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What is Ozone? Molecule containing three oxygen atoms unstable with respect to O2 Blue in color and has a strong odor Very reactive gas, and even at low concentrations it is irritating and toxic Very powerful oxidizing agent
Ozone Occurs naturally in small amounts in upper atmosphere and in the air of the lower atmosphere after a lightning storm. Oxidizes many organic compounds Powerful germicide, used to sterilize air and drinking water
Formation of Ozone Ozone can be formed when a mixture of O2 and NO2 is exposed to bright light. Such mixtures occur in the polluted air of large cities.
Earth’s Atmosphere Found in layers - Troposphere: lowest region, extends from the Earths surface up to about 10 kilometers (km) in altitude. -The next layer, the stratosphere, continues from 10 km to about 50 km.
Environmental Issues Photochemical “smog”/ pollution Health problems Greenhouse gas Loss of ozone layer
Ground-Level Ozone In the troposphere, ground-level or "bad" ozone is a pollutant that is a significant health risk It damages crops, trees and other vegetation. It is a main ingredient of urban smog.
Ozone Pollution A concern during the summer months because strong sunlight and hot weather result in harmful ozone concentrations
Ozone Alert The concentration of ozone in the air can reach levels that are dangerous for plants and animals. The U.S. Environmental Protection Agency characterizes ozone levels as "unhealthful" when they exceed the National Ambient Air Quality Standard of 125 parts per billion (ppb). In addition to posing a threat to health, ozone in the air also damages polymeric materials such as rubber and plastics, causing them to deteriorate prematurely.
Stratosphere Most atmospheric ozone is concentrated in a layer in the stratosphere
Stratospheric Ozone The stratosphere, or "good" ozone layer protects life on Earth from the suns harmful ultraviolet (UV) rays. Was gradually depleted by man-made chemicals like chlorofluorocarbons (CFCs). A depleted ozone shield allows more UV radiation to reach the ground.
Greenhouse Gas The increases Ozone is also a greenhouse gas in in primary the upper atmosphere greenhouse and, therefore, plays a role in Earths gases, such as climate. carbon dioxide, may affect how the ozone layer recovers in coming years.
Ultraviolet Radiation Protection Absorbs a portion of the radiation from the sun, preventing it from reaching the planets surface Most importantly, it absorbs the portion of ultraviolet light called UVB. UVB has been linked to many harmful effects
Ozone-Depleting substances(ODS) Chlorofluorocarbons (CFCs) Other chlorine-containing compounds include methyl chloroform, a solvent, and carbon tetrachloride, an industrial chemical. Halons, extremely effective fire extinguishing agents, and methyl bromide, an effective produce and soil fumigant, contain bromine.
Chlorofluorocarbons Stable, low in toxicity, and inexpensive to produce Noncorrosive, nonflammable Used as refrigerants, solvents, foam blowing agents, and in other smaller applications Used in fire extinguishers, as propellants in aerosols, solvents in electronics manufacture, and as foaming agents in plastics.
Ozone Depletion The CFCs are so stable that only exposure to strong UV radiation breaks them down. When that happens, the CFC molecule releases atomic chlorine. One chlorine atom can destroy over 100,000 ozone molecules. The net effect is to destroy ozone faster than it is naturally created.
Ozone Hole An annual ozone “hole” has been documented over Antartica every spring since the early 1980s. Ozone depletion is focused mainly over Antarctica, and to a lesser degree the North Pole.
Montreal Protocol Discontinue the production of CFCs, halons, carbon tetrachloride, and methyl chloroform and industry has developed more "ozone-friendly" substitutes. Montreal Protocol is widely considered to be the most successful of the global environmental treaties. The ozone layer is expected to recover over the next 50 years or so.
If CFC’s Weren’t Regulated… http://www.youtube.com/watch?v=P- VZ3q7tbag
Expected LearningOutcomes Discuss the differences between “good” and “bad ozone” Discuss how ozone is produced by human activity Discuss the Montreal Protocol