Ozone (O3)

Ozone if formed by the action of sunlight on oxygen. Ozone forms a layer at about 50 Km from the earths surface. On the surface it is considered to be a polluting gas. However the ozone layer is important as it protects us from harmful ultraviolet radiations coming from the sun. Ozone in the upper layer gets destroyed and regenerates which is a natural process.

Ozone Layer depletion

 It takes place when the destruction of the ozone takes place at a greater rate than the regeneration. This is fatal as it allows the harmful UV radiations to enter the earth’s atmosphere.

Causes of ozone layer depletion:

1. CFCs used in refrigerants and aerosols contain chlorine which reacts with ozone and degenerates it.
2. Some other harmful chemicals like halo derivatives, oxides and nitrogen containing compounds coming from industrial effluents also damage the Ozone.
3. Fertilizers also contain chemicals that can damage the ozone layer.

Effects of Ozone layer depletion:

1. Human ailments due to exposure to harmful UV rays can be caused. These include skin diseases.
2. UV rays can also affect vision and cause cataracts.
3. UV rays affect crops and some micro organisms. This alters the food chain and brings imbalance to the ecosystem.
4. Decrease in vegetation leads to increase in CO2 levels.
5. UV rays also lead to melting of ice caps causing rise in sea levels which leads to submergence of coastal towns and cities.

OZONE :

Ozone is a blue coloured triatomic allotrope of oxygen with a characteristic pungent smell. Christian Schohnbein named it in 1839 as 'ozone' because of its peculiar smell. In the stratosphere ozone is continuously being created by the absorption of short wave-length ultra violet radiations. Ultraviolet radiations less than 242 nanometers decompose molecular oxygen into atomic oxygen by photolytic decomposition.

                              O2 + hv = O + O

The atomic oxygen rapidly reacts with molecular oxygen to form ozone.

                                O + O2 = O3

Ozone Depletion :

Ozone layer depletion is the gradual thinning of the earth’s ozone layer in the upper atmosphere caused due to the release of chemical compounds containing gaseous bromine or chlorine from industries or other human activities.

In the stratosphere UV radiation breaks CFC molecule and releases chlorine atom.

                    UV + chlorofluorocarbon = Cl
                       Cl+O3 = ClO+O2
                       ClO+O = Cl+O

CAUSES :

• Cooling agents such as conditioners ,refrigerators, freezers and coolers release 30% of CFGs.
• Aerosols include hair spray ,deodorants ,paints ,insect repellents ,fumigants liberates 25% of chloroflourocarbons.
• Solvents used for woolen garments and electronic circuits release 20% of chloroflourocarbons .
• Foaming agents used for furniture and car seats ,package materials ,insulators ,fast food containers ,polystyrene cups ,shaving foams liberate 25% of chlorofluorocarbons.

EFFECTS :

• The ultra violet 'B' rays affect DNA ,any change in DNA can result in mutation and cancer.
• Easy absorption of UV rays by the lens and cornea of eye will result in increase in incidents of cataract.
• Melanin producing cells of the epidermis will be destroyed by UV-rays resulting in immuno-suppression.
• Crops like peas ,beans ,melons ,cabbage ,potato tomato ,sugar beet, and radish are sensitive and get damaged very easily.
• Paints and fabrics will fade faster.
• Ultraviolet radiation deep in aquatic water bodies effects phytoplanktons ,shrimps ,crabs ,fish etc.