ENVIRONMENT AND ENVIRONMENTAL PROBLEMS - III : LONG ANSWERS

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1. Describe sources of air pollution in brief.
   

   ANS :

   
   
   • The two types of sources of air pollution are : Natural sources and man-made sources.
   • Natural sources(factors) polluting the atmosphere are : volcanoes, forest fires, decaying plants, storms, pollen grains, lightening-induced chemicals, etc.
   • Man-made sources of pollution are : Burning of firewood, burning of fossil fuels, automobile smoke, aeroplanes, power stations, industrialisation, agriculture, wars, atomic explosions, deforestation, mining, oil refineries, etc.
     

   
   

   
   
2. Mention harmful effects of water pollution.
   

   ANS :

   
   
   • Mercury mixed with water causes the disease Minamata. It is a poisonous disease and may cause death. It was first observed in coastal area of Minamata city of Japan.
   • Chemicals like mercury, cadmium, cobalt, etc. present in water cause diarrhoea.
   • Biological Oxygen Demand(BOD) of clean water is less. BOD of polluted water increases and harms aquatic organisms, sometimes causing their destruction.
   • Accumulation of domestic sewage and fertilisers results in the increase of nitrates and phosphates in water. These promote the growth of algae and other microorganisms. Thus, there is excessive loading of aquatic ecosystem with nutrients and algal growth, a phenomenon called eutrophication. Due to eutrophication BOD increases and organisms die.
     

   
   

   
   
3. Describe the interrelationship between population, environment and development.
   

   ANS :

   
   
   • Exploding population at increasing speed has become a major problem to environment and development at global level.
   • Increase in population leads to increase in demand for food. This leads to increase in the use of fertilisers and pesticides.
   • Excessive use of fertilisers and pesticides causes pollution which has direct and indirect effect on human health.
   • Increasing demand for space due to population explosion results in encroachment of fertile and agricultural land, forests and habitat of wild life.
   • To maintain the existence of human life, the balance between population, environment and development must be maintained.
     

   
   

   
   
4. List out different laws for environmental protection.
   

   ANS :For the protection and conservation of environment, following laws have been enacted by the Government of India :
   

   
   
   • Environment (Protection) Act, 1986
   • Forest (Conservation) Act, 1980
   • Water (Prevention and Control of Pollution) Act, 1974
   • Wildlife (Protection) Act, 1972
   • The Motor Vehicle Act, 1983
   • Prevention of Cruelty to Animals Act, 1966
   • Air (Prevention and Control of Pollution) Act, 1981
   • The Insecticide Act, 1968
     

   
   

   
   
5. Describe harmful effects of air pollution.
   

   ANS :

   
   
   • Burning sensation in eyes, nose and throat.
   • Diseases of lungs like bronchitis, asthma, etc. caused by pollutant gases like SO₂ and NO₂.
   • Diseases of respiratory system spread through dust particles. Silicosis is caused by silica and asbestosis is caused by asbestos.
   • Cancer caused by carcinogenic pollutants.
   • Heavy metals inhaled through air cause poisonous effects.
   • Increase in ultraviolet radiation reaching earth due to depletion of ozone layer causes skin cancer, damage to eyes and damage to immune system.
   • Dissolution of atmospheric gases like SO₂, SO₃, NO₂ in moisture results in formation of sulphuric acid and nitric acid. This causes acid rain which harms organisms, various monuments and buildings.
   • Carbon dioxide and methane absorb heat and increase the temperature of earth's atmosphere. This is known as Greenhouse effect. This increase in temperature results in melting of ice on polar regions and causes sea level to rise.
     

   
   

   
   
6. Write a descriptive note on Prevention and Control of Air Pollution.
   

   ANS :Two types of methods are used for prevention and control of air pollution :

   
   
   1. Methods for controlling gaseous pollutants :
      
      
      1. Combustion : This method is used for pollutants in the form of organic gases or vapours. These pollutants are converted into water vapour and relatively less harmful products such as CO₂ by flame combustion or catalytic process.
      2. Absorption : In this technique, the gaseous effluents are passed through specific scrubbers or absorbers. The gaseous pollutants are absorbed and air is purified.
         
      
      
   2. Methods for controlling particulate emissions :
      
      
      1. Wet Scrubbers : Wet scrubbers are used in chemical, mining and metallurgical industries to trap SO₂, NH₃, metal fumes, etc.
      2. Electrostatic Precipitators : The gas or air stream containing aerosols in the form of dust, fumes or moisture is passed between two electrodes. The aerosol particles get precipitated on the electrodes.
         
      
      

   
   

   
   
   
   NOTE : The diagram in the textbook showing WET SCRUBBER is actually the diagram of BAG FILTER.
   
7. Describe prevention and control of water pollution.
   

   ANS :Sewage treatment and Oxidation pond are the two methods of controlling water pollution.
   

   
   
   1. SEWAGE TREATMENT :
      
      
      • This method involves three steps.
      • During first step, large components and suspended matter are isolated by sedimentation and converted into harmless matter which can be used as fertiliser.
      • During second stage, air containing oxygen and bacteria is passed through water in an aeration tank. The bacteria degrade organic substances. Then chlorination is performed.
      • During tertiary(third) stage, substances like nitrates and phosphates are removed to obtain clean water.
        
      
      
   2. OXIDATION POND :
      
      
      • This method, developed by National Environment Engineering Research Institute(NEERI), Nagpur, is used to treat industrial effluents and sewage.
      • Oxidation pond is a shallow pond where domestic as well as industrial waste matter is stored.
      • This water is mixed with microorganisms and algae which oxidise carbonic components present in water and water gets purified.
        
      
      

   
   

   
   
8. 
   

   ANS :