AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Understanding Aqueous-Phase Isoprene-epoxydiol (IEPOX) Secondary Organic Aerosol (SOA) Production during SOAS 2013
Sri Hapsari Budisulistiorini, V. Faye McNeill, Havala Pye, JASON SURRATT, University of North Carolina at Chapel Hill
Abstract Number: 526 Working Group: The Role of Water in Aerosol Chemistry
Abstract The suspected importance of aqueous pathways of secondary organic aerosol (SOA) formation in the Southeastern United States in summer, and the combination of biogenic and anthropogenic influences on these processes, helped motivate the 2013 Southern Oxidant and Aerosol Study (SOAS). Measurements at the Look Rock, TN site during SOAS included high-resolution time-of-flight chemical ionization mass spectrometry (HR-ToF-CIMS) measurements of gas-phase IEPOX/ISOPOOH, IEPOX-OA PMF factor derived from aerosol mass spectrometric data acquired using an Aerosol Chemical Speciation Monitor (ACSM), and offline measurements of known particle-phase tracers for isoprene SOA, including IEPOX-derived organosulfates and 2-methyltetrols. On average, IEPOX-derived SOA tracer mass comprised ~26% of the IEPOX-OA factor mass, which accounted for 33% of the total OA (Budisulistiorini et al., 2015).
No correlation was observed between IEPOX-derived SOA and local aerosol liquid water or acidity at either the Look Rock or Centerville ground sites during SOAS, suggesting that these were not limiting factors in IEPOX SOA formation during the campaign. This was somewhat contrary to expectations, especially considering the positive correlations observed between IEPOX-derived SOA and aerosol sulfate. Detailed mechanistic modeling studies are needed to unravel these effects, in order to fully elucidate the lessons the valuable SOAS datasets provide regarding biogenic and anthropogenic impacts on aqueous SOA formation.
We will present the results of a detailed intercomparison study between the IEPOX-derived SOA predictions of the Community Multiscale Air Quality (CMAQ) model (Pye et al., 2013) and those of a recently introduced photochemical box model, simpleGAMMA (Woo and McNeill, 2015). This study was designed to characterize the impact of differences between the two model formulations on predictions, and agreement with ambient measurement data. Sensitivity to aerosol sulfate, aerosol liquid water, aerosol pH, and VOC precursor concentrations in both models was analyzed in order to provide mechanistic insight into the SOAS observations.