Ozone Depletion/Ozone Hole

Why in News?

According to World Meteorological Organization (WMO) Report, On 20 September 2020, Antarctic ozone hole grew rapidly and peaked at around 24.8 million square kilometres and spreading over most of the Antarctic continent.

Key Points:

What is Ozone?

• Ozone is form of oxygen that combines three atoms into each molecule.
• The chemical symbol of ozone is O₃.
• It absorbs and filters the harmful ultraviolet B radiation coming from the Sun.
• This way the ozone layer protects all life on earth.
• The Dobson Unit (DU) is the unit of measurement for total ozone.

 

Ozone Layer:

Ozone Layer is found in the Stratosphere. Which is “good” because it protects life on Earth by absorbing some of the sun’s harmful Ultra Violet (UV) rays.
Note: Ozone in the troposphere is “bad” because it dirties the air and helps to form smog, which is not good to breathe.
 

What is Ozone Depletion?

A steady decline in the concentration of ozone in the earth’s stratosphere is called ozone depletion.

Why is Ozone Depletion occur?

Due to the influx of several substances into the atmosphere which react with ozone and destroy it. For Example - When chlorofluoro carbon (CFC) and halon gases, formerly found in aerosol spray cans and refrigerants are released into the atmosphere and they cause chemical reactions that break down ozone molecules and reduce the concentration of them.

Ozone-depleting Substances:

• chlorofluorocarbons (CFCs)
• Halon gases
• Carbon Tetrachloride (CCl4)
• Methyl Chloroform (CH3CCl3)
• Hydrochlorofluorocarbons (HCFCs)
• Hydrobromofluorocarbons (HBFCs)
• Methyl Bromide (CH3Br)
• Bromochloromethane (CH2BrCl)
• Nitrogen Oxides.

 
UV Rays:
The UV rays cause direct damage to the genetic material or DNA of animal and plant cells. Exposure of mammals to UV light has been shown to act on the immune system, thereby making the body more susceptible to diseases.
 

Why ozone hole occurs over Antarctica?

The severe depletion of the Antarctic ozone layer known as the “ozone hole” occurs because of the special atmospheric and chemical conditions that exist there and nowhere else on the globe. The very low winter temperatures in the Antarctic stratosphere cause polar stratospheric clouds (PSCs) to form. Special reactions that occur on PSCs, combined with the relative isolation of polar stratospheric air, allow chlorine and bromine reactions to produce the ozone hole in Antarctic springtime. Satellite images of the earth over last decades observed that the atmospheric ozone layer is getting thinner. On 20 September, 2020, the ozone hole was recorded to its maximum size of 28.2 million sq.km over Antarctica. The size of the ozone hole is larger than the size of continent of North America.

Harmful Effect of Ozone Depletion:

• Depletion of the ozone layer has consequences on human, animal, plants and micro-organisms.
• The ozone holes allow the ultraviolet radiation to enter and cause of global warming, skin cancer, eye cataract and even blindness.

 
To protect the ozone layer for our future generation, avoid using products which are emitting pollutants such as aerosol sprays, blowing agents for foams and packing materials, as solvents and as refrigerants.

Also Read: Weather and Climate
 
Source: NCERT