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Write short note on :- ( a) BOD ( b) Photo chemical smog (c).Ozone hole. |
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Answer» (a) BOD: Biochemical oxygen demand is defined as the amount of oxygen required microorganisms to oxidise the organic pollutants presents in water. Water having BOD less than 5ppm is clean water and greater than 17ppm is polluted water (b) Photo chemical smog: It consists of oxides of nitrogen which absorb light and form free radicals. It is extremely harmful and is oxidizing in nature. (c) Ozone hole: ozone layer is depleted near Antarctica and it is called ozone hole. |
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