Abstract View
Vapors are Lost to Walls, Not to Particles on the Wall: Development of Artifact-Corrected Parameters and Implications for Global Secondary Organic Aerosol
KELSEY BILSBACK, Charles He, Jeffrey R. Pierce, Nga Lee Ng, John Seinfeld, Shantanu Jathar, Colorado State University
Abstract Number: 367
Working Group: Aerosol Chemistry
Abstract
Secondary organic aerosol (SOA) is formed through the oxidation of volatile organic compounds and makes up a large fraction of fine particulate matter. Chemical transport models typically rely on SOA parameters derived from environmental chambers that are subject to experimental artifacts. These artifacts include losses of particles to the walls and the losses of vapors to the particles on the wall and the wall directly. Accurately accounting for these artifacts is critical to representing organic aerosol (OA) evolution in models. To investigate these artifacts, first, we used the Statistical Oxidation Model (SOM) with Two-Moment Aerosol Sectional (TOMAS) model and data from chamber experiments to develop artifact-corrected parameters for important SOA precursors (e.g., isoprene, monoterpenes, aromatics, and IVOCs). We found that the parameters produced larger SOA mass yields as we accounted for losses of particles and vapors to the walls but the parameters and SOA mass yields were unaffected by the losses of vapors to the particles on the wall because this process is much slower. Additionally, we found that our schemes substantially impacted the SOA mass yield, depending on the SOA precursor, NOx condition, and OA mass concentration. Next, we ran pseudo atmospheric simulations using the artifact-corrected parameters, the output of which was used to develop d volatility basis set (VBS) parameters at atmospherically relevant OA concentrations. The updated VBS parameterizations were implemented in GEOS-Chem to evaluate how the artifact-correction schemes impacted global SOA concentrations. Preliminary GEOS-Chem results also suggested that updating the yield parameters for α-pinene alone can change estimated OA by up to 22% in some regions. Overall, we developed a novel systematic method for developing artifact-corrected SOA parameters for chamber studies and demonstrated the effects of these schemes in a global chemical transport model. We expect our results will lead to improved measurement-model agreement for OA.