G. Mouvier

The chemistry of carbonyl compounds in the atmosphere—A review

Abstract Carbonyl compounds are very important for the trophospheric physico-chemistry because they are the result of the first photo-oxidation stage of almost all organic compounds and they are the essential originators of the free radicals. In the present review we make a synthesis of the studies on the carbonyl compounds chemistry in the trophosphere by successively examining: measurement methods in the trophosphere, sources of primary carbonyl compounds, formation of secondary carbonyl compounds in the atmosphere, reactivity of carbonyl compounds in the atmosphere.

Relative decay index and sources of polycyclic aromatic hydrocarbons

Abstract An optimized method for the analysis of polycyclic aromatic hydrocarbons (PAH) in atmospheric aerosols with short sampling times (1h) has been used to determine the daily variations of PAH in the atmosphere. Of the various physicochemical parameters controlling the disappearance of PAH, the most important seem to be the thermic dependence and the chemical reactions with gaseous pollutants ( NO x , O 3 , HNO 3 , OH). The RDI is used to identify the different sources of urban pollution: domestic heating, vehicle traffic (petrol and diesel), refineries, foundries, incinerators and power stations (coal, gas and oil) and to quantify the results for standard conditions. The characteristic concentration ratios from each source are often different from those in the literature, where the data are based on long sampling times and are affected by PAH reactivity differences. The results obtained are parameters for setting up a mathematical model for calculating concentrations of PAH at any receptor site.

Long range transport and gas/particle distribution of polycyclic aromatic hydrocarbons at a remote site in the Mediterranean sea

Abstract Polycyclic aromatic hydrocarbon (PAH) concentrations have been determined for 14 successive days in a remote site of the Mediterranean Sea situated in Corsica, France. Both particulate and gas phases were collected and analyzed. For any receptor site the concentration of adsorbed PAH on particles is determined by three parameters, in order of decreasing importance: the source area, nearby sources and precipitation along the trajectory followed by the particles. For two air masses originating from the same source area, PAH concentrations can be reduced by 60% by particle scavenging during precipitation events. The identification of the source area is in complete agreement with the classification based on the mineral elements. The gas phase concentrations are determined by the source area only; they remain high compared to the concentrations in the industrial zone, thus proving that the gaseous PAH are not strongly degraded by chemical aggressors during transport. Factor analysis clearly shows the different effects involved during transport. The gas/particle ratio is determined essentially by the temperature and molecular weight of the PAH and not by the origin of the emissions. However precipitation influences this ratio to a non-negligible extent through scavenging of the aerosols. For example, the gas/particle ratio, for pyrene, varies from 2 to 4 between two ‘dry’ episodes with a temperature difference of 2.2° C, and from 6 to 13 because of the particle scavenging by rain. These results can be used as a data base and are expected to guide the conception of transport models including the parameters considered in this study.

A receptor model adapted to reactive species: Polycyclic aromatic hydrocarbons; Evaluation of source contributions in an open urban site—I. Particle compounds

Abstract Contributions from three urban sources of PAHs: domestic heating, petrol vehicles and diesel vehicles, were evaluated for various times of year and various times of day. Contributions were calculated by chemical mass balance from histograms of six PAHs that are present in the atmosphere only in particle form. The urban site studied (Paris, France) is an open site well suited to the use of a piston reactor model. This model has been modified to take into account the differences in reactivity between the particle PAHs and adapted to conserve its linearity. The correction is brought to bear upon the histograms from measurements taken at the receptor site, and leads to the construction of virtual profiles from which the contributions of the various sources are calculated. Evidence of seasonal and hourly variations is brought out. The results are very realistic and can be compared with information about vehicle traffic density and about energy consumption. They also show that the difference observed between summer and winter concentrations is mainly due to variations in production, and not to the decay of PAHs.

Field studies of aldehyde chemistry in the Paris area

Abstract Measurements of carbonyl compound concentrations at different sites in the Paris area have been carried out. Interpretation of the results made use of the following data: general meteorological conditions, wind field analysis and type of primary pollutant sources. The principal phenomena observed were: a sharp formaldehyde decrease during rainfall; concentration levels of lower aldehydes in rural sites comparable to those found in the literature; an important variation in the ratio of primary aldehydes to secondary aldehydes depending on meteorological conditions; a significant increase in lower aldehyde concentrations downwind from the urban center despite vertical dispersion of the pollutants.

Sulfur dioxide oxidation over atmospheric aerosol—X-ray photoelectron spectra of sulfur dioxide adsorbed on V2O5 and carbon

Abstract Adsorption and oxidation of sulfur dioxide over V2O5 and carbon are studied by X-Ray Photoelectron Spectroscopy (XPS). SO2 does not chemisorb onto V2O5 below 150°C, and it oxidizes at 200°C into adsorbed sulfate and sulfur trioxide. Over carbon, chemisorption and oxidation occur from room temperature upwards, but at 200°C reduction of SO2 by carbon also takes place, giving elementary sulfur and carbon disulfide. From these results, it is concluded that the V2O5 aerosols contribute little to the production of atmospheric sulfuric acid below 150°C, whereas carbon particles can catalyse SO2 oxidation even at low temperatures, and produce at higher temperature secondary adsorbed pollutants such as elementary sulfur and carbon disulfide.

Formaldehyde Background Levels over the Atlantic Ocean during the Polarstern Crossing from Bremerhaven to Rio Grande Do Sul

During the POLASTERN crossing from Bremerhaven to Rio Grande do sul (15 september to 9 october 1988) we have measured the formaldehyde atmospheric concentrations at about 30 m above the ocean. The used experimental technique is the very same that we have used during the campaign at the “pointe de Penmarc’h” in July 1988. Outside of the area under continental influence the average levels are 0,4 ppbv in the north hemisphere, 0,3 ppbv in the south hemisphere and about 2 ppbv in the intertropical convergence zone. While the main values observed outside the ITCZ are in agreement with those expected from the methane oxidation and the formaldehyde photochimical depletion, these obtained in the ITCZ can only be explained by taking into account the relative high concentrations of alcenes found in this area and their fast oxidation.

Identification Des Sources D’Hydrocarbures Aromatiques Polycycliques Particulaires Dans L ’ Atmosphere Urbaine

To analyze PAH a method with short sampling (1 hour) on representative sites of various origins in urban areas was optimized: residential heating, gasoline and diesel-fuel powered vehicles, ihcinerators, oil reffinery, casting work and coal-fired power plant. The current methods for identifying: profiles or histograms and characteristic ratio, were used and compared to the values of the scholarly literature. It is very important to count with PAII reaetivity differences to obtain significative ratio. Only data obtained with short times and well determined samplings conditions must be considered.

Optimisation des Methodes de Prelevement et D’Analyse des Hydrocarbures Aromatiques Polycycliques et de Leurs Derives Azotes — Determination de Leur Stabilite dans L’Atmosphere

A highly sensitive and fast method for analyzing polycyclic aromatic hydrocarbons by HPLC with fluorimetric detection was developed. This method permits to execute daily several samplings and treat them without any risk of degradation during filter collection and analysis, so that it is possible to observe significantly the diurnal Variation of these Compounds. From this study, a scale of PAH reactivity in atmosphere was determined.

Quelques Aspects de la Chimie des Aldehydes dans la Basse Troposphere

L’etude de la chimie des aldehydes dans la basse troposphere a ete abordee par deux voies complementaires : d’une part, la determination de la reactivite des aldehydes vis-a-vis des radicaux hydroxyles et nitrates sous conditions atmospheriques simulees en vue de l’estimation de leur temps de residence tropospherique et d’autre part l’etude des facteurs sources et puits d’aldehydes dans les masses d’air transitant au-dessus de la region parisienne.