The sulfur dioxide concentration has been measured in the outskirts of Seoul （KAERI） since 1976, and the accumulated data have been statistically analyzed to modify the simple urban air pollution model developed by Gifford and Hanna.
The dispersion of the effluents in the air depends on the meteorological characteristics and topographical factors in an area. The sulfur dioxide concentration increases due to decreases in the mixing effect of the atmosphere in accordance with the deepening of the inversion and may travel over 5 to 20 km from the source. The mixing height is usually lowest before sunrise and highest in late afternoon, while the concentration of sulfur dioxide peaks at about 1 or 2 hours after sunrise and is lowest before sunset.
The modified urban air pollution model, χ=（μg/㎥）=55(F/S)^0.58(γ·Q/U) seems to give a correct prediction of annual average concentration from the two meterological factors, wind direction and the frequency of calm. It was also assumed that the predominant emission sources are located in the west to southwest region of Seoul.