13 2 The Ozone Shield Ozone is a

13. 2

The Ozone Shield Ozone is a layer of the stratosphere that absorbs UV light from the sun (like sunscreen).

Chemicals That Cause Ozone Depletion • CFC’s = chlorofluorocarbons • When these break apart in the ozone, they destroy parts of it.

• thinning of ozone during spring over the north and south poles • caused by cold temperatures and CFC’s

The Ozone Hole 2005 Ozone Layer Hole

How Does the Ozone Hole Form?

How Does the Ozone Hole Form? • During the dark polar winter, strong circulating winds over Antarctica, called the polar vortex, isolate cold air from surrounding warmer air. – Air within the vortex is extremely cold.

• Polar stratospheric clouds form at high altitudes. • composed of water vapor and nitric acid

On the surfaces of polar stratospheric clouds, the products of CFCs are converted to molecular chlorine

• When sunlight returns to the South Pole in the spring, molecular chlorine is split into two chlorine atoms by UV radiation. – The chlorine atoms rapidly destroy ozone.

Ozone from pollution may stay in the troposphere and react with other chemicals.

UV light damages DNA Effects of Ozone Thinning on Humans

Causes: increase in skin cancer

Premature aging of skin

Cataracts – clouding of the lens

Effects of Ozone Thinning of Animals and Plants

Kills phytoplankton and disrupts food chain

Kills amphibian eggs

Interferes with photosynthesis in plants

Protecting the Ozone Layer 1987 – Montreal Protocol Limits the use of CFCs

Review – The Ozone Shield 1. What is the ozone layer and what is its function? 2. What is ozone made up of? 3. What are CFC’s? 4. How do CFCs affect ozone? 5. What is the ozone hole? 6. What is a polar vortex? 7. Explain how does the ozone form? 8. Name 3 ways ozone thinning affects humans. 9. Name 3 ways ozone thinning affects plants and animals. 10. How are we protecting the ozone today?

Chemicals That Cause Ozone Depletion 1. CFC’s chlorofluorocarbons 2. When these break apart in the ozone they destroy parts of it. 3. Ozone Hole: thinning of ozone during spring over the north and south poles. (caused by cold temperatures + CFC’s) 4. Problems: damage to plant & animal life

How Does the Ozone Hole Form? • You may be thinking, “If ozone is also being produced as air pollution, why does this ozone not repair the ozone hole in the stratosphere? ” • The answer is that ozone is very chemically reactive. • Ozone produced by pollution breaks down or combines with other substances in the troposphere long before it can reach the stratosphere to replace ozone that is being destroyed.

How Does the Ozone Hole Form? • When sunlight returns to the South Pole in the spring, molecular chlorine is split into two chlorine atoms by UV radiation – The chlorine atoms rapidly destroy ozone. • The destruction of ozone causes a thin spot, or ozone hole, hole which lasts for several months.