Surface Ozone Concentration in the Presence of Oxides of Nitrogen

Abstract

Assuming a photochemical equilibrium with regard to the concentration of NO₂ in the polluted air, the following equation is obtained; where k₁ and k₂ are the rates of reactions of ozone respectively with NO₂ and NO; k_a, the rate of absorption of ultraviolet solar radiation by NO₂; φ, the quantum yield of NO₂ photolysis.
To examine the validity of this equa t i on, simultaneous measurements of ozone, NO₂, NO and the spectral intensity of the solar radiation (wave-length,370-395mμ) were done in April and May,1964, at the western suburb of Tokyo. The results showed that the concentrations of these constituents mostly ranged from 1 to 3 pphm. Although the observed ozone concentration on most of the days was about twice as high as the calculated value, there was a good parallelism between the diurnal variations of observed and calculated values. The discrepancy between observed and calculated ozone concentrations may be due to some uncertainties in the estimated values of constants in the above equation. If this discrepancy is disregarded, one can say that the concentration of ozone during most of daylight hours is controlled by the presence of oxides of nitrogen.