Abstract
Photochemical oxidant (Ox) is one of the most remarkable pollutants in Japan. Ox concentration more than twice as high as the environment standard is often observed in the big cities. In this study, a two-layer box model which divided into the upper-and lower-layer on the basis of the upper surface of mixing layer, combining with Carbon Bond Mechanism IV was developed to investigate the relationship between Ox generation and emission intensity of primary pollutants, such as nitrogen oxide (NOx) and hydrocarbon (HC). In the box, the composure to ventilation, surface deposition process and air pollution emissions are taken into consideration. The pollutant concentration of a typical summer day with active photochemical reactions for three areas (A: 44 km×44 km, B: 27 km×27 km, C: 26 km×33 km) set up in Hyogo and Osaka regions was calculated. The calculated concentration with emission sources reasonably agreed with spatial average of observed data. The simulation analysis suggested that ozone (O3) concentration decreased with reduction of HC emission. For example, O3 concentration decreased 40 ppb with 50% reduction of HC emission in C-BOX. Among HC, xylene was the most effective one for decrease in O3 generation. However, with increase in reduction of NOx emission, it was suggested that 03 concentration increased above the uncontrolled value before it decreased.
