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Etude de la fraction carbonée de l'aérosol atmosphérique à Chamonix et St Jean de Maurienne : évolutions saisonnières, sources et caractéristiques chimiques

Abstract : The atmospheric aerosols play an important role in the earth climatic system. They are also at the origin of air pollution problems in urban areas. However, their influence on the global climactic change, as well as their chemical properties in urban zone, is still very poorly known. One of the main reasons to that is the lack of information on one of the major components of aerosol, the carbonaceous matter. This work focuses on a better knowledge of this particulate carbonaceous matter. This study presents measurements of carbonaceous matter (OC and EC) in aerosol (PM10) performed within the framework of the program POVA, between February 2001 and June 2003 in Chamonix and St Jean de Maurienne (French Alps). This series represents one of the first of this type for basic sites of alpine valleys, characterized by emissions located in the bottom of the valleys and strong temperature inversions in winter, limiting the dispersion of pollutants. The POVA program, centred on the study of air pollution in these valleys, was proposed following the closing of the “Tunnel du Mont Blanc”, in 1999. One of the main objectives was to evaluate the sources of pollution by particles, in particular the share due to the international heavy duty traffic. We could establish that, on the two sites and while the international heavy duty traffic was not restored in the Chamonix Valley, this source represented approximately a third of the observed mass of particles, and was at the origin of a weaker fraction of the carbonaceous matter mass. The extremely primary character of the carbonaceous matter is a remarkable specificity of our sites. The source of carbonaceous matter represented by light vehicles emissions could not be studied. Then, it appears that combustion of biomass (probably from fireplaces) plays an important role, increased in the case of low temperatures, on the levels of pollution by particles. Lastly, the potential impact of the semi-volatile matter condensation at the low temperatures remains an assumption to be tested. On a more general point of view, several results can be pointed out concerning the organic matter : 1. The conversion factor of organic carbon mass to organic matter mass is undoubtedly very variable for a given site (in particular, its variability is probably largely higher than 0,2). 2. The generally allowed assumptions for the calculation of the secondary fraction of OC appeared false in the case of our study, and the method seems in the general case very dubious. 3. The soluble fraction of OC is very important on our sites. The primary source of biomass combustions is an important primary source of WSOC. This result is in disagreement with the general assumption that WSOC is mostly with a secondary origin.
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https://tel.archives-ouvertes.fr/tel-00008918
Contributor : Gilles Aymoz <>
Submitted on : Friday, April 1, 2005 - 10:54:17 AM
Last modification on : Thursday, November 19, 2020 - 3:54:26 PM
Long-term archiving on: : Friday, April 2, 2010 - 9:23:11 PM

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Gilles Aymoz. Etude de la fraction carbonée de l'aérosol atmosphérique à Chamonix et St Jean de Maurienne : évolutions saisonnières, sources et caractéristiques chimiques. Océan, Atmosphère. Université Joseph-Fourier - Grenoble I, 2005. Français. ⟨tel-00008918⟩

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