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The Ozone Layer
The document discusses ozone, its importance for protecting life on Earth from UV radiation, and the problem of ozone depletion caused by ozone depleting substances (ODS) like CFCs. It notes that ozone exists in different layers of the atmosphere and that the ozone layer in the stratosphere shields the planet from harmful UV rays. It then explains how certain man-made chemicals released into the air can destroy ozone molecules, leading to ozone depletion. The document outlines international agreements like the Montreal Protocol to phase out the production of ODS and protect the ozone layer. It concludes by suggesting individual actions people can take to help limit ozone depletion.
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The Ozone Layer
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- 2. Objectives of thisSession The objective of this session is to understand: • What is Ozone • Why is it soooooooooooo important • What is Ozone Depletion • What can we do to prevent Ozone Depletion
- 3. What is Ozone? •Allotrope of Oxygen – Oxygen Molecule – O2 – Ozone Molecule – O3 • Health hazard and pollutant when present in the Troposphere • Vital for human
- 4. Ozone in theAtmosphere
- 5. Ozone Layer The ozonelayer is a deep layer in the stratosphere, encircling the Earth, that has large amounts of ozone in it.
- 6. Ozone Layer The layershields the entire Earth from much of the harmful ultraviolet radiation that comes from the sun.
- 7. Why Protect theOzone Layer? • Ozone layers acts as protective screen against UV radiation • Excessive UV radiation leads to: – More skin cancers and eye cataracts. – Less crop yields – Loss of immunity to diseases.
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- 9. Ozone Depletion • Thedecrease in the concentration of Stratospheric Ozone due to chemicals (known as Ozone Depleting Substances or ODS)
- 10. Common Ozone Depleting Substances •CFC • HCFC • Methyl Bromide • Halons
- 11. Chlorofluorocarbons (CFC) CFC’s arecreated and used in refrigerators and air conditioners. These are not harmful to humans and have been a benefit to us. Once released into the atmosphere, chlorofluorocarbons are bombarded and destroyed by ultraviolet rays. In the process chlorine is released to destroy the
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- 13. Policy Responses toOzone Depletion • Coordinating committee on Ozone Layer (CCOL) established by UNEP in the 1970’s • Vienna Convention for the protection of the ozone layer held in 1985
- 14. Policy Responses toOzone Depletion • Montreal Protocol to ban substances that deplete the ozone layer (ODS) held in 1987 • Amendments to the Montreal Protocol: London - 1990, Copenhagen - 1992 Montreal - 1997. and Beijing, 1999 • 158 countries signed the Beijing amendment,
- 15. Phase-out of ODS SubstanceReduction Date Halons 100% January 1, 1994 Carbon tetrachloride 100% January 1, 1995 CFCs 100% January 1, 1996 Methyl chloroform 100% January 1, 1996 HBFCs 100% January 1, 1996 Methyl bromide 25% 50% 70% 100% January 1, 1998 January 1, 2001 January 1, 2003 January 1, 2005 HCFCs (includes HCFC- 22 and HCFC-123) 35% 65% 90% 99.5% 100% January 1, 2004 January 1, 2010 January 1, 2015 January 1, 2020 January 1, 2030
- 16. Ozone Protection –Doing our Part • Limit use of aerosol cans and sprays
- 17. Ozone Protection –Doing our Part • Avoid use of products containing CFC’s
- 18. Ozone Protection –Doing our Part • Recycle foam packaging products
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Editor's Notes
- #9 UV-A (400-315 nm)UV-B (315-280 nm)UV-C (280-100 nm)UV-C, which would be very harmful to humans, is entirely screened out by ozone at around 35 km altitudeUV-B radiation can be harmful to the skin and is the main cause of sunburn; excessive exposure can also cause genetic damage, resulting in problems such as skin cancer. The ozone layer is very effective at screening out UV-B; for radiation with a wavelength of 290 nm, the intensity at Earth's surface is 350 billion times weaker than at the top of the atmosphere. Nevertheless, some UV-B reaches the surface. Most UV-A reaches the surface; this radiation is significantly less harmful, although it can potentially cause genetic damage