Validation of an experimental setup to study atmospheric heterogeneous ozonolysis of semi-volatile organic compounds

International audienceThere is currently a need for reliable experimental procedures to follow the heterogeneous processing simulating the atmospheric conditions. This work offers an alternative experimental device to study the behaviour of semi-volatile organic compounds (SVOC) that presumably exhibit extremely slow reactivity (e.g. pesticides) towards the atmospheric oxidants such as ozone and OH. Naphthalene was chosen as a test compound since it was widely studied in the past and hence represents a good reference. Prior to ozone exposure, the gaseous naphthalene was adsorbed via gas-solid equilibrium on silica and XAD-4 particles. Then, the heterogeneous reaction of ozone with adsorbed naphthalene was investigated in specially designed flow tube reactors. After the reaction, the remaining naphthalene (adsorbed on particles surface) was extracted, filtered and analyzed by Gas Chromatography-Flame Ionization Detector (GC-FID). Thus, the kinetics results were obtained following the consumption of naphthalene. Using this procedure, the rate constants of heterogeneous ozonolysis of naphthalene (kO3 silica=2.26 (±0.09)×10−17 cm3 molec−1 s−1 and kO3 XAD-4=4.29 (±1.06)×10−19 cm3 molec−1 s−1) were determined for silica and XAD-4 particles, at 25°C and relative humidity <0.7%. The results show that the nature of the particles significantly affects the kinetics and that heterogeneous ozonolysis of naphthalene is faster than its homogeneous ozonolysis in the gas phase

Development of an analytical methodology for obtaining quantitative mass concentrations from LAAP-ToF-MS measurements

Laser ablation aerosol particle-time of flight mass spectrometer (LAAP-ToF-MS) measures the size number of particles, and chemical composition of individual particles in real-time. LAAP-ToF-MS measurements of chemical composition are difficult to quantify, mostly because the instrument sensitivities to various chemical species in the multicomponent atmospheric aerosol particles are unknown. In this study, we investigate a field-based approach for quantitative measurements of ammonium, nitrate, sulfate, OC, and EC, in size-segregated atmospheric aerosols, by LAAP-ToF-MS using concurrent measurements from high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), and multi-angle absorption photometer (MAAP). An optical particle counter (OPC) and a high-resolution nanoparticle sizer (scanning mobility particle sizer, or SMPS), were used to measure the particle size distributions of the particles in order to correct the number concentrations. The intercomparison reveals that the degree of agreement of the mass concentrations of each compound measured with LAAP-ToF-MS and HR-ToF-AMS/MAAP increases in the following order NH4+ <SO42- <NO3- <EC <OC <Cl- with r2 values in the range of 0.4–0.95 and linear regression slopes ranging between 0.62 and 1.2. The factors that affect the mass concentrations measured by LAAP-ToF-MS are also discussed in details. Yet, the matrix effect remains one of the strongest limiting factor to achieve an absolute quantification of the aerosol chemical composition. In the future we suggest the development of a methodology based on the calculation of the response factors generated by different types of particles, which could possibly resolve certain difficulties associated with the matrix effect

Corrigendum to “Seasonal variations of Quercus pubescens isoprene emissions from an in natura forest under drought stress and sensitivity to futureclimate change in the Mediterranean area”

International audienc

Secondary organic aerosol formation from gasoline vehicle emissions in a new mobile environmental reaction chamber

We present a new mobile environmental reaction chamber for the simulation of the atmospheric aging of different emissions sources without limitation from the instruments or facilities available at any single site. Photochemistry is simulated using a set of 40 UV lights (total power 4 KW). Characterisation of the emission spectrum of these lights shows that atmospheric aging of emissions may be simulated over a range of temperatures (-7 to 25°C). A photolysis rate of NO2, JNO2, of (8.0±0.7)×10-3 s-1 was determined at 25°C. We demonstrate the utility of this new system by presenting results on the aging (OH=12×106 cm-3h) of emissions from a modern (Euro 5) gasoline car operated during a driving cycle (New European Driving Cycle, NEDC) on a chassis dynamometer in a vehicle test cell. Emissions from the entire NEDC were sampled and aged in the chamber. A thorough investigation of the composition of the gas phase emissions suggests that the observed SOA is from previously unconsidered precursors and processes. This large enhancement in PM mass from gasoline vehicle aerosol emissions due to SOA formation, if it occurs across a wider range of gasoline vehicles, would have significant implications for our understanding of the contribution of on-road gasoline vehicles to ambient aerosols.JRC.F.8-Sustainable Transpor

Characterization of Gas-Phase Organics Using Proton Transfer Reaction Time-of-Flight Mass Spectrometry : Cooking Emissions

Cooking processes produce gaseous and particle emissions that are potentially deleterious to human health. Using a highly controlled experimental setup involving a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS), we investigate the emission factors and the detailed chemical composition of gas phase emissions from a broad variety of cooking styles and techniques. A total of 95 experiments were conducted to characterize nonmethane organic gas (NMOG) emissions from boiling, charbroiling, shallow frying, and deep frying of various vegetables and meats, as well as emissions from vegetable oils heated to different temperatures. Emissions from boiling vegetables are dominated by methanol. Significant amounts of dimethyl sulfide are emitted from cruciferous vegetables. Emissions from shallow frying, deep frying and charbroiling are dominated by aldehydes of differing relative composition depending on the oil used. We show that the emission factors of some aldehydes are particularly large which may result in considerable negative impacts on human health in indoor environments. The suitability of some of the aldehydes as tracers for the identification of cooking emissions in ambient air is discussed

Contribution à l'étude de la partition des HAP entre les phases gazeuse et particulaire (validation de la technique de prélèvement par tube denuder annulaire)

En raison de leur toxicité, les Hydrocarbures Aromatiques Polycycliques (HAP) font partie des polluants atmosphériques devant faire l'objet d'une surveillance (directive cadre européenne 96/62/CE du 27 septembre 1996). De par leurs propriétés physico-chimiques, certains de ces composés sont présents dans l'atmosphère simultanément en phases gazeuse et particulaire. Leur impact sanitaire et environnemental, différent selon la phase considérée, impose le prélèvement et l'analyse séparée des deux phases. Actuellement, la méthode la plus couramment utilisée pour l'échantillonnage simultané et séparé des phases gazeuse et particulaire est les préleveur à haut-débit. Mais de nombreux auteurs ont montré que cette méthode engendrait des artefacts de prélèvement qui induisaient des erreurs dans l'estimation des concentrations. Ce travail de thèse répond à la nécessité de disposer d'un outil de prélèvement HAP dépourvu d'artefact de prélèvement. Dans ce contexte, nos recherches ont porté sur la validation de la méthode de prélèvement par tube denuder multi-annulaire. Cette validation s'est articulée autour de tests en conditions contrôlées (banc à perméation, banc à rouleaux) afin d'évaluer l'impact des principaux paramètres susceptibles d'influer sur les performances du tube (température, humidité, concentration en HAP, taille des particules, conditions de prélèvement), et de prélèvements d'échantillons réels (atmosphériques) pour évaluer l'effet de la matrice environnementale. Elle a été complétée par une comparaison avec le préleveur conventionnel, à partir de prélèvements à l'émission d'un véhicule diesel (banc à rouleaux). Il ressort de l'ensemble de ces tests que le tube denuder multi-annulaire est une méthode adaptée au prélèvement simultané des HAP en phases gazeuse et particulaire, dans une gamme de conditions expérimentales couvrant largement le domaine de conditions généralement rencontrées dans l'environnement. Pour un étude plus précise du phénomène de distribution gaz-particule des HAP, le remplacement des préleveurs conventionnels par des systèmes "tube denuder" est ainsi fortement souhaitable.AIX-MARSEILLE1-BU Sci.St Charles (130552104) / SudocSudocFranceF

Evaluation of an annular denuder tubes for atmospheric PAH partitioning studies—1: evaluation of the trapping efficiency of gaseous PAHS

International audienc

Evaluation of an annular denuder for atmospheric PAH partitioning studies—2: evaluation of mass and number particle losses

International audienc

Evaluating on-line solid-phase extraction coupled to liquid chromatography–ion trap mass spectrometry for reliable quantification and confirmation of several classes of antibiotics in urban wastewaters

International audienc