Air pollution refers to the undesirable change occurring in air causing harmful effects on man and domesticated species.
# Air Pollutants : The common air pollutants are : Dust, Smoke, Carbon monoxide (CO), Ammonia (NH3), Sulphur dioxide (SO2), Hydrogen sulphide (H2S), Nitrogen dioxide (NO2), Hydrogen cyanide, Hydrogen fluorides, Chlorines, Phosgenes, Arsines, Aldehydes, Ozone, Ionising and radiations. CO2 is not a normal air pollutant. There is 0.03% CO2 in the air its higher percentage is the cause of green house effect.
Types of air pollutants : It is two types :
- (a) Primary air pollutants : Air is polluted by poisonous gases and undesirable substances. They are released by burning fossil fuels. These substances are called primary air pollutants. The primary air pollutants are the following :
Soot released from unburned fuel.
Sulphur dioxide (SO2).
Benzopyrene (hydrocarbon) released from cigarette smoke.
Ammonia (NH3).
Oxides of nitrogen.
Carbon monoxide (CO).
Lead (Pb).
- (b) Secondary air pollutants : Secondary air pollutants are poisonous substance formed from primary air pollutants. In bright sun light nitrogen, nitrogen oxides, hydrocarbons and O2 interact to produce more powerful photochemical oxidants like ozone (O3), peroxyacetyl nitrate (PAN), aldehydes, sulphuric acid, peroxides, etc. All these constitute photochemical smog, which retard photosynthesis in plants.
# Causes of air pollution
(a) Agriculture : Hydrocarbons released by plants, pollen grains, insectisides etc. cause air pollution.
(b) Dust : Dust in the air is increased by dust storms wind, volcanoes, automobiles, etc.
(c) Industries : Combustion of fossil fuels like coal, petroleum, etc. Industrial smoke is the main source of pollution.
(d) Automobiles : The combustion of petrol and diesel in automobiles releases harmful gases into the air. They also produce dust.
(e) Ionising radiations : Ionizing radiations include alpha particles, beta particles and gamma rays. They are released into the air on testing atomic weapons.
(f) Freons : Use of freons and other chloro-fluoro-carbon compounds in refrigerants, coolants and as filling agents in aerosol also cause pollution.
(g) Aerosols : Aerosols are small particles of all sorts of solid or liquid substances suspended in the air. They block the stomata of plants and prevent the gaseous exchanges between plants and atmosphere. They may also change the climate of an area.
Biological Indicators : Some plants are sensitive to certain air pollutants. These plants are used to indicate the presence of these substances. These plants are called biological indicators. e.g.,
The tissues present in the tip of dusheri mango turns black when they are exposed to sulphur dioxide (SO2) fumes.
Pinto beans and Petunias are used to indicate the presence of peroxy acetyl nitrate (PAN).
Tobacco and annual blue–grass plants are used to show the presence of ozone (O3). Lichens are biological indicaters of air pollution caused by SO2.
# Ecological effects of air pollution
(a) Death : When air is polluted with poisonous gases, death comes as a result immediately. Bhopal episode is a good example. Bhopal episode – On 2nd December 1984 about 3000 human beings died, about 5000 paralysed and thousands of cattles, birds, dogs and cats died in one night at Bhopal. This mass death is due to the leakage of methyl isocyanate (toxic gas) into the air from an insecticide plant managed by Union Carbide Corporation.
(b) Chlorosis : The disappearance of chlorophyll is called chlorosis. It is caused by SO2, nitrogen dioxide, ozone and fluorides.
(c) Necrosis : The breakdown of cells is called necrosis. It is caused by SO2, nitrogen dioxide, ozone and fluorides.
(d) Green house effect : CO2 is released into the air by the combustion of fuels. It is estimated that CO2 content of the air is increasing at the rate of 0.4% per annum. This will result in an appreciable warming up of the earth. This is called green house effect. It is very likely that this will cause the melting of polar ice caps resulting in a rise of nearly 60 feet on the sea level. Coastal regions and low lying areas all over the world will be go under water.
Not only CO2 but CFC and to some extent methane and oxides of nitrogen disturb the temperature of earth hence they all are described as green houses gases.
3.0 pH has been recorded in acid rain.
(e) Crop losses : Heavy loss of crop is caused by smog. Smog denotes a combination of smoke and fog. The important components of smog are ozone and PAN (peroxy acetyl nitrate). They damage leafy vegetables, cereals, textile crops, ornamental plants, fruits and forest trees.
(f) Respiratory disorders : Excessive ethylene accelerates respiration causing premature senescence (old age) and abscission (accumulation of yellow fluid (pus) in the body). Aldehydes irritate nasal and respiratory tracts. Chlorine and phosgenes (carbonyl chloride) cause pulmonary oedema. Bronchitis is another bad effect of air pollution.
(g) Nausea : H2S smells like rotten eggs and causes nausea.
(h) Vomiting : SO2 causes vomiting.
(i) Jaundice : Arsines induce RBC breakdown and jaundice.
(j) Oxygen carrying capacity : CO reduces O2 carrying capacity of RBC by its permanent combination with haemoglobin.
(k) Coughing : Coughing is induced by phosgenes (carbonyl chloride).
(l) Headache : SO2 causes headache.
(m) Cancer : Cancer is caused by air pollutants like ash, soot, smoke, chromium, nickel and readioactive elements.
(n) Mutation : Radioactive elements produce mutation. Ozone produces chromosomal aberrations.
(o) Cardiac diseases : Cadmium causes high blood pressure and heart diseases.
(p) Pneumonia : Pneumonia is caused by breathing in too much of manganese particles.
(q) Depletion of Ozone umbrella : In the atmosphere, about 30 km above the surface of the earth, the ozone molecules (O3) form an umbrella. It prevents the penetration of harmful ultra violet radiation from the sun and thus protects the life of the earth. It is now feared that there is danger of depletion of the ozone umbrella, which may occur by the use of freons and other CFC-compounds in refrigerants, coolants in domestric refrigenrators and cold storage facilities, and as filling agents in the form of plastics and in aerosol packages. On reaching the ozone umbrella, they destroy ozone molecules as a result of photochemical reactions. Over the past 16 years, the density of the ozone layer has been diminishing at an average rate of 3%. It is calculated that the depletion of ozone layer by 1% results in an increase in the incidence of skin cancer by 5% to 7%. A hole in O3 layer has been discovered in Antarctica.
(r) Acid rain : One of the major environmental issues facing human society at the national and international level is the problem of rain water having low pH. The rainwater is always slightly acidic as CO2 in the atmosphere gets dissolved in it. However during recent years, it has been noted a further lowering of pH of rain water often as low as 2.4. This lowering of pH is due to the dissolution of acids in the rain water. Precipitation of oxides of sulphur and nitrogen with rain is termed acid rain. Acid rain is caused by air pollution. When atmospheric air contains sulphur dioxide (SO2) and oxides of nitrogen such as nitrous oxide (N2O) and nitric oxide (NO), they dissolve in rain water forming sulphuric acid and nitric acid. The rain water falls as acid rain. The main source of releasing oxides of sulphur and nitrogen are the power plants based on coal and oil. They contribute more than 60% of all sulphur oxides and 25 to 30% of nitrogen oxides in the atmosphere. Automobiles make a substantial contribution in large cities. Ozone is now recognised as a major factor in the formation of acid rain.
Acid rain affects both materials and organisms. It attacks building materials principally sandstone, limestone, marble, steel and nickel. In plants, it leads to chlorosis (gradual yellowing in which the chlorophyll making mechanism is impeded) or depigmentation of leaves. The concentration of SO3 in atmosphere is around 0.01 ppm.
Acid rain increases the acidity of lakes and rivers. Vast tracts of forests and lakes in Europe and North America have been destroyed by acid rain. Acidity kills fish, bacteria and algae and the aquatic ecosystem collapses into sterility leaving a crystal clear but ultimately a dead lake.
# Control of air pollution
(a) The emission of exhaust from automobiles can be reduced by devices such as positive crankcase ventilation valve and catalytic converter.
(b) Electrostatic precipitators can reduce smoke and dust from industries.
(c) Gaseous pollutants arising from industries can be removed by differential solubility of gases in water.
(d) A finepray of water in the device called scrubber can separate many gases like NH3, SO2, etc. from the emitted exhaust.
(e) Certain gases can be removed by filtration or absorption through activated charcoal.
(f) Certain gases can be made chemically intert by chemical conversion.
(g) At the Government level pollution can be controlled by framing legislations.
(h) Vehicles based on compressed natural gas (CNG) should be introduced.
Air pollution refers to the undesirable change occurring in air causing harmful effects on man and domesticated species.
# Air Pollutants : The common air pollutants are : Dust, Smoke, Carbon monoxide (CO), Ammonia (NH3), Sulphur dioxide (SO2), Hydrogen sulphide (H2S), Nitrogen dioxide (NO2), Hydrogen cyanide, Hydrogen fluorides, Chlorines, Phosgenes, Arsines, Aldehydes, Ozone, Ionising and radiations. CO2 is not a normal air pollutant. There is 0.03% CO2 in the air its higher percentage is the cause of green house effect.
Types of air pollutants : It is two types :
- (a) Primary air pollutants : Air is polluted by poisonous gases and undesirable substances. They are released by burning fossil fuels. These substances are called primary air pollutants. The primary air pollutants are the following :
Soot released from unburned fuel.
Sulphur dioxide (SO2).
Benzopyrene (hydrocarbon) released from cigarette smoke.
Ammonia (NH3).
Oxides of nitrogen.
Carbon monoxide (CO).
Lead (Pb).
- (b) Secondary air pollutants : Secondary air pollutants are poisonous substance formed from primary air pollutants. In bright sun light nitrogen, nitrogen oxides, hydrocarbons and O2 interact to produce more powerful photochemical oxidants like ozone (O3), peroxyacetyl nitrate (PAN), aldehydes, sulphuric acid, peroxides, etc. All these constitute photochemical smog, which retard photosynthesis in plants.
# Causes of air pollution
(a) Agriculture : Hydrocarbons released by plants, pollen grains, insectisides etc. cause air pollution.
(b) Dust : Dust in the air is increased by dust storms wind, volcanoes, automobiles, etc.
(c) Industries : Combustion of fossil fuels like coal, petroleum, etc. Industrial smoke is the main source of pollution.
(d) Automobiles : The combustion of petrol and diesel in automobiles releases harmful gases into the air. They also produce dust.
(e) Ionising radiations : Ionizing radiations include alpha particles, beta particles and gamma rays. They are released into the air on testing atomic weapons.
(f) Freons : Use of freons and other chloro-fluoro-carbon compounds in refrigerants, coolants and as filling agents in aerosol also cause pollution.
(g) Aerosols : Aerosols are small particles of all sorts of solid or liquid substances suspended in the air. They block the stomata of plants and prevent the gaseous exchanges between plants and atmosphere. They may also change the climate of an area.
Biological Indicators : Some plants are sensitive to certain air pollutants. These plants are used to indicate the presence of these substances. These plants are called biological indicators. e.g.,
The tissues present in the tip of dusheri mango turns black when they are exposed to sulphur dioxide (SO2) fumes.
Pinto beans and Petunias are used to indicate the presence of peroxy acetyl nitrate (PAN).
Tobacco and annual blue–grass plants are used to show the presence of ozone (O3). Lichens are biological indicaters of air pollution caused by SO2.
# Ecological effects of air pollution
(a) Death : When air is polluted with poisonous gases, death comes as a result immediately. Bhopal episode is a good example. Bhopal episode – On 2nd December 1984 about 3000 human beings died, about 5000 paralysed and thousands of cattles, birds, dogs and cats died in one night at Bhopal. This mass death is due to the leakage of methyl isocyanate (toxic gas) into the air from an insecticide plant managed by Union Carbide Corporation.
(b) Chlorosis : The disappearance of chlorophyll is called chlorosis. It is caused by SO2, nitrogen dioxide, ozone and fluorides.
(c) Necrosis : The breakdown of cells is called necrosis. It is caused by SO2, nitrogen dioxide, ozone and fluorides.
(d) Green house effect : CO2 is released into the air by the combustion of fuels. It is estimated that CO2 content of the air is increasing at the rate of 0.4% per annum. This will result in an appreciable warming up of the earth. This is called green house effect. It is very likely that this will cause the melting of polar ice caps resulting in a rise of nearly 60 feet on the sea level. Coastal regions and low lying areas all over the world will be go under water.
Not only CO2 but CFC and to some extent methane and oxides of nitrogen disturb the temperature of earth hence they all are described as green houses gases.
3.0 pH has been recorded in acid rain.
(e) Crop losses : Heavy loss of crop is caused by smog. Smog denotes a combination of smoke and fog. The important components of smog are ozone and PAN (peroxy acetyl nitrate). They damage leafy vegetables, cereals, textile crops, ornamental plants, fruits and forest trees.
(f) Respiratory disorders : Excessive ethylene accelerates respiration causing premature senescence (old age) and abscission (accumulation of yellow fluid (pus) in the body). Aldehydes irritate nasal and respiratory tracts. Chlorine and phosgenes (carbonyl chloride) cause pulmonary oedema. Bronchitis is another bad effect of air pollution.
(g) Nausea : H2S smells like rotten eggs and causes nausea.
(h) Vomiting : SO2 causes vomiting.
(i) Jaundice : Arsines induce RBC breakdown and jaundice.
(j) Oxygen carrying capacity : CO reduces O2 carrying capacity of RBC by its permanent combination with haemoglobin.
(k) Coughing : Coughing is induced by phosgenes (carbonyl chloride).
(l) Headache : SO2 causes headache.
(m) Cancer : Cancer is caused by air pollutants like ash, soot, smoke, chromium, nickel and readioactive elements.
(n) Mutation : Radioactive elements produce mutation. Ozone produces chromosomal aberrations.
(o) Cardiac diseases : Cadmium causes high blood pressure and heart diseases.
(p) Pneumonia : Pneumonia is caused by breathing in too much of manganese particles.
(q) Depletion of Ozone umbrella : In the atmosphere, about 30 km above the surface of the earth, the ozone molecules (O3) form an umbrella. It prevents the penetration of harmful ultra violet radiation from the sun and thus protects the life of the earth. It is now feared that there is danger of depletion of the ozone umbrella, which may occur by the use of freons and other CFC-compounds in refrigerants, coolants in domestric refrigenrators and cold storage facilities, and as filling agents in the form of plastics and in aerosol packages. On reaching the ozone umbrella, they destroy ozone molecules as a result of photochemical reactions. Over the past 16 years, the density of the ozone layer has been diminishing at an average rate of 3%. It is calculated that the depletion of ozone layer by 1% results in an increase in the incidence of skin cancer by 5% to 7%. A hole in O3 layer has been discovered in Antarctica.
(r) Acid rain : One of the major environmental issues facing human society at the national and international level is the problem of rain water having low pH. The rainwater is always slightly acidic as CO2 in the atmosphere gets dissolved in it. However during recent years, it has been noted a further lowering of pH of rain water often as low as 2.4. This lowering of pH is due to the dissolution of acids in the rain water. Precipitation of oxides of sulphur and nitrogen with rain is termed acid rain. Acid rain is caused by air pollution. When atmospheric air contains sulphur dioxide (SO2) and oxides of nitrogen such as nitrous oxide (N2O) and nitric oxide (NO), they dissolve in rain water forming sulphuric acid and nitric acid. The rain water falls as acid rain. The main source of releasing oxides of sulphur and nitrogen are the power plants based on coal and oil. They contribute more than 60% of all sulphur oxides and 25 to 30% of nitrogen oxides in the atmosphere. Automobiles make a substantial contribution in large cities. Ozone is now recognised as a major factor in the formation of acid rain.
Acid rain affects both materials and organisms. It attacks building materials principally sandstone, limestone, marble, steel and nickel. In plants, it leads to chlorosis (gradual yellowing in which the chlorophyll making mechanism is impeded) or depigmentation of leaves. The concentration of SO3 in atmosphere is around 0.01 ppm.
Acid rain increases the acidity of lakes and rivers. Vast tracts of forests and lakes in Europe and North America have been destroyed by acid rain. Acidity kills fish, bacteria and algae and the aquatic ecosystem collapses into sterility leaving a crystal clear but ultimately a dead lake.
# Control of air pollution
(a) The emission of exhaust from automobiles can be reduced by devices such as positive crankcase ventilation valve and catalytic converter.
(b) Electrostatic precipitators can reduce smoke and dust from industries.
(c) Gaseous pollutants arising from industries can be removed by differential solubility of gases in water.
(d) A finepray of water in the device called scrubber can separate many gases like NH3, SO2, etc. from the emitted exhaust.
(e) Certain gases can be removed by filtration or absorption through activated charcoal.
(f) Certain gases can be made chemically intert by chemical conversion.
(g) At the Government level pollution can be controlled by framing legislations.
(h) Vehicles based on compressed natural gas (CNG) should be introduced.