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Photodegradation of α-Pinene Secondary Organic Aerosol Dominated by Moderately Oxidized Molecules
V. Pospisilova, D.M. Bell, H. Lamkaddam, A. Bertrand, L. Wang, , X. Zhou, J. Dommen, A.S.H. Prevot, U. BaltenspergerShow More
Published in American Chemical Society
PMID: 33961408
Volume: 55
Issue: 10
Pages: 6936 - 6943
Atmospheric secondary organic aerosol (SOA) undergoes chemical and physical changes when exposed to UV radiation, affecting the atmospheric lifetime of the involved molecules. However, these photolytic processes remain poorly constrained. Here, we present a study aimed at characterizing, at a molecular level and in real time, the chemical composition of α-pinene SOA exposed to UV-A light at 50% relative humidity in an atmospheric simulation chamber. Significant SOA mass loss is observed at high loadings (∼100 μg m-3), whereas the effect is less prevalent at lower loadings (∼20 μg m-3). 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). ©
About the journal
JournalData powered by TypesetEnvironmental Science and Technology
PublisherData powered by TypesetAmerican Chemical Society
Open AccessNo