AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Modeling Biogenic Secondary Organic Aerosol (BSOA) with CMAQ: A Case Study of the SOAS Campaign
Momei Qin, PETROS VASILAKOS, Christopher Boyd, Nga Lee Ng, Armistead G. Russell, Athanasios Nenes, Georgia Institute of Technology
Abstract Number: 174 Working Group: Effects of NOx and SO2 on BVOC Oxidation and Organic Aerosol Formation
Abstract Biogenic secondary organic aerosol (BSOA) has important impacts on climate and air quality, particularly in locations with high biogenic volatile organic carbon (BVOC) emissions. In this work, summertime BSOA formation was simulated using the Community Multi-scale Air Quality (CMAQ) model, with a focus on the Southeast United States during the Southern Oxidant Aerosol Study (SOAS) campaign. We utilize an extended version of CMAQ, that includes the mechanism for the formation of IEPOX-derived SOA (Pye et al. 2013), further constrained with the 2013 SOAS observations by adjusting the highly uncertain reaction rate constants, partitioning coefficients and deposition coefficients of the relevant species (Vasilakos et al. 2016).
In the revised model update, we incorporate SOA yields of monoterpenes+NO3 reactions based on recent experimental results (Boyd et al., 2015), with a modified representation of BSOA production from individual monoterpenes. As a result, monoterpene-derived BSOA is enhanced by ~60% during the nighttime, exhibiting a strong correlation with less-oxidized oxygenated OA (LO-OOA), although the model concentration was still biased low. After implementing the multigenerational oxidation scheme, the simulated OA was similar to the observations, suggesting that important sources are missing in the current model. Sensitivity tests were also conducted to predict the response of BSOA to reduction in NOx and SOx emissions in the future.
The simulations validated the fact that isoprene-derived SOA is mediated by the abundance of sulfate, while LO-OOA is controlled by monoterpenes reacting with the nitrate radical (NO3) during the nighttime, consistent with the main findings of the SOAS campaign.