Which of the following act as secondary pollutants ?

Options

A. `CO_(2)`
B. `SO_(3)`
C. `NO_(2)`
D. `O_(3)`

Answer

To determine which of the given options act as secondary pollutants, we first need to understand the definitions of primary and secondary pollutants.

### Step 1: Define Primary Pollutants
Primary pollutants are substances that are emitted directly into the atmosphere from a source. They are typically less toxic and can include gases or particles. Examples include:
- Carbon Dioxide (CO2)
- Carbon Monoxide (CO)
- Sulfur Dioxide (SO2)
- Nitric Oxide (NO)
- Nitrogen Dioxide (NO2)

### Step 2: Define Secondary Pollutants
Secondary pollutants are not emitted directly. Instead, they form in the atmosphere through chemical reactions between primary pollutants and other atmospheric components. These pollutants are often more toxic than primary pollutants. Examples include:
- Ozone (O3)
- Sulfur Trioxide (SO3)

### Step 3: Analyze the Given Options
Now, let's analyze the given options:
1. **CO2** - This is a primary pollutant as it is emitted directly from sources like combustion.
2. **SO3** - This is a secondary pollutant formed from the reaction of sulfur dioxide (SO2) in the presence of oxygen.
3. **NO2** - This is a primary pollutant as it is emitted directly from sources like vehicle emissions.
4. **O3** - This is a secondary pollutant formed from the reaction of nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of sunlight.

### Step 4: Conclusion
Based on the definitions and analysis:
- **Secondary Pollutants**: Ozone (O3), Sulfur Trioxide (SO3)
- **Primary Pollutants**: Carbon Dioxide (CO2), Nitrogen Dioxide (NO2)

Thus, the correct answers for the question "Which of the following act as secondary pollutants?" are **SO3 and O3**.

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