AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Evaluation of Organic Aerosol Production and Chemical Aging Modeling Schemes against Ground and Airborne PEGASOS Campaign Measurements
ELENI KARNEZI, Benjamin Murphy, Spyros Pandis, Carnegie Mellon University
Abstract Number: 500 Working Group: Aerosol Chemistry
Abstract We simulate the atmospheric organic aerosol (OA) using its volatility-oxygen content distribution (2D-VBS) during the two PEGASOS campaigns in the Po Valley in Italy during 2012 and Hyytiälä, Finland during 2013. Extensive measurements were performed both at the ground and aloft with a Zeppelin. Po Valley has major air quality problems due to industrial and agricultural sources and Hyytiälä is characterized by high biogenic secondary OA (SOA) levels. Seven aging schemes with different assumptions about functionalization, biogenic SOA aging, and fragmentation were found to reproduce well the ground and Zeppelin O:C and OA measurements. In the Po Valley, anthropogenic SOA from VOCs was predicted to contribute between 15 and 25% of the total OA and SOA from the oxidation of intermediate volatility compounds oxidation between 20 and 35%. The contribution of biogenic SOA varied from 15 to 45%, depending on the parameterization scheme. Primary OA (POA) was around 5%, the OA from long range transport varied from 6 to 8% and the SOA from evaporation of the primary and subsequent oxidation from 7 to 11%. These results are encouraging because despite the uncertainty introduced by the different schemes, their predictions about source contributions are relatively robust. Assuming significant later generation net bSOA production resulted in overpredictions of the OA. There was also surprising low sensitivity of predicted OA concentration and O:C to enthalpy of vaporization.
Despite the very different environment, the performance of all seven parameterizations was surprisingly similar in the boreal forest atmosphere. Despite their differences, the seven schemes predicted once more similar OA composition: 40-63% biogenic SOA, 11-18% SOA from anthropogenic VOCs, 14-27% SOA from IVOCs, 4% POA, 4-6% SOA from evaporated POA, and 5-6% from long range transport. This agreement is encouraging about our ability to constrain the SOA sources.