The key atmospheric processes that form the core of our research can be qualitatively described in the following four steps, as also depicted in the figure below.
- Volatile organic compounds (VOC) are emitted to the atmosphere.
- Atmospheric oxidants initiate chemical reactions in the VOC.
- These reactions result in a wealth of oxidized VOC (OVOC), with various volatilities.
- The OVOC with low enough volatility can form secondary organic aerosol (SOA).
The general mechanism of VOC transformation and related SOA formation can thus be summarized in the preceding four fairly simple steps. However, for a detailed understanding of these steps, for example on the level at which they could be incorporated into a model framework with predictive capabilities, many more aspects will complicate the picture. What are the sources of VOC (anthropogenic/biogenic)? What are the actual VOC molecules? What are the atmospheric conditions influencing the oxidation pathways (radiation, temperature, trace gas composition)? How can we measure the thousands of OVOC that exist in the atmosphere? What are the volatilities, and what are the reactivities of these VOC? What is the role of multi-phase chemistry in the formation of SOA? What are the properties (volatility, reactivity, hygroscopicity) of the resulting SOA?
Within the above questions lies the scope of the research conducted in our Atmospheric Physical Chemistry group. The approach to tackle these, as outlined in the COALA project, is to always try to conduct comprehensive studies where several of the questions are probed at the same time. This allows us to keep focusing on the most important outstanding issues in VOC-OVOC-SOA conversion.