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Environmental issues

Biology Index

Soil pollution

It is an alternation in soil caused by removal or addition of substance and factors which decreases its productivity, quality of plants and groundwater. Negative soil pollution is a reduction in soil productivity due to erosion and over-use. Positive soil pollution is a reduction in soil productivity due to the addition of undesirable products ( industrial wastes, air pollution wash down by rain). Landscape pollution is converting the fertile land into barren one by dumping wastes ( ash, sludge, garbage, industrial wastes).

Sources of soil pollution

  1. Pesticides: They include insecticides, fungicides, algaecides, weedicides,and rodenticides.
    1. Organochlorine – These include DDT, BHC etc. They are persistent, fat-soluble and show biomagnifications.
    2. Organo-pesticides- Deradeble but toxic to workers eg, malathion, parathion, carbamates.
    3. Inorganic pesticides – They contain arsenic and sulfur and is persistent.
    4. Weedicides – Often persistent and harmful.
  2. Fertilizers: Excessive use causes natural microflora. Leaching down causes pollution of underground water salts entering crop plants in excess may prove harmful. For example, nitrate-rich leaves, fruits,and water produce nitrate in the alimentary canal that enters the blood combines with haemoglobin which forms methaemoglobin and reducing oxygen transport. It may prove fatal for infants.
  3. Industrial effluents/ wastes: They include scrap, effluents, sludge, flyash and radioactive wastes. Industrial solid wastes and sludge add a lot of toxic chemicals into the soil. Flyash is fall-out from industrial emissions especially thermal plants. Radioactive wastes from testing laboratories and other sources also pollute the soil.
  4. Municipal wastes: they include domestic wastes market wastes, sweepings, wastes from commercial complex, plastic can etc.
  5. E-wastes: Electronic wastes are irreparable computers, mobile,and other electronic goods.

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Control of solid wastes

  1. Recovering and recycling It is carried out with the help of rag pickers. The articles which can recover and recycled are tins, cans, other metal wastes, glass, plastic, polyethylene, rags, paper,and cardboard. Metal waste can be melted and purified.
  2. Source reduction Garbage and other organic wastes are taken out of the urban area and used for formation of compost, biogas,and manure. Three R's-Reduce, Reuse and Recycle of wastes.
  3. Burning Burning is combustion of solid wastes having organic materials in open space. It produces offensive odour and air pollution. Better methods are incineration and pyrolysis.
    • Incineration: It is controlled aerobic combustion of wastes inside chambers of temperature 900 -1300oC. Incinerators are fitted with scrubbers and electrostatic precipitators to prevent the release of smoke and toxic chemicals.
    • Pyrolysis: It is combustion inside chambers in the absence of oxygen at a temperature of 1650OC. It does not yield pollutants but industrial gas and other substances are produced.
  4. Construction material Flyash is being converted into bricks for construction work. Flyash, industrial effluents containing toxic chemicals and hazardous metals can be used as bedding material or road construction.
  5. Dumping Dumping is piling of waste on selected low lying land. It is of two types, open and sanitary.
    • Open dumping: It is accumulating waste on uncovered low lying area. The waste is piled up as high as the equipment can easily do. The waste is periodically burnt or compressed at intervals to reduce its bulk.
    • Sanitary dumping: The waste is compacted and covered over by a layer of earth.

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