Impact of emission changes on secondary inorganic aerosol episodes across Germany

In this study, the response of secondary inorganic aerosol (SIA) concentrations to changes in precursor emissions during high PM10 episodes over central Europe in spring 2009 was investigated with the Eulerian Chemistry Transport Model (CTM) REM-Calgrid (RCG). The model performed well in capturing the temporal variation of PM10 and SIA concentrations and was used to analyse the different origin, development and characteristics of the selected high PM10 episodes. SIA concentrations, which contribute to about 50% of the PM10 concentration in northwestern Europe, have been studied by means of several model runs for different emission scenarios. SO2, NOx and NH3 emissions have been varied within a domain covering Germany and within a domain covering Europe. It was confirmed that the response of sulfate, nitrate and ammonium concentrations and deposition fluxes of S and N to SO2, NOx and NH3 emission changes is non-linear. The deviation from linearity was found to be lower for total deposition fluxes of S and N than for SIA concentrations. Furthermore, the study has shown that incorporating explicit cloud chemistry in the model adds non-linear responses to the system. It significantly modifies the response of modelled SIA concentrations and S and N deposition fluxes to changes in precursor emissions. The analysis of emission reduction scenario runs demonstrates that next to European-wide emission reductions additional national NH3 measures in Germany are more effective in reducing SIA concentrations and deposition fluxes than additional national measures on SO2 and NOx.