En poursuivant votre navigation sur ce site, vous acceptez le dépôt de cookies dans votre navigateur. (En savoir plus)
Portail > Offres > Offre UMR7583-GENTUA-061 - (H/F) Chercheur - Propriétés optiques et hygroscopiques des poussières désertiques lors du vieillissement par les composés organiques volatils : étude experimentale

(M/F) -Researcher - Optical and hygroscopic properties of desert dusts during ageing by volatile organic compounds: experimental study

This offer is available in the following languages:
- Français-- Anglais

Date Limite Candidature : mardi 5 mars 2024

Assurez-vous que votre profil candidat soit correctement renseigné avant de postuler

Informations générales

Intitulé de l'offre : (M/F) -Researcher - Optical and hygroscopic properties of desert dusts during ageing by volatile organic compounds: experimental study (H/F)
Référence : UMR7583-GENTUA-061
Nombre de Postes : 1
Lieu de travail : CRETEIL
Date de publication : mardi 13 février 2024
Type de contrat : CDD Scientifique
Durée du contrat : 12 mois
Date d'embauche prévue : 1 avril 2024
Quotité de travail : Temps complet
Rémunération : 2,889.51 euros gross per month (approximately 2,359.79 euros net per month)
Niveau d'études souhaité : Niveau 8 - (Doctorat)
Expérience souhaitée : 1 à 4 années
Section(s) CN : Earth System: superficial envelopes

Missions

The CLImate relevant processing of Mineral Dust by volatile Organic compounds (CLIMDO) project funded by ANR has the ambitious goal of producing new knowledge of two important forcers in the global climate: primary mineral dust and secondary organic aerosols (SOA).
This research project will focus on the evolution of optical and hygroscopic properties of the dust/MGL system as a function of (photo)chemical aging. The CESAM instrumentation will provide the spectral optical properties of scattering and extinction (nephelometer, attenuated phase-shift spectrometers and two in situ White cells serving a high resolution UV-VIS and IR spectrometer) and particle humidity growth factor (HTDMA). It will be performed concurrently with the characterization of the chemical composition of the organic fraction of the VOC-processed dust aerosols by online and offline techniques, including an ACSM-ToF. Analysis of those data streams will be performed to link the changes in the optical and hygroscopic properties to processing of dust by organics and changes in the physio-chemical properties of the dust. The optical and hygroscopic properties derived for aged dust through its exposure to MGL will be formatted for implementation in the LMDz-INCA global climate model.
Depending on advancement, the observed evolution of the spectral optical properties of mineral dust due to aging will be modelled to derive advanced products such as the complex refractive index, the fundamental property relating the composition to the optical properties.

Activités

The successful candidate (M/W) will be leading the experiments on the CESAM simulation chamber. The role will involve:
• Design and carry out the simulation ageing experiments
• Prepare and operate the whole instrumental suite, with a special emphasis on optical instrumentation and HTDMA operation
• Perform the experimental data analysis and interpretation
• Perform optical calculations
• Present results at one international meeting
• Publish results on a high-impact peer-reviewed journals (one publication at least)

Compétences

Applicants (M/W) should hold a doctorate/PhD in either atmospheric physics or chemistry, or related field, with a strong experience in experimental work (aerosol, optics and/or spectroscopy).
Candidates are expected to demonstrate:
• Ability to drive and perform novel experimental work of international standing
• Working knowledge of optical codes (Mie theory, core-shell….)
• The ability to work collaboratively, yet independently, as part of a team
• Ability to interpret and combine experimental results from multiple and diverse instruments
• Strong computing skills, including the knowledge of at least one of the following high-level languages for analysis of large datasets: R, Python, Igor, IDL, Matlab….
• Good English language skills.

The successful candidate (M/W) for this position will be a contractual staff member of the Centre National de la Recherche Scientifique (CNRS), one of the world's leading research organisations for its excellent research and innovation results. The proposed initial 12-month contract may be renewed.

Contexte de travail

The Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA) is an international leading French institute in atmospheric chemistry and physics for climate, air pollution and human health.
Joint research unit of the CNRS, the University Paris-Est Créteil and University of Paris, the LISA is based in Créteil, in the outskirts of Paris, less than 30 minutes by public transport (metro and suburban train) from the Paris city centre.
The successful candidate (M/W) will beneficiate of the international working environment of MEREIA group at LISA (around 15 staff members, post-doc and graduate students of various nationalities), and will profit from an interdisciplinary, innovative and dynamic extensive training, in addition to personal development possibilities. The candidate (M/W) will also benefit from the training provided by the technical team of engineers in charge of the CESAM platform.

Informations complémentaires

Aerosols contribute the largest uncertainty to global radiative forcing budget estimates. This steams from our still poor knowledge of global aerosol distribution, properties and impacts as they age in the atmosphere. This is true in particular for natural aerosols, representing a severe limiting factor to assess the baseline state of climate, and to quantify and attribute total climate forcings, finally reducing our ability to predict evolutions over time and develop adaptation strategies for the future.
Aerosolized mineral dust from aeolian erosion of dry surfaces is a major natural component of the Earth's system, making up nearly half of annual particle emissions to the atmosphere, and a dominant to large fraction of the aerosol optical depth both in source and transport regions. Mineral dust influences global climate in multiple ways, including by interacting directly with radiation (scattering and absorption) and indirectly by serving as cloud condensation nuclei (CCN).
Additionally, mineral dust aerosols are able to uptake and heterogeneously react with atmospheric gases, notably volatile organic compounds (VOCs). The heterogeneous reactions do not only alter the direct and indirect effect of mineral dust on the Earth's radiative budget, but can also trigger novel oxidation pathways. As a consequence, mineral dust could play a significant but yet unquantified role in the formation secondary organic aerosol (SOA) in the atmosphere. SOA formed from the atmospheric oxidation products of VOCs and gas-particle transfer are relevant to a number of atmospheric processes, climate and human health. A number of models suggest that SOA account for 30%+ of ambient aerosols in certain regions, have large direct effects (up to -0.4 Wm-2) and could be responsible for 50%+ of the CCN in continental locations. However, the total climate impact of SOA remain unconstrained and difficult to understand, as we miss fundamental knowledge of the processes involved.
The combination of the complex reaction pathways and processing mechanisms inherent to the dust/organic system is hampering our understanding of the role of dust and SOA aerosols on global climate and atmospheric composition, and their role in modulating or amplifying the global and regional climate change, with consequences for life over this densely-populated area.
CLIMDO proposes the first laboratory/modelling comprehensive study on the heterogeneous interaction of mineral dust with one of the most common organic SOA precursors: methylglyoxal (MGL). MGL have anthropogenic and biogenic sources, but mostly result from the OH-oxidation of isoprene. They are ubiquitous in the atmosphere but particularly concentrated in densely populated areas such as the Euro-Mediterranean basin and sub-Saharan Africa, major source and transport areas of dust.
The CLIMDO working hypothesis is that MGL's ability to undergo oligomerization, hydration, and hemi-/acetal formation can drastically alter the physical (size, shape, viscosity) and chemical (hygroscopicity, oxidation state) properties of particles on which they adsorb. The adsorption of MGL and subsequent reactions will alter the interactions of mineral dust with radiation and water, and affect both the global/regional SOA budget and dust radiative effects.
The proposed research will be based on realistic ageing experiments of the interactions between dust and MGL on atmospheric time-scales. Experiments will be conducted in the CESAM multi-phase simulation chamber at LISA (www.cesam.cnrs.fr; Wang et al., 2011), a world-class facility equipped with a unique dust generator using natural soils, and reproducing the generation processes to achieve aerosolized dust with realistic mineralogy and size distribution (Di Biagio et al., 2014).
Simulation experiments will be conducted on the generated aerosol dust at concentrations ranging from background to storm conditions, and on different size classes using an Aerodynamic Aerosol Classifier (AAC). MGL will then be introduced at concentrations typical of anthropogenic areas to study the dust/organic combined systems at various relative humidity conditions, and with and without irradiation. Online measurements and offline sampling will be performed to characterize the physico-chemical, optical and hygroscopic properties of the particles. The acquired experimental data will be combined with numerical modelling to determine the essential optical properties of across the UV-Vis-IR spectrum.
References:
Di Biagio, C., Formenti P., Styler S. A., Pangui E., and Doussin, J.-F.: Laboratory chamber measurements of the longwave extinction spectra and complex refractive indices of African and Asian mineral dusts, Geophys. Res. Lett., 41, 6289–6297, https://doi.org/10.1002/2014GL060213, 2014
IPCC, Intergovernmental panel on climate change, fifth assessment report—the physical science basis, http://www.ipcc.ch, 2013.
IPCC, 2021: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2391 pp. doi:10.1017/9781009157896.
Wang, J., et al., Design of a new multi-phase experimental simulation chamber for atmospheric photosmog, aerosol and cloud chemistry research, Atmos. Meas. Tech., 4, 2465-2494, https://doi.org/10.5194/amt-4-2465-2011, 2011.
Missions
This research project will focus on the evolution of optical and hygroscopic properties of the dust/MGL system as a function of (photo)chemical aging. The CESAM instrumentation will provide the spectral optical properties of scattering and extinction (nephelometer, attenuated phase-shift spectrometers and two in situ White cells serving a high resolution UV-VIS and IR spectrometer) and particle humidity growth factor (HTDMA). It will be performed concurrently with the characterization of the chemical composition of the organic fraction of the VOC-processed dust aerosols by online and offline techniques, including an ACSM-ToF. Analysis of those data streams will be performed to link the changes in the optical and hygroscopic properties to processing of dust by organics and changes in the physio-chemical properties of the dust. The optical and hygroscopic properties derived for aged dust through its exposure to MGL will be formatted for implementation in the LMDz-INCA global climate model.
Depending on advancement, the observed evolution of the spectral optical properties of mineral dust due to aging will be modelled to derive advanced products such as the complex refractive index, the fundamental property relating the composition to the optical properties.