1. Ozone Depletion Chapter 22

2. Ozone Gas Unstable gas composed of three atoms of oxygen Naturally exists 12 to 15 miles up in the atmosphere Formed when ultraviolet radiation bombards atmospheric oxygen Atoms break apart and recombine - Adds an additional oxygen

3. Ozone Gas (continued) Formed a molecule of O3, which is an ozone gas Ozone gas builds up in the stratosphere Forms a layer called the ozone layer This shields the Earth from ultraviolet radiation

4. Ozone Layer When ozone struck by high-energy ultraviolet radiation - Breaks apart and converts energy to heat - Releases of heat causes temperature to increase, in high altitudes of the stratosphere - Preventing high- energy ultraviolet radiation from reaching Earth - Atoms split and recombine forming more ozone

5. Ozone Layer (continued) Process of destruction and regeneration Reached new state of dynamic equilibrium Over time, amount destroyed= amount re- formed

6. Measuring Stratospheric Ozone Ozone level changes with seasons Levels change with global circulation of the atmosphere Naturally changes were minimal until the 1970’s - Noticed ozone levels were decreasing - This was not understood at first Deletion results in human- created gases - Interrupted natural chemistry of the ozone layer

7. Measuring Stratospheric Ozone (continued) Chlorofluorocarbon- CFC - Used in refrigerators and air conditioners - Also used as propellants in aerosol spray cans - Used for foam production and cleaning electrical parts - Composed of fluorine, chlorine, and carbon

8. Effects of Ozone Depletion Greater amount of ultraviolet radiation striking Earth - Leads to potential damage of the ecosystem - Can damage cells exposed to the atmosphere Damage structure of cells Leads to skin cancer in humans Degradation of the eyes Weakend immune systems

9. Measuring Stratospheric Ozone (continued) High- level ultraviolet radiation breaks it apart Chlorine atoms freed and join with oxygen Creates chloride compounds Removes oxygen from the stratosphere Causes decrease in oxygen molecules Causes decreases in production of ozone Bromide and halons also destroy the ozone

10. The Ozone Hole Monitoring of stratospheric ozone revealed decreases over Antarctica South pole levels depleted rapidly in the last 20 years Low levels over Antarctica are called ozone hole

11. Ozone Hole ( continued) Similar loss over North Pole in spring Other parts of the globe also experience loss Mid- latitudes have lost 4 to 6% Equator to 20 degrees north and south Direct relationship to skin cancer in humans

12. Reducing Ozone Depletion 1996 CFCs banned around the world Leftover CFCs still in atmosphere Old refrigerators, air conditioners in wrecked cars will leak CFCs Removal will take 50 to 100 years Protect your skin