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Environmental issues

Biology Index

1. Pollution

Pollution is any change in physical, chemical or biological characteristics of the environment that has the potentiality to harm human life, other species, natural resources.
Contamination is the presence of harmful organisms or their toxins that cause discomfort or disease.

Causes of pollution

  1. The major cause of pollution is
    • Automobile exhaust.
    • Increasing use of pesticides, insecticides,and herbicides.
    • Waste chemical production from factories.
    • The rise in atmospheric CO2.
    • Radioactive substances.
  2. Natural pollution is pollution caused by natural sources. Example: Volcanic eruption,the release of methane by paddy fields and cattle, the release of carbon monoxide of plants and animals, emission of natural gas,ozone, nitrogen oxide, soil erosion, dust storms, ultra-violet rays etc. 99.95% of pollution is natural.
  3. Man-made or anthropogenic pollution is pollution resulting from human activities like the burning of fossil fuels, deforestation, mining, sewage, industrial effluents, pesticides, fertilizers etc. Amount of man-made pollution is hardly 0.05% of total but more dangerous than natural pollution.
  4. On the basis of emission, pollution may be :
    • Point source pollution: It is from a single point. Example municipal sewage and chimney.
    • Line source pollution: It is passed along a narrow belt. Example Road due to automobile exhaust.
    • Area source pollution: It is over a large area. Example. Sprayed fertilizers or pesticides through runoff.

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2 Classification of pollutants

On the basis of their existence in nature pollutants are of two types:
  1. Quantitative pollutants: These normally occurs in nature but are also added in large quantities by man. Examples: CO, CO2 and nitrogen oxide.
  2. Qualitative pollutants: They do not occur in an environment normally but are added by man. Example: D.D.T, insecticides.
On the basis of form, pollutants are of two types
  1. Primary pollutants: These persist in the form in which they are added to the environment. Example DDT, plastics, CO.
  2. Secondary pollutants: These are formed by reacting amongst the primary pollutants. Example nitrogen oxide and hydrocarbons react in presence of sunlight to form two secondary pollutants such as PAN ( peroxy acyl nitrate). Secondary pollutants are more toxic than the primary pollutants. The phenomenon of increase in toxicity by reaction among the pollutants is called synergism.
On the basis of their nature of disposal the pollutants are of two types:
  1. Non-degradablepollutants: Pollutants which cannot be broken down by a micro-organism. Example: DDT, phenolic compounds, ABS, hydrocarbons.
  2. Biodegradable pollutants: Pollutants which can be broken down by a micro-organism. Example Sewage.

3 Effect of pollution

Pollution has an adverse effect like:
  1. Crop production change.
  2. Causes different diseases
  3. Soiling of building and textiles
  4. Loss of resources.
  5. Metal corrosion
  6. Money, funds, manpower involved in pollution control

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