3. What Is Ozone ?
Ozone is a natural gas composed of three atoms of oxygen.
It chemical symbol is O3.
It is blue in color and has a strong odor.
Normal oxygen (O2), which we breathe, has two oxygen atoms and is
colorless and odorless.
OR
Sprinkled throughout the atmosphere are pale blue molecules of a toxic
gas that are essential to most life on Earth This gas is ozone.
Environmental scientists have classified O3 into two types
1) Good Ozone and
2) Bad Ozone.
4. 1) Good Ozone
Good ozone (also called Stratospheric Ozone) occurs naturally in the
upper Stratosphere.
Where does good Ozone come from?
The air is full of gases reacting with each other, even though our eyes do
not see.
When UV light strikes (Oxygen) O2 molecules, they are split into two
individual O atoms — O and O.
When one of the O atoms combine with O2 molecule, ozone (O3) is
created.
Even though Ozone is only a small part of the gases in this layer, it plays
a vital role because it shields us from the sun's harmful UV rays.
It is called Good Ozone, for obvious reasons—because it protects
humans, life and animals on earth.
5. 2) Bad ozone:
Bad Ozone is also known as Tropospheric Ozone, or ground level
ozone.
This gas is found in the troposphere, the layer that forms the immediate
atmosphere.
Bad Ozone does not exist naturally.
Human actions cause chemical reactions between oxides of nitrogen
(NOx) and volatile organic compounds (VOC).
Where does bad ozone come from?
Each time there is a reaction of chemicals such as those found in cars,
power plants and factory emissions, in the presence of sunlight (UV
light), Bad Ozone is created.
Bad ozone contaminates (dirties) the air and contributes to what we
typically experience as "smog" or haze.
6. The Ozone Layer
This is simply a layer in the stratosphere containing a relatively high
concentration of ozone.
The earth's atmosphere is divided into several layers, and each layer
plays an important role.
The first region extending about 10km upwards from the earth's surface
is called the troposphere.
Many human activities like mountain climbing, gas balloons and
smaller aircrafts operate within this region.
The next layer, extending about 15-60 km is called the stratosphere.
The ozone layer is mainly found in the lower portion of the stratosphere
from approximately 20 to 30 kilometres (12 to 19 mi) above earth,
though the thickness varies seasonally and geographically
9. What is Ozone Depletion?
Ozone layer depletion, is simply the wearing out (reduction) of the
amount of ozone in the stratosphere.
Unlike pollution, which has many types and causes, Ozone
depletion has been pinned down to one major human activity.
Industries that manufacture things like insulating foams, solvents,
soaps, cooling things like Air Conditioners, Refrigerators and
‘Take-Away’ containers use something called chlorofluorocarbons
(CFCs).
These substances are heavier than air, but over time, (2-5years) they
are carried high into the stratosphere by wind action.
10. Depletion begins when CFC’s get into the stratosphere.
Ultra violet radiation from the sun breaks up these CFCs.
The breaking up action releases Chlorine atoms.
Chlorine atoms react with Ozone, starting a chemical cycle that
destroys the good ozone in that area.
One chlorine atom can break apart more than 100,000 ozone
molecules.
11. How do volcanoes affect stratospheric ozone?
When volcanoes erupt, they produce massive clouds of ashes into the
troposphere, and then they drift upward into the stratosphere .
These ashes contain high concentration of bromine and chlorine.
Ashes can stay in the stratosphere for about two to five years, and
within this period, there are chemical reactions that destroy the
stratospheric ozone molecules.
In these volcanic ashes are some chemicals including bromine and
chlorine belong to a group of highly reactive elements called halogens,
that need electrons to become stable. They get these electrons from the
Ozone gas.
13. How Ozone Depletion Affects UV Levels?
UV-A: wavelength 315-399nm ,95% reaches on
earth (not harmful).
UV-B: wavelength 280-314nm ,reaches to some
extent(harmful).
UV-C: wavelength 100-279nm ,not reaches to
earth(very harmful).
14. Effects Of Ozone Depletion
1) Humans :High levels of UV Rays cause non-melanoma skin cancer
2) Plants:, Timing of development and growth, distribution of plant nutrients
and metabolism, etc.
3) Marine (or water) Ecosystems: Affect the development stages of of
fish, shrimp, crab, amphibians and other animals. When
this happens, animals in the upper food chain that feed
on these tiny fishes are all affected.
4) Effects on Biogeochemical Cycles: Higher UL levels affect the
natural balance of gasses (and greenhouse gases) in the
biosphere: e.g., carbon dioxide (CO2), carbon monoxide (CO),
carbonyl sulfide (COS) and ozone.
15. What Is Ozone Hole?
Top atmospheric researchers confirm that Ozone levels vary by
season and latitude. Sometime in 1979, it was observed the there
considerable Ozone depletion in the upper latitudes, Arctic and
Antarctic. This massive stretch of ozone depletion (hole) is
estimated to be about the size of America.
Particularly in the Antarctic, satellite images were released
showing a disturbing thinning of the ozone layer. The phenomenon
is what we usually call the Ozone hole.
17. What Can Be Done? (Conclusion)
People ask if we cannot produce our own ozone gas to replenish what is lost in
the stratosphere. That’s a good question. The sun naturally produces ozone with
immense energy and over time. To do the same, we will be looking at using
immense energy too, about twice the energy used in the USA. That is just not
practical.
The only way to do that is to remove the excess chlorine and bromine from the
stratosphere.
And the only way to do that is to stop making CFCs and several other
chemicals.
This is why in the 1990s a meeting of the worlds big nations met and agreed to
reduce the usage of CFCs and also encouraged other nations to do the same.
That was decided in the Montreal Protocol.
