Athens air quality and importance of biogenic emissions: a case study

Two three dimensional Eulerian air quality models, PMCAMx and UAM-AERO are used to
predict the concentrations of various pollutants in the Greater Athens Area (GAA) during the
episode of June 22-26, 2003. The predicted levels of gases and aerosol pollutants are
compared with measured concentrations from monitoring stations, in order to evaluate the
performance of the models. Comparison of the results reveals that PMCAMx simulated the
ozone diurnal pattern better than UAM-AERO, as the predicted by UAM-AERO maximum
daytime concentrations were much higher than those of PMCAMx and way above the
measured ones. PMCAMx also shows signs of superiority in terms of its ability to predict the
NO2 and NO concentrations. Two sets of simulations, one with both anthropogenic and
biogenic emissions and one without biogenic emissions were performed. Comparison of the
two simulations reveals the important role that biogenic emissions play in the formation of O3,
NOx and secondary aerosols. Additional simulations with PMCAMx show that the
concentrations of all the pollutants depict a highly non-linear behaviour, when anthropogenic
VOC emissions are reduced in the GAA.