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5.6 Depletion of Stratospheric Ozone

5.6 Depletion of Stratospheric Ozone. Composition of the atmosphere. N = 78.1% O = 20.9% Ar = 0.9% CO 2 = 0.03%. UV. O. O. O. O. O. O. O. O. The 2 separate Oxygen atoms are ‘high energy’ and have enough energy to combine with other oxygen ‘Diatoms’ to create Ozone.

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5.6 Depletion of Stratospheric Ozone

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  1. 5.6 Depletion of Stratospheric Ozone

  2. Composition of the atmosphere • N = 78.1% • O = 20.9% • Ar = 0.9% • CO2= 0.03%

  3. UV O O O O O O O O The 2 separate Oxygen atoms are ‘high energy’ and have enough energy to combine with other oxygen ‘Diatoms’ to create Ozone. UltraViolet is an energy coming from the sun. The Oxygen “Diatom” (literally two atoms joined) is joined together by sharing electrons. The energy in UV is enough to split the pair of atoms. Splitting the atoms uses up the energy in the UV ray.

  4. It can also collide with other lone oxygen molecules to make diatoms again, Or it can collide with diatoms to make other ozone molecules.

  5. So……. • Ultra violet energy is absorbed when ozone is made and when it is destroyed.

  6. A little about UV • UV is split into 3 main types depending on its wavelength: • UVB – Mid wavelength, mid energy, somewhat harmful, about 10 to 30% able to penetrate the atmosphere. • UVA – Long wavelength, low energy, less harmful, able to penetrate the atmosphere easily. • UVC – Short wavelength, Hi energy, very harmful, not able to penetrate the atmosphere easily.

  7. Ozone creation and depletion video: http://www.youtube.com/watch?v=k2kpz_8ntJY&feature=related

  8. Ozone depletion by halogens • Chlorine, flourine, and bromine (halogens) have a strong affinity(“liking”) for oxygen. • They can strip the ‘extra’ oxygen from an Ozone O3 molecule because the bond is weaker than the normal bond of O2. • A CFC molecule has 3 Cl and 1 Fl atoms joined to a carbon. If a Cl comes into contact with an ozone molecule it can strip an oxygen atom off it creating ClO and O2 Fl The Cl atoms can dissociate from the CFC. Cl Cl c o Cl o o

  9. ClouroFlouroCarbons deplete ozone faster than it can get made by UV. So with more CFCs the ozone levels get less. • CFCs can have long ‘Persistence’. (Up to 400 years!) • One chlorine atom can destroy over 100,000 ozone molecules. • CFCs and other widely-used chemicals produce roughly 84% of the chlorine in the stratosphere. The other 16% comes from natural sources like volcanoes. http://www.epa.gov/ozone/science/sc_fact.html click here for more great stuff!

  10. Environmental effects of ozone depletion If more UV gets through to the lower atmosphere: 2. More acid deposition (rain) leading to damage to buildings, increased erosion, changes in soil (Al availability) and damage to plants. If more UV gets through to the lower atmosphere: 1. More ‘photochemical smog’ is formed as the UV creates more ozone at ground level and more Nitrous oxides, Sulphur oxides.

  11. Health effects of Ozone depletion • Cataracts, • Sun burn, potentially leading to skin cancer, • Respiratory disease, • Lowered immunity.

  12. …and that’s just humans. • Have you ever seen a dolphin put on sun screen? • If 1 hour in the sun damages the DNA in skin cells what do you think the damage will be to leaves that spend 12hours? How do you think this might affect crop yields? • Food chains may be damaged due to algae and plankton being damaged by too much UV. What effect will this have on the food chains?

  13. Find out about Slip, slap, slop, seek, slide: http://scarletwords.com/wp/images/2009/11/SlipSlopSlapSeekSlidewords.jpg

  14. http://www.epa.gov/ozone/downloads/spd_poster_11x17-1.jpg click here for the bigger picture!

  15. The World's Reaction • The initial concern about the ozone layer in the 1970s led to a ban on the use of CFCs as aerosol propellants in several countries, including the U.S. However, production of CFCs and other ozone-depleting substances grew rapidly afterward as new uses were discovered.

  16. Protocols and conventions. Through the 1980s, other uses expanded and the world's nations became increasingly concerned that these chemicals would further harm the ozone layer. In 1985, the Vienna Convention was adopted to formalize international cooperation on this issue. Additional efforts resulted in the signing of the Montreal Protocol in 1987. The original protocol would have reduced the production of CFCs by half by 1998.

  17. After the original Protocol was signed, new measurements showed worse damage to the ozone layer than was originally expected. In 1992, reacting to the latest scientific assessment of the ozone layer, the Parties to the Protocol decided to completely end production of halonsby the beginning of 1994 and of CFCs by the beginning of 1996 in developed countries. More information on the phase out of ozone depleting substances is found here.

  18. Now the good news…… Because of measures taken under the Montreal Protocol, emissions of ozone-depleting substances are already falling. Levels of total inorganic chlorine in the stratosphere peaked in 1997 and 1998. The good news is that the natural ozone production process will heal the ozone layer in about 50 years.

  19. http://earthobservatory.nasa.gov/Features/Ozone/ • A little tutorial from NASA. Worth looking at.

  20. Highly depleting substances Lower depleting substances will be phased out completely from 2014 Back

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