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: Differentiate between primary and secondary pollutants.
- Primary pollutants originate directly from emission sources like industries, vehicles, or natural phenomena (e.g., volcanic eruptions, dust storms). Examples include SO\(_2\), NO\(_x\), CO, SPM, and VOCs.
- Secondary pollutants are not directly emitted. Instead, they form in the atmosphere through chemical reactions involving primary pollutants, often catalyzed by sunlight or oxidizing conditions. Examples are Ozone (O\(_3\)), Peroxyacetyl Nitrate (PAN), and smog.

Step 2: Evaluate each option.
- (A) Suspended particulate matter (SPM): Dust, soot, smoke are emitted directly, classifying them as Primary.
- (B) Oxides of nitrogen (NO, NO\(_2\)): These are released directly from combustion processes and are therefore Primary.
- (C) Volatile organic compounds (VOCs): Emitted directly from fuels, solvents, and vegetation, these are classified as Primary.
- (D) Peroxyacetyl Nitrate (PAN): Identified as a photochemical oxidant, PAN is formed via reactions between VOCs and NO\(_x\) under sunlight. Consequently, it is a Secondary pollutant and thus NOT a primary pollutant.

Step 3: Conclusion.
Peroxyacetyl Nitrate (PAN) is the sole pollutant among the options that is classified as not primary.

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