Introduction of ozone and ozone depletion
Ozone, (g) is a highly reactive pale-blue gas that found in the
stratosphere of our atmosphere as the ozone layer. Ozone layer is located
between 17 km o 25 km above the surface of the Earth, so it is known as the
high-level ozone. Ozone molecule with a penetrating odour is a combination of
three atoms of oxygen. A stable oxygen molecule, is split by the
ultraviolet radiation or electrical discharge to form an ozone molecule. (
Figure 4.0 shown in Appendices 4). Hence, ozone in maintained by the action of
the ultraviolet rays light on ozone. Ozone layer acts in the role of shielding
organisms from excessive ultraviolet radiation from the sun in the upper atmosphere.
( high-level ozone )However, ozone will leads to the stunted growth in plants,
asthma in living organisms and causes particular material to be corroded when
it is at the ground level( low-level ozone). Ozone depletion occurs when the
ozone layer is becoming thinner and thinner and more ultraviolet ray radiation
is reached on the Earth.
Causes of ozone depletion
Ozone depletion can happened through
two ways, that is naturally and caused by human activities. By natural, ozone
molecules will combine with the nitrogen oxide to form nitrogen dioxide. Then,
nitrogen dioxide will bind with oxygen atom to form nitrogen oxide and oxygen.
The used of refrigerator and air-conditioner by human will cause large amount
of chlorofluorocarbon, CFC to be released into the environment. This is because
CFC is used as a coolant in both refrigerator and air-conditioner. The uses of
fire extinguishers containing halogenated hydrocarbon or halon and other ozone
depleter such as carbon tetrachloride and methyl chloroform will result in the
thinning of the ozone layer. For most of the ozone depleters are made up of
chorine or bromine which is chemically stable compounds. The intense
ultraviolet radiation will break those molecules once they are at the upper
atmosphere. Ultraviolet radiation strikes a CFC molecule and causes a highly
reactive single chlorine radical to break away. The free chlorine radical
collides with an ozone molecule and combine with oxygen atom to form chlorine
monoxide and oxygen. When a free atom of oxygen collides with chlorine
monoxide, two oxygen atoms form a molecule of oxygen. The chlorine atom is thus
released and free to destroy more ozone molecules. ( Figure 4.1 shown in
Appendices 4). Besides, the use of the organic or inorganic fertilisers will
also causes the thinning of the ozone layer as they release nitrous oxide to the
atmosphere which is also known as a type of the ozone-depleting chemicals. The
increased number of vehicles such as cars, motorcycles, vans and buses on the
road also contribute to the release of nitrous oxide gases. Researches have
shown that the 5 out of 100 per cent of the nitrous oxide is released by the
vehicle and yet the number of people using vehicles to go working or schooling
does not show a decline but increase in number.
Examples of ozone depletion in the world
The extreme condition of ozone
depletion is forming a continent-size hole known as ozone hole over Antarctica.
CFC is parts of the reason for the formation of the ozone hole. In 1989, the
depletion increases by 47% as compared to the 3% over the Artic. It is believed
that the ozone will continued to deplete at a rate of 5% for every decades (
Figure 4.2 shown in Appendices 4). A strong stratospheric wind will blows
around the surface of the Earth during the Antarctic winter, resulting the
Stratosphere, over Antarctica to be separated from the rest of the atmosphere,
to be extremely cold. As the result, ice cloud that is known as polar
stratospheric clouds ( PSCs ) will be formed. They remove nitrogen dioxide that
will leads to the removal of to stop and lead to the accumulation of chlorine
molecules. The equation will be : . When it is spring
time, free chlorine atoms are formed due to the breakdown of chorine molecules
formed during winter time. Thus, the ozone depleting reactions are continued.
Every single chlorine radical is able to breakdown thousands of ozone molecules
before deactivate by a nitrogen dioxide, or a hydrocarbon.
Although ozone depletion in Antarctica is getting worse than ozone depletion in
Artic, people should take concerned on both of the regions. There is an
investigation showing that the ozone layer is decreased over 29% in the Artic region.
Effect of ozone depletion on human health
99.9% of the harming ultraviolet
radiation coming from the Sun is filtered by the ozone layer. Thus thinning of
the ozone layer will causes the prolonged exposure to the ultraviolet radiation
by human. This can lead to higher risks for eye cataracts and sunburns, causes
mutation that will result in skin cancer such as melanoma. The “ozone hole”
that is found over Antarctica has increased the medical case of skin cancer in
Effect of ozone depletion on human immune system
The ultraviolet radiation is strong
enough to weaken our immune system and our body abilities to resist the
infectious diseases. As a result, we will get sick easily and more frequently.
For an example, the weakening of the immune system due to the ultraviolet
radiation will result in the activation of herpersimples virus on the skin. The
rate of getting the skin diseases such as leishmaniasis or leprosy will be
highly increase as they are affected by the sell-mediated immune response. The
risk of getting ultraviolet light-related skin cancer will also be high
increased among the people who are immune-suppressed for organ transplant.
Effect of ozone depletion on crop
The depletion of the ozone allowing
ultraviolet radiation from the Sun reduces the nutrient contents and crop
yields of plants such as soya beans and peas. The leaf cells and chlorophyll
are damaged by the high intensity of the ultraviolet radiation result in the
decline in the rate of photosynthesis and therefore reducing the yield of the
crop. This causes the loss in food become uncountable.
Effect of ozone depletion on food chain
The high intensity of the ultraviolet
radiation will disturb the food chain. It will kill microorganisms and
phytoplankton that acts as the producer or that are at the bottom of the marine
food chain as ultraviolet radiation has a high penetration power up to twenty
meters down the sea. As the phytoplankton are at the bottom of the marine food
chain, it will changes the amount of the production of the marine like the
fishes, crabs, shrimp, prawns and much more. This will lead to the shortage of
the food supply as most of the world population depends on it. The penetration
of the ultraviolet radiation does not only affect the marine food chain but
also affect the food chain on land. It causes mutation in living organisms and
reduced in the number of population of the animals that feed on the marine
lives such as fish.
the Antarctic organisms are badly affected as they are only having a low
tolerance for the ultraviolet
Effect of ozone depletion on climate of the Earth
Ozone depletion will also lead to the
increased in the temperature of the Earth. The high intensity of the sunlight
may causes global warming and result in the melting of the polar ice caps and
glaciers. Consequently, low-lying areas will be flooded and caused
people to loss their habitats or homes, damaged of the furniture and lots of
loss. Time and lots of efforts are required to rebuild their homes causes them
to spend extra expenses.
Ways to prevent ozone depletion
It is very important to maintain the
amount of the chlorine at the normal range in the atmosphere. To achieve this, we
can reduce the release of CFC. The hydrochlorofluorocarbon (HCFC) that is a
compound consisting of hydrogen, chlorine, fluorine and carbon atoms and hydrofluorocarbon (HFC) that is a
compound consisting of hydrogen, fluorine and carbon atoms are used to replace
CFC in order to prevent the thinning of the ozone layer. This is because these gases will breakdown in
the atmosphere and return to the Earth in the form of rainwater unlike CFCs.
We can also release the amount of CFC
by reducing the use of the air-conditioners. Switch on the fan if the weather
is not so hot and always switch off the air-conditioners at home when we are
away from our home or when they are not in use or not necessary. We should
avoid the habit of switching on the air-conditioners whenever we like but not
because of the hot weather.
In 1978, certain countries like the
United States, Switzerland and Canada have made their move to ban the use of
the CFCs as the aerosol products as they are aware of the consequent harmful
effect that can bring to. Therefore to continue this effort, people around the
world should also avoid buying the aerosol propellants can contain CFCs.
we know that the uses of
fire extinguishers containing halogenated hydrocarbon or halon that can leads
to the ozone depletion, so we can find a way to recycle it properly like
through waste centres. We also must have the fully understanding on the ways to
recycle it so that it is still useful without the ozone-depleting chemical.
Besides, we should stop releasing the chemicals
that can cause the ozone depletion. Usually, this type of chemical is from
agriculture. Therefore, the farmers must take note of the fertilisers that they
are using. Fertilisers that release the nitrous oxide that will leads to the
thinning in the ozone layer are reduced to their maximum. A suitable place for
the use of fertilisers should be created so that the loss of the nitrous oxide
to the atmosphere is at its lowest. We can also ensure that the absorption of
the nitrogen by the crops is at its maximum by observing and recording the
suitable timing to use the fertilisers.
Nitrous oxide is also released from
the vehicles. We can find that a family will be having two cars or more than
that which are not necessary. Therefore, we should practice carpooling or use
public transport like LRT, MRT, monorails for transportation. For a destination
that is near, we should just walk there or riding a bicycle to there. I believe
that there is no need to travel a place by car if we can reach there in 5 to 10
minutes by walking.
Moreover, we should buy the things either
food or goods that are manufactured in our own country. This is because
different things that are on sale are produced from various countries. So, the
further they are manufactured, the longer distance they have to travel. As a
result, the amount of the nitrous oxide that will be produced increases and
this lead to further depletion of the ozone layer.
As the saying goes a small step for a
man, one giant leap for mankind. So, we should not only practice the methods
that we can do but also advice our family members and friends to do so. We
should encourage the people around us to do the same things to protect our
ozone layer from depletion.
Proof that ozone hole over Antarctica is healing
The latest news from NASA have given
the first proof of the ozone layer is recovering. They have seen that the
action from the authorities and the action of banning the chemicals have
effectively decreases CFC levels and help in the recovering of the ozone layer.
( Figure 4.3 shown in Appendices 4) Therefore, these efforts that I mentioned
earlier should be continued.