Photochimie de l'ozone dans la stratosphère sous l'action des oxydes d'azote et des composés de l'hydrogène

The nature of the minor constituents which may have a controlling effect on the stratospheric ozone is discussed and the results of calculation are given. It is shown that there is practically no direct action on the ozone molecules as it is always assumed. All reactions involve atomic oxygen in photochemical equilibrium with ozone. A catalytic destruction of ozone by water vapor occurs through reactions of hydroxyl and hydroperoxyl radicals produced in the oxidation of H2O by excited oxygen atoms O(1D). With mixing ratios greater than 3 ppmv, water vapor represents a significant ozone-destroying agent in the upper stratosphere. The catalytic destruction by nitrogen oxides requires a concentration of NO2 molecules greater than 109 cm-3 above 25 km. Injection of water vapor and of nitric oxide at stratospheric levels will have a controlling effect on the ozone concentration in the upper stratosphere if it leads to mixing ratios greater than 3 ppmv and 3 ppbv for H2O and NO2, respectively. In the lower stratosphere (< 25 km) dynamic considerations must be introduced since there is a complete departure from photochemical equilibrium conditions which require several years.Nicolet Marcel. Photochimie de l'ozone dans la stratosphère sous l'action des oxydes d'azote et des composés de l'hydrogène. In: Bulletin de la Classe des sciences, tome 57, 1971. pp. 935-956