The Ozone layer is in a layer called the Statosphere
Ozone molecules are called O3
The Ozone Layer is constantly being replaced
Ozone is formed when UV
Radiation from the Sun hits oxygen
molecules
If the right amount of UV Radiation is absorbed by an
oxygen molecule, the oxygen molecule splits into
separate atoms or free radicals
The free radicals then combine with other
oxygen molecules to form Ozone moleciules
O + O --> O2 + O --> O3
O + hv --> O + O
Where hv is a quantum of UV Radiation
UV Radiation can also reverse
the formation of Ozone
O3 + hv --> O2 + O
The Ozone Layer protects the Earth
The UV Radiation from the Sun is made up of different frequencies
These frequencies are grouped into 3 band
UVA UVB UVC
UVC has the highest
frequency and the most energy
UVB can damage the DNA in cells and cause skin cancer
We need UV radiation to make Vitamin D
The Ozone layer removes all the high energy
UVC Radiation and about 90% of UVB
These types of UV Radiation are harmful to
humans and most other life on Earth
The Ozone Layer is Breaking Down
In the 1970s and the 1980s, scientists
discovered that the ozone layer about
Antarctica was getting thinner
These holes in the Ozone layer are bad because the
allow more harmful UVB Radiation to reach the
Earth
CFCs absorb UV Radiation and split to form chlorine free radicals
These free radicals destroy ozone molecules
and are then regenerated to destroy more
ozone
One Chlorine atom can destroy 10,000 ozone molecules
before it can form a stable compound
CFCs are non toxic, non-flammable and chemically inert
NO free radicals from nitrogen oxides
destroy ozone too
Nitrogen oxides are produced by car and
aircraft engines AND thunderstorms
The reactions can be represented by these
equations, where R represents either Cl or NO
R + O3 --> RO + O2
RO + O --> R + O2
Formed when UV breaks down O2
The overall reaction is O3 + O --> 2O2
What is Being done to Slow down the
Depletion of the Ozone Layer?
The Montreal Protocol
The Montreal Protocol sets out guildlines for developed and
developing countries for all the major ozone depleting substances,
including CFCs, halons and less damaging transitional chemicals
such as HCFCs.
The Montreal Protocol targets 96 chemicals in thousands of
applications across more than 240 industrial sectors.
Other Ways to Reduced Greenhouse Gas Emmision
Governments are successfully using a wide
range of policies and measures to address
climate change, including regulations and
standards, taxes and charges, tradable permits,
voluntary agreements, subsidies, financial
incentives, research and development programs
The Protocol has been further admended - London
1990, Copenhagen 1992, Vienna 1995, Montreal 1997
and Beijing 1999
Which have brought forward phase out schedules
and added new ozone depleting substances to the list
of substances controlled under the Montreal Protocol.
CFCs have then been banned
They were found in:
Hairspray
Coolants for Pridges
Air Conditioning Systems
Since the Montreal Protocol came into effect, the atmospheric
concentrations of the most important chlorofluorocarbons and related
chlorinated hydrocarbons have either leveled off or decreased
Halon concentrations have continued to increase, as the halons presently stored in fire extinguishers are
released, but their rate of increase has slowed and their abundances are expected to begin to decline by about
2020.
The Montreal Protocol has often been called the most successful
international environmental agreement to date
Halon concentrations have continued to increase, as the halons
presently stored in fire extinguishers are released, but their rate of
increase has slowed and their abundances are expected to begin to
decline by about 2020.