A. Global Warming
Most of the solar radiation entering the earth’s atmosphere is reflected back into the space. However some of the heat is absorbed by the gases like the carbon dioxide. This serves to keep the earth warm much like the greenhouses. Greenhouses are glasshouses which maintain a temperature higher than the surroundings for the plants to grow and yield better. The other gases that contribute to this are water vapour, methane, chlorofluorocarbons (CFCs) and nitrous oxide. These gases are called the greenhouse gases.
While greenhouse effect is a necessary and natural phenomenon. Every year the temperature are going up due to pollution and the levels of these greenhouse gases is also going up. This is called global warming. According to estimates, at the current rate of increase, the average global temperature will go up by 3oC to 8oC in the next 100 years.
This will have the following effects:
• Climate of different regions
• Distribution of plants and animals
• Disturbance in agriculture and food production
• Melting of snow caps and resultant increase in sea levels. This will submerge parts of coastal cities of Calcutta, New York, London and other major cities.
B. Formation of Photochemical Smog
When pollutants like hydrocarbons and nitrogen oxides combine in the presence of sunlight, smog is formed. This is a mixture of gases and since it is formed by photochemical reactions, it is called the photochemical smog. The word ‘smog’ is derived from the two words-smoke and fog.
It forms a yellowish brown haze especially during winter and hampers visibility. It also causes many respiratory disorders and allergies as it contains polluting gases.
C. Formation of Acid Rain
Sulphur dioxide and nitrogen oxides react with water in the atmosphere producing sulphuric acid and nitric acid. These acids come down along with the rain. This phenomenon is called acid rain. The pH of acid rain varies from 3-6. The composition of acid rain is sulphuric acid, nitric acid and weak carbonic acid.
It has the following adverse affects on the environment:
• Causes respiratory and skin disorders.
• Affects productivity of plants by damaging the leaves.
• Enters the soil and affects the soil pH and other conditions.
• Enters the ground and river waters which causes harm to the aquatic life.
• Causes damage to marble and thus damages buildings and monuments like the Taj Mahal
D. Aerosol Formation
Aerosol is formed by the dispersion of solid or liquid matter in the atmosphere. There are natural aerosols also in the atmosphere. However, polluting aerosols are formed by the pollutant particulate matter like carbon particles.
If the aerosols form a thick layer in the troposphere, they affect the weather conditions by blocking the solar radiation. Aerosols are also deposited on the leaves and affect the photosynthesis. Aerosols disperse the organic metallic pollutants far and wide.
E. Depletion of Ozone
The stratosphere of the atmosphere has ozone (O3). Ozone is known to absorb the Ultraviolet (UV) rays present in the sun’s radiation. The UV rays are believed to cause skin cancer and mutations. Thus, the ozone protects us from the harmful effects of the UV rays.
However, hydrocarbons such as the chlorofluorocarbons (CFCs) destroy the ozone molecules which deplete the ozone layer. Ozone holes have been detected in the atmosphere which permit the UV rays to reach the earth’s surface. The harmful effects of the UV rays are visible in the countries such as Australia and New Zealand where the rate of skin cancer is higher than the other regions of the world.
Harmful Effects Of Air Pollution Caused By Industrial and Domestic Wastes
|Carbon monoxide||Automobile exhaust, photochemical reactions in the atmosphere, biological oxidation by marine organisms, etc.||Affects the respiratory activity as haemoglobin has more affinity for Co than for oxygen. Thus, CO combines with HB and thus reduces the oxygen-carrying capacity of blood. This results in blurred vision, headache, unconsciousness and death due to asphyxiation (lack of oxygen).|
|Carbon di oxide||Carbon Burning of fossil fuels,depletion of forests (that remove excess carbon dioxide and help in maintaining the oxygen-carbon dioxide ratio).||Global warming as it is one of the greenhouse gases.|
|Sulphur dioxide||Industries, burning of fossil fuels, forest fires, electric generation plants, smelting plants, industnal boilers, petroleum refineries and volcanic eruptions.||Respiratory problems, severe headache,reduced productivity of plants, yellowing and reduced storage time for paper, yellowing and damage to limestone and marble, damage to leather, increased rate of corrosion of iron, steel, zinc and aluminium.|
|Hydrocarbons Polynuclear Aromatic Compounds(PAC) and Polynuclear Aromatic Hydrocarbons(PAH)||Automobile exhaust and industries,leaking fuel tanks, leaching from toxic waste dumping sites and coal tar lining of some water supply pipes.||Carcinogenic (may cause leukemia)|
|Chlorofluoro carbons (CFCs)||Refngerators, air conditioners, foam shaving cream, spray cans and cleaning solvents.||Destroy ozone layer which then permits harmful UV rays to enter the atmosphere.|
|Nitrogen Oxides||Automobile exhausts, burning of fossil fuels, forest fires,electric generation plants, smelting plants, industnal boilers, petroleum refineries and volcanic eruptions||Forms photochemical smog, at higher concentrations causes leaf damage or affects the photosynthetic activities of plants and causes respiratory problems in mammals.|
|PAN – peroxylacetyl -nitrate||Photochemical reactions of hydrocarbons and nitrogen oxides.||Irritation of eye, throat and respiratory tract, damage to clothes, paint and rubber articles, damage to leaves and stomatal tissue in plants.|
|Particulate matter Lead halides (lead pollution)||Combustion of leaded gasoline products||Toxic effect in man.|
|Asbestos particles||Mining activities||Asbestosis – a cancerous disease of the lungs|
|Silicon dioxide||Stone cutting, pottery, glass manufacturing and cement industries.||Silicosis, a cancerous disease.|
|Biological matter like the pollen grains||Flowers||Allergy|
|Fungal spores, bacteria, virus, etc||Microbes||Infectious deseases|