What Is Ozone? Why Should We Care
about Something We Can’t See?
Dr. Michael J Passow
Earth2Class Introduction
19 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
• NASA provides info
about O3 maps,
meteorology, facts,
multimedia, and
education
http://
ozonewatch.gsfc.nasa.gov/
http://blogs.agu.org/wildwildscience/files/201
1/05/ozone_hole_large.jpg
http://ozonewatch.gsfc.nasa.gov/
2013 Season
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