Presentation on theme: "OZONE LAYER DEPLETION Why the hole in the atmospheric ozone layer above us? What has been done about this? Why should I worry ourselves about the Ozone."— Presentation transcript:
1 OZONE LAYER DEPLETIONWhy the hole in the atmospheric ozone layer above us?What has been done about this?Why should I worry ourselves about the Ozone Layer Depletion?
2 Good life at the beach threatened? Mr. OZONE: Will I be able to continue enjoying this life without problems?
3 What is Ozone? Ozone Layer? Ozone (O3) is a highly-reactive from of oxygen.Unlike oxygen (O2), ozone has a strong scent and is blue in color.Ozone exists within both the tropospheric and stratospheric zones of the Earth’s atmosphereIn the troposphere, ground level ozone is a major air pollutant and primary constituent of photochemical smogIn the stratosphere, the ozone layer is an essential protector of life on earth as it absorbs harmful UV radiation before it reaches the earth.
4 CFC’s and ozone depletion Chlorofluorocarbons are created and used in refrigerators and air conditioners. These chlorofluorocarbons 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 ozone molecules
5 Destruction of ozone by chlorine Molecular oxygen is broken down in the stratosphere by solar radiation to yield atomic oxygen, which then combines with molecular oxygen to produce ozone. The ozone is then destroyed by chlorine atoms.
6 Ozone destruction by UV rays UV radiation from the sun releases the radicals Cl and ClO.Ozone is a highly unstable molecule so it readily donates its extra oxygen molecule to free radical species such as hydrogen, bromine, and chlorine.These compound species act as catalysts in the breakdown of ozone molecules.
16 Image of the ozone hole over the South pole: July 10 2003
17 Image of the ozone hole over the North pole: July 10 2003
18 Ozone status: full day global image, July 9th 2003
19 Effects of UV rays on Aquatic Ecosystems Ozone depletion causes increases in UV rays’s effects on aquatic ecosystems by:1. decreasing the abundance of phytoplankton – affects the food stock for fishes and the absorption of CO22. decreasing the diversity of aquatic organisms – reduces food stock and also destroys several fish and amphibians.
20 Effects of UV rays on Terrestrial Ecosystems Damage to plant cell DNA molecules - makes plants more susceptible to pathogens and pestsReductions in photosynthetic capacity in the plant - results in slower growth and smaller leavesCauses mutations in mammalian cells and destroys membranes
21 Harmful effects of UV rays on people Skin cancerPremature aging (photoaging) of the skin (different from normal chronological aging)Cataracts and eye disorders (corneal sunburn and blindness)Immune system damage
22 Correlation between Ozone depletion and skin diseases
23 The Ultraviolet Exposure Index INDEX VALUES EXPOSURE0 – = Minimal= Low= Moderate= High= Very High
24 Factors affecting UV exposure Clouds cover - partly cloudy days do little to reduce UV exposure but rainy or substantially overcast days reduce UV exposuresThe time of day – peak exposure time is 12:00 noon - 1:00 p.m. UV intensity is reduced by about half at three hours before and three hours after the peak exposure time.
25 Factors affecting UV exposure..2 The time of year - more UV is received in the late spring and early summer and much less is received in the late fall and early winter.Life style – determines a person’s risk to UV exposure. Skiing, sunbathing, or swimming can lead to extremely high exposures. Use of tanning parlors also increase risk.
26 Policy responses to Ozone depletion Mario Molina and Sherwood Rowland showed in 1974 that CFC gases destroy ozoneCoordinating committee on Ozone Layer (CCOL) established by UNEP in the 1970’sVienna Convention for the protection of the ozone layer held in 1985Montreal Protocol to ban substances that deplete the ozone layer held in 1987Amendments to the Montreal Protocol: London , Copenhagen and Montreal