Contact LISA : M. Beekmann

PI: M. Beekmann

The European FP7 MEGAPOLI project (Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation 2008-2011) intends to provide a quantitative and comprehensive description of the impact of megacities on air quality and the chemical composition of the troposphere.

In this framework, LISA coordinated a major field campaign in and around the Paris agglomeration, considered as an example of a tertiary type megacity located in temperate latitudes. The specific objective was a better quantification of primary and secondary organic aerosol sources and formation pathways. In two intensive campaigns of each one month in summer 2009 and winter 2009/2010, a consortium of twenty five European and French teams has implemented a large number of state-of-the- art instrumentation on several fixed sites, mobile platforms and on the ATR-42 research aircraft (Figure 1). This allowed a detailed characterization of the chemical composition of particles, of their physicochemical properties, of gaseous precursors, and of the vertical structure of the lower troposphere.

During these campaigns, LISA has performed a set of comprehensive gas phase measurements at the sub-urban SIRTA site in Palaiseau, and on the ATR-42 aircraf twhich was deployed to sample the pollution plume. It also carried out spectroscopic measurements on the roof of the University of Créteil (UPEC). All together, these measurements will allow the determination of HOx radicals sources, to study the link between the oxidation of VOCs, the formation of photo-oxidants (in the gas phase) and the formation of secondary organic aerosol (SOA). Simulations with the explicit chemical model (GECKO-A model ) are performed to reproduce the different AOS formation pathways from gaseous and particulate precursors. Simplified representations of these processes are implemented into the CHIMERE air quality model, in order to simulate the contribution of different regional and local sources (anthropogenic, biogenic VOC, primary organic aerosol) to organic aerosol formation. In parallel, scenario simulations will be performed with CHIMERE for several megacities in Europe. to assess the impact of their future development on regional scale air quality. In a first step idealized scenarios, with more or less dense megacity emissions, will be performed.

The project is co-financed by the French ANR, of the national program CNRS/INSU LEFE-CHAT, ADEME and the region Ile-de-France (SEPPE). For more information, refer to the website