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A lot of applications of carbon nanostructures (CNS) have been developed for the last fifteen years. Besides some particular electronic properties, such structures possess considerable adsorption capacities and so could be proposed both for gas treatment and for gas sampling and analysis. In this work, nanostructured carbon based composite samples were elaborated by the Catalytic Pyrolysis Method over the catalyst beds containing different transition metals supported by activated alumina (γ-Al2O3). Their efficiencies for volatile organic compounds (VOC) trapping, compared with the ones of Tenax-TA as the reference material, were evaluated in dynamic conditions. The obtained results show a real interest for new active material application for VOC adsorption procedures.

To quantify the vertical diffusive mass transfer of trichloroethylene (TCE) in a low water-saturated porous medium, diffusion experiments were conducted in soil columns using a medium-size quartz sand at two different water saturations; namely, completely dry and at irreducible water saturation. Advective transport of TCE vapors was mainly generated by density gradients in the soil gas during diffusion of TCE vapors in the vertical direction. The maximum stationary TCE vapor concentrations measured at the column outlet attained only 70 to 75% of the prescribed inlet vapor concentration, indicating a strong influence of density-driven advective mass transport on vertical diffusion of TCE. Without taking into account the density of the vapors, the measured apparent TCE diffusion coefficient was about seven and five times smaller than the coefficients predicted by the model for dry sand and sand at irreducible water saturation, respectively. A numerical transport model was used to interpret the experimental results. The numerical results fit the experimentally measured TCE breakthrough curves well. A sensitivity study demonstrated that the simulated vapor breakthrough curves were not very sensitive to variations in the dimensionless Henry9s constant, the gas–solid or water–solid phase partitioning coefficients but were sensitive to modification of the intrinsic permeability and the gas tortuosity–connectivity parameter. Two series of numerical simulations were also conducted to analyze the steady-state conditions of vertical vapor transport. The results highlighted how both the relative density of TCE vapors and the height of the soil column, expressed as a dimensionless Rayleigh number, might reduce the vertical diffusive mass flux.

International audience; Measurements of volatile organic compounds (VOCs) and in particular biogenic VOCs were taken near Chamonix, in the alpine valleys within the framework of the POVA program (Alpine Valley Pollution). The general topics of the program were the comparative studies of air quality in the Chamonix and Maurienne valleys (France) and the modelling of atmospheric chemistry. The main objective is to characterize the pollution sources and study the relationship between atmospheric dynamics and pollution events. To do this, it was necessary to take into account all quantifiable and localizable sources. Measurements of VOCs showed an abnormally high quantity of monoterpene concentrations (around 10% in mass of the total VOC concentrations). Isoprene and monoterpenes produced mainly by vegetation are among the most abundant natural VOCs, but these measurements were carried out in winter and during this season biogenic emissions are weak. The aim of this present work is to determine and understand this phenomenon. Domestic heating, generally not taken into account in studies of outdoor air, had a considerable impact on terpene concentrations in the valley.

International audience; An international campaign involving six teams was organized in Ny-Ålesund, Svalbard, in order to understand better the origin of atmospheric mercury depletion events (AMDEs). Special emphasis was given to determining the source region of the observed events and the physical and chemical processes leading to AMDEs. Five AMDEs were recorded during a one-month field experiment (10 April-10 May, 2003). The different events presented various characteristics, especially in terms of mercury species formation, atmospheric particle variations and meteorological conditions. After careful examination of each event, we postulate that two were probably due to advection of already depleted air masses and three were a product of local or regional chemistry. The roles of different surfaces (frost flowers, snow, ice aerosol in clouds) involved in heterogeneous reactions leading to AMDEs are also discussed. We speculate that ice clouds may explain the particle variations observed during the three more local events.

The use of renewable energy sources is becoming increasingly necessary to diminish the greenhouse effect gases production. Biomass is the most common form of renewable energy, widely used in the third world. Pyrolysis, which corresponds to the thermal decomposition of biomass under the action of heat and without any oxidant, is particularly well-adapted to the valorisation of lignocellulosic products such as wood or straw. The BIOCARB programme of the Commissariat a l'Energie Atomique (CEA), to which the Groupe de Recherche sur l'Environnement et la Chimie Atmospherique (GRECA) contributes, aims to produce carburant from the gasification of biomass. This fuel can be either pure hydrogen, or gasoil produced by the Fischer–Tropsch process after the pyrolysis and syngas production. It is absolutely necessary to control the different parameters of the pyrolysis (gas composition, formation of tars) to maximise the production of hydrogen or syngas. The new coefficient of pyrolytic valorisation presented here helps to meet this requirement. This work presents also experiments on the pyrolysis of straw and fescue in a 550–650 °C temperature range with different residence times, on which was based our investigation.

We have carried out relative rate experiments (T = 294 ± 2 K, atmospheric pressure) to investigate the OH-oxidation of o-, m-, and p-ethyltoluene and n-nonane (k1, k2, k3, and k4 respectively). The experiments were performed in a 2-m3 smog chamber with Teflon coated walls. The rate constants obtained are (in cm3 molecule−1 s−1 with two sigma uncertainties): k1 = (1.36 ± 0.07) × 10−11; k2 = (2.12 ± 0.26) × 10−11; k3 = (1.47 ± 0.04) × 10−11, and k4 = (0.95 ± 0.02) × 10−11. The measured rate constants are in accordance with previously published data, so that a coherent group of values for the compounds studied can be established. Atmospheric implications, ozone, and particle production are discussed. In addition, we have determined the amount of o-, m-, and p-ethyltoluenes in different types of gasoline. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 367–378 2004

A study was done in order to determine how the sampling conditions can influence the quantitative measure of PAHs in air, done with a solid-phase microextraction device. The PAHs studied were naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, fluoranthene, pyrene. A comparison between static and dynamic samplings and a plan of experiments were done to study the influence of the gaseous flow, the exposure time, and the number of PAHs in sample, on the mass trapped on the fiber. Then, the performances of PDMS 100 w m and 7 w m fibers for the extraction of PAHs in air were compared. The mass trapped by the fiber, the equilibrium time, the reproducibility, and the performances of the fiber in a dynamic sampling were also tested and compared.

Dioxins are among aromatic compounds that at present arouse the most part of discussions as environment pollutants. In the present works from the French norm AFNOR, there is no simple way of sampling and analysis for gas emissions. Solid-phase microextraction (SPME) proves to be an adapted technology for dioxin sampling in gaseous phase due to its rapidity, reliability, and simplicity of material. In this study, a sample preparation method with a 100 w m polydimethylsiloxane fiber interfaced with a gas chromatography has been optimized for a monochlorinated dibenzo- p -dioxin: exposure of the fiber into the gaseous sample during 1 hr at 125°C. The partition coefficient fiber/matrix of the 1-monochlorinated dibenzo- p -dioxin has also been calculated versus temperature (K = 5.85 at 125°C).

This paper presents an innovative smart sensor used for water quality monitoring. This smart sensing system utilizes spectroscopic techniques combined with the measurement of physico-chemical variables, to estimate global pollution parameters in water samples, particularly the Chemical Oxygen Demand (COD). This estimation is computed using a multisensor fusion approach, by means of an artificial neural network algorithm. The smart sensor has been tested successfully over a set of 71 wastewater samples of the city Pierre Benite (France) and it was shown that the estimated values of COD were in good agreement with the observed COD values, which were measured with a conventional method.

A diffusive sampler with a 2,4-dinitrophenylhydrazine (2,4-DNPH)-impregnated filter as collection media has been developed for the monitoring of low concentrations of aldehydes. The collecting medium depth has been optimised in order to obtain quantitative samples. The samplers have been calibrated by exposing them in an exposure chamber, and relations between uptake and exposure dose have been established. The badge utilisation has been validated by sampling in a real atmosphere with a comparison with pumped samples.

Perkin-Elmer tubes packed with Tenax TA have been tested for the monitoring of low concentrations of aromatic compounds and linear alkanes using diffusive sampling. The uptake rates have been investigated for different exposure doses. A particular hexane and benzene behaviour has been observed: their uptake rates decrease rapidly in the lower exposure doses and so follow an exponential curve. The uptake rates of heavier compounds adopt another tendency: a slow decrease with time following a linear profile. The relative humidity influence has been studied too, and no water perturbation has been recorded.

The rate constants of the isopropyl acetate, n-propyl acetate, isopropenyl acetate, n-propenyl acetate, n-butyl acetate, and ethyl butyrate reactions with OH radicals were determined in purified air under atmospheric conditions, at 750 torr and (295 ± 2) K. A relative rate experimental method was used; n-heptane, n-octane, and n-nonane were the reference compounds, with, respectively, rate constants for the reaction with OH of 7.12 × 10−12, 8.42 × 10−12, and 9.70 × 10−12 molecule−1 cm3s−1. The following rate constants were obtained in units of 10−12 molecule−1 cm3s−1; isopropyl acetate, (3.12 ± 0.29); n-propyl acetate, (1.97 ± 0.24); isopropenyl acetate, (62.53 ± 1.24); n-propenyl acetate, (24.57 ± 0.24); n-butyl acetate, (3.29 ± 0.35); and ethyl butyrate, (4.37 ± 0.42). Tertiary butyl acetate has a low reactivity with OH radicals (

Attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR) can be successfully used for the quantitative determination of small amounts of pollutants like the organic fraction of aerosols. The relation between sample concentration and reflectance is described by the Kubelka-Munk equation and was found to be linearly proportional to the absorption band of some functional group. Several parameters like the matter of solid matrix, the cleaning of the sampling support, the treatment of reflectance spectra and the base line correction considerably influenced the reflectance spectra and facilitated data interpretations. The feasibility of the ATR-FTIR was evaluated by the monitoring of specific organic group bands on filters collected in the French cities of Grenoble and Clermont-Ferrand. We have obtained for hydroxyl group a calibration curve by plotting the relative intensity of reflectance versus the concentration. The linearity was obtained for OH from 1x10(-1) to 1x10(0)molL(-1) with r(2)=0.9959. We can consider that for a direct measurement of the intensity of reflectance, it is possible to perform quantitative ATR-FTIR organic group analysis.

International audience; Mercury (Hg) is a toxic pollutant and it can be strongly accumulated in the food chain, especially in Polar Regions. This paper presents a part of the work that has been on-going for 3-4 years in Ny-Alesund, Svalbard within the frame of an international collaboration. In Ny-Alesund in spring 2003, the atmospheric chemistry of mercury has been studied so as to better understand the formation of oxidized mercury species in the atmosphere that could be deposited onto snow surfaces. The role of snow as a potential source of mercury to the atmosphere or as a sink has also been approached to better understand the behavior of this metal. Chemical and biological processes seem to play a major role in Hg storage in snow. When melting, snow could be a major source of Hg into the various ecosystems and this toxin could therefore be accumulated into the food chain.

A bibliography review led to detail the mechanisms of exchange between phases and transport of volatile organic compounds in the vadose zone, to put in equations their transfer, to set experimental devices and to define relevant tests.The pollutant in question is trichloroethylene, the porous media is a medium sand and the experiments were implemented in column.Once, an analytical method was available to quantify aqueous, gaseous and sorbe TCE, predominant transfers mechanisms were quantified separately especially with diffusion experiments through a sand at three different water contents (dry, residual saturation and saturated). Then, these mechanisms have been coupled in a TCE transfer experiment in sand with a hydrostatic water content profile. Each type of test was dimensioned, if it's possible duplicated and interpreted with the multiphasic software Comsol whose flow equation was changed to consider the gravity driven convection.By strictly controlling external factors and boundary conditions, it was possible to carry out transfer experiments reproducible and interpretable with a volatile and reactive compound in a very permeable porous medium. A good reproducibility of experimental results by simulation was achieved with minor changes in basic parameters: report permeability on viscosity, tortuosity (Millington, 1959) and aerodynamics conductivity curve setting parameter (Thomson et al., 1997). This work has resulted in a fine understanding of gas transfers in the vadose zone, especially in the capillarity fringe., Une synthèse bibliographique a permis de faire un bilan sur les mécanismes d'échanges entre phases et de transport d'un composé organo-volatil présent en zone non saturée, de mettre en équations son transfert et de définir les dispositifs expérimentaux d'étude ainsi que les essais pertinents.Le polluant considéré est le trichloréthylène, le milieu poreux est un sable moyen et les expériences ont été réalisées en colonne.Après la mise au point d'une méthode d'analyse du TCE aqueux, gazeux et sorbé, les mécanismes prédominants des transferts ont été quantifiés isolement essentiellement par le biais d'essais de diffusion en sable sec, à saturation résiduelle en eau et saturé. Puis, ces mécanismes ont été couplés au sein d'une expérience de transfert de TCE en sable avec un profil de teneur en eau réel (hydrostatique). Chaque type d'essai a été dimensionné, si possible dupliqué et interprété grâce au code multiphasique Comsol dont l'équation de l'écoulement a été modifiée afin de considérer la convection gravitaire.En contrôlant rigoureusement les facteurs externes influents ainsi que les conditions aux limites, il a été possible de réaliser des expériences reproductibles et interprétables de transfert de TCE, un composé volatil et réactif en milieu poreux très perméable. Une bonne reproductibilité des résultats expérimentaux par la simulation a été obtenue moyennant de légères modifications des paramètres de base : rapport perméabilité sur viscosité, tortuosité(Millington, 1959) et paramètre de calage de la courbe de conductivité aéraulique (Thomson et al., 1997). Ce travail a permis une compréhension fine des transferts gazeux en ZNS, en particulier en frange capillaire.

Currently, few studies related to Volatile Organic compounds (VOC) emissions in indoor air were realised from combustion sources (heating, cooking ...). Indeed, the use of fireplaces will increase next years due to oil price: wood valorisation is one of the alternative sources for residential heating. There are not many studies about this subject because analytical techniques to determine weak concentration are difficult to implement. The main goal of this work is to evaluate the impact of VOC emissions due to wood combustion, and more particularly in indoor air. In order to understand the role of compounds emitted on air quality, a kinetic study of a specific marker was carried out in an atmospheric simulation chamber.Thus, after having studied the possibilities of news analytical supports containing carbon nanostructures (CNS), we evaluated VOC emissions from different wood fireplace. This study showed it was possible to find a marker in relation to wood type burning.Creosol was highlighted as this marker and its kinetic study showed that it was very reactive (very high constant). This compound was also at the origin of secondary compounds sometimes more toxic for human health. Finally at this time the CNS showed unequalled analytical qualities and requires complementary studies for a reliable analytical application, L'atmosphère terrestre est un milieu très complexe, perpétuellement en interaction, dont sa composition est fortement influencée par les activités humaines qui émettent de nombreux composés. Peu d'études liées aux émissions de composés organiques volatils (COV) en air intérieur à partir des sources de combustion (différents modes de chauffage, cuisine, ...) ont été conduites à ce jour. En effet, l'utilisation de cheminées ne peut que s'accentuer ces prochaines années compte tenu de l'augmentation importante du coût du pétrole et de la valorisation du bois en tant que source alternative. Une partie de la carence en études dans de domaine est liée au manque de techniques analytiques permettant d'accéder aux composés émis à des niveaux très faibles.Le travail entrepris a pour principal objectif l'évaluation de l'impact des émissions de COV dû à la combustion du bois, plus particulièrement dans les atmosphères intérieures. Afin de mieux appréhender le rôle des composés émis sur la qualité de l'air et la santé, une étude cinétique de photodégradation d'un traceur spécifique de la combustion a été réalisée : le créosol. Ainsi après avoir étudié les possibilités de nouveaux supports analytiques à base de nanostructures de carbone (NSC) nous nous sommes attachés à évaluer les caractéristiques des émissions de différents foyers individuels à bois. Cette étude a montré qu'il était possible d'isoler certains composés « traceurs » en relation avec le type de combustion et l'essence de bois brûlé. Les NSC ont montré des qualités analytiques inégales à ce jour et demande encore des études complémentaires. Un traceur type : le créosol, à été mis en évidence dont son étude cinétique a montré qu'il était très réactif avec une constante très élevée et qu'il était à l'origine de composés secondaires parfois plus toxiques pour la santé humaine (composés oxydés).