Correct Answer:
B. Particulate Matter
The correct answer is Particulate Matter. While smog is a complex mixture of various air pollutants, the specific particle that is a defining component of smog—especially the classic "London‑type" and modern photochemical smog—is particulate matter (PM), a suspension of fine solid and liquid particles in the air.
Particulate Matter and Smog Formation
- What Smog Contains: Smog is an amalgam of smoke and fog. Historically, it was dominated by soot and sulfur compounds from coal burning. Today, photochemical smog is driven by nitrogen oxides, volatile organic compounds, and sunlight, producing ground‑level ozone. However, the term "added particle" specifically points to the suspended particulates that give smog its characteristic haze.
- PM as the Visible Component: Particulate matter (PM₂.₅ and PM₁₀) consists of microscopic solids or liquid droplets that are small enough to be inhaled and cause health problems. They are the visible, harmful particulate fraction of smog.
- Other Pollutants Are Gases: Sulfur dioxide is a gas that can react to form sulfate particles, but it is not itself the particle. Carbon monoxide is a toxic gas, and ozone is a secondary gaseous pollutant formed in photochemical smog. None of these are "particles" added to smog; only particulate matter fits that description.
- Health and Environmental Impact: PM penetrates deep into the lungs, causing respiratory and cardiovascular diseases. It is the primary metric for measuring smog severity.
Thus, the specific particle added in smog is particulate matter.