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| Causes of Water Pollution |
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| Unlike air pollution, water pollution has to be studied in the spatial perspective to understand the causes. Hence, causes of water pollution can be classified as |
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 Main source of pollution - where in pure water is mixed with pollutant for first time |
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 Secondary source of pollution - where polluted water is further polluted when the water is traversing on the surface or below the surface of soil. |
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| The causes in main source and secondary source of pollution may be same or different, the pollutant of main source and secondary source may be same or different. When the same pollutant pollutes the water two or more times during main and secondary source, the concentration of pollutant increases. But, as the concentration has inverse relationship with distance traversed the pollutant concentration is also subjected to constant decrease. |
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| When two or more pollutants cause pollution, then, their concentrations are independent of each other. |
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| Main sources of water pollution can be |
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 Agriculture |
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 Industries |
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 Sanitary wastes |
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 Solid wastes |
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 Natural reasons |
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| They are further classified into groups as follows. |
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| Agriculture |
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 Fertilizers - For e.g., Nitrate pollution, Ammonia pollution, |
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| phosphate pollution |
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 Pesticides |
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| a) Weedicides - For e.g., Atrazine pollution, 2,4-D pollution, Butachlor pollution |
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| b) Insecticides - For e.,g Carbofuran pollution, DDT pollution, BHC pollution, Endosulphan pollution |
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| c) Fungicides - For e.g., Pollution due to zineb, ziram |
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 Manures - For e.g., Pollution due to farm yard manures |
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| Industries |
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 Paper industries - For e.g., chlorinated effluents |
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 Textile industries - For e.g., Ammoniated effluents |
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 Thermal plants - For e.g., Hot water |
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 Fertilizer, food and chemical industries - For e.g., acidic / corrosive effluents |
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 Petroleum industries - For e.g., oily effluents |
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 Leather industries - For e.g., sulphur - based effluents |
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| Sanitary wastes |
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 human and animal excreta |
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| Solid wastes |
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 City droppings - For e.g., carbaneaceous paper / cloth / wooden materials |
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 Animal droppings and slaughter house wastes - For e.g., decomposable drug / slaughter house wastes |
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 Domestic wastes - For e.g., vegetable / food wastages |
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 Industrial solid wastes - For e.g., paper wastes, iron filings, metal chips |
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 Market Wastes - For e.g., vegetable / fruit rottings |
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| Natural Resources |
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 Death of animals, birds Reasons - Ammonia released by carcasses of animals, birds. |
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 Water collection from forest areas - For e.g., Nitrates and ammonia compounds from rich forest soils |
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 Natural mineral deposits - For e.g., Deposits of bauxites |
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| The secondary source of water pollution can be any of the above source - but necessarily after one of the pollutant is already available in water. Either primary or secondary source can be more concentrated. It is the concentration of pollutant and the type of pollutant - which decide how dangerous the water pollution can be rather that source of pollution. |
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| Some pollutants like DDT in water, sanitary wastes in water can be highly dangerous even in small quantities. However, pollutants like cadmium, copper compounds or ammonia compounds can be dangerous - if their concentration is high. Some other pollutants like atomic wastes have long term effects if contaminated water is used, though no short term effects are noticed. |
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| The causes of water pollution can always be |
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| point source |
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| where the pollutant entering the water course affects the quality of water in the vicinity of pollution. |
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| For e.g., Sanitary water entering drinking water source through leakage of pipes |
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| non - point source |
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| where the pollutant entering the water course affects the quality of water at a far off place, where no pollutant would have been added. |
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| For e.g., DDT found in sea water |
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| The pollutants in river water can be |
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 due to agricultural activities in catchment area |
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 due to industrial activities at its banks |
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 due to pollutants from organic wastes in forest areas |
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 due to dead animals in the course of water |
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 due to natural deposits of minerals |
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| The pollutants in underground water can be due to |
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 agricultural activities around the place of pollution |
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 entry of sanitary water |
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 decomposition of debris |
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 many other non - point sources |
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| The pollutants in sea water can be due to |
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 polluted river water |
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 decomposition of aquatic weeds and animals |
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 accidental leakages, sinking of ships |
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 industrial activities on sea coast |
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