Ozone in the Stratosphere - Formation and Destruction

  • In an unpolluted stratosphere, the production and destruction of O3 are in balance, and hence the concentration of O3 remains constant with time
  • When CFCs are released into the lower troposphere, they diffuse up into the stratosphere since their lifetime is 50-100 years
  • When the CFCs reach the middle stratosphere, UV radiation liberates the chlorine atom:
    • CFC + UV --> Cl
  • Cl is then able to destroy as many as 100,000 O3 molecules before it is itself destroyed

Production = Destruction

O+O2+M --> O3

O3 + UV -->> O + O2 or O3 + O --> 2O2 or O3 + O3 --> 2O2

Production < Destruction

Cl + O3 --> ClO + O2

ClO + O --> Cl + O2