CBSE Class 12 Biology Environmental Issues Worksheet

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 ENVIRONMENTAL ISSUES
 
Human population explosion increases the demand for food, water, home, electricity, roads, automobiles etc. It leads to pollution of air, water and soil.
 
Pollution is any undesirable change in physical, chemical or biological characteristics of air, land, water or soil. Agents that cause pollution are called as pollutants. The Government of India has passed the Environment (Protection) Act, 1986 to control environmental pollution and protect and improve the quality of our environment.
 
AIR POLLUTION AND ITS CONTROL
 
Causes of air pollution:
 
• Particulate & gaseous air pollutants from smokestacks of thermal power plants, smelters etc.
According to Central Pollution Control Board (CPCB), particulate size of less than 2.5m in diameter (PM 2.5) causes greatest harm to human health. It causes respiratory problems, irritation, inflammations & damage to lungs and premature deaths.
• Pollutants from automobiles.
 
Harmful effects of air pollution:
 
• Air pollutants cause injury to all living organisms.
• They reduce growth and yield of crops and cause premature death of plants.
• Air pollutants affect the respiratory system.
 
Control of air pollution
 
• Particulate matters must be separated/filtered out before releasing the harmless gases into the atmosphere.
• Use of lead-free petrol or diesel.
• Use of catalytic converters (having platinum-palladium & rhodium as the catalysts). It reduces emission of poisonous gases. This converts unburnt hydrocarbons to CO2 & water, and carbon monoxide and nitric oxide to CO2 and nitrogen gas, respectively. Motor vehicles having catalytic converter should use unleaded petrol because lead in the petrol inactivates the catalyst.
• Phasing out of old vehicles
• Use of low-sulphur petrol and diesel
• Application of pollution-level norms for vehicles, etc.
• In Delhi, compressed natural gas (CNG) in public
 
transport (buses) is used. CNG is better than petrol & diesel because CNG burns most efficiently and very little of it is left unburnt. CNG is cheaper than petrol or diesel, cannot be siphoned off by thieves and adulterated like petrol or diesel. The main problem with switching over to CNG is the difficulty of laying down pipelines to deliver CNG through distribution points/pumps and ensuring uninterrupted supply.
 
Electrostatic precipitator: (For figure see TB page: 271)
- It is the device widely used to remove particulate matter.
- It can remove over 99% particulate matter present in the exhaust from a thermal power plant.
- The electrons released from electrode wires (maintained at several thousand volts) attach to dust particles and give a negative charge. The collecting plates attract the charged dust particles.
- The velocity of air between the plates must be low enough to allow the dust to fall.
- A scrubber removes gases like SO2. In a scrubber, the exhaust is passed through a spray of water or lime.
- Very small particulates are not removed by this precipitator. In India, the Air (Prevention & Control of Pollution) Act (1981) was amended in 1987 to include noise as an air pollutant. Noise is undesired high level of sound.
 
Sources of noise pollution:
 
Music instruments, loudspeaker, crackers, industries etc.
 
Harmful effects of noise:
 
• Noise causes psychological and physiological disorders.
• The sound level above 150 dB (generated by takeoff of a jet plane or rocket) may damage ear drums.
• Chronic exposure to relatively lower noise may damage hearing abilities of humans.
• Sleeplessness, increased heartbeat & breathing, stress etc.
 
Control of noise pollution:
 
• Use of sound absorbent materials in industries.
• Delimitation of horn-free zones around hospitals & schools.
• Permissible sound-levels of crackers and loudspeakers.
• Delimit the timings of using loudspeakers.
 
Laws & policies in India to control vehicular pollution:
 
• Auto fuel policy has laid out a roadmap to cut down vehicular pollution in Indian cities.
• Euro II norms: It stipulates that sulphur be controlled at 350 parts-per-million (ppm) in diesel and 150 ppm in petrol. Aromatic hydrocarbons are to be contained at 42% of the concerned fuel. The goal is to reduce sulphur to 50 ppm in petrol and diesel and bring down the level to 35%. Vehicle engines will also need to be upgraded.
 
• The Bharat Stage II: All automobiles and fuel were to have met the Euro III emission specifications in these 11 cities from 1 April 2005 and have to meet the Euro-IV norms by 1 April 2010. The rest of the country will have Euro-III emission norm compliant automobiles and fuels by 2010.
 
WATER POLLUTION AND ITS CONTROL
 
- Water bodies are lifeline of all living organisms.
- Due to human activities, the ponds, lakes, stream, rivers, estuaries and oceans are becoming polluted.
- The Government of India has passed the Water (Prevention and Control of Pollution) Act, 1974 to safeguard our water resources. Domestic Sewage and Industrial Effluents
- A mere 0.1 % impurities make domestic sewage unfit for human use. They include suspended solids (sand, silt, clay etc), colloidal materials (faecal matter, bacteria, cloth, paper fibres etc) and dissolved materials (nutrients like nitrate, NH3, phosphate, Na, Ca etc).
 
- Solids are easy to remove. Removal of dissolved materials, organic compounds and toxic metal ions are most difficult.
- Domestic sewage contains biodegradable organic matter. It is decomposed by microorganisms, which can multiply using these organic substances as substrates and hence utilize some of the components of sewage.
- The amount of biodegradable organic matter in sewage water is estimated by measuring Biochemical Oxygen Demand (BOD).
- During biodegradation, microorganisms consume a lot of O2. It results in a sharp decline in dissolved O2. This causes death of aquatic organisms.


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