Air pollution is the “world largest single environmental health risk” (WHO, 2016). According to the World Health Organization, every year ambient air pollution leads to more than 3 million premature deaths, and 84% of the global population is exposed to atmospheric aerosol levels higher than the limits set to protect human health (WHO, 2016). One of the most abundant, and still less characterized components of atmospheric aerosol is organic aerosol (OA). In particular, OA sources, formation mechanisms, atmospheric ageing, and effects on climate and human health are still subject of research.
OA is a mixture of thousands of chemical species, characterized by different physical, chemical, and toxicological properties. Such properties define the effects of OA, and particulate matter, on climate, air quality, and human health (Goldstein and Galbally, 2007). Traditional analytical techniques, based on the identification of single molecular species, describe only a limited fraction of OA mass, generally lower than 30% (Hallquist et al., 2009). During the last decade the use of bulk OA spectrometric analysis introduced simplified descriptions of OA. Such approaches depict OA as formed by a few components with different degrees of oxidation (Aerosol mass spectrometry - AMS) (Zhang et al., 2005), or as the sum of different organic functional groups, (Fourier transform infrared spectrometry - FTIR (Maria et al., 2003), or proton nuclear magnetic resonance spectrometry - H-NMR (Decesari et al., 2007)).