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]