Some characteristics of surface ozone concentration observed in an urban atmosphere

Some characteristics of surface ozone concentration were obtained from continuous observation, with time resolution of 1 s. These are compared with the concentrations of NO and NO2 and meteorological conditions which were observed simultaneously. The observed concentrations of O3 and NO showed a hyperbolic relationship approximately described as [O3]×[NO]=21.6 ppb2. This is consistent with a proposal that the photochemical reaction in the O3–NOx system was dominant in controlling the O3 concentration near the surface layer. An inverse linear relationship of [O3]+[NO2]=30 ppb is also recognized, and the background O3 concentration in the Nagakute area is estimated to be about 30 ppb from this relation. The yearly average background O3 concentration calculated from the equation for transportation by wind approximates the value obtained above. The positive dependency of O3 production on solar radiation and the negative relationships of NO2 concentration due to the NO2 photolysis process were recognized and both the dependencies on the solar radiation became very close during the winter season. The summer maximum cannot be explained by seasonal variations in the background O3 concentration the sensitivity to solar radiation intensity, and the photochemical reaction only in the O3–NOx system.