atmosphere: a mixture a gases that surrounds the planet Earth.

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Marcia Bridges
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1 atmosphere: a mixture a gases that surrounds the planet Earth. 78% nitrogen 21% oxygen the atmosphere is held to the Earth by the force of gravity. Due to the smaller mass of planets like Mercury, less atmosphere can be held in place. Thinner atmosphere means less insulation. Therefore, Mercury has greater temperature extremes (840 to 275 Fahrenheit) Brewer 1

Consider the planet Venus approximately the same size and mass as Earth

temperatures are never below 750 Fahrenheit Consider Uranus gas giant

Fahrenheit Note how much larger Uranus is than the Earth.

2 Consider the planet Venus approximately the same size and mass as Earth 96% of the atmosphere is composed of the greenhouse gas carbon dioxide. temperatures are never below 750 Fahrenheit Consider Uranus gas giant with thick clouds of deadly methane gas temperatures average 360 Fahrenheit Note how much larger Uranus is than the Earth. What effect would the relative size of Uranus have on the total atmosphere of the planet? Brewer 2

3 The relative thickness of the Earth's atmosphere to the rest of the Earth can be compared to the skin of an apple compared to the rest of an apple Brewer 3

4 ES 2.1: The Thin Blue Blanket The Earth's atmosphere becomes thinner with increasing elevation. This is due to a decrease in the force of gravity with increasing distance from a center of mass (i.e. center of the Earth) mountain climber w/ O 2 tank warm clothing due to low temperatures caused by thinning atmosphere Brewer 4

5 The Ozone Shield a Natural Sunscreen Recall approximately 21% of the atmosphere is O 2 O 2 molecules can be split by ultraviolet light and lightning. These free O atoms then combine with other O2 molecules to form ozone, O 3 Molecule Building activity Brewer 5

6 Brewer 6

7 The Ozone Shield a Natural Sunscreen Ozone is measure in parts per million (ppm) by volume The cycle of ozone creation (UV light) and destruction (nitric oxide) is continuous and natural. Ozone formation depends on the amount of UV light and temperature Equilibrium is achieved when the rate of creation equals the rate of destruction of ozone. Ozone depletion occurs when the rate of destruction is greater than that of creation. Brewer 7

8 CFCs The Risks and Benefits of Technology Beginning in the 1970's, scientists began to study the effect of chemicals produced by human activities on the ozone shield Paul Crutzen discovered that nitrogen oxides from supersonic jets could damage the ozone layer. Brewer 8

Environmental Science chlorofluorocarbons (CFC's): compounds containing carbon, fluorine, and chlorine that can destroy the ozone layer Characteristics of CFC's: 1) nontoxic 2) nonflammable 3)

9 Environmental Science chlorofluorocarbons (CFC's): compounds containing carbon, fluorine, and chlorine that can destroy the ozone layer Characteristics of CFC's: 1) nontoxic 2) nonflammable 3) inexpensive to produce When CFCs meet Ozone.mpeg Used as a replacement coolant in refrigerators and air conditioners because the methyl chloride used was toxic. Extremely stable in the troposphere, where UV light splits chlorine from CFC's. A single Cl atom can then destroy 100,000 ozone molecules. CFC's eventually return to the lower atmosphere and are washed out by rain. Brewer 9

10 Ozone Reactions Formation of Ozone O 2 + UV light > O + O O + O + 2O 2 + catalyst > 2O 3 Net: 3O 2 > 2O 3 Natural Destruction of Ozone O 3 + NO > O 2 + NO 2 O 3 + UV light > O 2 + O NO 2 + O > NO + O 2 Net: 2O 3 > 3O 2 Ozone Accumulation 3O2 > 2O3 3O2 < 2O3 3O2 <> 2O3 Brewer 10

11 CFC's Attack on Ozone Reaction CFCl 3 + UV light > CFCl 2 + Cl Cl + O 3 > ClO + O 2 O 3 + UV light > O 2 + O ClO + O > Cl + O 2 Cl + O 3 > ClO + O 2 Result 2O 3 > 3O 2 Brewer 11

Biological Effects Ozone protects life from harmful UV (black light) UV types (by wavelength) UV A: necessary for synthesis of vitamin D in the skin UV B: causes aging of the skin, skin cancers,

12 Biological Effects Ozone protects life from harmful UV (black light) UV types (by wavelength) UV A: necessary for synthesis of vitamin D in the skin UV B: causes aging of the skin, skin cancers, cataracts, and may impair immune system response not necessary for photosynthesis, and can be harmful to plants and microbes plants become more susceptible to insects and pathogens UV C: most deadly form of UV, but absorbed by ozone and oxygen in atmosphere Brewer 12

13 Environmental Science Biological Effects CO2, H2O, nutrients and heat are factors in how much effect UV radiation will have on plants UV may also reduce the rate of photosynthesis of phytoplankton in the ocean. Frog eggs and coral reefs are also sensitive to UV light and interferes with their development. Marine ecosystems near the poles experience the greatest effects. Brewer 13

Warning Not Heeded Scientists first discovered the link between CFC's and ozone depletion in 1974.

, Canada, and others banned the use of CFC's in aerosols Although other sources existed at that time,

Presently, the ozone is being destroyed at a faster rate than it is being produced.

14 Warning Not Heeded Scientists first discovered the link between CFC's and ozone depletion in In 1977 the U.S., Canada, and others banned the use of CFC's in aerosols Although other sources existed at that time, industry lobbyists enticed politicians to allow industrial use of CFC's. Presently, the ozone is being destroyed at a faster rate than it is being produced. Ozone depletion is greatest over Antarctica. During the spring, Antarctica's unique weather patterns further the depletion. Contrary to popular belief, there is no physical "hole" in the ozone; rather, the ozone layer is very thin in these regions. Brewer 14

15 The Montreal Protocol The major cause of ozone destruction is chlorine from CFC's Solutions: 1. Stop production of CFC's 2. Prevent the release of CFC's in the atmosphere Protocol now seeks total elimination of CFC's The global nature of ozone requires international cooperation in order to provide protection Ozone will not return to pre 1980 levels until Brewer 15

Finding Alternatives CFC's are banned in industrialized countries exceptions: when no other option is available Developing countries still use CFC's Recycled CFC's can be used for equipment High cost

16 Finding Alternatives CFC's are banned in industrialized countries exceptions: when no other option is available Developing countries still use CFC's Recycled CFC's can be used for equipment High cost of replacements encourages illegal use of CFC's HCFC's are less stable and fewer molecules reach the atmosphere production must stop by 2030 replacement chemical must be: CFC molecule 1. nonflammable 2. noncorrosive 3. low toxicity 4. reasonably priced HCFC molecule Halons are used in fire exstinguishers replacement by CO 2 CO 2 only works for certain kinds of fires CO 2 weighs more (impractical for airplanes) Brewer 16

17 What You Can Do Recycle your refrigerants (don't forget your car) Avoid the sun between 10 and 3 Use sunscreen that blocks UV A and UV B Wear sunglasses that block UV radiation Brewer 17

18 Attachments When CFCs meet Ozone.mpeg

STRATOSPHERIC OZONE DEPLETION. Adapted from K. Sturges at MBHS

STRATOSPHERIC OZONE DEPLETION. Adapted from K. Sturges at MBHS STRATOSPHERIC OZONE DEPLETION Adapted from K. Sturges at MBHS Ozone Layer Ozone is Good up high Stratosphere Bad nearby Troposphere Solar Radiation - range of electromagnetic waves UV shortest we see if