AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Simulation of the Volatility-Oxygen Content Distribution of Organic Aerosol during the PEGASOS Campaigns
ELENI KARNEZI, Benjamin Murphy, Spyros Pandis, Carnegie Mellon University
Abstract Number: 160 Working Group: Aerosol Chemistry
Abstract The two-dimensional volatility basis set (2D-VBS) is used for the simulation of the OA distribution as a function of its volatility and oxygen content. A one-dimensional Lagrangian chemical transport model (PMCAMx-Trj) is used as the host model for the simulations. PMCAMx-Trj simulates the chemical evolution of a column of air as it travels towards a user-selected receptor site. The Hybrid Single Particle Lagrangian Integrated Trajectory HYSPLIT model (Draxler et al., 2009) is used to calculate 72 h back trajectories arriving at the receptor sites in the heavily polluted from both industrial and agricultural sources Po Valley in Northern Italy. We evaluate different parameterizations of secondary organic aerosol formation and processing of the 2D-VBS with the measurements of OA collected in the PEGASOS field campaign using among other airborne measurements collected by a Zeppelin. The predicted vertical profiles of the OA concentration are rather sensitive to the evaporation enthalpy and the chemical aging mechanism. This state-of-the-art dataset allow us to constrain further the different parameterizations and mechanisms of OA chemical aging used in the 2D-VBS scheme. The simplest approach parameterizing the chemical aging of anthropogenic compounds assuming a reduction of volatility by one bin during every aging step accompanied by an increase of one or two oxygen atoms with an equal probability is the most successful. The model shows remarkable skill in reproducing the observations of quite oxidized OA with little diurnal variation in O:C during the day.