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Chapter Contents Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 Air Pollution and its Control Water Pollution and its Control Solid Wastes Agro-chemicals and their Effects Radioactive Wastes Greenhouse Effect and Global Warming Ozone Depletion in the Stratosphere Degradation by Improper Resource Utilisation and Maintenance Deforestation Human population size has grown enormously over the last hundred years. This means increase in demand for food, water, home, electricity, roads, automobiles and numerous other commodities. These demands are exerting tremendous pressure on our natural resources, and are also contributing to pollution. Major issues relating to environmental pollution and depletion of valuable natural resources vary in dimension from local regional to global levels. Pollution is any undesirable change in physical, chemical or biological characteristics of air, land, water or soil. Agents that bring about such an undesirable change are called as pollutants. In order to control environmental pollution, the Government of India has passed the Environment (Protection) Act, 1986 to protect and improve the quality of our environment (air, water and soil). AIR POLLUTION AND ITS CONTROL It is the occurrence or presence of any material or gas in the air in such a concentration which is harmful to man, vegetation, animals and their environment. Substances and factors which cause air pollution are called air pollutants. Air pollution is both natural and anthropogenic. Anthropogenic pollution comes from both mobile and fixed sources. Air pollutants coming directly from the pollution sources are called primary air pollutants (CO, SO2, NOx, hydrocarbons). Reaction between two or more primary air pollutants gives rise to secondary air pollutants (ozone, PAN). Causes of Air Pollution (i) Smokestack of thermal power plants, smelters and other industries release particulate and gaseous air pollutants together with harmless gases such as N2 and O2. Chapter 21 Environmental Issues
112 Environmental Issues NEET Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 (ii) Pollutants from automobiles, locomotives, aircrafts and exhausts in cities constitutes the major part of the total air pollution. (iii) Incomplete and complete combustion of the carbon contents of fossil fuel wood and charcoal produce carbon monoxide and carbon dioxide along with sulphur dioxide. (iv) Natural sources include pollen, dust and smoke (from forest fires and volcanic ash) which are emitted into the atmosphere. We are dependent on air for our respiratory needs. Air pollutants cause injury to all living organisms. They reduce growth and yield of crops and cause premature death of plants. Air pollutants also deleteriously affect the respiratory system of humans and animals. Harmful effects depend on the concentration of pollutants, duration of exposure and the organism. Common Air Pollutants : These are basically of two types i.e., gaseous materials and particulate matter. (a) Gaseous Materials Pollutant Source Effect (1) Carbon monoxide (Major air pollutant) Incomplete combustion of fossil fuels in automobiles. Produces which carboxyhaemoglobin reduces the O2 carrying capacity of the blood resulting in giddiness, decreased vision, headache etc. (2) Sulphur dioxide Oil refineries, smelters of ores combustion of sulphur containing fuels. (i) It inhibits ETS in plants. (ii) Acid rains. (iii) Stone cancer. (iv) Eye irritation. (v) Severe respiratory problems. (vi) Phaeophytization in lichens. Yellowing of Taj Mahal is reported to be caused by SO2 pollution. (3) NOX Combustion of fossil fuels at high temperature in automobile engines. Heart and lung problems. (4) Hydrocarbons Incomplete combustion as unburnt discharge, newly manufactured carpet. Cancer (b) Particulate Matter These are added into the air by industries, automobiles and by many operations like blasting, drilling, crushing, grinding, mixing etc. These pollutants may be either solid or liquid particles. It is differentiated into Settleable ( 10 m, settles out in less than one day) and Suspended ( 10 m) remaining in air for weeks.
NEET Environmental Issues 113 Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 S.No. Pollutant Effect Source 1. Aerosols : Smoke : Dust and Mist : Vapour chemicals in the form of Fluorocarbons, Chlorofluorocarbon, Oxides of sulphur and nitrogen 2. Visible suspension of carbon 3. Both are more than 1 m in size but dust is solid and mist is liquid in nature. 4. Pollen, spores, cyst and bacteria   Emission of Jet and Supersonic aeroplanes       Refrigerators and air conditioners use aerosols as refrigerant [CF Cl or Freon] Solid plastic foams. Fog is an aerosol of water droplets. Burning and smouldering of organic matter. The power stations throw out large amount of (Fine particulate matter produced during coal burning) is a combination of smoke, chemical fumes and fog. Released from industries Air 2 2 flyashes Smog Causes O depletion 3               Causes respiratory problems like asthma and bronchitis in humans. Decreases visibility due to suspension of particles in air. Byssinosis (Cotton dust) Asbestosis (Asbestos industry) Silicosis (Stone grinders) Siderosis (Iron mills) Pneumoconiosis (Coal mines and Flour mills) Manganese poisoning (welders) Allergic reactions Bronchial asthma Emphysema T.B. Lung cancer Hay fever is very common form of pollen allergy. Causes : Causes : According to Central Pollution Control Board (CPCB) particulate size 2.5 m or less in diameter are responsible for causing the greatest harm to human health. These fine particulates can be inhaled deep into the lungs and cause breathing and respiratory symptoms, irritation, inflammation and damage to the lungs and premature deaths. Control of Air Pollution Separation of pollutant from harmless gases (a) Electrostatic precipitator : (i) It is most effective device to remove over 99% of particulate matter present in the exhaust from a thermal power plant.
114 Environmental Issues NEET Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 (ii) It has electrode wires that are maintained at several thousand volts which produce a corona that releases electrons. These electrons attach to dust particles giving them a net negative charge. (iii) The collecting plates are grounded and attract the charged dust particles. (iv) The velocity of air between the plates must be low enough to allow the dust to fall. Clean air Water/lime spray Discharge corona Negatively charged wire Dust particles Dirty air Particulate matter Dirty air Clean air Collection plate grounded Electrostatic precipitator Scrubber Fig.: Electrostatic precipitator (b) Scrubber : The industries which produce SO2 as a by product must have scrubbing mechanism installed in them. In this method, effluents containing sulphur dioxide are passed through a slurry of water and crushed limestone (CaCO3). The calcium in limestone combines chemically with the sulphur to produce calcium sulphate (CaSO4) which is separately collected. (c) Control of Automobile Exhaust (i) Automobiles are major cause for atmospheric pollution atleast in the metro cities. Proper maintenance of automobiles along with use of lead free petrol or diesel can reduce the pollutants they emit. (ii) Catalytic converters have costly metals like platinum-palladium and rhodium as catalysts. Exhaust gases first pass through catalytic converter. Hydrocarbons which have been left unburnt are oxidized to produce carbon dioxide and water. Carbon monoxide is also oxidized to form carbon dioxide. However, nitrogen oxide splits up to form nitrogen gas. Automobiles fitted with catalytic converter should not use leaded petrol because lead inactivates the catalyst of the converter. The Air (Prevention and Control of Pollution) Act, 1981 : The Act deals with the preservation of air quality and the control of air pollution with a concern for the detrimental effects of air pollutants on human health and also on the biological world. In 1987, important amendement to Air Act 1981 was made and noise was recognised as an air pollutant. Noise Pollution Noise is usually defined as unwanted sounds which is being dumped into the atmosphere to disturb the unwilling ears. Noise is measured by a sound meter and is expressed in a unit called decibel (dB). Any value more than 80 dB causes noise pollution. Noise becomes unbearable at 140 dB. The intensity of sound in normal conversation is 30-60 dB. Sources of Noise Pollution Noise can either be natural like thundering sound or man-made. The main sources of man-made noise pollution are: (i) Annoying and damaging sounds of various industries. (ii) Defence material like rockets, tanks etc.