Evaluation of Seven Chemical Aging Modeling Schemes with the 2D-VBS Framework Against Ground and Airborne PEGASOS Campaign Measurements

The 2D-VBS framework describing the organic aerosol (OA) distribution as a function of its volatility and O:C is used in PMCAMx-Trj, a one–dimensional Lagrangian chemical transport model. The model is used to simulate the atmospheric OA during two PEGASOS campaigns in the Po Valley in Italy during 2012 and in Hyytiala, Finland during 2013. Po Valley is an area with many industrial and agricultural sources and Hyytiala is characterized by high biogenic secondary OA (SOA) levels. The simulations are evaluated with AMS measurements both at the ground and aloft with a Zeppelin airship. There were seven aging schemes with different assumptions about functionalization, biogenic SOA aging, and fragmentation that succeeded in reproducing the AMS measurements within measurement error. For all seven schemes, the assumed enthalpy of evaporation had a surprisingly small effect on the diurnal and vertical profiles of O:C and OA concentration. Even if the seven schemes have relatively different characteristics and assumptions, all provide a rather similar picture about the different sources and processes contributing to the total OA in these two very different areas.