Ozone Depletion

1. Ozone Depletion Prepared by: Alev Saglam TagandurdyBerdiyew

2. What do youknowaboutozone? • What is themainfunction of ozonelayer? • Whataretheconsequences of ozonedepletion? • Discussabouttheseconseptsfor a fewminutes.

3. What is ozone? • Composed of three oxygen atoms • Unevenly distributed, 90% in stratosphere • Low ozone amounts=damaging to animals, plants, and humans • High ozone amounts on ground level=health and agricultural problems

4. CFC`s • Chlorofluorocarbons(CFC)-organic compounds made from carbon, chlorine, flourine, and oxygen • Developed in the 1930`s as non-toxic, non-flamable refrigerants. Created for industrial and commercial applications • The first Chlorofluorocarbon was CFC-12, a single carbon with two chlorines and two Fluorines attached to it. Today many different CFC's are produced and worldwide consumption in 1988 was estimated at over billion kilograms. • RespReact in the atmosphere to isolate chlorine • onsible for low ozone levels • Extremely stable-do not dissolve in rain

5. Depletion • Begins when CFC`s and other ozone depleting substances are emitted into the air • Wind mixes substances through tropophere • After several years, the substances in the troposphere reach the stratosphere, 10 KM above Earth • UV light then begins to braek apart the ozone depleting substances

6. Depletion • UV light breaks apart CFC`s to release chlorine • The broken atoms, not intact molecules attack the ozone • 1 chlorine atom can destroy 100,000 ozone molecules into Oxygen before being destroyed

7. Depletion • Large increases in chlorine have upset the natural ozone balance • Depleting faster than natural production

8. Formation and destruction of Ozone • Sunlight is the major energy source • for both making and destroying • stratospheric ozone: • When an Oxygen molecule absorbs a photon of light with a wavelength shorter than 200 nanometers (1 billionth of a meter) the energy splits the molecule into two Oxygen atoms. One of these atoms can react with another Oxygen molecule to form an Ozone molecule. • Up to 98% of the sun's high-energy ultraviolet light(UV-B and UV-C) are absorbed by the destruction and formation of atmospheric ozone. The global exchange between ozone and oxygen is on the order of 300 million tons per day.

11. Chemical Process • Initiated by Polar Night, when high latitudes receive no sunlight • Air above cools and vortex is formed • Catalytic cycle • Cl + O3----> ClO + O2 • ClO + O----> Cl + O2 • Result: O3 + O----> 2O2

14. Removal of Chlorine • In the stratosphere the major mechanisms for chlorine removal involve the formation of HCl: OH + ClO ---->HCl + O2 • O2H + Cl ------> HCl + O2 • HCl is water soluble and is eventually precipitated out of the stratosphere by water droplets or crystals. The estimated lifetime of HCl in the stratosphere is about 2 years. CH4 and other Hydrogen-containing organics compounds, including HCFC's, can also convert active chlorine to HCl.

15. UV facts • Ozone absorbs 99% of sun’s UV radiation • Radiation consists of three bands: A, B, C • Ozone blocks out all C (highest energy) • Ozone blocks half of B (2nd highest) • And it blocks small amount of A (lowest)

17. Results of UV Radiation • UV radiation causes 95% of all skin cancers • 15-40 year lag between high UV exposure and cancer • Melanoma (type of tumor) growing 4% a year • People who get 3 bad burns before age 20 are 5 time more likely to develop melanoma

18. Results of UV Radiation • Best way to avoid this while ozone levels are low: stay out of sun during peak hours and avoid the tanning salon • Skin cancer exists in three types: Squamous, Basal, and Melanoma • If ozone depletion persists, skin cancer cases are expected to rise severely

19. Squamous

20. Basal

21. Melanoma

22. Results of Ozone Depletion • Increased UV levels reaching Earth • Causes skin cancers • Impacts phytoplankton activity • Alters photochemical reaction rates • Increases smog and surface layer ozone

24. Montreal Protocol • Meeting of 36 nations to cut emissions of CFC’sthatstructured around several groups of halogenated hydrocarbons that have been shown to play a role in ozone depletion. • Aimed to reduce emissions by 35% between 1989 and 2000 • Also includes carbon tetrachloride, and methyl chloroform • Landmark international agreement

25. Montreal Protocol • Amended in 1990, 1992, and 1997 • As a result CFC production fell 85% • China and India have refused to sign • Scientists estimate 10%-30% of ozone will be depleted in Northern hemisphere by 2080

26. Clean Air Act • Motor vehicle air conditioning • Phase out of ozone depletion substances • Product labeling

27. Motor Vehicle Air Conditioning • CFC’s have been used as a coolant in motor vehicles • Scientists wanted to make sure existing CFC is used efficiently and not wasted • This act lists provisions for new machines to make sure they meet standards for emissions

28. Alternatives to CFCs • HCFCs • HFCs • Helium • HCs

29. Break down fast 90% less danger to ozone Can be used in refrigeration, air conditioning, and cleaning agents Disadvantages Greenhouse gases Expensive Health risks unknown Low efficiency HCFCs Advantages

30. HFCs Advantages • Break down fast • Do not contain ozone depleting chlorine • Can be used in refrigeration, air conditioning, and cleaning agents Disadvantages • Greenhouse gases • Flammable and toxic • Produces methyl chloroform which can seriously deplete the ozone layer

31. Helium Advantages • Effective coolant • Disadvantages • May become scarce if widely used

32. HCs Advantages • Cheap • Not patentable • Easily made in developing countries • Disadvantages • Flammable and poisonous • Increases ground level pollution