Air pollution by SO2 at Tonghua city is one of the serious air pollution problems in China. In order to investigate the characteristics of the air pollution and occurrence of high SO2 cencentration in this area, atmospheric SO2 concentration at ground level was examined by comparing simulation by diffusion models and observation, and the types of air pollution were classified with fuzzy cluster analysis.
(1) Fairly reasonable agreement on SO2 concentration was obtained between the simulation and observation (r2=0.65). The Hanna-Gifford and the Pasquill models were useful to estimate the ground surface concentration.
(2) The contribution of area-souces, e.g. low chimneys, to total ground surface SO2 concentration was about 77.1%, which clearly indicated the importance of air pollution from area-sources in this area.
(3) The highest SO2 concentration occurred under F-type of atmospheric stability (strong stable atmospheric condition) and SSW wind direction in cold period. These highest SO2 episodes occurred at the meshes of NO. 8, which is close to a power plant, and No. 29, which is densely populated with high consumption of coal.
(4) The difference between the maximum and minimum SO2 concentrations in a year was more than 13 folds.
(5) The characteristics of SO2 air pollution were classified into three types. Differences of the three types were based on the type of pollution sources, amount of coal consumption, and the difference between SO2 concentration in 1990 and that in 1993. This method of analysis was clearly useful to evaluate the types of the air pollution objectively and quantitatively.
