Which term in the Gaussian plume equation acts as the source term?

Which term in the Gaussian plume equation acts as the source term?

• A. u
• B. Q (the emission rate).
• C. σ_y
• D. σ_z

Answer: (B)

The emission rate Q is the source term. In the Gaussian plume model, Q represents how much pollutant is released per unit time into the atmosphere, and it scales the overall amount of contaminant entering the room for transport and dilution downwind. The other factors control how that pollutant spreads and moves: the wind speed u governs advection—the plume is carried downwind—while the dispersion coefficients σ_y and σ_z describe how the plume widens laterally and vertically due to turbulence. They shape the concentration distribution but do not supply pollutants themselves. Intuitively, doubling Q doubles the total pollutant released and, all else equal, increases concentrations, whereas increasing wind speed or dispersion spreads the plume more, reducing peak concentrations at a given location.

The emission rate Q is the source term. In the Gaussian plume model, Q represents how much pollutant is released per unit time into the atmosphere, and it scales the overall amount of contaminant entering the room for transport and dilution downwind. The other factors control how that pollutant spreads and moves: the wind speed u governs advection—the plume is carried downwind—while the dispersion coefficients σ_y and σ_z describe how the plume widens laterally and vertically due to turbulence. They shape the concentration distribution but do not supply pollutants themselves. Intuitively, doubling Q doubles the total pollutant released and, all else equal, increases concentrations, whereas increasing wind speed or dispersion spreads the plume more, reducing peak concentrations at a given location.