Constraining RO2 Fate in Environmental Chambers: A Systematic, Model-Informed Approach for Laboratory Studies of SOA Formation
HANNAH KENAGY, Matthew Goss, Nadia Tahsini, Colette L. Heald, Jesse Kroll,
Massachusetts Institute of Technology Abstract Number: 578
Working Group: Aerosol Chemistry
AbstractMany of the quantitative descriptions of secondary organic aerosol (SOA) formation in regional and global models are derived from environmental chamber experiments, an experimental approach commonly used to assess multi-phase product distributions from atmospheric oxidation pathways. As such, model accuracy for predicting aerosol abundance hinges on the atmospheric relevance of laboratory experiments. In addition to matching the physical conditions of the atmosphere, atmospherically relevant laboratory studies of SOA formation must also match the fate of organic peroxy radicals (RO
2) in the atmosphere. However, matching the distribution of both bimolecular (reaction with HO
2, NO) and unimolecular (isomerization) pathways for RO
2 in environmental chambers to the respective distributions in the global atmosphere is non-trivial because of constraints inherent to laboratory experiments. Here, we systematically explore the parameters available in typical chamber experiments and determine how the distribution of bimolecular and unimolecular RO
2 fates accessible in the laboratory overlaps with RO
2 fates in the chemical environments of the atmosphere. Our approach uses modeling of RO
2 fates on multiple scales: detailed modeling of chamber chemistry with the Master Chemical Mechanism (MCM) in the Framework for 0D Atmospheric Modeling (F0AM) and global modeling using GEOS-Chem. We show that achieving conditions for SOA laboratory experiments in which the distribution of bimolecular and unimolecular RO
2 reaction pathways matches those of the global atmosphere is challenging but achievable with a careful, systematic approach.