What Affects the Concentration of a Pollutant?
The concentration of a pollutant decreases as it travels from the site of release because the pollutant spreads out. The amount of this dilution, or dispersion, in the air depends on weather — especially wind direction and speed. Dispersion also depends on the terrain, whether it is on flat or mountainous land or in a valley. Other factors can affect the concentration, or level of a pollutant at a given location. The amount of a pollutant at any one location can vary over time depending on the pattern of releases. For example, industrial processes can release some pollutants only at certain times and other pollutants continuously. The location of the release affects the concentration — a pollutant can be released from smoke stacks high in the air or can leak from equipment or storage tanks near the ground. The ground-level concentration near a facility is generally lower when a pollutant is released from high stacks because the pollutant is more diluted when it reaches the ground. Ot
