Depletion of Ozone Layer

6S Yeung Wut Pan

6S Tsang Chi Ho

What is ozone layer?

a layer in Earth’s atmosphere contains relatively high concentrations of

ozone (O3) absorbs 93-99% of the sun's high frequency

ultraviolet light located in the lower portion of the

stratosphere

The following equations describe how ozone is formed- O2 ------------O + O O+ O2 ------------O3

Ozone and ultraviolet

Ultraviolet is a kind of radiation Divided into three categories Harmful to humans Absorbed and screened by ozone

What caused ozone depletion?

By free radical catalysts Emissions from jumbo jets and civil aircraft increased concentrations of chlorine and

bromine, nitrogen oxides, and hydrogen liberated by the action of ultraviolet light initiate and catalyze a chain reaction

How the ozone layer is destroyed?

CFCs (chlorofluorocarbons) commonly used in refrigeration and aerosol broken down by UV radiation and give out

chlorine atoms which acts as the catalyst:

CFCl3---------CFCl2 + Cl

Cl +O3 ------- ClO +O2

ClO +O ------- Cl +O2

The Cl atom is then used again to destroy more ozone molecules.

Where does the most ozone depletion occur?

A very large ozone hole forms at Antarctica.

November 27, 2008

Results of ozone layer depletion

Ozone levels drop being unable to absorb ultraviolet radiation an increase of skin cancer and eye cataract yield of crops decrease Economic loss global warming

What have been done?

Monitor the use of CFCs Compounds containing C–H bonds

designed to replace CFCs Lower sulphur jet aircraft fuel and

redesigned engines Reduce vehicles’ exhaust emissions Develop less polluting propulsion systems

Is the ozone layer recovering?

The report from United Nations Environmental Programme in 2006 states that the Montreal Protocol is working. The ozone layer is expected to recover to pre-1980 levels in 2050. If all emissions of ozone depleting substances were eliminated, the recovery will advance by 15 years.

What can we do to help?

Use no CFCs items Conduct regular inspection and

maintenance of air-conditioning and refrigeration appliances

CFCs containing items should be recovered or recycled

Sources

http://www.nasa.gov/vision/earth/environment/ozone_resource_page.html

http://www.epd.gov.hk/epd/textonly/english/environmentinhk/air/ozone_layer_protection/wn6_protect.html

http://esrl.noaa.gov/csd/assessments/2002/qandas.html

http://ozone.unep.org/index.shtml

The end