The brown , hazy fumes of photochemical smog are due to

Options

A. nitrogen dioxide
B. PAN formation
C. aldehydes
D. `SO_(2)`

Explanation

**Step-by-Step Solution:**

1. **Understanding Photochemical Smog**: Photochemical smog is a type of air pollution that occurs when sunlight reacts with pollutants such as volatile organic compounds (VOCs) and nitrogen oxides (NOx) in the atmosphere.

2. **Formation of Photochemical Smog**: The primary components that lead to the formation of photochemical smog include unsaturated hydrocarbons, which are oxidized by ozone (O3) and other oxidizing agents. This oxidation process produces various compounds, including aldehydes and ketones.

3. **Role of Nitrogen Dioxide (NO2)**: One of the key components of photochemical smog is nitrogen dioxide (NO2). NO2 is a brown-colored gas that contributes to the brownish haze associated with photochemical smog.

4. **Formation of Peroxyacetyl Nitrate (PAN)**: In addition to NO2, the reaction of aldehydes with nitrogen oxides can lead to the formation of peroxyacetyl nitrate (PAN), which is another component of photochemical smog. The formula for PAN is RCO3NO2.

5. **Conclusion**: The brown, hazy fumes of photochemical smog are primarily due to the presence of nitrogen dioxide (NO2). While other components like PAN and aldehydes are present, the distinctive brown color is attributed to NO2.

**Final Answer**: The brown, hazy fumes of photochemical smog are due to nitrogen dioxide (NO2).

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