AIR

  • Hole over the antarctic has been present since 1980
    • Cause? CFC- chlorofluorocarbons
    • Good refrigerant
    • Diffuse everywhere
    • Mix with the atmosphere
    • Doesn’t react with anything so it doesn’t react to the natural air cleaner built into the earth
      • goes into the stratosphere
      • the sun rays can now break apart the CFC

Chlorine from cfc is left to interact with the ozone→ converts the ozone back into oxygen causing a hole in the ozone layer

  • HFCs– hydrofluorocarbons are not as destructive because the natural air cleaning system can clean them up better

    • Still have similar properties and aren’t great (greenhouse gasses) but don’t make it to the stratosphere

  • HC- hydrocarbons (propane)

  • Montreal protocol– international decision to stop releasing chlorofluorocarbons

  • Ozone depletion is not global– it’s just over the south pole

    • Ozone is being created in the stratosphere and is constantly being created
    • There is CFC being emitted all over the world so it seems like there should be chlorine everywhere in the stratosphere depleting ozone
    • Chlorine actually stays in reservoir compounds (chlorine nitrate)
      • In the south pole there are polar stratospheric clouds which cause the chlorine to be made into cl2 (gas) which attaches to the ozone and breaks it apart
      • The polar stratospheric cloud (PSC) are the causes of the break down of chlorine to gas which is why ozone depletion only happens over the south pole
      • It also has to be -80 degrees C (193 K) in order to have the chlorine crystals to form which doesn’t happen at the North Pole

    Where does the ozone in the atmosphere come from?

    • Is created in the stratosphere
    • The sun?
    • Oxygen
    • O2 + UV-c breaks O+O, another oxygen hits and become O3
    • Second reaction (O2 + O→ O3) produces heat 
      • so the production of the ozone produces heat
      • Stratosphere is relatively warm

    What is a dobson unit?

    • Unit of measurement for the ozone layer
    • Amount of molecules
    • If you were to take all the ozone from a column? and compressed until 0° C and 1atm pressure- the thickness of the layer would be equal to the min dobson unit
    • 300 DU→ 3 mm
      • 300 DU is average
    • So today the minimum ozone reading would read as 1.85 millimeters
      • 185 DU → 1.85 mm
    • The lower the ozone is, the less able it is to do its job– protecting from UV rays
    • Any area below 220 DU is considered apart of the ozone

  • Background: Electromagnetic Spectrum

    • Sun emits all kinds of wavelengths

The peak in the sun's radiation is in visible light

  • UVC is blocked
    • O2 blocks UVC from getting to the ground
    • When O2 is broken apart it combines with O2 to make O3
    • O2→ O + O
    • O2 + O→ O3