Question

Select the option(s) which is/are NOT considered as primary air pollutant(s).

• A. Suspended particulate matter
• B. Oxides of nitrogen
• C. Volatile organic compounds
• D. Peroxyacetyl Nitrate

Hint:

Shortcut: Primary = directly emitted, Secondary = formed later. Remember PAN, ozone, and photochemical smog are classic secondary pollutants.

Answer 1

The Correct Option is D

Step 1: Definition of primary vs secondary pollutants.
- Primary pollutants are directly emitted from sources such as industries, vehicles, or natural events (e.g., volcanic eruptions, dust storms). Examples: SO\(_2\), NO\(_x\), CO, SPM, VOCs.
- Secondary pollutants are not directly emitted but are formed in the atmosphere due to chemical reactions among primary pollutants under sunlight/oxidizing conditions. Examples: Ozone (O\(_3\)), Peroxyacetyl Nitrate (PAN), smog.

Step 2: Analyze each option.
- (A) Suspended particulate matter (SPM): Dust, soot, smoke → emitted directly → Primary.
- (B) Oxides of nitrogen (NO, NO\(_2\)): Directly released from combustion → Primary.
- (C) Volatile organic compounds (VOCs): Directly emitted from fuels, solvents, vegetation → Primary.
- (D) Peroxyacetyl Nitrate (PAN): A photochemical oxidant, formed from VOCs + NO\(_x\) under sunlight → Secondary, hence NOT a primary pollutant.

Step 3: Conclusion.
The only pollutant here that is not primary is Peroxyacetyl Nitrate (PAN).

Final Answer: \[ \boxed{\text{(D) Peroxyacetyl Nitrate}} \]