The Ozone Layer
Author: Patrick Mathias
Purpose: To understand how the ozone layer protects people
from UV radiation, and how the ozone layer is depleted.
13 July 2010
• Sunlight contains a wide variety of waves
– Ultraviolet (UVA, UVB, UVC)
– Visible (the light we know/see)
– Infrared (electromagnetic energy that reaches earth; IR-A, IR-B, IR-C)
http://www.swpc.noaa.gov/primer/primer_graphics/Sun.png
Crest to Crest
Trough to Trough
• Wavelength = distance from one crest (or trough) to the
next
• Wavelength inversely related to energy - shorter
wavelengths = greater energy
Solar Radiation
• Wavelengths emitted by the sun are on
the scale of nanometers (one billionth of a
meter)
• How small is a nanometer?
• A human hair is about 100 micrometers in
diameter - a nanometer is 100,000 times
smaller
http://ncf.colorado.edu/aboutnano/scale_of_things_web.jpg
http://upload.wikimedia.org/wikipedia/commons/4/4c/Solar_Spectrum.png
Ultraviolet (UV) Radiation
• Lower wavelengths than visible to our
eyes (higher energy)
Vitamin D
• Beneficial Effects
– Vitamin D production
– Tanning
To take advantage of these benefits, get 15
minutes of direct sunlight per day during
the summer months!
Important for:
Bone Health
Immunity
Cancer Prevention
http://upload.wikimedia.org/wikipedia/commons/3/3d/Cholecalciferol-3d.png
Harmful Effects of UV
• Too much UV = DNA Damage
– Sunburn
– Cancer
Malignant Melanoma
http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/2501.jpg
http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/9314.jpg
If you’re outside during the summer for
more than 15 min, wear sunscreen!
Earth’s Atmosphere
• One role of the planet’s
atmosphere is to protect us
from sunlight
• Atmosphere mostly made up
of nitrogen and oxygen
http://upload.wikimedia.org/wikipedia/commons/7/7a/Atmospher
e_gas_proportions.svg
What is ozone?
• Ozone is a gas made up of three oxygen
atoms (O3).
• There are two types.
• It occurs naturally in small (trace) amounts
in the upper atmosphere (the
stratosphere). Ozone protects life on Earth
from the Sun’s ultraviolet (UV) radiation.
http://ozonewatch.gsfc.nasa.gov/facts/ozone.html
What is ozone?
• In the lower atmosphere (the troposphere)
near the Earth’s surface, ozone is created
by chemical reactions between air
pollutants from vehicle exhaust, gasoline
vapors, and other emissions. At ground
level, high concentrations of ozone are
toxic to people and plants.
Ozone Depleting Substances
• Chlorofluorocarbons (CFCs) - refrigerants,
aerosols
• Nitrous Oxide - laughing gas, engines
http://static.howstuffworks.com/gif/aerosol-can-2.gif
http://www.scottwinger.com/i/Purge.jpg
Hole in the Ozone Layer
• In the 1970s scientists discovered that
chlorofluorocarbons (CFCs) were stable in
the atmosphere for up to 100 years
• In 1985 for the first time scientists were
able to show the hole in the ozone - it was
much bigger than anyone expected
Ozone Hole
http://en.wikipedia.org/wiki/File:160658main2_OZONE_large_350.png
September 2006
The Montreal Protocol
• International treaty enacted in 1989 to ban
the manufacture of CFCs
• CFC concentrations in the atmosphere
have recently decreased or leveled off
• The growth of the ozone hole has slowed
but still appears to be getting larger
Nitrous Oxide and Ozone
• Nitrous oxide is an ozone depleter that is
freely made
• Probably the number one source of ozone
depletion today
• A little bit of sun without the sunscreen is
good for you - don’t overdo it!
• REMEMBER: If you are in the sun for
more than 15 minutes during the summer,
WEAR SUNSCREEN!
Your assignment
• You are going to make two
diagrams/drawings. In the first diagram
depict how ozone is helpful to us. In the
second diagram depict how the ozone is
depleted.
Bell Work - Review
• What is the chemical formula of ozone?
• Name the two compounds considered to
be most responsible for ozone destruction:
• What is the name and year of the ‘treaty’
that banned the production of one of these
compounds and tell which one it banned?
• Name the layer of the atmosphere in
which ozone is beneficial: and harmful:
Resources
• Wikipedia: UV Radiation, Earth’s
Atmosphere, Chlorofluorocarbons, Nitrous
Oxide, Montreal Protocol