Photodegradation of α-Pinene Secondary Organic Aerosol Dominated by Moderately Oxidized Molecules

• DOI: 10.1021/acs.est.0c06752
• Publication Date: 2021-05-08T14:31:11Z
• Authors: Veronika Pospisilova; David M. Bell; Houssni Lamkaddam; Amelie Bertrand; Liwei Wang; Deepika Bhattu; Xueqin Zhou; Josef Dommen; Andre S.H. Prevot; Urs Baltensperger; Imad El Haddad; Jay G. Slowik
• Keywords: Pinene; Mass fraction; Photodegradation; Fraction (chemistry)

Atmospheric secondary organic aerosol (SOA) undergoes chemical and physical changes when exposed to UV radiation, affecting the atmospheric lifetime of involved molecules. However, these photolytic processes remain poorly constrained. Here, we present a study aimed at characterizing, molecular level in real time, composition α-pinene SOA UV-A light 50% relative humidity an simulation chamber. Significant mass loss is observed high loadings (∼100 μg m–3), whereas effect less prevalent lower (∼20 m–3). For vast majority molecules measured by extractive electrospray time-of-flight spectrometer, there fraction that photoactive decays radiation appears photorecalcitrant. The are most contain between 4 6 oxygen atoms, while more highly oxygenated compounds dimers do not exhibit significant decay. Overall, photolysis results reduction volatility SOA, which cannot be explained simple evaporative losses but requires either change related functional groups or parameters (i.e., viscosity).