Experimental and Modeling Studies of Secondary Organic Aerosol Formation and Some Applications to the Marine Boundary Layer

A series of controlled experiments were carried out in the Calspan Corporation\u27s 600 m3environmental chamber to study some secondary organic aerosol formation processes. Three precursor-ozone systems were studied: cyclopentene-ozone, cyclohexene-ozone, and α-pineneozone. Additionally, SO2 was added to the initial gas mixture in several instances and was likely present at trace levels in the ostensibly organic-only experiments. It was found that all three systems readily formed new submicron aerosols at very low reactant levels. The chemical composition of formed aerosols was consistent with some previous studies, but the yields of organic products were found to be lower in the Calspan experiments. A three-step procedure is proposed to explain the observed particle nucleation behavior: HO · production → H2SO4 formation → H2SO4-H2O (perhaps together with NH3) homogeneous nucleation. It is also proposed that some soluble organic products would partition into the newly formed H2SO4-H2O nuclei, enhance water condensation, and quickly grow these nuclei into a larger size range. While the observations in the two cycloolefin-ozone systems could be well explained by these proposed mechanisms, the exact nature of the nucleation process in the α-pinene-ozone system remains rather opaque and could be the result of nucleation involving certain organics. The results from three simple modeling studies further support these proposals. Their applicability to the marine boundary layer (MBL) is also discussed in some detail. Particularly, such a particle nucleation and growth process could play an important role in secondary aerosol formation and, quite likely, CCN formation as well in certain MBL regions

Tests of some reduction hypotheses made in photochemical mechanisms, Atmos

Abstraet--The purpose of this paper is to evaluate the errors induced by different hypotheses used to elaborate reduced kinetic mechanisms of tropospheric chemistry. To do that, a reference chemical kinetic scheme was developed: it includes a limited number of representative primary species (6 alkanes, 4 alkenes, 2 aromatics) for which up to date kinetic constants and mechanisms were used. This chemical scheme constitutes a reference against which the various reduction methods were tested. The tests were performed for three different scenarios characterised by various VOC/NO x ratios (5,10, 20). These scenarios are assumed to correspond to the chemical state of the atmosphere in urban areas and in rural situations. In a first step, the high NO x approximation (i.e. a chemical scheme without treatment of peroxy + HO = and peroxy + peroxy reactions) was tested. The results show that this scheme does not produce significant error on the simulated concentrations for NO concentrations above 2 ppb. In a second step, three successive reduction methods were applied to the reference mechanism: (1) use of the chemical operator concept to treat the organic peroxy chemistry, (2) loss of information on the organic peroxy class, (3) lumping of secondary organic species into surrogate species. The use of chemical operators provides a satisfactory representation of the organic peroxy chemistry for NO concentration down to 100 ppt. The scheme obtained after the loss of information on the organic peroxy class increases only slightly the error

Glycerin for New Biodiesel Formulation

Biofuels are an important way of progress for limiting greenhouse gas emissions, improving air quality and finding new energetic resources. For diesel engines, FAE (Fatty Acid Ester), coming from transesterification of vegetable oils, have shown their potentials as fuel substitutes. Nevertheless, this transesterification induces the production of glycerin (or glycerol) as fatal co-product. Finding an outlet to this glycerol is fundamental for the FAE network. In the same time, oxygenated compounds have been shown to have great potential for the reduction of diesel particulate emissions. Transforming glycerol into new oxygenated compounds, which could be formulated with diesel fuel, would be a very promising way. Different oxygenates derived from glycerol, such as acetals, ethers and carbonates, have been synthesized and evaluated as blending components for Diesel fuel. Our objective was to evaluate their potential, compared with RME (Rapseed Methyl Ester) blends in term of pollutant emissions with different new engine technologies and to select the most promising of them. GTBE (Glycerol Ter Butyl Ether) was the most interesting compound and it was formulated with biodiesel with the respect of the physicochemical criteria required by EN14214 standard. This new biofuel (92.5% RME + 7.5% GTBE + 1000 ppm pro cetane) was incorporated in diesel fuel (5% vol.) and compared with a mixture containing 5% RME. After various tests carried out on vehicle and engine, focusing on pollutant emissions and possible fouling problems, it is possible to conclude that this new biodiesel does not present any technical disadvantage. The decision to use this glycerol derivatives in diesel fuel formulation will thus be controlled by economical criteria

Reduction des emissions polluantes et du CO_2 : etat des connaissances, etat des recherches dans le monde

Available from INIST (FR), Document Supply Service, under shelf-number : RP 400 (2335) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEAgence de l'Environnement et de la Maitrise de l'Energie (ADEME), 92 - Vanves (France)FRFranc

A 3d Regional Scale Photochemical Air Quality Model. Application to a 3 Day Summertime Episode over Paris

International audienceThis paper presents AZUR, a 3D Eulerian photochemical air quality model for the simulation of air pollution in urban and semi-urban areas. The model tracks gas pollutant species emitted into the atmosphere by transportation and industrial sources, it computes the chemical reactions of these species under varying meteorological conditions (photolysis, pressure, temperature, humidity), their transport by wind and their turbulent diffusion as a function of air stability. It has a modular software structure which includes several components dedicated to specific processes :-MERCURE, a meso-scale meteorological model to compute the wind field, turbulent diffusion coefficients, and other meteorological parameters. It is a 3D regional scale model accounting for different ground types and urban densities. It includes a complete set of physical parameterizations in clear sky. -MIEL, an emission inventory model describing the pollutant fluxes from automotive transportation, domestic and industrial activities. This model includes a mobile source inventory based on road vehicle countings together with global information on transportation fluxes extracted from statistical population data. It uses specific emission factors representative of the vehicle fleet and real driving patterns. -MoCA a photochemical gas phase model describing the chemistry of ozone, NOx, and hydrocarbon compounds. This model, with 83 species and 191 reactions, is a reduced mechanism well adapted to various air quality conditions (ranging from urban to rural conditions). For interpretative reasons, the identity of primary hydrocarbons is preserved. -AIRQUAL, a 3D Eulerian model describing the transport by mean wind flux and air turbulent diffusion of species in the atmosphere, associated with a Gear type chemical equation solver. The model has been applied to a 3-day summertime episode over Paris area. Simulation results are compared to ground level concentration measurements performed by the local monitoring network (Airparif)

A 3d Regional Scale Photochemical Air Quality Model. Application to a 3 Day Summertime Episode over Paris Un modèle photochimique 3D de qualité de l'air à l'échelle régionale. Application à un épisode de 3 jours à Paris en été

This paper presents AZUR, a 3D Eulerian photochemical air quality model for the simulation of air pollution in urban and semi-urban areas. The model tracks gas pollutant species emitted into the atmosphere by transportation and industrial sources, it computes the chemical reactions of these species under varying meteorological conditions (photolysis, pressure, temperature, humidity), their transport by wind and their turbulent diffusion as a function of air stability. It has a modular software structure which includes several components dedicated to specific processes :-MERCURE, a meso-scale meteorological model to compute the wind field, turbulent diffusion coefficients, and other meteorological parameters. It is a 3D regional scale model accounting for different ground types and urban densities. It includes a complete set of physical parameterizations in clear sky. -MIEL, an emission inventory model describing the pollutant fluxes from automotive transportation, domestic and industrial activities. This model includes a mobile source inventory based on road vehicle countings together with global information on transportation fluxes extracted from statistical population data. It uses specific emission factors representative of the vehicle fleet and real driving patterns. -MoCA a photochemical gas phase model describing the chemistry of ozone, NOx, and hydrocarbon compounds. This model, with 83 species and 191 reactions, is a reduced mechanism well adapted to various air quality conditions (ranging from urban to rural conditions). For interpretative reasons, the identity of primary hydrocarbons is preserved. -AIRQUAL, a 3D Eulerian model describing the transport by mean wind flux and air turbulent diffusion of species in the atmosphere, associated with a Gear type chemical equation solver. The model has been applied to a 3-day summertime episode over Paris area. Simulation results are compared to ground level concentration measurements performed by the local monitoring network (Airparif). Cet article présente AZUR, un modèle photochimique eulérien 3D de qualité de l'air pour la simulation de la pollution de l'air dans les zones urbaines et semi-urbaines. Ce modèle suit les évolutions des espèces polluantes gazeuses émises dans l'atmosphère par les transports routiers et les sources industrielles, il prend en compte les réactions chimiques auxquelles sont soumises ces espèces pour des conditions météorologiques en évolution (photolyse, pression, température, humidité), leur transport par le vent et leur diffusion turbulente en fonction de la stabilité de l'air. Le logiciel a une structure modulaire avec plusieurs composants dédiés à des processus spécifiques : -MERCURE est un modèle météorologique à moyenne échelle pour déterminer les champs de vents, les coefficients de diffusion turbulente et d'autres paramètres météorologiques. C'est un modèle 3D à l'échelle régionale qui prend en compte les différentes configurations de sols et les zones de densité urbaine. Il comprend un système complet de paramètres physiques associés à des situations de ciel dégagé. -MIEL est un modèle d'inventaire d'émissions décrivant les flux de polluants provenant des transports automobiles et des activités domestiques ou industrielles. Ce modèle comprend un inventaire des sources mobiles basé sur des comptages de véhicules sur routes associés à des informations globales sur les flux de transports déduites de données statistiques sur la population. Il utilise des facteurs d'émission spécifiques correspondant aux flottes de véhicules et à des conditions de conduites réalistes. -MoCA est un modèle photochimique en phase gazeuse décrivant la chimie de l'ozone, des NOx, et des composés hydrocarbonés. Ce modèle, avec 83 espèces et 191 réactions, correspond à un mécanisme réduit bien adapté à des conditions variées de qualité de l'air (allant de conditions en sites urbains à celles en sites ruraux). Pour des raisons de commodité d'interprétation, l'identité des hydrocarbures primaires est conservée. -AIRQUAL est un modèle eulérien 3D décrivant les phénomènes de transport par les vents et la diffusion turbulente des espèces dans l'atmosphère, il est associé à un solveur d'équations chimiques du type Gear. Le modèle a été appliqué à un épisode estival de 3 jours au-dessus de la région parisienne. Les résultats de la simulation sont comparés aux mesures de concentrations opérées par le réseau local de surveillance (Airparif)

A 3d Regional Scale Photochemical Air Quality Model. Application to a 3 Day Summertime Episode over Paris

This paper presents AZUR, a 3D Eulerian photochemical air quality model for the simulation of air pollution in urban and semi-urban areas. The model tracks gas pollutant species emitted into the atmosphere by transportation and industrial sources, it computes the chemical reactions of these species under varying meteorological conditions (photolysis, pressure, temperature, humidity), their transport by wind and their turbulent diffusion as a function of air stability. It has a modular software structure which includes several components dedicated to specific processes :-MERCURE, a meso-scale meteorological model to compute the wind field, turbulent diffusion coefficients, and other meteorological parameters. It is a 3D regional scale model accounting for different ground types and urban densities. It includes a complete set of physical parameterizations in clear sky. -MIEL, an emission inventory model describing the pollutant fluxes from automotive transportation, domestic and industrial activities. This model includes a mobile source inventory based on road vehicle countings together with global information on transportation fluxes extracted from statistical population data. It uses specific emission factors representative of the vehicle fleet and real driving patterns. -MoCA a photochemical gas phase model describing the chemistry of ozone, NOx, and hydrocarbon compounds. This model, with 83 species and 191 reactions, is a reduced mechanism well adapted to various air quality conditions (ranging from urban to rural conditions). For interpretative reasons, the identity of primary hydrocarbons is preserved. -AIRQUAL, a 3D Eulerian model describing the transport by mean wind flux and air turbulent diffusion of species in the atmosphere, associated with a Gear type chemical equation solver. The model has been applied to a 3-day summertime episode over Paris area. Simulation results are compared to ground level concentration measurements performed by the local monitoring network (Airparif)