The Effects of Acid-Catalyzed Multiphase Chemistry on the Hygroscopicity and Deposition Ice Nucleation of Complex Inorganic-Organic Mixed Aerosols

Sining Niu, Christopher Rapp, Yeaseul Kim, Zezhen Cheng, Gregory W. Vandergrift, Jason Surratt, Gourihar Kulkarni, Daniel Cziczo, Alla Zelenyuk, Swarup China, YUE ZHANG, Texas A&M University

     Abstract Number: 366
     Working Group: Aerosols, Clouds and Climate

Abstract
Aerosol-cloud interactions are one of the largest uncertainties in estimating the radiative forcing and predicting future climate. The physicochemical properties of aerosols can significantly alter their cloud condensation and ice nucleation properties. This study aims to bridge the scientific gap by investigating the impacts of multiphase reactions on the chemical composition, phase state, mixing state, and morphology of the particles, and examining how the modification of the physicochemical properties would jointly affect the cloud condensation and ice nucleation activities.

The SOAs derived from four BVOCs (α-pinene, limonene, β-caryophyllene, and isoprene) are generated from a potential aerosol mass (PAM) reactor, with both neutral ammonium sulfate (AS) and acidic ammonium bisulfate (ABS) seed particles so as to distinguish between ocndensation and multiphase reactions. Both online and offline techniques are utilized to monitor the change of the chemical composition, specifically, the formation of OS through multiphase oxidation. Filter samples are collected, and the concentration and chemical composition of OS is determined by high resolution Aerosol Mass Spectrometer and Nanospray Desorption Electrospray Ionization coupled with Orbitrap mass spectrometer. The SOAs are also collected onto the TEM grids with their morphology and phase state being analyzed with a Scanning Electron Microscope. The cloud condensation and ice nucleation (IN) activities of the SOAs undergoing multiphase reactions are measured by the Cloud Condensation Nucleus (CCN) Counter and the Continuous Flow Diffusion Chamber (CFDC) in real-time to derive hygroscopicity parameter κ and ice nucleation onset RH, respectively.

Our results show that the hygroscopicity of the OS containing BVOC-derived SOA drastically decreased compared with the inorganic ABS seed particles, indicating a reduction of CCN and change of the IN activity during the multiphase reactions.