SAChE Atmospheric Dispersion (ELA967) Module 2 Practice Test

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In the Gaussian plume model, how does increasing wind speed affect ground-level concentration for a fixed emission rate?

Concentrations increase due to faster advection.

Concentrations stay the same.

Concentrations decrease only with distance independent of wind.

Concentrations decrease due to dilution and shorter plume residence time.

Increasing wind speed lowers ground-level concentration for a fixed emission rate because the plume is carried away faster and is mixed into a larger volume of air more quickly. In the Gaussian plume framework, the ground-level concentration at a downwind location is inversely related to the wind speed (and to the plume’s lateral and vertical spread). As wind speed rises, the pollutant spends less time near the source and is advected past the receptor more quickly, leading to greater dilution. So, higher wind speeds reduce the concentration measured at ground level.