Question

Which of the following is a secondary air pollutant?

• A. Carbon monoxide
• B. Ozone (tropospheric)
• C. Sulphur dioxide
• D. Lead

Hint:

Examples: \[ \boxed{ \begin{aligned} \text{Primary pollutants} &: \text{CO, SO}_2,\ \text{NO},\ \text{Lead}\\ \text{Secondary pollutants} &: \text{O}_3,\ \text{PAN},\ \text{Photochemical smog} \end{aligned} } \]

Answer 1

The Correct Option is B

Step 1: Define primary versus secondary pollutants.
A primary pollutant is released straight from a source, while a secondary pollutant forms afterward through chemical reactions in the atmosphere.
Step 2: Check each option against this rule.
Carbon monoxide, sulphur dioxide and lead are all emitted directly from combustion or industrial sources, making them primary pollutants.
Step 3: Explain tropospheric ozone.
Ozone near the ground is not emitted directly. It forms when nitrogen oxides and volatile organic compounds react together under sunlight, which is the classic definition of a secondary pollutant.
\[ \boxed{\text{Ozone (tropospheric)}} \]