In predicting oxidants concentration, the most important fact is to select a suitable photochemical reaction mechanism. Sensitivity analysis of O3 and other important photochemical oxidants concentrations was conducted by using CBM-IV model. The predicted oxidants concentration was considerably related with the initial concentration of formaldehyde, [NO2]/[NO],NOx, RH and RCHO. As the initial concentration of formaldehyde increased, concentration of NO2 increased. O3 concentration was proportional to the [NO2]/[NO] ratio. When the initial concentrations of RH and RCHO were high, photochemical reaction was more reactive, including more rapid conversion of NO to NO2 and increased oxidants. Also, the sensitivities of ozone formation to rate constants, Kl,K2andK3 in the NO2 photolysis were studied.

The number of cases exceeding environmental standards of atmospheric ozone in the major cities in Korea has steadily increased during the past decades. In order to understand and analyze the atmospheric reactions in the atmosphere, especially the secondary photochemical reactions, smog chambers studies have been performed very actively by many research groups worldwide. However, these studies have focused on the mechanism of photochemical reactions in high concentration conditions, not at the ambient levels. Therefore, in-depth studies in these conditions are essentially needed to realize exact mechanism in the atmosphere near the earth surface, especially at Korean atmospheric conditions. In this experiment, the mechanism of photochemical smog was examined through a comparative experiment of smog chambers under sun light and black light conditions. The results of our study indicated that concentrations of ozone, aldehyde, and PAN increased as the radiation of light source increases. Photochemical reaction patterns can be considered quite similar for both black light and sun light experiments. Based on our experiments using toluene as a reactant which is present at significant high levels in ambient air relative to other VOCs, it was found that toluene could contribute notably to oxidize NO to NO2, this reaction can eventually generate some other photochemical oxidants such as ozone, aldehyde, and PAN. The results of simulation and experiments generally showed a good agreement quite well except for the case of O3. The restriction of oxidization of NO to NO2 seems to cause this difference, which is mainly from the reaction of peroxy radical itself and other reactants in the real gas.