Pollutant responsible for causing phaeophytization is

Options

A. `SO_(2)`
B. NOx
C. `CO_(2)`
D. Aeroallergens

Answer

To solve the question regarding the pollutant responsible for causing phaeophytization, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Phaeophytization**:
- Phaeophytization refers to the process where chlorophyll breaks down and is replaced by a brown pigment called pheophytin. This process is often an indicator of environmental stress in aquatic ecosystems, particularly in algae and lichens.

2. **Identifying the Pollutants**:
- The options provided are:
- Sulfur dioxide (SO₂)
- Nitrogen oxides (NOx)
- Carbon dioxide (CO₂)
- Aeroerosion

3. **Analyzing Each Pollutant**:
- **Sulfur Dioxide (SO₂)**: This is a well-known air pollutant that can lead to acid rain and has detrimental effects on plant life. It is known to cause phaeophytization by promoting the breakdown of chlorophyll.
- **Nitrogen Oxides (NOx)**: These gases are primarily involved in the formation of smog and ozone but are not directly linked to the process of phaeophytization.
- **Carbon Dioxide (CO₂)**: While it is essential for photosynthesis, an increase in CO₂ does not directly cause phaeophytization.
- **Aeroerosion**: This term refers to the erosion caused by airborne particles and does not relate to the breakdown of chlorophyll.

4. **Conclusion**:
- Based on the analysis, sulfur dioxide is the pollutant that directly causes phaeophytization by leading to the breakdown of chlorophyll and the formation of pheophytin. Therefore, the correct answer is **sulfur dioxide (SO₂)**.

### Final Answer:
The pollutant responsible for causing phaeophytization is **sulfur dioxide (SO₂)**.

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