow tube reactor (AFT) to understand oxidation and atmospheric aging of a
pure compound.
Objectives:
Using the observations of the experiments mentioned above, the work will concern the
improvement of the modeling of the fate of regulated and unregulated pollutants emitted by recent
vehicles (nomes Euro 5 and Euro 6). Based on the measured emissions of the various SOA
precursors, the parameterizations used for the aging of the different compounds (Majdi et al., 2019,
Chrit et al., 2017 and Couvidat et al., 2012) will be reviewed to represent the measurements in the
chamber. Wall effects will be taken into account for the different compounds.
In a second step, the urban air quality model will be modified to include the emissions and
parameterizations of the aging of SOA precursors of recent vehicles.
Collaboration:
Collaborations with IFTSTTAR and “Laboratoire Chimie Environment” experimenters are to be
expected for model comparisons to chamber measurements. Collaborations with INERIS are to be
expected in the framework of joint development of a 0D model of aerosols (ssh-aerosol).
Profile:
The candidate must have a thesis in air quality modeling and / or aerosols, and have demonstrated
abilities to publish first author in scientific journals of rank A. Strong skills in thermodynamics and
chemistry are desirable. Good knowledge and programming experience in C ++, Python and Fortran
are also essential.
Duration:2 years from the autumn of 2019. The post-doc will be based on the CEREA site at
Ecole des Ponts (Champs sur Marne).
How to apply:Please send a cv and motivation letter to karine.sartelet@enpc.fr

Bergström, R., Denier van der Gon, H. A. C., Prévôt, A. S. H., Yttri, K. E., and Simpson, D., 2012.
Modelling of organic aerosols over Europe (2002–2007) using a volatility basis set (VBS) framework:
application of different assumptions regarding the formation of secondary organic aerosol, Atmos. Chem.
Phys., 12, 8499-8527, doi:10.5194/acp-12-8499-2012
Chrit M., Sartelet K., Sciare J., Pey J., Marchand N., Couvidat F., Sellegri K. and Beekmann M. (2017),
Modelling organic aerosol concentrations and properties during ChArMEx summer campaigns of 2012
and 2013 in the western Mediterranean region Atmos. Chem. Phys., 17, 12509-12531,
doi:10.5194/acp-17-12509-2017.
Couvidat F., Debry E., Sartelet K.N., Seigneur C., 2012. A hydrophilic/hydrophobic organic (H2O) aerosol
model: Development, evaluation and sensitivity analysis. J. Geophys. Res., 117, D10304,
doi:10.1029/2011JD017214.
Kim Y., Sartelet K., Seigneur C., Charron A., Besombes J.-L., Jaffrezo J.-L., Marchand N., Polo L., 2016.
Effect of measurement protocol on organic aerosol measurements of exhaust emissions from gasoline and
diesel vehicles Atmos. Env.,140, 176-187.
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Jansen E., Kirtman B., Knutti R., Kanikicharla K.K., Lemke P., Marotzke J., Masson-Delmotte V., Meehl
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particulate matter in the Euro-Mediterranean in 2007: sensitivity to some parameterizations of emissions
in air quality models. Atmos. Chem. Phys., 19,785-812,doi:10.5194/acp-19-785-2019.
Ministère de l'écologie, du développement durable et de l'énergie. Bilan de la qualité de l’air en France en
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Sartelet K., Zhu S., Moukhtar S., André M., André J.M., Gros V., Favez O., Brasseur A., Redaelli M. (2018),
Emission of intermediate, semi and low volatile organic compounds from traffic and their impact on
secondary organic aerosol concentrations over Greater Paris. Atmos. Env., 180, 126-137,
doi:10.1016/j.atmosenv.2018.02.031.
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M., Curci, G., Diehl, T., Easter, R.C., Ghan, S.J., Gong, S.L., Hodzic, A., Hoyle, C.R., Iversen, T., Jathar,
S., Jimenez, J.L., Kaiser, J.W., Kirkevåg, A., Koch, D., Kokkola, H., Lee, Y.H., Lin, G., Liu, X., Luo, G.,
Ma, X., Mann, G.W., Mihalopoulos, N., Morcrette, J.-J., Müller, J.-F., Myhre, G., Myriokefalitakis, S.,
Ng, N.L., O’Donnell, D., Penner, J.E., Pozzoli, L., Pringle, K.J., Russell, L.M., Schulz, M., Sciare, J.,
Seland, Ø., Shindell, D.T., Sillman, S., Skeie, R.B., Spracklen, D., Stavrakou, T., Steenrod, S.D.,
Takemura, T., Tiitta, P., Tilmes, S., Tost, H., van Noije, T., van Zyl, P.G., von Salzen, K., Yu, F., Wang, Z.,
Wang, Z., Zaveri, R.A., Zhang, H., Zhang, K., Zhang, Q., Zhang, X., 2014. The AeroCom evaluation and
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doi:10.5194/acp-14-10845-2014