Which pollutant is mainly responsible for thermal inversion-related smog episodes in urban areas?
Show Hint
Thermal inversion traps pollutants near the ground, especially
\[
\boxed{\text{Particulate Matter (PM}_{2.5}\text{ and PM}_{10}\text{)}}
\]
resulting in severe smog episodes.
Step 1: Recall what thermal inversion does. Normally warm air near the ground rises and mixes with cooler air above, but during an inversion a layer of warm air sits above cooler ground level air and traps it in place. Step 2: Follow what happens to pollutants under this trapped layer. With vertical mixing blocked, pollutants released near the ground cannot disperse upward and instead build up close to the surface. Step 3: Identify which pollutant creates the visible smog. Fine particulate matter accumulating under the inversion layer scatters light and forms the dense, visible smog associated with these episodes. \[ \boxed{\text{Particulate matter}} \]