Enhanced Organosulfates Production from Multiphase Reactions of Terpenes with Acidified Sulfate Seeds Using LED-powered Environmental Smog Chamber
YUE ZHANG, Miska Olin, Sining Niu, Hannah LeClear, Christopher Rapp, Jiayun Zhao, Jason Surratt, Daniel Cziczo, Texas A&M University
Abstract Number: 621
Working Group: Aerosol Chemistry
Abstract
Previous studies have demonstrated that isoprene could undergo multiphase reactions with acidic sulfate particles to form isoprene-derived secondary organic aerosols (SOA). However, it remains unclear if gas-phase oxidation products from terpenes also undergo similar multiphase reactions to form SOA. To bridge this knowledge gap, a Texas A&M environmental chamber (TAMEC) was used to allow limonene and beta-caryophyllene to react with hydroxyl radicals (OH) in the presence of ammonium bisulfate (acid) and ammonium sulfate (neutral) seed particles. The TAMEC consists of a 10-m3 fluorinated ethylene propylene (FEP) bag in a temperature-controlled insulated enclosure (between −40 and 40 C) that is equipped with LED UV-C 273 nm lights. An aerosol dynamics model, namely TUTAMU Chamber Aerosol Model (TUTAMUChAM), was utilized in real-time during the experiments to assist in avoiding self-nucleation and deriving precise organic coating thickness on the seed particles for multiphase reactions to happen. By using a Vocus Chemical Ionization Mass Spectrometer (CIMS) in the ammonium mode, a high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), and other particle characterization techniques, we have demonstrated that intermediate peroxides species from limonene photo-oxidation was partitioning into the acidic aerosols to initiate multiphase reactions. The presence of acidic sulfate seed particles enhanced the production of SOA from limonene but suppressed the production of SOA from beta-caryophyllene, while a significant increase of the abundance of organosulfates were observed in both conditions. Such increase in organosulfate were also accompanied by changes in the physicochemical properties of aerosols. Given that ambient aerosols are often acidic, especially in the Southeastern U.S. areas with abundant terpene emissions, such results may provide improved parameterizations in predicting air quality and understanding the climate impacts of aerosols.