Modelling the formation and atmospheric transport of secondary inorganic aerosols with special attention to regions with high ammonia emissions

Regional simulations of sulfate, nitrate and ammonium aerosols were performed by a nested application of the online-coupled three-dimensional Eulerian model system COSMO-MUSCAT. This was done in a domain covering the northern part of Germany and surrounding regions for the full month of May and a 6-week period in August/September 2006 with the primary focus on secondary inorganic aerosol levels caused by ammonia emissions from domesticated animals and agricultural operations.The results show that in situations with westerly winds ammonium nitrate dominates with concentrations of about 5–10 μg m−3 whereas the ammonium sulfate concentrations are about 5 μg m−3. In situations with winds mainly from the East characterized by warmer and dryer air the ammonium sulfate concentrations have their maximum at about 10 μg m−3 whereas at the same time no ammonium nitrate is present.A reduction of agricultural NH3 emissions by 50% in a regional scale reduces the ammonium nitrate concentrations to a maximum of 30%, while the ammonium sulfate concentrations are unchanged. The reduction of NH3 emissions in a more limited area (here in the Federal state of Germany Niedersachsen) does have no noticeable effect neither on ammonium sulfate nor on ammonium nitrate.