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What Is Ozone? Why Should We Care about Something We Can’t See?
Dr. Michael J PassowEarth2Class Introduction
19 Oct 2013
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What is Ozone?
• Simply explained, ozone is a highly reactive form of oxygen molecules O3
Ozone poses two biological problems, depending on whether it is:• “Tropospheric Ozone” or• “Stratospheric Ozone”
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Tropospheric Ozone
• Produced mainly by reaction of sunlight, oxygen, and exhaust from combustion engines (hydrocarbons/nitrogen oxides)
• Major component of photochemical smog• Dangerous to people with respiratory ailments• Also damages plants, especially in North
American and European forests
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Stratospheric Ozone
• Above 11 km (7 mi)• “Ozone Shield” protects against solar
ultraviolet radiation• Satellites have monitored significant declines
over past few decades• Most noticeable declines over Antarctica• “Peaked” (?) in 2006
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• Measured in DOBSON UNITS
• Number of O3 molecules in a vertical column of the atmosphere
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Progress in Monitoring
• 1979 – 1993: NASA/NOAA Nimbus-7
• 1993 – 1994: Metor-3 (USSR)
• 1996 – 2004: NASA Earth Probe TOMS
• 2004 – present: OMI instrument aboard Aura (KNMI/NASA)
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NASA Ozone Monitoring
NIMBUS-7 TOMS INSTRUMENT AND SATELLITE INFORMATIONhttp://ozoneaq.gsfc.nasa.gov/n7sat.md
Other satellites and platforms (balloon sondes)
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Nimbus 7 Satellite
http://ozoneaq.gsfc.nasa.gov/displayImage.md?image=n7art.gif&alt=Nimbus-7%20Drawing
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Ozone Hole Watch• NASA provides info
about O3 maps, meteorology, facts, multimedia, and education
http://ozonewatch.gsfc.nasa.gov/
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http://blogs.agu.org/wildwildscience/files/2011/05/ozone_hole_large.jpg
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http://ozonewatch.gsfc.nasa.gov/
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2013 Season
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What Probably Created the Ozone Hole?
Chlorofluorocarbons (CFCs)• Synthetic hydrocarbons in which H is replaced by
halogens (e.g., CHF2Cl, CFCl3, CF2Cl2)• Also, Br compounds• Widely used refrigerants and propellants• In the atmosphere, may take 60 – 100 years to
decompose• 1987 Montreal Protocol established scheduled
reduction in use
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What Else Depletes Ozone?
• Nitrous Oxide (N2O)• Like CFCs, stable in stratosphere and able to
deplete O3
• Unlike CFCs, 60% derived from natural sources >decomposition of N compounds in soil and water >burning fossil fuels & plants (deforestation) >use of manure, fertilizers on crops
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Some Dangers of N2O
• Montreal Protocol does not regulate N2O• In troposphere, potent greenhouse gas
(~300 x as potent as CO2)• Impact on ozone hole not definitively
established, but of concern to scientists
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Ozone Hole History
• ://www.theozonehole.com/ozoneholehistory.htm
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NOAA’s Ozone Page
• http://www.oar.noaa.gov/k12/html/ozone2.html
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References
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/O/Ozone.htmlhttp://ozoneaq.gsfc.nasa.gov/n7sat.mdhttp://ozonewatch.gsfc.nasa.gov/http://blogs.agu.org/wildwildscience/files/2011/05/ozone_hole_large.jpghttp://www.theozonehole.com/ozoneholehistory.htmhttp://www.oar.noaa.gov/k12/html/ozone2.html