AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Improvement of Simulation of Fine Inorganic PM Levels through Better Descriptions of Coarse Particle Chemistry
ERICA TRUMP, Christos Fountoukis, Neil Donahue, Spyros Pandis, Carnegie Mellon University
Abstract Number: 316 Working Group: Aerosol Chemistry
Abstract Three-dimensional chemical transport model PMCAMx is updated to improve predictions for the mass and chemical composition of both fine- (PM1) and coarse- (PM10-1) mode particles. ISORROPIA II is used in the new model to extend the inorganic thermodynamic system to the reactive dust constituents Ca2+, K+, Mg2+. The hybrid mass transfer method is used allowing for the dynamic calculation of mass transfer to coarse-mode particles while maintaining computational efficiency by assuming that the fine-mode particles are in equilibrium. The resulting model is applied to Europe and evaluated for the period of May 2008 against ground-based and airborne Aerosol Mass Spectrometer measurements from the EUCAARI campaign.
Earlier implementations of PMCAMx for Europe used a bulk-equilibrium approach to calculate mass transfer to all particles. This approach was able to predict PM1 OA and sulfate concentrations quite well [Fountoukis et al., 2011]. However, the simulations had difficulties in reproducing the observed PM1 nitrate concentrations for locations in which there were relatively high coarse-mode particle concentrations (significant sea-salt or dust concentrations). This shortcoming was apparent for the Mace Head site in Ireland, where a large amount of nitrate is associated with sea-salt, as well as for sites in the Eastern Mediterranean where Saharan dust has a strong presence. The improved simulation of the coarse-mode particle chemistry and dynamics results in significant improvement of the predictions of PM1 nitrate and ammonium, particularly in locations having significant amounts of sea-salt or dust.
References
Fountoukis et al., Atmospheric Chemistry and Physics 2011, 11, 10331-10347