A218-0007
Modification of Particle Viscosity and Morphology of Secondary Organic Aerosols with the Uptake of Isoprene Epoxydiols (IEPOX)
Wednesday, 16 December 2020
Poster
Ziying Lei1, Nicole Olson2, Yue Zhang3, Yuzhi Chen4, Andrew T Lambe5, Zhenfa Zhang6, Natalie J White7, Avram Gold6, Joanna M Atkin8, Andrew P Ault9, Jing Zhang10, Jason D Surratt11 and Mark M Banaszak Holl12, (1)University of Michigan Ann Arbor, Ann Arbor, MI, United States, (2)University of Michigan Ann Arbor, Department of Chemistry, Ann Arbor, United States, (3)Harvard University, School of Engineering and Applied Sciences, Cambridge, MA, United States, (4)University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, (5)Aerodyne Research Inc., Billerica, MA, United States, (6)University of North Carolina at Chapel Hill, Department or Environmental Sciences and Engineering, Gillings School of Global Public Health, Chapel Hill, NC, United States, (7)University of Michigan, Ann Arbor, United States, (8)University of North Carolina at Chapel Hill, Chapel Hill, United States, (9)University of Michigan Ann Arbor, Department of Chemistry, Ann Arbor, MI, United States, (10)Monash University, Melbourne, Australia, (11)UNC-Environment Sci & Eng, Chapel Hill, NC, United States, (12)Monash University, Chemical Engineering, Melbourne, Australia
Abstract:
Secondary organic aerosol (SOA), accounting for a large portion of atmospheric fine particulate matter, are formed by the oxidation of volatile organic compounds (VOCs) and are typically co-present (mixed) with inorganic aerosol constituents. Resolving the chemical complexity, morphology, and viscosity of atmospheric SOA is crucial for understanding its formation and aging processes as well as its impact on climate. Viscosity can be defined in terms of the spreading ratio of impacted particles. The chemical composition of particles and relative humidity (RH) both affect viscosity and need to be accounted for when determining and predicting aerosol particle spreading ratios. However, viscosity of atmospheric particles is currently poorly quantified, and understanding the relationship between spreading ratios of size-selected aerosol particles and viscosity is still incomplete. Morphology also plays an important role in understanding atmospheric aerosols since it affects mixing state, heterogeneous chemical reactions, and optical properties, but is hard to quantify in SOA models due to complex chemical compositions and diverse ambient conditions.
This study investigated size-dependent spreading ratios and morphologies of SOA generated from the oxidation of toluene, α-pinene, isoprene, and β-caryophyllene in the presence of acidic sulfate aerosol before and after reactive uptake of isoprene epoxydiols (IEPOX) uptake. Results show that phase separated morphology was observed for all types of SOA. Spreading ratios significantly changed as a function of the type, among which β-caryophyllene SOA had the highest viscosity, followed by toluene, isoprene and α-pinene SOA before IEPOX uptake. After IEPOX reactive uptake, increased spreading ratios were observed for both α-pinene and β-caryophyllene SOA while the spreading ratios of toluene and isoprene SOA remain similar values. Core-shell and complex morphology were observed for four types of SOA particles, indicating that the physicochemical properties of these particles was modified upon reaction with IEPOX. The results from this study can be used to improve estimates of SOA physicochemical properties and determine future impacts of SOA on the global climate and air quality.
