Stratospheric Ozone Formation

Question 1

Describe the importance of the atmosphere in the evolution of life

Answer 1

1. Initially H2/He (2nd atmosphere) formed from rock degassing
2. UV radiation damaging (skin cancer)
3. Photosynthetic organisms evolved due to increase in oxygen and ozone
4. Atmosphere provides a protective screen where live could not survive without

Question 2

Why is there an optimal altitude for oxygen production (graph)

Answer 2

See notes

• Negative exponential line for O2 conc
• Positive exponential line for photodissociation rate
• Point of bisection = optimum O atom production rate
• Y-axis labelled with altitude
• X-axid no label? check with Professor

Question 3

Why is there an optimal altitude for oxygen production

Answer 3

1. Concentration of O2 decreases with altitude as the total pressure also decreases (surely gases exist more at lower pressures? I am confused by this point)
2. More UV radiation the higher you go therefore O2 photodissociation rate will increase
3. Optimal altitude for O production

Question 4

Explain the Chapman mechanism for ozone formation

Answer 4

O2 -> O + O (wavelength less than 242nm - above arrow)
O + O2 -> O3 (M above arrow, third body, stabilisation, read up why)
O3 + O -> O2 + O2
O3 -> O2 + O (wavelength less than 1180nm - above arrow)

Question 5

Reconstructing the Chapman Cycle steady state analysis

Answer 5

• ** COVER *****
• Why is steady state analysis carried out
• What is it used for
• How do you do it
• Being able to understand it all
• Watch youtube video
• Chapman cycle graph too, and then having ability to plot ozone with changes in altitude
• Problems with the Chapman cycle producing 5 times more ozone in the ozone layer.