Survey of the Effect of Functional Groups on Observed SOA Growth from Photo-Oxidation

An analysis of the effect of molecular structural features on secondary organic aerosol (SOA) growth was conducted systematically with an emphasis on organic functionalgroups serving as the foundation. SOA yields were determined for a series of various organics ranging from alkanes such as Octane to larger, more functionalized moleculesincluding -Caryophyllene. Organic SOA yield was calculated by standardizing with SO2 as 100% yield. SOA growth was observed following oxidation by OH radicals initiatedfrom HONO photolysis in a photolytic flow reactor. Cyclic compounds dominate as the highest SOA yielding structural feature, followed by double bonds. Carbonyl-containingcompounds procured minor growth. Alcohols, triple-bond compounds, aromatics, epoxides, and alkanes were not effective at growing SOAs. When more than one doublebond is present, or a double bond is present with another functional group as seen with 1,2-epoxydec-9-ene, SOA yield is notably increased. Our first generation oxidationproducts are presumed to be the primary species contributing to the SOAs. Since these are first generation products crucially contributing to SOA growth, the molecularstructure of the precursor molecule is determinant.Therefore, molecular pathways undertaken by the precursor organic species were essential to understanding ourexperimental findings.