AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Modeling Regional Secondary Organic Aerosol from Isoprene in Southeast United States Using the Master Chemical Mechanism
Jingyi Li, QI YING, Texas A&M University
Abstract Number: 136 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract In this study, the Community Multiscale Air Quality (CMAQ) model driven by the gas phase Master Chemical Mechanism (MCM) version 3.2 linked with a secondary organic aerosol (SOA) (CMAQ-MCM-SOA) was modified to include SOA formation from traditional and non-traditional pathways: (1) traditional equilibrium partitioning of semi-volatile products predicted by the gas phase MCM mechanism; (2) reactive uptake of isoprene epoxidiols (IEPOX) and methacrylic acid epoxide (MAE) formed under low and high NOx conditions, respectively; (3) equilibrium partitioning of dihydroxy-dihydroperoxides and methyl-tetrols and (4) reactive uptake of glyoxal and methylglyoxal. Oligomerization was modeled as a simple first-order decay process as used in the original CMAQ SOA mechanism. The acidity dependent reactive uptake coefficient of IEPOX was based on nonlinear fit of multiple lab experiments. The modified CMAQ-MCM-SOA mechanism in a box model setting was able to reproduce most of the reported SOA yields in the Caltech chamber experiments (Kroll et al. 2005, 2006) of isoprene under low and high NOx conditions. It was found that semi-volatile products alone could not explain the observed SOA under high NOx conditions and reactive surface uptake of MAE, glyoxal and methylglyoxal were necessary. The modified CMAQ-MCM-SOA model will be applied to study SOA formation in Southeast United States during a one-week long summer episode in August 2006 to determine the overall isoprene SOA and the importance of different pathways will be discussed.