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Research Interests: Environmental Engineering, Chemistry, Atmospheric Chemistry, Chemical Kinetics, Atmospheric sciences, and 10 moreAqueous Two Phase System, Room Temperature, Structure activity Relationship, Aqueous Solution, Estimation Method, Organic Compound, Organic Acid, Atmospheric Environment, Rate Constant, and Robust estimator
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. The characterization of the molecular composition of organic carbon in both gaseous and aerosol is key to understand the processes involved in the formation and aging of secondary organic aerosol. Therefore a technique using active... more
. The characterization of the molecular composition of organic carbon in both gaseous and aerosol is key to understand the processes involved in the formation and aging of secondary organic aerosol. Therefore a technique using active sampling on cartridges and filters and derivatization followed by analysis using a Thermal Desorption-Gas Chromatography/mass spectrometer (TD-GC/MS) has been used to study the molecular composition of organic carbon in both gaseous and aerosol phases during an intensive field campaign which took place in Corsica during the summer 2013: the ChArMEx (Chemistry and Aerosol Mediterranean Experiment) SOP1b (Special Observation Period 1B) campaign. These measurements led to the identification of 51 oxygenated (carbonyl and or hydroxyl) compounds in the gaseous phase with concentrations comprised between 21 ng m−3 and 3900 ng m−3 and of 85 compounds in the particulate phase with concentrations comprised between 0.3 and 277 ng m−3. Comparisons of these measurements with collocated data using other techniques have been conducted showing fair agreement in general for most species except for glyoxal in the gas phase and malonic, tartaric, malic and succinic acids in the particle phase with disagreements that can reach up to a factor of 8 and 20 on average, respectively for the latter two acids. Comparison between the sum of all compounds identified by TD-GC/MS in particle phase with the total Organic Matter (OM) mass reveal that 18 % of the total OM mass can be explained by the compounds measured by TD-GC/MS for the whole campaign. This number increase to 24 % of the total Water Soluble OM (WSOM) measured by PILS-TOC if we consider only the sum of the soluble compounds measured by TD-GC/MS. This highlights the non-negligible fraction of the OM mass identified by these measurements but also the relative important fraction of OM mass remaining unidentified during the campaign and therefore the complexity of characterizing exhaustively the Organic Aerosol (OA) molecular chemical composition. The fraction of OM measured by TD-GC/MS is largely dominated by di-carboxylic acids which represents 49 % of the PM2.5 content detected and quantified by this technique. Other contributions to PM2.5 composition measured by TD-GC/MS are then represented by tri-carboxylic acids (15 %), alcohols (13 %), aldehydes (10 %), di-hydroxy-carboxylic acids (5 %), monocarboxylic acids and ketones (3 % each) and hydroxyl-carboxylic acids (2 %). These results highlight the importance of poly functionalized carboxylic acids for OM while the chemical processes responsible for their formation in both phases remain uncertain. While not measured by TD-GC/MS technique, HUmic-LIke Substances (HULIS) represent the most abundant identified species in the aerosol, contributing for 59 % of the total identified OM mass on average during the campaign. 14 compounds were detected and quantified in both phases allowing the calculation of experimental partitioning coefficient for these species. The comparison of these experimental partitioning coefficients with theoretical ones, estimated by three different models, reveals large discrepancies varying from 2 to 7 orders of magnitude. These results suggest that the supposed instantaneous equilibrium being established between gaseous and particulate phases assuming a homogeneous non-viscous particle phase is questionable.
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We present UNREAL project, funded by the french research agency. The main objectives of this project are: 1) To determine the mechanism behind vPM formation in the engine exhaust and if there is a link with fuel composition 2) To... more
We present UNREAL project, funded by the french research agency. The main objectives of this project are: 1) To determine the mechanism behind vPM formation in the engine exhaust and if there is a link with fuel composition 2) To establish a sampling protocol for vPM measurements that can be used in certification processes 3) To determine the impact of fuel chemical composition on the physico-chemical properties of vPM and nvPM
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A certified matrix reference material (CRM) for the measurement of benzene in ambient air has been developed at Laboratoire National de Métrologie et d'Essais. The production of these CRMs was conducted using a gravimetric method... more
A certified matrix reference material (CRM) for the measurement of benzene in ambient air has been developed at Laboratoire National de Métrologie et d'Essais. The production of these CRMs was conducted using a gravimetric method fully traceable to the International System of Units. The CRMs were prepared by sampling an accurate mass of a gaseous primary reference material of benzene, using a high-precision laminar flowmeter and a mass flow controller, with a PerkinElmer sampler filled with Carbopack™ X sorbent. The relative standard deviations obtained for the preparation of a batch of 20 tubes loaded with 500 ng of benzene were below 0.2%. Each CRM is considered independent from the others and with its own certified value and an expanded uncertainty estimated to be within 0.5%, lower than the uncertainties of benzene CRMs already available worldwide. The stability of these materials was also established up to 12 months. These CRMs were implemented during proficiency testing, to evaluate the analytical performances of seven French laboratories involved in benzene air monitoring.
Research Interests: Engineering, Chemistry, Environmental Monitoring, Medicine, Biological Sciences, and 13 moreUncertainty Estimation, Absorption, Gas Chromatography, Proficiency testing, CHEMICAL SCIENCES, Benzene, Analytical and Bioanalytical Chemistry, Certified Reference Material, Air Pollutants, Gravimetric Analysis, Certified Reference materials, Reference standards, and Relative Standard Deviation
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<p>The complex refractive index (CRI) is one of the key parameter driving aerosol spectral optical properties and direct radiative effects (DRE). Its value and spectral variation under different conditions, such as... more
<p>The complex refractive index (CRI) is one of the key parameter driving aerosol spectral optical properties and direct radiative effects (DRE). Its value and spectral variation under different conditions, such as anthropogenic− and biogenic−dominated environments and anthropogenic−biogenic mixing situations, remains not fully understood. As a consequence, oversimplified representations of aerosol optical properties are generally used in climate models. Therefore, measurements of aerosol CRI in different environments and their inclusion in models are needed. The field observations from the ACROSS campaign, performed in June-July 2022 in the Ile de France region, are used in this study to deepen the knowledge of aerosol optical properties, aiming to improve the aerosol representation in the CHIMERE model and provide the best constraint for DRE simulations. Measurements obtained both at the Paris city center and the Rambouilllet rural forest sites during ACROSS are considered, in order to explore the CRI variability from anthropogenic−dominated to biogenic−dominated environments, including anthropogenic−biogenic mixing situations. The CRI retrievals at seven different wavelengths, performed by combining the Mie theory with optical and size distribution measurements, are representative of different atmospheric conditions, aerosol loadings as well as type and chemical compositions. In fact, the June-July 2022 period was characterized by highly diversified weather conditions: 1) two strong heatwaves, promoting SOA build-up and favoring the export of the Paris pollution plume towards the forest site; 2) Saharan dust events transported from the upper atmosphere to the ground; 3) biomass burning episode; 4) periods with reduced anthropogenic influence. The CRI retrievals under these different conditions and their link to particulate chemical composition is investigated. Hence, the CRI dataset presented here constitutes a unique dataset from which models can benefit to validate and constrain simulations and DRE estimations, under both urban and biogenic emissions influence. These data, in conjunction with those from the aircraft observations during ACROSS, are used to initialize and perform sensitivity studies on the aerosol DRE, using the CHIMERE−WRF coupled model, the OPTSIM model for the aerosol optical properties and the Rapid Radiative Transfer Model for GCMs (RRTMG).</p> <p><strong>Keywords:</strong><strong> </strong>Complex refractive index, direct radiative effect, aerosol mixing, urban, forest</p>
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<p>The western coast of southern Africa off Namibia is characterized by a semi-permanent and widespread stratocumulus (Sc) cloud deck,... more
<p>The western coast of southern Africa off Namibia is characterized by a semi-permanent and widespread stratocumulus (Sc) cloud deck, very frequent coastal fog, and the oceanic northern Benguela upwelling system (nBUS). It is also the crossroad of large quantities of natural and anthropogenic aerosols of distant and local origins (biogenic, anthropogenic, biomass burning, sea salt and mineral dust) from continental and marine sources, with significant differences in terms of physico-chemical and optical properties, water affinity, scale and height of transport, which are not well represented in climate models.</p><p>In this presentation we will illustrate the results of the first extensive chemical and microphysical characterisation of aerosol particles in the area that has been conducted since 2016 at  the coastal Henties Bay experimental site (22°6’ S, 14°17’ E) in the framework of the AErosol, RadiatiOn and CLOuds in southern Africa (AEROCLO-sA) and the Atmospheric Research in the Southern Africa and Indian Ocean (ARSAIO) projects.</p><p>Synergetic filter sampling and online measurements provide examples of the numerous new particle formation in link with marine biogenic emissions and the apportionment of maritime sulfate aerosols, including their biogenic component.</p>
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Estimating agriculture’s contribution to air pollution and global warming is needed to understand and limit its impacts on the environment and climate. It is equally important to estimate the capacity of agricultural practices to mitigate... more
Estimating agriculture’s contribution to air pollution and global warming is needed to understand and limit its impacts on the environment and climate. It is equally important to estimate the capacity of agricultural practices to mitigate these emissions and to characterize atmospheric deposition and the impacts of air pollutants on agroecosystems. This chapter presents methods for measuring air pollutant concentrations, their fluxes at the soil-vegetation-atmosphere interface, and emissions from livestock facilities. Methods for measuring air concentrations are described with a focus on compounds emitted from or impacting agriculture (including forests): ammonia, nitrogen oxides, pesticides, volatile organic compounds including methane, abiotic and biotic particles, and ozone. The main methods for measuring emission and deposition fluxes of air pollutants between terrestrial surfaces, especially agroecosystems, and the atmosphere are described with a specific focus on the eddy covariance method as well as on emissions from livestock buildings. Then the general principles of source apportionment methods for estimating emissions spatial variability are presented. To address the questions on atmospheric chemistry, the methods used for measuring the reactivity of atmospheric compounds are presented. Finally, an insight is given on the developments of measurement methodologies to address new compounds and improve the sensors’ sensitivity and response time as well as provide estimates of spatial variability of concentrations and fluxes at larger scales.
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Trace gas measurements were performed during the LANDEX (the LANDes EXperiment) Episode 1 field campaign in the summer 2017, in one of the largest European maritime pine forests (> 95% Pinus pinaster) located in southwestern France.... more
Trace gas measurements were performed during the LANDEX (the LANDes EXperiment) Episode 1 field campaign in the summer 2017, in one of the largest European maritime pine forests (> 95% Pinus pinaster) located in southwestern France. Efforts have been focused on obtaining a good speciation of 20 major biogenic volatile organic compounds (BVOCs, including pinenes, carenes, terpinenes, linalool, camphene, etc.). This was made possible by the development of a new and specific chromatographic method. In order to assess the role of BVOCs in the local gas phase chemistry budget, their reactivity with the main atmospheric oxidants (hydroxyl radicals (OH), ozone (O3) and nitrate radicals (NO3)) and the corresponding consumption rates were determined. When considering the OH reactivity with BVOCs, isoprene and linalool accounted for 10-47% of the OH depletion during daytime, and monoterpenes for 50-65%, whereas monoterpenes were the main contributors during the night (70-85%). Sesquiterpenes and monoterpenes were the main contributors to the ozone reactivity, especially β-caryophyllene (30-70%), with a maximum contribution during nighttime. Nighttime nitrate reactivity was predominantly due to monoterpenes (i.e. 90-95%). Five specific groups have been proposed to classify the 19 BVOCs measured in the forest, according to their reactivity with atmospheric oxidants and their concentrations. The total amount of BVOCs consumed under and above the forest canopy was evaluated for 7 BVOCs (i.e. isoprene, α-pinene, β-pinene, myrcene, limonene + cis-ocimene and Δ3-carene). The reactivity of atmospheric oxidants and BVOCs at a local level are discussed in order to highlight the compounds (BVOCs, other VOCs), the atmospheric oxidants and the main associated reactive processes observed under the canopy of a maritime pine forest.