Write short note on:(a) BOD(b) Ozone hole(c) Photochemical Smog.

1.	Write short note on:(a) BOD(b) Ozone hole(c) Photochemical Smog.
Answer» (a) BOD: It is referred to as Biochemical Oxygen Demand. It is defined as the amount of oxygen required by bacteria to breakdown the organic matter present in a certain volume of a sample of water. (b) Ozone hole: Ozone hole is formed due to depletion of ozone layer in the stratosphere due to presence of chlorofluoro carbon (CFC). In 1980s, atmospheric scientists working in Antarctica reported about depletion of ozone layer commonly known as ozone hole over the South pole. (c) Photochemical smog: It occurs in warm, dry and sunny climate. The main components of the photochemical smog result from the action of sunlight on unsaturated hydrocarbons and nitrogen oxides produced by automobiles and factories. It has high concentration of oxidising agents and is therefore, known as oxidising smog.

Answer»

(a) BOD: It is referred to as Biochemical Oxygen Demand. It is defined as the amount of oxygen required by bacteria to breakdown the organic matter present in a certain volume of a sample of water.

(b) Ozone hole: Ozone hole is formed due to depletion of ozone layer in the stratosphere due to presence of chlorofluoro carbon (CFC). In 1980s, atmospheric scientists working in Antarctica reported about depletion of ozone layer commonly known as ozone hole over the South pole.

(c) Photochemical smog: It occurs in warm, dry and sunny climate. The main components of the photochemical smog result from the action of sunlight on unsaturated hydrocarbons and nitrogen oxides produced by automobiles and factories. It has high concentration of oxidising agents and is therefore, known as oxidising smog.

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