Secondary Aerosol Formation in the MEDiterranean – SAF-MED

The work is divided into one management task and 4 technical tasks: ground measurements (Task 1), airborne measurements (Task 2), modeling (Task 3) and comparison of modeling to measurements (Task 4). The methodology used to answer the questions detailed in the objectives is specific to each task.

A campaign of measurements is set up for this summer 2013.

After the campaign of measurements, observations will be treated to meet the project objectives, and comparisons will be made to modelling.

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SAF-MED aims to develop a better understanding of the origins of the high secondary organic aerosol (SOA) concentrations observed in the western Mediterranean in summer with a focus on the role of atmospheric chemical processing and particle properties in SOA formation, in the framework of ChArMEx (The Chemistry-Aerosol Mediterranean Experiment, charmex.lsce.ipsl.fr).
SOA are a significant fraction of atmospheric Particulate Matter (PM) and, therefore, are believed to contribute to adverse health effects and climate change. High SOA concentrations have been observed over the Mediterranean basin, where high natural emissions (biogenic and oceanic) are common and where aged anthropogenic plumes are transported. Understanding the formation of SOA is complicated because of difficulties to correctly characterize the gas-phase oxidant chemistry and the multi-step oxidation of volatile organic compounds (VOC) that leads to SOA formation. Most state-of-the-art air quality models (AQM) may actually not be valid far from source regions because SOA formation in AQM is based only on the first and, in some cases, second VOC oxidation steps. Consequently, a better description of PM concentrations and characteristics (particle size distribution, chemical composition, volatility, hygroscopicity and mixing state) from both measurements and modelling is desirable to improve our understanding of the origins, evolution, and properties of SOA.
Our strategy is based on a combination of ground-based and airborne measurements during a summer field campaign and 3D modeling. A better characterization of SOA and PM will allow us to evaluate existing AQM. Not only PM concentrations, but also PM properties will be compared to measurements, leading to stronger constraints on AQM. This will allow us to improve our insights into the processes that need to be improved for air quality modelling. As a large part of SOA may be formed from the interactions between biogenic and anthropogenic precursors, improvements in the modeling of natural and anthropogenic aerosols will allow us to better quantify the part of biogenic SOA that can be controlled.