For the purpose of understanding the photochemical reactions of polluted air, continuous observation of NO, NO₂and ozone were carried in Nagakute, the suburban area of Nagoya, using fast spectroscopic instruments by which fluctuations in trace gas concentrations due to weather changes were easily detected.

An inverse proportional relation between the surface ozone concentration and simultaneous measured NO density was observed, and NO_x was found to participate in the ozone formation and consumption process near the ground. A potential ozone (PO) concentration about 30 ppb was obtained from the relationships between ozone and NO₂ concentration. On the other hand, using the one dimensional transportation equation for ozone creation and consumption, the background ozone concentration was estimated to be 30.4 ppb from the relationship between the ozone concentration and the wind velocity; this value was equal to the PO concentration. It was then considered that the ozone concentration over a wide area around Nagakute throughout the year was about 30 ppb. Particularly in summer, the PO concentration was estamited to be 50 ppb, close to an environmental standard, and it became clear that the standard achievement is not easy.

The distribution of the concentration between ozone and NO slightly deviated from inverse proportional relationship. In order to investigate the cause, a one-dimensional simulation of the photochemical reaction was done and the influence of hydrocarbons on the ozone formation was found . In the ozone formation, NO_x plays the main role, however, the influence of hydrocarbons was considered to also be an overlapping formation process.