Atmospheric photochemistry of O3-NOX-RH were considered theoretically, to clarify the reasons for the different trends of between the formation of photochemical oxidants (OX) and its primary pollutants for the Low- and High-NOX regimes. Equations of OH, HO2, and production of ozone (O3) as a function of nitrogen oxides (NOX) and reactive hydrocarbons (RH) were represented in this study. For the Low-NOX regime, HO2 radical is proportional to RH but independent of NOX. OH radical is proportional to NOX but inversely-proportional to RH. O3 production is proportional to NOX but has a weak dependence on RH. For the High-NOX regime, OH and HO2 radicals concentrations and O3 production are proportional to RH but inversely-proportional to NOX. In addition, the Osaka Bay and surrounding areas of Japan were evaluated with the mass balance of odd-hydrogen radicals (Odd-H) using CBM-Ⅳ photochemical mechanism, in order to distinguish the Low- and High-NOX regimes. The Harima area (emission ratio, RH/NOX = 6.1) was classified to the Low-NOX regime. The Hanshin area (RH/NOX = 3.5) and Osaka area (RH/NOX = 4.3) were classified to the High-NOX regime.

In this study, characteristics of fog at Mokpo as the west coastal area of Jeonnam were investigated, using statistical analysis of observed fog and meteorological data. Higher frequency of the fog occurrence at Mokpo was showed in spring(32%) and summer(34%) due to the seasonal high atmospheric pressure. Regional characteristics as radiation cooling, advection of fog and water vapor from surrounding sea and Yeongsan lake, and frontal fog had major effect on the coastal fog at Mokpo on the meteorological conditions of north-west/south wind and calm(0～2m/s). Also, as the results of analyzing data of before and after the construction of Yeongsan dam, the frequency of annual mean fog days increased 41%, specially increased 178% in autumn. The increase of fog days mainly resulted from evaporation during colder seasons and from temperature inversion during warmer seasons over the water surface of Yeongsan lake. The construction of Yeongsan dam had a little effect on the meteorological conditions concerning fog occurrence, because Yeongsan dam which only supplies the water for use do not always carry out outlet of the cold water. In addition, the sea fog at Heuksando located in offshore had not effect on the occurrence of fog at Mokpo.