Question

Differentiate between primary and secondary pollutants.

Answer 1

Primary pollutants; Pollutants that enter directly from the sources into the atmosphere are called primary pollutants.

Secondary pollutants: Pollutants that are formed due to interactions between primary air pollutants and other atmospheric components are called secondary pollutants. These interactions can be physical or chemical.

Primary pollutants	Secondary pollutants
Have a direct effect on the environment and organisms and have an indirect effect by being involved in the formation of secondary pollutants.	Highly reactive when photochemical agents are involved in their formation.
2. Can be controlled by controlling man-made activities causing pollution.	2. These are difficult to control. because understanding the reactions involved in secondary pollutants formation is difficult.
3. For Example - Particulate matter like aerosols, soot, dust, etc. Hydrocarbons$\left(\mathrm{HCs}\right)$. Sulphur dioxide$\left({\mathrm{SO}}_2\right)$ Nitrogen oxide$\left({\mathrm{NO}}_{\mathrm{x}}\right)$. Carbon monoxide$\left(\mathrm{CO}\right)$.	3. For Example - Acid rain. Photochemical smog. Peroxyacetyl nitrate$\left(\mathrm{PAN}\right)$.