56.

Discuss sources and sinks of CO₂ in the atmosphere.
Or
Discuss the role of CO₂ as a pollutant. 
Or
Carbon dioxide is inert and harmless gas, yet it is considered to be a serious pollutant. Explain. 

Source of CO₂: The main sources of CO₂ are:

(i) Complete combustion of fuels and carbon compounds and carbonates. 


(ii) Auto-exhaust and many industrial processes also produce a lot of carbon dioxide.

(iii) Carbon dioxide is also produced by the biological decay of plants.

Sinks of CO₂:
(i) The most important sink of CO₂ is the ocean; ocean contains most of the dissolved CO₂ in the form of carbonates, bicarbonates and organic compounds.

(ii) Another sink of CO₂ is the living green plants where photosynthesis process occurs which results in the removal of CO₂ in the atmosphere.
CO₂ as a pollutant.
The increasing concentration of CO₂ (presently 325 ppm) can lead to increase in the earth’s temperature i.e. green house effect occurs. A slight increase in the earth’s temperature can cause havoc in times of change in world climate, melting of glaciers, flooding of the coastal plains and change in biological activity of the ocean.
Plants maintain a balance in the atmospheric CO₂ level by using it in photosynthesis


Control of CO₂ pollution:
CO₂ pollution can be controlled by using following steps:
(i) The release of CO₂ from various industrial processes should be controlled. 
(ii) The production of CO₂ from vehicles exhaust should be checked.
(iii) To adjust the balance of CO₂ in the atmosphere, the main sink of CO₂ i.e. forests should be developed.