Traditional Culture Encyclopedia - Weather inquiry - Why is the air quality the worst when there is fog?

Why is the air quality the worst when there is fog?

Due to the recent stable atmospheric structure, high air humidity near the ground, weak ground pressure field, low wind force and low temperature at night, heavy fog appears. Because the atmosphere is in a stable state, there is neither vertical movement nor horizontal flow, which makes the pollutants in the air unable to spread and leads to smog, so the air quality is the worst.