The Main Gases that Polluted our Atmosphere are given below:
1. Carbon Dioxide:
Carbon dioxide is one of the natural gases present in the atmosphere and is used by plants for photosynthesis. It is chiefly produced during the combustion of fuels in households, factories, power stations, etc. The increasing content of C02 in the atmosphere is likely to have the following effects:
i. A rise in atmospheric temperature due to greenhouse effect would cause a decrease in the precipitation and soil moisture content.
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ii. More C02 will dissolve in water and the water in the oceans would be more acidic. This will lead to reduced productivity of the marine ecosystem.
iii. The rise in temperature due to more C02 would cause melting of continental and mountain glaciers leading to flooding of coastal areas of some countries.
2. Carbon Monoxide:
It is produced as a result of incomplete combustion of fossil fuels like coal, petroleum and wood charcoal. Automobiles using diesel and petroleum are the major sources of carbon monoxide.
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Carbon monoxide is more dangerous than carbon dioxide. It is a poisonous gas leading to respiratory problems. When it reaches the blood stream, due to its high affinity for hemoglobin, it replaces oxygen, and reduces oxygen carrying capacity of the blood. It also causes giddiness, headache and heart diseases.
3. Sulphur Dioxide:
It is produced by the burning of coal in powerhouses and automobiles. It is mainly absorbed by water and goes into the soil as sulphuric acid.
It causes chlorosis and necrosis of vegetation, irritation in eyes, asthma and bronchitis. It is also responsible for discolouration and deterioration of buildings, fabrics, leather, etc. It also causes acid rain.
Acid rain Emissions of sulphur dioxide and oxides of nitrogen from power stations, factories, and motor vehicles cause the formation of sulphuric and nitric acids in rain clouds. If rain falls through polluted air it picks up more of these gases and increases its acidity. This is called acid rain. Plants damaged by acid rain.
4. Smog:
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Smog is a mixture of smoke, dust particles and small droplets of fog. Smog may cause necrosis and develop a white coating on the leaves (silvering) of plants. In human beings and animals, it may cause asthma and allergies.
5. Hydrocarbons:
Hydrocarbons are produced due to incomplete combustion of burnt fuel. The most prominent hydrocarbon in air is methane (CH4). Hydrocarbons are a cause of smog. Hydrocarbons in air cause skin cancer, irritation in eyes and respiratory system.
6. Aerosol Spray Propellants:
The suspended fine particles in the air are known as aerosols. It is a group of chemicals, which are released into the air with force in the form of vapours or fine mist. Aerosols contain chlorofluorocarbons (CFCs) and fluorocarbons which cause depletion of the ozone layer.
7. Oxides of Nitrogen:
A few oxides of nitrogen, such as nitric oxide (NO), nitrous oxide (N20) and nitrogen dioxide (N02) are important air pollutants. Oxides of nitrogen are produced by natural processes as well as from thermal power stations, factories, automobiles and aircrafts (due to burning of coal and petroleum). Oxides of nitrogen reduce the oxygen carrying capacity of blood, may cause irritation in eyes and skin cancer in human beings.
8. Pesticides:
Extensive use of pesticides pollutes the environment as they are not biodegradable. For example, DDT that gradually accumulates in the cells and tissues of plants is harmful to animals as well as human beings.
9. Peroxy-Acetyl Nitrate (PAN):
PAN is formed due to the photochemical reaction of nitrogen oxides and hydrocarbons. In human beings, it causes stinging of eyes, cough, headache, pulmonary congestion, hemorrhage, dry throat, breathing problems and early ageing of the lung tissues.