ENVIRONMENTAL ISSUES

 

ENVIRONMENTAL ISSUES

  • Pollution: is any undesirable changed in physical chemical or biological characteristics of air, land, water or soil.
  • Pollutant: Any solid, liquid or gas released into the environment in such a huge quantities that make our environment unhealthy is called pollutant.
  • Environment (protection) Act, 1986 to protect and improve the quality of our environment (air, water and soil)

AIR POLLUTION AND ITS CONTROL:

Effect of air pollution:

  • Cause injury to all living organisms.
  • Reduce growth and yield of crops.
  • Cause premature death of plants.
  • Affects the respiratory system of human being.
  • Particulate size 2.5 micrometers or less are responsible for breathing and respiratory symptoms like irritation, inflammations and damage to the lungs and premature death.

Pollution caused by thermal power plant:

  • Sources of particulate matter: thermal power plant, smelters
  • These plants release particulate matter and gaseous air pollutant.
  • A harmless gas released by these plants is Nitrogen and Oxygen.

Prevention of air pollution: ways to remove particulate matter:

  • Electrostatic precipitator
    • Widely used to remove particulate matter in the exhaust from a thermal power plant.
    • Electrode wires that are maintained at several thousand volts, which produce a corona that release electrons.
    • Electron binds with particulate matter giving them a net negative charge.
    • Positively charged collecting plates attract the charged dust particle.

  • Scrubber:
    • Removes gases like sulphur dioxide.
    • The exhaust is passed through a spray of water or lime.

  • Methods to reduce vehicular pollution:
    • Use of lead free petrol or diesel can reduce vehicular pollution.
    • Catalytic converter:
      • Having expensive metals namely platinum, palladium and rhodium as the catalyst.
      • These metals reduce emission of poisonous gases.
      • The unburnt hydrocarbons are converted into CO2 and H2O.
      • Carbon monoxide and nitric oxide are changed to carbon dioxide and nitrogen gas respectively.
      • Motor vehicle equipped with catalytic converter should use unleaded petrol because lead in the petrol inactivates the catalyst.

Controlling Vehicular pollution: A case study of Delhi:

  • Use of CNG (compressed natural gas):

Advantages of CNG

  • CNG burns most efficiently.
  • Very little remain unburnt.
  • Cannot be siphoned
  • Cannot be adulterated like petrol or diesel.
  • CNG is cheaper than petrol and diesel.

Problem of use of CNG:

  • Difficulty in laying down pipelines to deliver CNG
  • Non-assurance of uninterrupted supply.
Other parallel steps taken in Delhi:
  • Phasing out old vehicles.
  • Use of unleaded petrol.
  • Use of low-sulphur petrol and diesel.
  • Use of catalytic converter in vehicle.
  • Application of strict pollution level norms for vehicle.
New auto fuel policy to cut down vehicular pollution.
  • Steadily reducing the sulphur and aromatic content in petrol and diesel fuels.
  • Euro-II norms
    • Sulphur reduced to 350 ppm in diesel.
    • Sulphur reduced to 150 ppm in petrol
    • Aromatic hydrocarbon to be reduced to 42 %.
    • Up gradation of vehicle engines.

  • Due to above steps taken by Delhi Govt. there is substantial fall in CO2 and SO2 level between 1997 and 2005.

 

CBSE Biology (Chapter Wise) Class XII ( By Mr. Hare Krushna Giri )
Email Id : [email protected]

Biology - Mr. Hare Krushna Giri

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