Note on Water Pollution and Greenhouse Effects(Global warming)

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Water Pollution

Water is a neutral, nontoxic and unusual chemical. An intermolecular hydrogen bond is responsible for the unusual behaviour of water like a wide liquid range, high boiling point, good solvent for polar solutes and collision without chemical interaction, floating of ice etc. Water acts as a medium to transport many substances dissolved in it.

It is an inevitable medium for life processes and life in the absence of water has no existence. Earth is lively because of water and water is considered as the life-blood of the earth. It means water is an essential substance, not only for aquatic life but also for human beings, animals and plants. Rain water, river water, pond water, lake and sea water are the natural sources of water. The mobility of water in the earth is due to series of changes known as the water cycle.

Water Cycle
source:www.weatherwizkids.com
fig:Water Cycle

Natural water from all the sources is useful for living things but water from a source by environmental degradation may become unsuitable for the survival of aquatic life and others. The survival of aquatic life depends on primarily upon the amount of dissolved gases such as oxygen and carbon dioxide present in water. The freshness of water and useful ingredients present in it decide the healthy existence and longevity of human, animal and aquatic life. The presences of unwanted matters in dissolved state, colloidal state and sediment states make the water unsuitable for ingestion. Contaminations in water which hinder the natural growth and existence of living things ( human, animals and aquatic life ) are called water pollutants.

Types of water pollution

There are differents types of pollutants of water pollution. Types of water pollution, their sources and their effects are discussed here.

  1. Oxygen demanding pollutants

    Food waste and dead plant and animal tissue that consumes oxygen dissolved in water during its degradation, thus depleting oxygen required for survival of fish, other marine animals, and marine plants. Organic matters as nutrients are present in sewage from domestic waste and industrial sources such as food processing industry. They are oxygen demanding chemicals. Presences of too many nutrients in water brings about eutrophication. It is a process of excessive growth of algae and aquatic plants due to presences of excessive organic matters in fresh water. So excess organic matters as nutrients are water pollutants which by delay lower the oxygen demand in water and affects the survival of normal aquatic life such as fish species etc. such water is also unsuitable for domestic use unless proper treatment is done.

  2. Disease-causing pollutants

    They are called pathogens and they are mainly microbes and carcinogens. Microbes bring about various types of water born diseases like diarrhoea, cholera, typhoid, jaundice etc . Carcinogens are the chemical which causes cancer. They occur and mix in water where there are uncontrolled wastes and dense population .
  3. Organic chemical pollutants

    They are such as pesticides , polychlorinated biphenyls , petroleum wastes and detergents come from spillages and agricultural use affects all form of life depending upon their concentration in water. They can also cause eutrophication.
  4. Inorganic chemical pollutants

    They are such as acids, bases, salts and trace elements which come from industry, mining and from the leaching of refuse dumps when mix in the river, pond and well affects the quality of water and they affects the health of living beings.
  5. Radio nuclide as pollutants

    Nuclear power stations, the disposal of nuclear wastes and mining of certain type of rocks can lead to accumulate radio nuclide in water. Radio nuclide beyond certain limit also produces health hazard to all sorts of life .
  6. Warn water pollution

    Temperature is also an agent for water pollution. One effect of thermal pollution is that the solubility of dissolved gases like oxygen in water is reduced as the temperature rises and it affects aquatic life. Warm water , produced from any thermal plant or from any other sources, entering a lake can slow down the circulation of lake water and it causes the water at the bottom of the lake to have a low oxygen demand ( anaerobic ) sometimes throughout the year. At the same time, warm water of the surface of lake encourages the growth of algae ( green algae at 30 - 35º C ) . These phenomena disrupted the normal ecological balance of the water system .

Green house Effects (Global Warming )

The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere. The phenomenon is similar to that of green house in which the environment. Hence, green house effects are also called global warming and the gases responsible for it are called green house gases.

The green house effect was for the first time suggested by J. Fourier (1827). The gases responsible for green house effect are carbon dioxide (CO2), chlorofluorocarbons (CFCs), methane (CH4), nitrous oxide(N2O) , ozone (O3), and water vapours. These gases are released into the atmosphere by different human activities.

Relative contribution of relatively active gases to temp. rise
The relative contribution of relatively active gases to temp. rise

The figure shows that the main influence is by CO2 but the contributions of other green house gases, especially CH4 cannot be ignored 360 million hectares of rice fields and 1.2 billion cattle emit CH4.Some of these effects are listed below:

  1. Overall increase in annual temperatures ,Global Warming.
  2. Snow, sea ice and glacier coverage will decrease because of higher temperatures, resulting in rising sea levels and increased coastal flooding.
  3. Overall precipitation levels are expected to increase across most of the country and during all seasons .
  4. Heat waves are likely to increase in frequency and severity, resulting in higher risks of forest fires.
  5. There may be a greater risk of respiratory and cardiovascular problems and certain types of cancers, as temperatures rise and exacerbate air pollution.

Control of green house effects

In order to reduce the concentration of different green house effects including gases in the atmosphere and to copy with green house effects, the following strategies should be adopted:

  1. Reduction in the consumption of fossil fuels drastically.
  2. the increase of the efficiency of internal combustion engines used in automobiles so that the pollutants in the exhaust will be reduced.
  3. Use of scrubbers to remove CO2 from the emission of coal burning power plants and industries.
  4. Use of unleaded petrol in vechiles.
  5. Ethanol as a substitute to be used in the transport sector.
  6. Banding of deforestation.
  7. The banning of the use of chlorofluorocarbons (CFCs).
  8. Developing greeneries by undertaking massive afforestation programmes.

References :

Adhikari, N.R. Plus two practical chemistry. Nepal: Ed-mark Academic Enterprises Pvt. Ltd, 2004.

Jain, S.K. Conceptual Chemistry, Vol. I and II. S. Chand & Company Ltd., n.d.

Khatri, S.S. Elementary Principles of General Chemistry. TU Kathmandu: Curriculum Development Centre , 1997.

Wagley, Dr. P. Compressive Chemistry. Nepal: WorldWide Publication Pvt. Ltd, 2014.

 

  • The presences of unwanted matters in dissolved state, colloidal state, and sediment states make the water unsuitable for ingestion. Contaminations in water which hinder the natural growth and existence of living things ( human, animals and aquatic life ) are called water pollutants.
  • The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere.

 

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