AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Modeling SOA Formation in Mixed Anthropogenic Biogenic Plumes
MANISHKUMAR SHRIVASTAVA, Jerome Fast, Alla Zelenyuk, John Shilling, Chen Song, Richard Easter, Qi Zhang, Rahul Zaveri, Ari Setyan, Pacific Northwest National Laboratory
Abstract Number: 475 Working Group: Aerosol Chemistry
Abstract During the Carbonaceous Aerosols and Radiative Effects Study (CARES) conducted in June 2010 near Sacramento, a suite of ground based and aircraft instruments measured organic aerosol (OA) in mixed anthropogenic-biogenic plumes and also in relatively non-mixed conditions depending on ambient winds. In this study, we investigate the ability of the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) to simulate secondary organic aerosol (SOA) formation. We investigate challenges in representing either anthropogenic or biogenic SOA formation using the volatility basis set (VBS) approach. These include poorly constrained SOA precursor emissions, gas-phase aging parameterizations which have excluded fragmentation reactions, non-representative SOA yields measured in smog chambers, and our previous findings which suggest it rapidly transforms into a non-volatile and non-absorbing semi-solid due to particle phase processes as oligomerization. We show that before investigating the nature and magnitude of recently proposed anthropogenically enhanced biogenic SOA formation, models need to better constrain the individual contributions of anthropogenic and biogenic SOA in non-mixed plumes. After constraining our SOA model in regions dominated by either anthropogenic or biogenic SOA, we investigate the expected synergistic effects between anthropogenic and biogenic SOA formation in mixed plumes. In addition, we explore some additional mechanisms for enhanced biogenic SOA formation depending on VOC and NOx levels and peroxy radical chemistry, mainly related to anthropogenic emissions. We conduct model sensitivity to different OA mechanisms and evaluate the spatial and temporal variation of simulated OA against ground-based and aircraft measurements. We also investigate the role of delta OA to delta CO ratios which have been used to compare SOA formation in previous studies.