Assessing the Effect of Organic Coatings/Mixtures on Multiphase Chemistry of Isoprene Epoxydiols Leading to Secondary Organic Aerosol Formation
EMSL Project ID
49332
Abstract
Atmospheric chemistry models routinely fail to predict the formation rate, abundance and spatial distribution of secondary organic aerosol (SOA). On a global basis, isoprene (C5H8) emissions from terrestrial vegetation are larger than all anthropogenic VOC emissions, and their atmospheric oxidation is a potentially significant source of SOA, especially in the presence of anthropogenic pollutants such as acidified sulfate aerosol. SOA formation from isoprene oxidation is now recognized as one of the major sources of SOA in the atmosphere. Prior studies have demonstrated significant formation of SOA from the reactive uptake of isomeric isoprene epoxydiols (IEPOX), which are produced at yields greater than 75% from hydroxyl radical reactions with isoprene hydroxyhydroperoxides (ISOPOOH) under low-NO conditions, in the presence of "pure" acidified sulfate seed aerosol. However, atmospheric sulfate particles often contain co-existing SOA that could impact the multiphase chemical processes of IEPOX. Contrary to previous assumptions, it has recently been discovered that ambient aerosols may be in a glassy or semi-solid state. As a result, it is important to investigate this aspect of the IEPOX chemistry, especially since SOA coatings/mixtures might create diffusion or solubility limitations, and thus, impeding the uptake of IEPOX into acidic sulfate aerosol. Considering the likely importance of SOA coatings/mixtures in sulfate aerosol affecting the reactive uptake of IEPOX, we aim to understand its effect on reactive uptake kinetics by varying pre-existing SOA composition (and thus, atomic O-to-C ratios), viscosity, and coating thickness. This will be achieved through a combination of laboratory experiments and state-of-the-art instrumentation for on-line single particle analysis (miniSPLAT and SPLAT II) available only at EMSL in Dr. Alla Zelenyuk's lab, as well as off-line analysis of filter samples collected from these experiments by using ultra-performance liquid chromatography/electrospray ionization, high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-QTOFMS), and gas chromatography/electron ionization-mass spectrometry (GC/EI-MS) at UNC-Chapel Hill. The investigations using miniSPLAT and SPLAT II will also provide valuable information on physical and chemical parameters such as changes in particle composition, volatility, viscosity, and morphology associated with IEPOX-derived SOA formation. This work will be partly funded from Professor Surratt's lab by a National Science Foundation (NSF) grant titled "Collaborative Research: Quantifying Secondary Organic Aerosol Formation from the Reactive Uptake of Isoprene-derived Epoxides to Submicron Aerosol Particles." Thus, this research will lead to at least one peer-reviewed publication since a full-time graduate student from Surratt's lab will be sent to EMSL for this joint work. Further, parameterizations will likely be derived from this work that considers the role of organic coatings/mixtures on reactive uptake of IEPOX, and thus, helping to make explicit aerosol chemistry models more exact.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2016-10-01
End Date
2018-09-30
Status
Closed
Released Data Link
Team
Principal Investigator