Unit 5 b ch 13 s2 the ozone shield


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Unit 5 b ch 13 s2 the ozone shield

  1. 1. Chapter 13, Section 2: the ozone shield Standards: SEV4f ATMOSPHERE & CLIMATE CHANGE
  2. 2. • An area in the stratosphere where ozone is highly concentrated. • Ozone (O3) absorbs most of the UV light that comes from the sun. WHAT IS THE OZONE LAYER?
  3. 3. Chlorofluorcarbons (CFCs) • When first invented, were valued because they are • Nonpoisonous • Nonflammable • Do not corrode • Were used for decades as • Coolants in refrigerators & air conditioners • Component of Sytrofoam • Propellant in hair spray, deodorant, insecticides & paint • In 1970’s it was discovered they may be damaging the ozone layer. WHAT CHEMICAL IS ATTRIBUTED WITH CAUSING OZONE DEPLETION?
  4. 4. • At ground level, CFCs are stable & do not cause problems. • When air currents carry them to the stratosphere they can deplete the ozone. • Takes 10-20 years for the CFC’s to make it to the stratosphere and they get recycled while they are up there so they are persistent for 60-120 years • UV light from sun breaks CFC which releases a chlorine atom. • The chlorine atom breaks a molecule of ozone (O3) into an O2 molecule and an oxygen atom (O) which the chlorine attaches to and creates chlorine monoxide (ClO) • Chlorine monoxide (ClO) hits another ozone and the chlorine breaks off again and attacks another ozone molecule. • 1 chlorine from CFC can destroy 100,000 ozone molecules. HOW DO CFC’S DEPLETE THE OZONE?
  5. 5. Ultraviolet light hits a chlorofluorocarbon (CFC) molecule, such as CFCl3, breaking off a chlorine atom and leaving CFCl2. UV radiation Sun Once free, the chlorine atom is off to attack another ozone molecule and begin the cycle again. A free oxygen atom pulls the oxygen atom off the chlorine monoxide molecule to form O2. The chlorine atom and the oxygen atom join to form a chlorine monoxide molecule (ClO) The chlorine atom attacks an ozone (O3) molecule, pulling an oxygen atom off it and leaving an oxygen molecule (O2). Cl Cl Cl C F Cl Cl O O Cl O O O Cl O O O Cl O O
  6. 6. 1980’s scientists working in Antarctica noticed a thinning of the ozone by 50-98% that was occurring each spring. WHAT IS “THE OZONE HOLE”?
  7. 7.  During the dark winter months, VERY cold strong winds called polar vortex winds trap CFC’s and convert them to molecular Cl2  In the spring, UV rays split Cl2 and the individual Cl atoms break ozone down rapidly.  The thinning lasts for several months. HOW DOES THE OZONE HOLE FORM?
  8. 8. Ozone at ground level is highly reactive and reacts with other molecules of air pollution before it can even enter the stratosphere. WHY CAN’T OZONE CREATED AT GROUND LEVEL (AKA- BAD OZONE) HELP HEAL THE OZONE THINNING?
  9. 9. UV light can Damage DNA Premature aging Weakened immune system Increase chance of developing cataracts Increase susceptibility to skin cancer WHAT ARE THE EFFECTS OF OZONE THINNING ON HUMANS?
  10. 10.  Oceans  Kills phytoplankton which is the bottom of the marine food chain.  Disrupts food chains  Phytoplankton removes CO2 so if they die, CO2 levels would go up in atmosphere (global climate change)  Freshwater  Kill amphibian eggs  Survivors suffer birth defects  Populations decline  Land Plants  Interferes with photosynthesis  Reduces crop yield WHAT ARE THE EFFECTS OF OZONE THINNING ON ANIMALS & PLANTS?
  11. 11. Montreal Protocol (1987)  Meeting of several nations calling for reduction or elimination of CFCs in products.  Many manufacturers are switching to non-CFC propellants in aerosol cans.  You can help by:  Not buying Styrofoam products  If air conditioner leaks, fix it to prevent release to air. HOW CAN WE PROTECT THE OZONE LAYER?
  12. 12.  Describe the process by which chlorofluorcarbons destroy ozone molecules in the stratosphere.  Describe the process by which the ozone hole forms over Antarctica in the spring.  List five harmful effects that UV radiation could have on plants or animals as a result of ozone thinning.  Explain why it will take years for the ozone layer to recover, even though the use of CFCs has declined significantly. YOU SHOULD BE ABLE TO…