What is Ozone?
Ozone is a rare chemical component of the Earth’s atmosphere. Ozone is rare because in every ten million molecules of air only three are Ozone.
Where do we find Ozone?
Most of the Ozone is found in the upper atmosphere called Stratosphere, approximately between 10 to 50 KMs from the Earth’s surface.
Where else Ozone is found?
Ozone is also found in Troposphere, the lowest portion of the Earth’s atmosphere, approximately up to 7 miles from the surface.
How Ozone is formed?
Ozone is formed differently in Stratosphere and Troposphere.
How Ozone is formed in Stratosphere?
In Stratosphere Ozone is formed by chemical reactions between Sun’s Ultraviolet radiation and Oxygen molecules. The Sunlight splits Oxygen molecules (O2) into two separate Oxygen atoms (2 O) first. In the next step, each of these highly reactive Oxygen atoms combines with Oxygen molecules to form Ozone (O3).
How Ozone is formed in Troposhpere?
Troposphere Ozone: Very low concentration of Ozone occurs at ground level due to hydrocarbons released by plants and soil and also due to migration of small amount of stratospheric ozone.
However, with increased human activities most of the Ozone in Troposphere is formed by the chemical reaction of Sunlight with Hydrocarbons and Nitrogen Oxides emitted by automobiles, gasoline vapors, fossil fuel power plants, refineries and other industries.
What is Ozone Shield and why is it important?
The lower portion of the Stratosphere contains the Ozone Layer where the concentration is about 2 to 8 parts per million. This is much higher than the lower atmosphere (Troposphere) but still low compared to the main components of the atmosphere.
This layer is called the Ozone Shield as it absorbs the Ultraviolet radiation which is harmful radiation from the Sun.
If all of the Sun’s Ultraviolet radiation reaches the Earth’s Surface, then there would be no life on Earth. It is the protective umbrella of the Earth.
What about the Ozone in Troposphere?
While Ozone in Stratosphere protects us from the harmful radiation from the Sun, Ozone in Troposphere is largely considered as pollutant.
The Troposphere Ozone is called a Bad Zone because it can damage living tissue and break down certain materials such as Nylon and Rubber.
Some harmful effects of Ozone in Troposphere:
- Reduces growth and metabolism in plants and affects the crop yield
- Damages Skin and Mucous Membrane
- Leads to Respiratory Problems
What is Ozone Hole?
This is the area in the Ozone Shield (Remember the protective umbrella in the stratosphere) where we find highly reduced concentration of Ozone. It occurs especially over the Earth’s Poles.
The Antarctic Ozone Hole was discovered in 1985 by British Scientists Joseph Farman, Brian Gardiner and Jonathan Shanklin of the British Antarctic Survey.
The Ozone Hole occupies several million square kilometers, approximately 23 million sq km in 1992 and 28 million sq km in 2000.
What causes the Ozone Hole?
The major reason for the depletion of the Ozone layer is the use of ODS, Ozone Depleting Substances.
These substances (ODS) react with the Ozone in the Stratosphere and destroy it.
What are these ODS and how they destroy the Ozone Shiled?
The most common Ozone depleting substances are Chlorofluoro Carbons (CFC) and Halons Nitrous Oxide.
Watch this video on how Ozone is formed and destroyed by CFC and other manufactured compounds.
But where do we use these CFCs?
CFCs are man made highly stable, colorless, non toxic, nonflammable and chemically inert substances made out of carbon fluorine and chlorine. They are used in Aerosol propellant, refrigerants, industrial sterilization etc
Okay, what are the harmful effects of Ozone Depletion?
Well, a 1% reduction in the Ozone concentration can raise the UV penetration by 2% and it can:
- cause destruction of photosynthetic pigments of plants, lead to reduced productivity and failure of seed germination
- cause skin cancer and cataract reduction in eye sight
- reduce life span of lymphocytes and affect immunity of individuals making us susceptible to other diseases and infections
- result in decrease of ocean life
- increase the amount of CO2 in atmosphere increasing global warming.
Well, what is the action taken by countries and governments to protect the Ozone Shield?
Wait for the next part to learn about the Global Action taken to protect the Ozone Shield!
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