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Which of the following is a secondary pollutant?
(А) $\mathop {SO}\nolimits_2 $
(B) $\mathop {CO}\nolimits_{} $
(C) $\mathop O\nolimits_3 $
(D) $\mathop {CO}\nolimits_2 $

Last updated date: 18th Jun 2024
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Hint: Pollution is any undesirable change in physical, chemical or biological characteristics of air, land, water or soil. The toxic substances that bring about such an undesirable change are called pollutants. In the necessity to control environmental pollution, the Government of India has passed the Environment (Protection) Act, 1986 to protect, advance and improve the quality of our environment (air, water and soil) brought about through human activities.

Complete answer:
On the basis of the form of pollutant in which they persist after their release are of two types:
> Primary pollutants :- the pollutants that are emitted directly in the environment from some definite sources.
> Secondary pollutants :- the pollutants that are formed by the reaction of primary pollutants in the environment.
Now let us match this with given options :-
$\mathop {SO}\nolimits_2 $:- it is a primary pollutant as it is emitted directly. It is emitted from oil refineries and smelters of ores . It is also released from combustion of sulphur containing fuels.
$\mathop {CO}\nolimits_{} $ :- it is a primary pollutant as it is emitted directly. It is released as a result of incomplete combustion that is combustion in the absence of oxygen of the fossil fuels in automobiles.
$\mathop O\nolimits_3 $ :- it is a secondary pollutant as it is formed as a result of reaction between primary pollutants . Ozone is produced when reaction occurs between oxygen molecules and nascent free oxygen.
 $\mathop {CO}\nolimits_2 $:- it is kind of a quantitative pollutant. It becomes pollutant when its concentration reaches beyond a critical value in the environment otherwise it is not considered as a pollutant. It is a kind of primary pollutant.

Our required option is C that is $\mathop O\nolimits_3 $.

Note: We are dependent on air for our respiratory needs. Air pollutants cause injury to all living organisms. They reduce growth and yield of crops and cause premature death of plants. Air pollutants also deleteriously affect the respiratory system humans and animals. Dangerous and toxic effects depend on the concentration of pollutants, duration of exposure and for how much time pollution persists in the environment and the organism.