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

• Wavelength = distance from one crest (or trough) to the next

• Wavelength inversely related to energy - shorter wavelengths = greater energy

Crest to Crest

Trough to Trough

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)

• Beneficial Effects– Vitamin D production– Tanning

Vitamin D

http://upload.wikimedia.org/wikipedia/commons/3/3d/Cholecalciferol-3d.png

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

Harmful Effects of UV• Too much UV = DNA Damage

– Sunburn– Cancer

http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/9314.jpg

Malignant Melanoma

http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/2501.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/Atmosphere_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.gifhttp://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