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)

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

Ultraviolet (UV) Radiation Lower wavelengths than visible to our eyes (higher energy) Beneficial Effects –Vitamin D production –Tanning Vitamin D 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 Malignant Melanoma 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 e_gas_proportions.svg

What is ozone? Ozone is a gas made up of three oxygen atoms (O 3 ). 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.

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

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 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