Modeling Peroxy Radical Conditions of Historical SOA Chamber Studies

MATTHEW GOSS, Hannah Kenagy, Jesse Kroll, MIT

     Abstract Number: 110
     Working Group: Aerosol Chemistry

Abstract
Laboratory measurements of secondary organic aerosol (SOA) formation underpin the representation of aerosols in global chemical transport models (CTMs). However, many of these measurements were performed before important recent developments in our understanding of peroxy radical (RO₂) chemistry. Previous chamber experiments were typically carried out under limiting conditions (where all RO₂ were assumed to react with either NO or HO₂), but more recent research has demonstrated that other pathways such as RO₂ isomerization or RO₂-RO₂ reactions can be important, both in chamber experiments and in the atmosphere. In light of advances in our understanding of RO₂ chemistry, actual RO₂ fate and reported RO₂ fate from these earlier chamber studies may not always align, possibly skewing the SOA parameterizations that continue to be used in CTMs. Here, we identify past SOA yield studies that have been used to constrain CTMs, and model their chamber conditions using the Master Chemical Mechanism. This enables explicit estimates of relevant and typically-unquantified parameters such as RO₂ bimolecular fate and RO₂ lifetime, which directly affect experimental outcomes such as the degree of peroxy radical isomerization or peroxyacyl nitrate formation. Model outputs are compared with reported experimental conditions, and interpreted in the context of measured aerosol yields and CTM aerosol parameterizations.