A three‐dimensional modeling investigation of the evolution processes of dust and sea‐salt particles in east Asia

The evolution of sea‐salt and dust particles in East Asia is investigated using a three‐dimensional transport and chemistry model. A kinetic approach under thermodynamic constraint is utilized to model the condensation/evaporation processes, and other important aerosol processes and influential components (e.g., dust/sea‐salt generation, NH 3 emissions, gravitational settling, nucleation) are taken into account in this analysis. The model is used to study the Pacific Exploratory Mission‐West B period (March 1–6, 1994). It is found that (1) during strong continental outflow, in general, the fine aerosol mode (<2 μm in aerodynamic diameter) accommodates sulfate and ammonium and the cation‐rich coarse mode (>2 μm in aerodynamic diameter) attracts nitrate. However, in the dust plume, sulfate preferentially resides in the coarse mode due to larger coarse mode mass loading; (2) particulate nitrate coupled with particulate ammonium in the fine mode is predicted over regions where high gaseous NH 3 mixing ratios are present (lower courses of the Huang river); (3) dust and sea‐salt particles provide important reaction surfaces for sulfate production in the troposphere and increase sulfate production rates by 20–80%; and (4) soil dust and sea salt provide an important source of boundary layer and free troposhpere alkaline material, and these cations play an important role in controlling the partitioning of semivolatile HNO 3 throughout large portions of the troposphere, increasing particulate nitrate levels 10–50%.