Which one of the following is a secondary pollutant?

Options

A. CO
B. `O_(3)`
C. Pb
D. `CH_(4)`

Answer

To determine which of the given options is a secondary pollutant, we can follow these steps:

### Step 1: Understand the Definition of Secondary Pollutants
Secondary pollutants are not emitted directly into the atmosphere. Instead, they form when primary pollutants react with each other or with other substances in the atmosphere.

**Hint:** Remember that secondary pollutants are formed from the reaction of primary pollutants.

### Step 2: Identify Primary Pollutants
Primary pollutants are those that are directly emitted into the atmosphere. Common examples include carbon monoxide, sulfur dioxide, and nitrogen oxides.

**Hint:** Think about pollutants that come directly from sources like vehicles, factories, or natural events.

### Step 3: List Common Secondary Pollutants
Some common secondary pollutants include ozone (O₃), peroxyacetyl nitrate (PAN), and various photochemical oxidants. These pollutants are typically formed through chemical reactions involving primary pollutants.

**Hint:** Secondary pollutants often involve reactions with sunlight or other atmospheric conditions.

### Step 4: Analyze the Options
If the options provided include substances like ozone, carbon monoxide, lead, and methane, we can categorize them:
- **Ozone (O₃)**: Formed from the reaction of sunlight with primary pollutants like nitrogen oxides and volatile organic compounds. Therefore, it is a secondary pollutant.
- **Carbon Monoxide (CO)**: Directly emitted from combustion processes, making it a primary pollutant.
- **Lead (Pb)**: Typically emitted from industrial processes and is a primary pollutant.
- **Methane (CH₄)**: A greenhouse gas emitted from natural and anthropogenic sources, also a primary pollutant.

**Hint:** Look for the pollutant that is formed as a result of reactions in the atmosphere rather than one that is released directly.

### Step 5: Conclusion
Based on the analysis, the only secondary pollutant among the options is **ozone (O₃)**.

**Final Answer:** Ozone (O₃) is the secondary pollutant.

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