AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Simulation of Atmospheric Organic Aerosol Using Volatility-Oxygen Content during the PEGASOS Southern and Northern Europe Campaigns
ELENI KARNEZI, Benjamin Murphy, Spyros Pandis, Carnegie Mellon University
Abstract Number: 359 Working Group: Aerosol Chemistry
Abstract Two major field campaigns (under the PEGASOS project) took place in southern and northern Europe during the summers of 2012 and 2013. The campaigns characterized organic aerosol (OA) both at the ground with a combination of stationary and mobile measurements and aloft using a Zeppelin in two very different environments (Po Valley in Italy and Finland in Scandinavia) with different characteristics (e.g., industrial pollution, agricultural sources, clean environment with biogenic emissions, etc.). These measurements are used to evaluate and constrain the uncertain parameters of a Lagrangian chemical transport model (PMCAMx-Trj) that describes OA using a two-dimensional volatility basis set (2D-VBS). The OA module simulates the primary and secondary OA mass as a function of volatility and oxygen to carbon ratio (O:C).
For the polluted Po Valley atmosphere in Italy simulations suggest that anthropogenic secondary OA (SOA) from volatile and intermediate volatility organic compounds and biogenic SOA were the major OA components. PMCAMx-Trj reproduces reasonably well the OA concentrations and O:C for the ground, with an average predicted OA mass equal to 2.92 μg m-3 versus 2.9 μg m-3 observed and an average predicted O:C 0.63 versus 0.58 observed. Both PMCAMx-Trj and observations suggest relatively oxidized OA with little average diurnal variation.
The sensitivity of the PMCAMx-Trj predictions to the assumed organic compound vaporization enthalpy and homogeneous chemical aging schemes was examined. The sensitivity of the OA concentration and O:C to the vaporization enthalpy was surprisingly modest. This is due to the interplay between the gas-to-particle partitioning and the homogeneous gas-phase chemical aging rates. In general the higher vaporization enthalpies (around 100 kJ mol-1) were more consistent with the vertical OA and O:C profiles. The evaluation of the different aging schemes in the two environments will be discussed.