Question

Which of the following is a primary pollutant?
A) CO
B) $HNO_3$
C) $H_2SO_4$
D) $O_3$

Answer 1

Primary pollutants are directly released into the environment via a lot of sources. They can be natural (volcanic eruptions or fires), or anthropogenic (emissions from vehicles and industries).

Complete answer:
A pollutant is an undesirable substance in the environment that has harmful effects, or adversely affects the usefulness of a resource. It may cause long- or short-term harm to organisms. Biodegradable pollutants do not persist in the environment for long, but their degradation can cause the formation of even more harmful pollutants like DDE and DDD produced from the degradation of DDT.
There are different types of pollutants in nature like fund pollutants which do not cause harm to the environment unless the emission is high enough to exceed the environment’s absorptive capacity, for example, carbon dioxide.
Air pollutants from various industries are a cause of major concern and they can be natural or man-made. They can be classified as primary and secondary pollutants.

Primary pollutants- These are directly emitted from processes like volcanic eruptions, factories, fossil fuel consumption, etc.
->Oxides of Sulphur: Sulphur oxides are products of volcanoes, industrial processes, coal, petroleum, etc. When they combine with catalysts like $NO_2$, acid rain occurs.
Particulate matter: They are fine particles which can be either solid or liquid, suspended in the gas.
->Oxides of carbon: Carbon monoxide is a colorless, odorless, and non-irritating but very poisonous gas. It is the product of incomplete combustion of natural gas, coal, or wood. Vehicle exhaust is the major source of CO.
Secondary pollutants- These pollutants are not directly emitted and are formed by the interaction of primary pollutants. Sulphuric acid, nitric acid, ozone, etc. in the troposphere zone are very harmful and are formed by the interaction of their precursor molecules, also called primary pollutants.

Hence, the correct option is A, ‘CO’.

Note: Other primary air pollutants include Cadmium, Lead, Copper, etc. released from industrial processes. Chlorofluorocarbons (CFCs) are also one of the pollutants which damage the ozone layer. The emission of primary pollutants has decreased due to better regulations, technology, and economical changes.