Chapman oxygen-only mechanism

The simplest model for considering the stratospheric ozone layer is the Chapman oxygen-only mechanism (Figure 7.11), which describes the reactions steady-state ozone concentration as resulting from a... 

The chemistry of the stratospheric ozone will be sketched with a very broad brush in order to illustrate some of the characteristics of catalytic reactions. A model for the formation of ozone in the atmosphere was proposed by Chapman and may be represented by the following "oxygen only" mechanism (other aspects of... 

This simple oxygen-only mechanism consistently overestimates the O3 concentration in the stratosphere as compared to measured values. This implies that there must be a mechanism for ozone destruction that the Chapman model does not account for. A series of catalytic ozone-destroying reactions causes the discrepancy. Shown below is an ozone-destroying mechanism with NO/NO2 serving as a catalyst ... 

The chlorine not only destroys the ozone that is produced from reaction (2) in the Chapman mechanism, but it also inhibits the formation of ozone by sequestering oxygen atoms in the form of chlorine monoxide (CIO). Under certain meterological conditions the CIO is itself stored in the form of chlorine nitrate, to be re-released when the meterology changes. This is what makes the ozone depletion process so effective in forming the antarctic ozone hole, for example. 

Chapman (1930a, b) showed successfully that the characteristics of the height of the ozone layer and ozone density in the earth s atmosphere can be described by assuming only oxygen is present as a reactive species in the atmosphere, and this reaction scheme is called pure oxygen theory or Chapman mechanism. Photolysis of O2 occurs by the solar radiation of wavelength shorter than 242 nm (see Sect. 4.3.1). Only the photolytic process. 

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