Which factor can decrease the dispersion of air pollutants?

The factor that decreases the dispersion of air pollutants is stable air conditions. In stable atmospheric conditions, there is limited vertical mixing of air because the temperature tends to remain constant or increases with altitude, creating a situation where the air can become stratified. This stability inhibits the upward movement of air and the pollutants it carries, effectively trapping them near the ground. As a result, pollutant concentrations can increase in the areas where stable conditions exist, leading to poorer air quality.

In contrast, high wind speeds can enhance dispersion by increasing the horizontal movement of air, helping pollutants to spread out over a larger area. High temperatures can also contribute to increased vertical mixing, as warm air rises. Intense sunlight can lead to thermal convection, which further promotes the mixing of the atmosphere. Therefore, stable air conditions are particularly significant in reducing the dispersion of air pollutants in a given area.