Studies of Behavior of Secondary Air Pollutants

Abstract

In the early 1990s, acid rain (acidification) became a serious issue after the background ozone issue. A hybrid model was developed by combining trajectory and Eulerian models in order to predict and assess the long-range transport of sulfur compounds. The hybrid model performed well in predictions at sites influenced by nearby sources. By participating in the planning and implementation of phases I and II of the model intercomparison study, MICS-Asia, differences among the participating models and their causes became apparent. Continuous monitoring of gaseous and particulate matter began in Komae, Tokyo, in order to understand actual behavior. The observed seasonality of gas–aerosol partitioning of nitrate was well interpreted by a thermodynamic equilibrium model, which suggested that the particles were internally mixed. The MM5/CMAQ modeling system showed that emission reductions in Greater Tokyo were effective to some extent for the mitigation of secondary inorganic aerosol and that the sensitivity differed with the seasons and places. Analysis of aerosol composition in Jeju, Korea, by the thermodynamic equilibrium model indicated that fine-particulate ammonium nitrate would increase there with the NO_x and ammonia emissions in East Asia. In Fukue, episodes that nss-sulfate increased before the dust aerosol were observed, but one of them was influenced by the volcanic plumes from Mt. Miyake.