Stratospheric Ozone Depletion

Chapman Reactions

Ozone is naturally created and destroyed by the following set of reactions:

 

 

 

 

 

 

 

 

These reactions, proposed by Sydney Chapman in 1930, explain the presence of ozone in the stratosphere. Oxygen molecules can be photolysed by UV radiation to form oxygen radicals in reaction 1. In reaction 2, these reactive oxygen radicals can combine with a oxygen molecule to form ozone. The M in this reaction is any third molecule: M absorbs the heat from this reaction. The increasing temperature profile of the stratosphere results from this reaction. In reaction 3, ozone is destroyed by UV light to form an oxygen radical and an oxygen molecule. Ozone can also be destroyed by combination with a radical, as seen in reaction 4.

 

 

 

 

CHE244

O2 + UV(<242nm) -> O + O

(1)

O + O2 + M -> O3 + M

(2)

O3 + UV/visible -> O + O2

(3)

O3 + O -> O2 + O2

(4)