Modeling of carbonaceous aerosols with CHIMERE. Focus on secondary organic aerosols

Most of chemical transport models fairly simulate the major inorganic compounds in aerosols such as nitrate, sulfate, ammonium, chloride and sodium. The main pathways for the oxidation and gas/particle partitioning of inorganics are well identified, and above all, the number of species involved in those mechanisms is small. The organic fraction in aerosols is a complex mixture of hundreds major species interacting between each other and with the inorganic species. Organics can be emitted by resuspension of biogenic materials (waxes, vegetative and animal debris, etc... ) and by direct emissions of combustion processes. But a large amount of organic species are produced by oxidation of volatile organic compounds and condensation of the oxidation products or oligomerization of some condensed compounds. The resulting products (the so called SOA) are both biogenic and anthropogenic in origin. This particular chemistry involves a huge number of reactions and produces thousands of potential secondary organic species. Moreover, recent researches have pointed out that primary organic aerosols (POA) issued from the combustion processes could be an important source of SOA. These latter processes are not taken into account in models. The CHIMERE model used in the framework of the air quality forecasting system in France is now designed to account for carbonaceous species, a new SOA scheme has been implemented. Some applications are presented, the next key developments to improve SOA modelling are addressed