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What Is Ozone? Why Should We Care about Something We Can’t See? Dr. Michael J Passow Earth2Class Introduction19 Oct 2013
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”
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
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
Measured in DOBSON UNITS • Number of O3 molecules in a vertical column of the atmosphere
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)
NASA Ozone Monitoring NIMBUS-7 TOMS INSTRUMENT AND SATELLITE INFORMATION http://ozoneaq.gsfc.nasa.gov/n7sat.md Other satellites and platforms (balloon sondes)
Nimbus 7 Satellite http://ozoneaq.gsfc.nasa.gov/displayImage.md?image=n7art.gif&alt=Nimbus-7%20Drawing
Ozone Hole Watch http://ozonewatch.gsfc.nasa.gov/ NASA provides info about O3 maps, meteorology, facts, multimedia, and education
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
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
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
Ozone Hole History • ://www.theozonehole.com/ozoneholehistory.htm
NOAA’s Ozone Page • http://www.oar.noaa.gov/k12/html/ozone2.html
References http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/O/Ozone.html http://ozoneaq.gsfc.nasa.gov/n7sat.md http://ozonewatch.gsfc.nasa.gov/ http://blogs.agu.org/wildwildscience/files/2011/05/ozone_hole_large.jpg http://www.theozonehole.com/ozoneholehistory.htm http://www.oar.noaa.gov/k12/html/ozone2.html