Integrated model-measurement approaches to chamber SOA studies

Many 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 our ability to represent atmospheric conditions in chambers.  Here, we develop a new experimental approach that leverages both global modeling and detailed mechanisms to design chamber SOA experiments that capture atmospheric chemical environments for two key branching points in VOC oxidation: atmospheric oxidant balances and atmospheric RO2 chemistry. Using isoprene as a model system for multi-generation SOA production, we focus first on competition between oxidation by OH and Cl.  Global modeling indicates that multi-oxidant, multi-generation oxidation outcompetes single-oxidant, multi-generation oxidation in this system; we design and perform a series of chamber experiments to measure multi-phase product distributions from multi-oxidant, multi-generation isoprene oxidation.  Second, we develop a framework for quantitatively describing atmospheric RO2 chemistry and show that no previous experimental approaches to studying SOA formation have accessed the relevant atmospheric RO2 chemistry.  Leveraging multi-scale modeling, we design and perform a series of chamber experiments to measure isoprene SOA production under a range of atmospheric RO2 fate distributions.