Ozone Depletion

Sean Farrell

What is it?

• The ozone layer is a concentration of ozone molecules in the stratosphere.

• The stratosphere, the next higher layer, extends about 10-50 kilometers above the Earth's surface.

• Stratospheric ozone is a naturally-occurring gas that filters the sun's ultraviolet (UV) radiation.

• A diminished ozone layer allows more radiation to reach the Earth's surface.

• For people, overexposure to UV rays can lead to skin cancer, cataracts, and weakened immune systems.

• Increased UV can also lead to reduced crop yield and disruptions in the marine food chain.

How is it being depleted?• It is caused by the release of chlorofluorocarbons (CFCs),

hydro fluorocarbons (HCFCs), and other ozone-depleting substances (ODS), which were used widely as refrigerants, insulating foams, and solvents. The discussion below focuses on CFCs, but is relevant to all ODS. Although CFCs are heavier than air, they are eventually carried into the stratosphere in a process that can take as long as 2 to 5 years. Measurements of CFCs in the stratosphere are made from balloons, aircraft, and satellites.

• When CFCs and HCFCs reach the stratosphere, the ultraviolet radiation from the sun causes them to break apart and release chlorine atoms which react with ozone, starting chemical cycles of ozone destruction that deplete the ozone layer. One chlorine atom can break apart more than 100,000 ozone molecules.

• Other chemicals that damage the ozone layer include methyl bromide (used as a pesticide), halons (used in fire extinguishers), and methyl chloroform (used as a solvent in industrial processes for essential applications). As methyl bromide and halons are broken apart, they release bromine atoms, which are 60 times more destructive to ozone molecules than chlorine atoms.0

Causes of Depletion

• aerosol bomb propulsion• some fire extinguishers• refrigeration and freezing• air conditioners (mobile and fixed)• solvents• pesticides• plastic foams• miscellaneous uses

What we are doing about it

• In 1987, the U.S. and fewer than 30 other countries signed the Montreal Protocol treaty to phase out the production and use of ODS. In September 2009, the Montreal Protocol became the first international agreement to reach universal participation, with 196 Parties. The Protocol continues to phase out ODS worldwide. As international control measures reduce the release of ODS, natural atmospheric processes will repair the ozone layer during the second half of the 21st century.

Are we trying to slow it down?

• There are various ways and methods we can use to stop ozone depletion. Many scientists advice to minimize aircraft flights at high altitudes because it causes pollution and as a result it creates water vapor deposition and oxygen reduction. By minimizing rocket flights also water vapor deposition can be minimized.

Videos

• http://www.youtube.com/watch?v=qUfVMogIdr8&feature=related

• http://www.youtube.com/watch?v=vuFhaawqsNM&feature=related

Work cited

• http://www.cooldownglobalwarming.com/global-warming/ozone-depletion/index.html

• http://www.epa.gov/ozone/science/q_a.html

• http://wiki.answers.com/Q/What_can_we_do_to_protect_the_ozone_layer