The PAN (peroxyacetyl nitrate) is an important constituent of photochemical smog, however, it is aA. Corollary pollutantB. Primary pollutantC. Natural pollutant D. Secondary pollutant

The correct answer is:

D. Secondary pollutant

Explanation: PAN (peroxyacetyl nitrate) is a secondary pollutant because it is not directly emitted into the atmosphere but forms through chemical reactions in the atmosphere. PAN is primarily produced when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight, a process that occurs in photochemical smog. Since PAN forms as a result of these chemical reactions, it is classified as a secondary pollutant.

Primary pollutants are directly emitted into the atmosphere, such as carbon monoxide or sulfur dioxide.
Secondary pollutants are formed through chemical reactions in the atmosphere, like PAN, ozone, and acid rain.
Corollary pollutants are not a recognized category in environmental science.
Natural pollutants come from natural sources like volcanoes or forest fires.
Thus, PAN is a secondary pollutant because it is formed by reactions in the atmosphere.