Environmental Issues | Plus 2 Botany | Exam Capsule Notes (Web and PDF)


Causes of air pollution:

  •  Particulate & gases from thermal power plants, smelters.
  •  Pollutants from automobiles.

Harmful effects of air pollution:

  • Respiratory problems, damage lungs.
  • Reduced yield of crops and premature death of plants.

Control of air pollution:

  • Separate/filter out particulate matters.
  • Lead-free, low-sulphur petrol or diesel.
  • Use of catalytic converters.
  • Use of compressed natural gas (CNG).

Advantages of CNG:

  • Better and cheaper. Burns completely.
  • It cannot be siphoned off by thieves and adulterated.

Problem of CNG: Difficult to lay down CNG pipelines through distribution points/pumps.

Catalytic converter: A device to reduce emission of poisonous gases. It has platinum-palladium & rhodium as catalysts. 

Electrostatic precipitator: A device to remove particulate matter.

Laws & policies in India to control vehicular pollution

1. Auto fuel policy: To cut down vehicular pollution.

2. Euro III norms:

-   Control sulphur content at 350 ppm in diesel and 150 ppm in petrol.

-   Level of aromatic hydrocarbons is to be at 42% of the fuel.


Sources: Music instruments, loudspeaker, crackers, industries etc.

Harmful effects:

  • Psychological and physiological disorders.
  • The sound level above 150 dB damage ear drums.
  • Sleeplessness, increased heartbeat & breathing, stress etc.


  • 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.


Domestic Sewage and Industrial Effluents

  • Suspended solids: Sand, silt, clay etc.
  • Colloidal materials: Faecal matter, bacteria, cloth, paper fibres etc.
  • Dissolved materials: Nutrients like nitrate, NH3, phosphate, Na, Ca etc.

The amount of biodegradable organic matter in sewage water is estimated by measuring Biochemical Oxygen Demand (BOD).

During biodegradation, microbes consume O2. So O2 is declined causing death of aquatic organisms.

Effect of sewage discharge on some characteristics of a river

Algal bloom: Excess growth of planktonic algae due to more nutrients in water. It deteriorates the water quality causing death of fishes.

Biological magnification (Biomagnification)

Accumulation of the toxicant (mercury, DDT etc.) at successive trophic levels of a food chain.

Biomagnification of DDT in an aquatic food chain:

Water (DDT: 0.003 ppb) → zooplankton (0.04 ppm) → small fish (0.5 ppm) → large fish (2 ppm) → birds (25 ppm).

DDT disturbs calcium metabolism in birds → thinning of eggshell → premature breaking → bird population declines.


Natural aging of a lake by nutrient enrichment.

Nutrients (N2, P etc.) from streams → into the lake → increases lake’s fertility → plants & animals grow rapidly (e.g. Water hyacinth (Eichhornia - ‘Terror of Bengal’) is the most problematic aquatic weed.

Pollutants like effluents from industries and homes accelerate eutrophication. It is called Cultural or Accelerated Eutrophication.

Friends of the Arcata Marsh (FOAM): A citizens group in Arcata for Integrated Waste Water Treatment.

Ecological sanitation

A sustainable system for handling human excreta, using dry composting toilets.

Human excreta can be recycled into natural fertilizer.

There are ‘EcoSan’ toilets in Kerala & Sri Lanka.



(a)   Bio-degradable: Undergo natural breakdown.

(b)   Non-biodegradable: E.g. plastic packets, polybags, polystyrene etc.

(c)    Recyclable: E.g. Plastics, e-wastes etc.

E-wastes (electronic wastes): They are buried in landfills or incinerated. Recycling is the only eco-friendly solution to treat e-wastes.

Polyblend: It is a fine powder of recycled modified plastic. It is mixed with the bitumen and is used to lay roads.


Inorganic fertilisers, pesticides, herbicides, fungicides, etc. are toxic to non-target organisms. These are biomagnified in the terrestrial ecosystems.

Chemical fertilisers cause eutrophication.

Integrated Organic Farming: A cyclical, zero-waste procedure, where waste products from one process are cycled in as nutrients for other processes.


o  Accidental leakage. E.g. Three Mile Island incident & Chernobyl incident.

o  Safe disposal of radioactive wastes.

o  Nuclear radiation causes mutations.


Greenhouse effect is a natural phenomenon that causes heating of Earth’s surface and atmosphere.

Earth’s surface is heated due to solar radiation. Heat is re-emitted as infrared radiation. But a part of it is absorbed by atmospheric gases (CO2, CH4, CFCs, N2O etc.). These gases (greenhouse gases) radiate heat energy to Earth’s surface, heating it up again. It causes greenhouse effect.

Overheating of Earth due to increased level of greenhouse Gases is called global warming.

Impacts of global warming:

  • Climatic changes (e.g. El Nino effect).
  • Melting of polar ice caps, Himalayan snow caps etc.
  • Future impact: Rise in sea level submerging coastal areas.

Control of global warming:

  • Reduce the use of fossil fuel.
  • Reduce deforestation and plant trees.
  • Slowing down the growth of human population.
  • International initiatives to reduce greenhouse gases.


‘Bad’ ozone is formed in troposphere.

‘Good’ ozone is found in the stratosphere. It acts as a shield absorbing ultraviolet radiation from the sun.

Thickness of the ozone (O3) layer is measured in Dobson units (DU).

Ozone is depleted by chlorofluorocarbons (CFCs- used as refrigerant). It has formed Ozone hole over Antarctica.

Impacts of ozone depletion: UV-B causes DNA mutation. It causes aging of skin, skin cancers, inflammation of cornea (snow-blindness), cataract etc.

The Montreal Protocol: An international treaty to control emission of ozone depleting substances.


Soil erosion and desertification:

Over-cultivation, deforestation, grazing and poor irrigation practices, leads to soil erosion. It results in desertification.

Increased urbanization also creates desertification.


Water logging and soil salinity:

Irrigation without proper drainage of water leads to water logging in the soil.

It draws salt to the surface of the soil. The salt is deposited on the land surface or collects at the plant roots.


Conversion of forested areas to non-forested ones.

Reasons of deforestation:

  • Conversion of forest to agricultural land.
  • For timber, firewood, cattle ranching etc.
  • Slash & burn agriculture (Jhum cultivation). In this, forest trees are cut down and burn the plant remains. After cultivation, the area is left for several years for its recovery. Overpopulation & repeated cultivation decreased the recovery phase, resulting in deforestation.

Consequences of deforestation:

  • Atmospheric CO2 is enhanced.
  • Loss of biodiversity.
  • Disturbs hydrologic cycle.
  • Soil erosion & Desertification.

Reforestation: The process of restoring a forest.

People’s Participation in Conservation of Forests

  • Bishnoi movement
  • Chipko Movement of Garhwal Himalayas

Government of India introduced Joint Forest Management (JFM) to work closely with the local communities to protect and manage forests. 

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