Photodegradation of α-Pinene Secondary Organic Aerosol Dominated by Moderately Oxidized Molecules
Veronika Pospíšilová, David M. Bell, Houssni Lamkaddam, Amélie Bertrand, Liwei Wang, Deepika Bhattu, Xueqin Zhou, Josef Dommen, Andrê S. H. Prévôt, Urs Baltensperger, Imad El Haddad, Jay G. Slowik
Abstract
). For the vast majority of molecules measured by the extractive electrospray time-of-flight mass spectrometer, there is a fraction that is photoactive and decays when exposed to UV-A radiation and a fraction that appears photorecalcitrant. The molecules that are most photoactive contain between 4 and 6 oxygen atoms, while the more highly oxygenated compounds and dimers do not exhibit significant decay. Overall, photolysis results in a reduction of the volatility of SOA, which cannot be explained by simple evaporative losses but requires either a change in volatility related to changes in functional groups or a change in physical parameters (i.e., viscosity).