Ozone Depletion

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The World We CreateNATS 101Section 6
Turn in your Homework!
02/23
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Project 1
86.687.587.787.788.289.289.589.990
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UNIT 1
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UNIT 2 Environmental changes, Natural or
Man-Made?
UNDERSTANDING OZONE DEPLETION
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Ozone Layer
Last class we talked about the importance of the
Ozone Layer for life in our planet.
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95 penetrates
5 penetrates
0 penetrates
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Ozone Cycle Recap.
Natural destruction of Ozone UVB absorbed!
Lets analyze what you understood!
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The Ozone Cycle
UVB
GOALTo Model the Cycle of destruction an
formation of O3.
2 O3 ? 3 O2 3 O2 ? 2 O3
UVC

• Each small group will need
• 1 bag that includes
• Marsh mellows
• Gumdrops
• Tooth picks
• 1 white board per letter team.

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• If marsh mellows represent oxygen molecules, and
  tooth picks are chemical bonds

• Use these materials to model the cycle of
  destruction and formation of O3. You need to
  build a sequence of at least five 3D-frames
  (a single one of a series of still models)
  that shows the whole process.
• After your group is finished, let your TAs know.
  They will select a group that will draw the
  set of frames on a whiteboard to show to the
  rest of the class.

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UVB
2 O3 ? 3 O2 3 O2 ? 2 O3
UVC
You need at least 5 frames! One group will write
it on a white board for your team.
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The Natural Cycle
There is evidence that shows that pollutants
released by humans are interfering with this
cycle.
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An ozone hole?
Concern about thinning of the ozone layer over
Antarctica arose in the 1970s but it was not
monitored until in the 1980s
We know the amount of O3 is changing
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The Evidence
Cl
The presence of chlorine atoms Cl and ClO
molecules is inversely correlated with O3
concentration.
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Sources of chlorine

• Where are CFCs found?
• Foaming agents for plastics
• Solvents for cleaning
• Aerosol propellants
• Refrigerants
• Fire extinguishers

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CFCs are handy

• Nontoxic
• Not flammable
• Stable in the Troposphere? unreactive
• Many different forms so they have many
  different applications.

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Cl Action
UVC produces very reactive Cl atoms that affect
the natural cycle of O3 formation-destruction.
Cl 2 O3 ? 3 O2 Cl
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Cl Action

• If marsh mellows represent O, Gumdrops represent
  Cl, and toothpicks represent Chemical bonds
• Model how Cl atoms may be affecting the cycle of
  formation and destruction of O3. You need to
  build a sequence of four 3D-frames that show
  the effect of
• Cl atoms.
• Discuss why the action of Cl is SO problematic.

• After your group is finished, let your TAs know.
  They will select a group that will draw the
  set of frames on a whiteboard to show to the
  rest of the class.

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Cl 2 O3 ? 3 O2 Cl
Cl 2 O3

Cl 3 O2

The sequence should have at least 4 frames
(Including beginning and end)

• Hint ClO is formed in the process
• Discuss why the action of Cl is SO problematic.

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CFCs in the Stratosphere
CFCs take on average fifteen years to reach the
stratosphere, and they can remain in the
atmosphere for up to one hundred years.
However, once there, one single Cl. radical can
destroy over 100,000 ozone molecules!
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Cl Action
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The Effects

• The largest area of diminishing ozone has been
  documented in the stratosphere over Antarctica
  since the 1980s.

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What is happening in Antarctica?

• Here is a NASA movie of the ozone hole over
  Antarctica from July through December

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Average Size
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Size and Seasons

• This graph shows the area of ozone depletion
  in Antarctica.
• What is it telling us about the time of year when
  the area of ozone depletion is greatest?

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Artic vs. Antartic
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Why the Antarctic?

• What are these data telling us about the
  relationship between temperatures, seasons, and
  sunlight in the Arctic and Antarctica?

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Your Ideas

• In your groups discuss the relationships that you
  see among temperature, seasons, sunlight, and
  area of ozone depletion.

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Discussion

• How has the area of the ozone hole over
  Antarctica changed in the past 25 years?
• How does it change with seasons? How do you
  explain it?
• What differences do you observe between Antarctic
  ozone and Artic ozone? What may explain the
  difference?

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What has been done?
Ozone can be rebuilt if active pollutant agents
are eliminated from the atmosphere

• Legislation
• 1980s US banned the use of CFCs in aerosol
  cans
• 1987 Montreal Protocol? many nations agreed
  to stop use of CFCs and replace them with
  alternatives such as HCFCs
• Clean Air Act Amended to include Ozone
  Protection Program

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Recovery?

• Beginning of Ozone Recovery
• 15 years after decrease in CFC production
• 2005-2010

• Estimated ozone recovery Up to 100 years
  from 2006 2045-2060
• Estimate of the amount of ozone remaining
  58 /- 5

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Wrap-up How are they related?
Build as many connections between these concepts.
CLEARLY STATE THE CONNECTION USING A VERB OR
PHRASE.