Results of an extended version of the three-dimensional Eulerian Mesoscale Transport, Chemistry, and Stream Model (METRAS) for simulating size-segregated inorganic aerosols are presented. The extended version of METRAS includes aerosol transport by advection, diffusion, gravitational settling, and dry deposition. Aerosols are produced by homogeneous nucleation and by sea spray. They are modified by condensation and evaporation of inorganic aerosol precursor gases. Altogether, 73 inorganic and organic gas species are treated in the model by taking into account transport, deposition, emissions, and gas-phase reactions. The model is applied to simulate the mixing of marine and continental air in the coastal atmosphere over the German Bight. The simulation results give evidence for the importance of the uptake of nitric acid and ammonia by sea-salt aerosol for the dynamics of nitrogen compounds in the coastal atmosphere. As a result of the mixing of polluted continental air masses with marine air masses, the pH of the sea-salt aerosol reaches values as low as pH=2.1. ¿ 1999 American Geophysical Union