Stratospheric Ozone Depletion and Reducing Ozone Depletion

Question 1

What is the importance of stratospheric ozone to life on Earth? What kind of ray does the ozone NOT protect Earth’s organisms from?

Answer 1

• Naturally occurring ozone (O3) provides protection from UVB-UVC rays (NOT UVA)

Question 2

What is causing stratospheric ozone depletion?

Answer 2

• melting of ice crystals in the atmosphere at beginning of Antarctic spring
• anthropogenic emission of chlorofluorocarbons (CFCs)

Question 3

What is the effect of stratospheric ozone depletion? What are the human health consequences?

Answer 3

• increases UV rays that reach Earth’s surface
• thinning of ozone layers (especially at the poles)
• exposure to UV rays can lead to skin cancer and cataracts in humans

Question 4

What is the process by which the crystals melting during antarctica spring cause ozone depletion?

Answer 4

1. Antarctic winters can create stratospheric clouds full of ice crystals
2. Crystals melt at the beginning of spring
3. Chemical reactions convert less reactive chlorine to a more reactive form
4. Chlorine degrades ozone into atmospheric oxygen (O2)
5. The ozone layer thins

Question 5

How does stratospheric ozone depletion impact organisms?

Answer 5

• disruption of terrestrial and aquatic (phytoplankton) photosynthesis (lower primary productivity): too much UV radiation affects chlorophyll
• disruption of food chains/webs
• impacts populations of some organisms like amphibians (sensitive to sun’s radiation, they lay eggs that have no shells in the water and UV harms the eggs)

Question 6

How can ozone depletion be reduced? Why are HFCs not the optimal solution? How can the harmful consequences of HFCs be mitigated?

Answer 6

• can be reduced by replacing ozone-depleting chemicals with substitutes that do not deplete the ozone layer (Montreal Protocol)
• HFCs (hydrofluorocarbons) are one such replacement, but some are strong greenhouse gases
• properly dispose of old refrigerators, air conditions, coolant systems through recycling programs or approved MSW recovery centers to prevent the release of HFCs

Question 7

Montreal Protocol

• What does the treaty entail?
• What is the goal of the treaty?
• Who signed the treaty?
• How successful was it?

Answer 7

• International treaty to eliminate the production of ozone-depleting substances
• Main goal: protect the stratospheric ozone layer by phasing out substances including chlorofluorocarbons (CFCs), halons, and carbon tetrafluorides
• signed by all members of the United Nations
• very successful