What Is Ozone? Why Should We Care about Something We Can’t See?

Dr. Michael J PassowEarth2Class 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 INFORMATIONhttp://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/2011/05/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.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