Modeling SOA Formation in Indoor Environments: Impact of Lamps, NO2, Ozone, and Wet Inorganic Seed

Spencer Blau, MYOSEON JANG, University of Florida

     Abstract Number: 368
     Working Group: Indoor Aerosols

Abstract
a-Pinene and toluene are ubiquitous Volatile Compound Products (VCPs) in indoor spaces. In this study, the SOA formation potential from the oxidation of a-pinene bleeding with toluene has been simulated under varying environmental indoor conditions (lamps, NO2, ozone, and inorganic seed) using the UNIfied Partitioning Aerosol Reaction (UNIPAR) model. The UNIPAR-Indoor model utilizes lumping species that originate from explicitly predicted products, produced during the atmospheric oxidation of a precursor hydrocarbon, is employed to process products’ multiphase partitioning and aerosol phase reactions. The performance of the UNIPAR model coupled with CB6 was demonstrated using indoor chamber experiments in both the dark conditions and light conditions with commercialized fluorescent lamps or LED lamps. Overall, the model reasonably captured indoor chamber data. The sensitivity of the SOA mass formed under the atmospherically relevant conditions (10 ppb a-pinene with 30 ppb ozone) showed that the formation of SOA from a-pinene in the presence of NO2 with commercialized lamps was slower and lower than that from a-pinene dark ozonolysis. SOA formation significantly increases with increasing NO2 at given conditions. With the high level of NO2 in the dark condition (hydrocarbon ppbC/ NO2 <10), the significant amount of a-pinene SOA is contributed via the reaction with nitrate radicals. With 10 ppb a-pinene, 30 ppb ozone, and 50 ppb of toluene in the dark condition, the simulated sensitivity suggested that 15% of SOA mass of total SOA was contributed by toluene because toluene reacted with OH radicals, which created from the decomposition of ozonolysis products of a-pinene. The impact of wet-seed on a-pinene SOA is negligible, but wet-seed impacted SOA formed from the mix of on a-pinene and toluene increased due to the formation of reactive products from toluene oxidation for oligomerization in aqueous phase. We conclude that ozone and NO2, intruded from outdoor environments effectively oxidized terpene and furthermore aromatic hydrocarbons with the OH radical originating from ozonolysis of terpenes in both the dark and indoor lamp conditions. Overall, the dark reaction paths with ozone and radicals are more effective to form SOA than light conditions with commercialized lamps in indoor environments.