Question

What is meant by ozone shield? Name two ozone depleting substances. How do the ozone depleting substances affect the ozone shield? Write one damaging effect of ozone depletion on humans and plants respectively.

Answer 1

Ozone (O${}_3$) is a gas which is present in the the atmosphere which absorbs most of the sun's ultraviolet radiation and OZONE SHIELD is a region of Earth's atmosphere where ozone is present.

Two ozone-depleting substances

1. Chlorofluorocarbons (CFCs)

2. Methyl bromide

Ozone-depleting substances are transported into the stratosphere by winds. When these substances reach the stratosphere, they release halogen atoms through the photolysis process. Photolysis is a process in which photon is released, this leads to catalyzing or breakdown of Ozone (O${}_3$) into Oxygen (O${}_2$) and because of this breakdown ozone layer gets depleted and absorption of UV Rays gets lowered resulting in an increased amount of UV Rays reaching Earth's surface, leading to many hazardous problems or effects.

The damaging effect of ozone depletion on

• Plants: Retardation of plant growth

For example: In Rice crop, crop depends on cyanobacteria for retention of nitrogen and this bacteria is sensitive to UV Radiation. The growth of bacteria is very less in presence of UV rays.

• Humans: skin cancer, snow blindness etc.