Abstract
Strong atmospheric acidity primarily caused by high SO2 emissions was found to be responsible to a serious air pollution in China from our previous study. It was indicated that the aerosol H+ concentrations so-called net aerosol acidity at entirely distant sites were very different from each other, probably due to local site influences such as topography, distance from the source regions, i.e. transport of atmospheric acidic pollutants, and local neutralizing capacity of the air mass. The high atmospheric acidity was determined at a rural site located inabout 150 km downwind of the densest area of SO2 emissions in U. S. A., moreover the neutralizing capacity of the air mass was insufficient. In recent years, attention has been focused on acid aerosols and their potential health effects. Some significant laboratory researches had been done and reviewed. Four-step risk assessment, i.e., hazard identification, doseresponse estimation, exposure assessment and risk characterization was also emphasized in the review. However, the knowledge of acid aerosols has continued to grow at a slow pace in Japan and has been scarecely studied, especially for wintertime since the acid aerosol pollution phenomenon was difficult to be observed during the season. Furthermore, the causes introducting high aerosol acidity in Japan may be different from U. S. A. in type and intensity of emission sources and/or weather conditions, etc. Therefore, in order to propose an abatement strategy for acid aerosols in Japan and to estimate their risk, the systematic measurements and data accumulation of ambient aerosol acidity and its source apporionment are necessary. In this report, the first results on levels and distributions of ambient aerosol acidity were presented from a short-term field investigation at South-Kanto Area in early wintertime of 1990 when the weather conditions were being dominated by widespread stagnation. Although the behavior and source apportionments of ambient aerosols at two sampling sites of Urawa and Kanda were briefly discussed using a chemical mass balance method (CMB), here we present the spatial distributions of ambient aerosol acidity and its relationship with local emission sources over all sites.
