Abstract View
Impacts of Salted Aqueous Phase on Monoterpene SOA Produced under Different Atmospheric Oxidants
SANGHEE HAN, Myoseon Jang, University of Florida
Abstract Number: 351
Working Group: Aerosol Chemistry
Abstract
Typically, the terpene SOA formation during daytime is attributed to the oxidation with both OH and O3 while at night, this can be dominated by the reaction with O3 and NO3 radicals. Thus, daytime terpene products differ from those in nighttime due to the different oxidation pathways of monoterpenes under varying NOx levels. To date, the impact of inorganic salted aqueous phase on the terpene SOA formation produced in different oxidation pathways was not well understood. In this study, the SOA formation in both daytime and nighttime is simulated by using the UNIfied Partitioning Aerosol phase Reaction (UNIPAR) model that predicts the SOA mass via multiphase reactions of hydrocarbons. The oxidation products of terpenes are predicted by using the explicit gas mechanism (MCM v3.3.1) and autoxidation which forms low volatility products. The resulting products are lumped based on volatility and reactivity and distributed in gas, organic and inorganic aqueous phases to form SOA via multiphase partitioning and heterogeneous reactions in both organic and inorganic phase. The simulated SOA mass is compared to experimental data that are performed under varying conditions in the UF-APHOR chamber. Three different monoterpenes (α-pinene, β-pinene, and d-limonene) react with ozone at nighttime with NO or NO2 in the presence and the absence of inorganic salt aerosol. The nighttime terpene SOA mass is compared to the SOA that is produced via the photochemical reaction of terpene. The sensitivity of the SOA mass production to NOx levels and inorganic seed types is characterized by using the UNIPAR model for different SOA formed via different oxidation pathways. Overall, daytime SOA is more influenced by aqueous reactions than nighttime SOA.