title: Novel Approach for Evaluating Secondary Organic Aerosol from Aromatic Hydrocarbons: Unified Method for Predicting Aerosol Composition and Formation.
abstract: Innovative secondary organic aerosol (SOA) composition analysis methods normalizing aerosol yield and chemical composition on an aromatic ring basis are developed and utilized to explore aerosol formation from oxidation of aromatic hydrocarbons. SOA yield and chemical composition are revisited using 15 years of University of California, Riverside/CE-CERT environmental chamber data on 17 aromatic hydrocarbons with HC:NO ranging from 11.1 to 171 ppbC:ppb. SOA yield is redefined in this work by normalizing the molecular weight of all aromatic precursors to the molecular weight of the aromatic ring [Formula: see text], where i is the aromatic hydrocarbon precursor. The yield normalization process demonstrates that the amount of aromatic rings present is a more significant driver of aerosol formation than the vapor pressure of the precursor aromatic. Yield normalization also provided a basis to evaluate isomer impacts on SOA formation. Further, SOA elemental composition is explored relative to the aromatic ring rather than on a classical mole basis. Generally, four oxygens per aromatic ring are observed in SOA, regardless of the alkyl substitutes attached to the ring. Besides the observed SOA oxygen to ring ratio (O/R ∼ 4), a hydrogen to ring ratio (H/R) of 6 + 2n is observed, where n is the number of nonaromatic carbons. Normalization of yield and composition to the aromatic ring clearly demonstrates the greater significance of aromatic ring carbons compared with alkyl carbon substituents in determining SOA formation and composition.
authors.affiliation: Department of Chemical and Environmental Engineering, University of California, Riverside , Riverside, California 92521, United States.|College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, Riverside , Riverside, California 92507, United States.
authors.forename: Lijie
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Chemical and Environmental Engineering, University of California, Riverside , Riverside, California 92521, United States.|College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, Riverside , Riverside, California 92507, United States.
authors.forename: Ping
authors.initials: P
authors.lastname: Tang
authors.affiliation: Department of Chemical and Environmental Engineering, University of California, Riverside , Riverside, California 92521, United States.|College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, Riverside , Riverside, California 92507, United States.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Nakao
authors.affiliation: Department of Chemical and Environmental Engineering, University of California, Riverside , Riverside, California 92521, United States.|College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, Riverside , Riverside, California 92507, United States.
authors.forename: Mary
authors.initials: M
authors.lastname: Kacarab
authors.affiliation: Department of Chemical and Environmental Engineering, University of California, Riverside , Riverside, California 92521, United States.|College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, Riverside , Riverside, California 92507, United States.
authors.forename: David R
authors.initials: DR
authors.lastname: Cocker
mesh_terms: D000336:Aerosols; D002244:Carbon; D006841:Hydrocarbons, Aromatic; D010084:Oxidation-Reduction; D010100:Oxygen
chemical_list: D000336:Aerosols; D006841:Hydrocarbons, Aromatic; D002244:Carbon; D010100:Oxygen