Nitrogen comprises 78 percent of the atmosphere , the source of this atmospheric nitrogen is due to

Options

A. denitrification by bacteria in the soil
B. combustion of wood and fossil fuels
C. volcanic activity
D. all of the above

Explanation

To solve the question regarding the source of atmospheric nitrogen, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Atmospheric Composition**:
- Nitrogen constitutes about 78% of the Earth's atmosphere. This indicates that it is a significant component, and understanding its sources is essential.

2. **Analyzing the Options**:
- The question provides four options:
1. Denitrification by bacteria in the soil
2. Combustion of wood and fossil fuels
3. Volcanic activity
4. All of the above

3. **Evaluating Each Option**:
- **Denitrification by Bacteria**:
- Denitrification is a process where nitrates in the soil are converted back to nitrogen gas (N2) by bacteria. This nitrogen gas is then released into the atmosphere, contributing to the nitrogen content.
- **Conclusion**: This is a valid source of atmospheric nitrogen.

- **Combustion of Wood and Fossil Fuels**:
- The burning of organic materials (like wood) and fossil fuels can release nitrogen oxides (NOx) into the atmosphere. These compounds can contribute to the nitrogen content in the air.
- **Conclusion**: This is also a valid source of atmospheric nitrogen.

- **Volcanic Activity**:
- Volcanic eruptions can release various gases, including nitrogen compounds, into the atmosphere. This can also contribute to the nitrogen content in the air.
- **Conclusion**: This is another valid source of atmospheric nitrogen.

4. **Final Conclusion**:
- Since all three options (denitrification, combustion, and volcanic activity) contribute to the nitrogen content in the atmosphere, the correct answer is **All of the above**.

### Final Answer:
The source of atmospheric nitrogen is due to **All of the above**.

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