What impact can calm wind conditions have on pollutant dispersion?

Calm wind conditions significantly impact pollutant dispersion by reducing the natural mechanisms that facilitate the mixing and dilution of pollutants in the atmosphere. When the wind is calm, there is minimal air movement to carry pollutants away from their source. This lack of dispersion results in the accumulation of pollutants in the vicinity of the emission source, leading to higher concentrations.

In contrast, when wind speeds are higher, they contribute to better mixing of the air, which helps to transport pollutants away from their source. Calm conditions, therefore, create stagnant air where pollutants can remain trapped, leading to potential health and environmental hazards. Understanding this phenomenon is crucial for assessing air quality and potential risks associated with emissions, especially in urban areas or during specific weather patterns that can maintain calm conditions over extended periods.