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www.atmos-chem-phys-discuss.net/13/2913/2013/ doi:10.5194/acpd-13-2913-2013 © Author(s) 2013. CC Attribution 3.0 License. This discussion paper is/has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer... more
www.atmos-chem-phys-discuss.net/13/2913/2013/ doi:10.5194/acpd-13-2913-2013 © Author(s) 2013. CC Attribution 3.0 License. This discussion paper is/has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP if available.
Développement d’un modèle de chimie multiphase couplé à un modèle de microphysique quasi-spectral: Application à un événement nuageux échantillonné au Puy de Dôme Soutenue publiquement le 8 décembre 2000, devant la commission d’examen
Submitted for the MAR14 Meeting of The American Physical Society Effects of Aqueous Solvation on the Photochemistry of Pyruvic Acid ALLISON REED-HARRIS, University of Colorado at Boulder, BARBARA ERVENS, Cooperative Institute for Research... more
Submitted for the MAR14 Meeting of The American Physical Society Effects of Aqueous Solvation on the Photochemistry of Pyruvic Acid ALLISON REED-HARRIS, University of Colorado at Boulder, BARBARA ERVENS, Cooperative Institute for Research in Environmental Sciences (CIRES) / National Oceanic & Atmospheric Administration (NOAA), RICHARD SHOEMAKER, REBECCA RAPF, JAY KROLL, ELIZABETH GRIFFITH, University of Colorado at Boulder, ANNE MONOD, Aix Marseille Universite, VERONICA VAIDA, University of Colorado at Boulder — The role of organic compounds in atmospheric chemistry leading to aerosol formation is under investigation due to the necessity to understand the effects of aerosols on global climate change. It has recently been shown that important pathways in formation of organic aerosols are in aqueous environments where high molecular weight products are formed and can potentially contribute to atmospheric aerosol mass. This presentation describes the photochemistry of pyruvic acid in a...
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The Aerosol, Radiation and Clouds in southern Africa (AEROCLO-sA) project investigates the role of aerosols on the regional climate of southern Africa. This is a unique environment where natural and anthropogenic aerosols and a... more
The Aerosol, Radiation and Clouds in southern Africa (AEROCLO-sA) project investigates the role of aerosols on the regional climate of southern Africa. This is a unique environment where natural and anthropogenic aerosols and a semipermanent and widespread stratocumulus (Sc) cloud deck are found. The project aims to understand the dynamical, chemical, and radiative processes involved in aerosol–cloud–radiation interactions over land and ocean and under various meteorological conditions. The AEROCLO-sA field campaign was conducted in August and September of 2017 over Namibia. An aircraft equipped with active and passive remote sensors and aerosol in situ probes performed a total of 30 research flight hours. In parallel, a ground-based mobile station with state-of-the-art in situ aerosol probes and remote sensing instrumentation was implemented over coastal Namibia, and complemented by ground-based and balloonborne observations of the dynamical, thermodynamical, and physical propertie...
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Aerosol and molecular processing in the atmosphere occurs in a complex and variable environment consisting of multiple phases and interfacial regions. To explore the effects of such conditions on the reactivity of chemical systems, we... more
Aerosol and molecular processing in the atmosphere occurs in a complex and variable environment consisting of multiple phases and interfacial regions. To explore the effects of such conditions on the reactivity of chemical systems, we employ an environmental simulation chamber to investigate the multiphase photolysis of pyruvic acid, which photoreacts in the troposphere in aqueous particles and in the gas phase. Upon irradiation of nebulized pyruvic acid, acetic acid and carbon dioxide are rapidly generated, which is consistent with previous literature on the bulk phase photolysis reactions. Additionally, we identify a new C6 product, zymonic acid, a species that has not previously been reported from pyruvic acid photolysis under any conditions. Its observation here, and corresponding spectroscopic signatures, indicates it could be formed by heterogeneous reactions at the droplet surface. Prior studies of the aqueous photolysis of pyruvic acid have shown that high-molecular-weight c...
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Organic compounds of both anthropogenic and natural origin are ubiquitous in the multiphasic atmospheric medium. Their transformation in the atmosphere affects air quality and the global climate. Modelling provides a useful tool to... more
Organic compounds of both anthropogenic and natural origin are ubiquitous in the multiphasic atmospheric medium. Their transformation in the atmosphere affects air quality and the global climate. Modelling provides a useful tool to investigate the chemistry of organic compounds in the tropospheric multiphase system. While several comprehensive explicit mechanisms exist in the gas phase, explicit mechanisms are much more limited in the aqueous phase.<br><br> Recently, new empirical methods have been developed to estimate HO<sup>•</sup> reaction rates in the aqueous phase: structure-activity relationships (SARs) provide global rate constants and branching ratios for HO<sup>•</sup> abstraction from and addition to atmospheric organic compounds. Based on these SARs, a new detailed aqueous-phase mechanism, named the cloud explicit physico-chemical scheme (CLEPS), to describe the oxidation of hydrosoluble organic compounds resulting from isoprene oxidat...
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... Design of an environmental chamber for the study of atmospheric chemistry : New developments in the analytical device. ... Une chambre de simulation atmosphérique a été conçue et réalisée au Laboratoire interuniversitaire des systèmes... more
... Design of an environmental chamber for the study of atmospheric chemistry : New developments in the analytical device. ... Une chambre de simulation atmosphérique a été conçue et réalisée au Laboratoire interuniversitaire des systèmes atmosphériques (Lisa), afin de mener à ...
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The photooxidation of methylhydroperoxide (MHP) and ethylhydroperoxide (EHP) was studied in the aqueous phase under simulated cloud droplet conditions. The kinetics and the reaction products of direct photolysis and OH-oxidation were... more
The photooxidation of methylhydroperoxide (MHP) and ethylhydroperoxide (EHP) was studied in the aqueous phase under simulated cloud droplet conditions. The kinetics and the reaction products of direct photolysis and OH-oxidation were studied for both compounds. The photolysis frequencies obtained were JMHP=4.5 (±1.0)×10−5s−1 and JEHP=3.8 (±1.0)×10−5s−1 for MHP and EHP respectively at 6°C. The rate constants of OH-oxidation of MHP at
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Research Interests: Chemistry, Ion Chromatography, Atmospheric sciences, Aerosol, Secondary Organic Aerosol Formation, and 13 moreTime of Flight, Atmospheric Pressure, Isoprene, Chemical Analysis, High Pressure Liquid Chromatography, High Resolution, Age effect, Water soluble polymers, Chemical Properties, Chemical Composition, Aqueous Extract, Mass Spectrometer, and Thermal desorption
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The inlet of a commercial atmospheric pressure chemical ionizationmass spectrometer (APCI/MS/MS) has been modified to transform it into an aerosol mass spectrometer, named TD-API-AMS. The new inlet consists in a charcoal denuder (to trap... more
The inlet of a commercial atmospheric pressure chemical ionizationmass spectrometer (APCI/MS/MS) has been modified to transform it into an aerosol mass spectrometer, named TD-API-AMS. The new inlet consists in a charcoal denuder (to trap gas phase VOCs and ...
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First- and higher-generation products from the oxidation of isoprene and methacrolein with OH radicals in the presence of NO<sub>x</sub> have been studied in a simulation chamber: (1) significant oxidation rates have been... more
First- and higher-generation products from the oxidation of isoprene and methacrolein with OH radicals in the presence of NO<sub>x</sub> have been studied in a simulation chamber: (1) significant oxidation rates have been maintained for up to 7 h allowing the study of highly oxidized products, (2) gas-phase products distribution and yields are provided, and show good agreement with previous studies. Secondary organic aerosol (SOA) formation resulting from these experiments has also been investigated. Among the general dispersion exhibited by SOA mass yields from previous studies, the mass yields obtained here were consistent with the lowest values found in the literature, and more specifically in agreement with studies carried out with natural light or artificial lamps with emission spectrum similar to the solar one. An effect of light source is hence proposed to explain, at least in part, the discrepancies observed between different studies in the literature for both is...
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Secondary organic aerosol (SOA) represents a substantial part of organic aerosol, which affects climate and human health. It is now accepted that one of the important pathways of SOA formation occurs via aqueous phase chemistry in the... more
Secondary organic aerosol (SOA) represents a substantial part of organic aerosol, which affects climate and human health. It is now accepted that one of the important pathways of SOA formation occurs via aqueous phase chemistry in the atmosphere. Recently, we have shown in a previous study (Renard et al., 2013) the mechanism of oligomerization of MVK (methyl vinyl ketone), and suggested that unsaturated water soluble organic compounds (UWSOC) might efficiently form SOA in wet aerosol particles, even for weakly soluble ones like MVK. The atmospheric relevance of these processes is explored by means of process model studies (in a companion paper). In the present study we investigate the aging of these aqueous phase MVK-oligomers (Part 1). <br><br> We compared aqueous phase composition and SOA composition after nebulization, mainly by means of UPLC-ESI-MS and AMS, respectively. Both instruments match and show similar trend of oligomer formation and aging. The SMPS analysis ...
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ABSTRACT Secondary Organic Aerosol (SOA) were generated from the ozonolysis of α-pinene in the CESAM simulation chamber. The formation and ageing of the SOA were studied by following their optical, hygroscopic and chemical properties. The... more
ABSTRACT Secondary Organic Aerosol (SOA) were generated from the ozonolysis of α-pinene in the CESAM simulation chamber. The formation and ageing of the SOA were studied by following their optical, hygroscopic and chemical properties. The optical properties investigated by determining the particle Complex Refractive Index (CRI). The hygroscopicity was quantified by measuring the effect of RH on particle size (Growth Factor, GF) and scattering coefficient (f(RH)). The oxygen to carbon (O : C) atomic ratio of the particle surface and bulk were used as a sensitive parameter to correlate the changes in hygroscopic and optical properties of the SOA composition in CESAM. The real CRI at 525 nm wavelength decreased from 1.43-1.60 (±0.02) to 1.32-1.38 (±0.02) during the SOA formation. The decrease in real CRI correlates with a decrease in the O : C ratio of SOA from 0.68 (±0.20) to 0.55 (±0.16). In contrast, the GF stayed roughly constant over the reaction time, with values of 1.02-1.07 (±0.02) at 90% (±4.2) RH. Simultaneous measurements of O : C ratio of the particle surface revealed that the SOA was not composed of a homogeneous mixture, but with less oxidised species at the surface which would limit the water adsorption onto particle. In addition, an apparent change of both mobility diameter and scattering coefficient with increasing RH from 0 to 30% was observed for SOA after 16 h reaction. We postulate that this change could be due to a change in the viscosity of the SOA from a predominantly glassy state to a predominantly liquid state.