Sensitivity Analysis of Primary Pollutants on Generating Photochemical Oxidants over the Osaka Bay and its Surrounding Areas of Japan

Abstract

In this paper an attempt has been made to elucidate the relationship between the formation of photochemical oxidants and the emission rate of the primary pollutants such as nitrogen oxides (NO_X) and reactive hydrocarbons (RH) over the Osaka Bay and its surrounding areas of Japan, by using a three-dimensional grid model. In Harima area, reduction in the primary pollutant emission led to simple decrease in the peak O₃ concentration, and OH and HO₂ radical concentrations. In Osaka area, unlike the Harima area, reduction in NO_X emission led to an increase in OH and HO₂ radicals concentrations, and conversely to an increase in O₃ concentration. It has also been found that the time of peak O₃ concentration would appear earlier with reduction in NO_X emission, and later with reduction in RH emission. Under meteorological calm condition, the variations of the time of appearance of peak O₃ due to the emissions reduction scenario are small. Sea breeze may be one of the important meteorological phenomena responsible for the transport of pollutants such as NO_X, RH, and also O₃ in the polluted coastal areas. These important results suggest that a method for a well-balanced reduction in both NO_X and RH emissions is essential for the improvement of air quality from photochemical pollution over the Osaka Bay and its surrounding areas of Japan.