The organic aerosol component is important in many ways. It contributes to new particle formation and growths, and it contributes significantly to global tropospheric particle mass. Particulate organics modify hygroscopic and cloud activation properties of mixed inorganic/organic aerosols as well as their optical properties. Partitioning of semivolatile organic compounds provides a coupling between gas-phase and condensed-phase chemistry. Particulate organics can provide radical sinks and surfaces for specific photochemical reactions.

In spite of its importance the sources of number or mass of organic aerosols are not fully understood. The same is true for the chemical fate of organic aerosols during their lifetime in the atmosphere. Organic aerosol chemistry is in a dilemma: On the one hand detailed speciation is needed to elucidate sources, transformation processes and detailed chemical mechanisms. However, atmospheric fluxes of organic carbon can not be understood by summing up the individual contributions, since there are too many components and still too many unknowns. Consequently, on the other hand integral methods are needed which are able to account for total organic contributions. Both, speciation methods and integral methods made large progress during the last few years. It is thus timely to have a closer look at the newest findings by analytical techniques, statistical and modeling tools ranging from speciation of individual compounds, interpretation of mass spectral pattern and functional group analysis to total organic carbon methods. You are cordially invited to submit your contribution to the EGU 2008 general Section Microphysics and Chemistry of Aerosols.