AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Simulation of Isoprene SOA Formation Using UNIPAR: A Lumping Model Integrated with Explicit Gas Phase Kinetic Mechanisms and Aerosol Phase Reactions
ROSS BEARDSLEY, Yunseok Im, Myoseon Jang, University of Florida
Abstract Number: 370 Working Group: Aerosol Chemistry
Abstract The Unified Partitioning-Aerosol phase Reaction (UNIPAR) model, which was developed to predict the secondary organic aerosol (SOA) formation through multiphase reactions, has been applied to the photooxidation of isoprene/NO$_x in the presence and the absence of SO$_2. UNIPAR utilizes an explicit kinetic model to predict the gas phase oxidation of volatile organic compounds (VOC) whose products are then lumped by volatility (6 levels) and reactivity (5 levels) throughout the cycles of gas phase oxidation. In UNIPAR, organic matter (OM) formation is predicted as the sum of the OM formed by partitioning (OM$_P), via the module used in CMAQ 5.0.1, and the OM formed by aerosol phase reactions (OM$_(AR)), including oligomerization, acid-catalyzed reactions and organosulfate (OS) formation. Model performance was tested using SOA data produced using a large outdoor chamber (UF-APHOR). Day long experiments were performed for various VOC/NOx conditions in the presence and absence of SO$_2 under the diurnal patterns of ambient temperature and humidity. The updated UNIPAR model was found to reasonably predict isoprene SOA formation and OMAR was found to dominate the overall isoprene OM formation in the presence of SO$_2. The effect of both gas phase aging and organosulfate formation on isoprene SOA yields were evaluated using the model.