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Describe the following in brief: (i) Ozone depletion over Antarctica (ii) BOD and COD (iii) Eutrophication |
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Answer» (i) Ozone depletion over Antarctica: In summer season, nitrogen dioxide and methane react with chlorine monoxide preventing ozone depletion whereas in winter, special type of clouds called polar stratospheric could s are formed over Antarctica. These clouds provide surface on which chlorine nitrate molecules formed gets hydrolysed to form HOCl. It also reacts with HCls to give Cl2. When sunlight returns to Antarctica again ozone depletion starts by free radicals. (ii) BOD: It is amount of oxygen required by bacteria to decompose organize wastes present in water. COD: It is the amount of oxygen (in ppm) required to oxidize the contaminants. COD is determined by using chemical oxidizing agent K2Cr2O7. (iii) Eutrophication: The process in which nutrient-enriched water bodies support a dense plant population which kills animal life by depriving it of oxygen and results in subsequent loss of biodiversity is known as Eutrophication. |
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