Étude de contribution des sources de particules fines (PM_2,5) en Ile-de-France

The Paris region is characterized by chronic excee dances of limit values near road traffic and some years on the urban background stations. The implementation of efficient abatement strategies aiming to reduce fine aerosols concentrations requires a precise knowledge on the origin (location and sources) of particles which is still missing in Ile-de-France.

Following the example of other European big cities like London and Berlin, AIRPARIF, in association with the LSCE, has implemented a project in order to assess the contribution of the different sources of airborne particles and their geographical origin in the Ile-de-France region. Samplings are performed for a whole year from September 2009 11th over six sites spread over the Ile-de-France region. This article describes the methodology, the device and the analytical protocol implemented for the study.

The study is based on the Lenshow methodology [Lenshow et al. 2001], developed in Berlin in 2001. It assumes that PM concentration measured on a hot-spot (such as a traffic site) is composed of various and surimposed contributions: a regional background (mainly composed of long-range transported particles), a urban background contribution due to aerosols sources located within the agglomeration and a local influence due to the road traffic of nearby streets. Samplings on filters are carried out simultaneously every day on six sites carefully chosen to be representative of each of these geographical scales: three rural background sites located near the Ilede-France border, one suburban site, one urban background site located in the centre of Paris and one traffic site. The chemical analysis of the samples enables to assess the chemical composition of aerosols regarding their geographical origin. Chemical analyses are focused on PM mass and on the main aerosols components: organic and elemental carbon, ions and metals. A multianalytical approach has been implemented in order to better constrain EC, OC and POM fraction, which represent almost 50% of the mass of fine aerosols on the Ile-de-France region. Levoglucosan, which is a tracer of biomass burning, is also analyzed. Evaluation of the contribution of the main emission sources is achieved by coupling the PM chemical composition with an emission inventory specific of the geographical zone considered (traffic, urban, sub urban).

The results from chemical analysis over the first three months underline the consistency of sampling and analytical device. The agreement between PM measurements carried out with TEOM-FDMS and filters shows that the analytical methods implemented in this project allow documenting almost the entire mass of fine aerosols in Ile-de-France. These analyses will enable to constitute an important data base on chemical aerosols composition in Ile-de-France.