Earth Chapman cycle

As described earlier, in the stratosphere, a steady-state concentration of 03 is produced naturally by the Chapman cycle, reactions (l)-(4). Until about 1970, relatively little attention was paid to potential anthropogenic (i.e., man-made) perturbations of the stratosphere. At that time, Crutzen (1970) examined the potential role of NO and N02 formed in the stratosphere from reactions of N20 that was originally generated at the earth s surface. Because N20 is unre-active in the troposphere, it has a sufficiently long lifetime to end up in the stratosphere, where it can be converted into NO (see Chapter 12). Crutzen (1970) proposed that the NO and N02 formed from reactions of N20 can then participate in a chain reaction that destroys 03 ... 

Terrestrial stratospheric chemistry is closely linked to the ozone (O3) layer at 15-35 km, which shields the Earth s surface from harmful UV sunlight (X<300 nm) and dissipates the absorbed solar energy as heat. The abundance of O3 in the stratosphere is a balance between production, destruction, and lateral transport. Production and destruction of O3 in the absence of other perturbing influences is described by the Chapman cycle given in Table V. 

Ozone is considered a pollutant when it forms near the surface of the earth in the troposphere. When it forms in the stratosphere as part of the Chapman cycle, however, it has the beneficial attribute of protecting the planet from harmful UV radiation. 

Gill, R. (1996) Chemical Fundamentals of Geology, 2nd edn. Chapman Hall, London. Vcizer, J. (1988) The evolving exogenetic cycle. In Chemical Cycles in the Evolution of the Earth, ed. by Gregor, C., Garrels, R.M., Mackenzie, F.T. Maynard, J.B., pp. 175-220. Wiley, New York. 

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