If Q doubles while wind speed and dispersion characteristics remain unchanged, what happens to predicted concentrations?

If Q doubles while wind speed and dispersion characteristics remain unchanged, what happens to predicted concentrations?

• A. Maximum concentrations approximately double, assuming linear relationship.
• B. They triple
• C. They decrease
• D. They remain the same

Answer: (A)

Doubling the emission rate while wind speed and dispersion characteristics stay the same makes the concentration field scale linearly with the source term. In the Gaussian plume framework, the concentration at a receptor is proportional to Q divided by the advection and dispersion terms (C ∝ Q/(u σ_y σ_z)). If u, σ_y, and σ_z are unchanged, doubling Q simply doubles the concentration everywhere, including the maximum on the plume centerline. The other outcomes would require nonlinear effects or changes in dispersion, which aren’t present here. So the predicted maximum concentrations will approximately double.

Doubling the emission rate while wind speed and dispersion characteristics stay the same makes the concentration field scale linearly with the source term. In the Gaussian plume framework, the concentration at a receptor is proportional to Q divided by the advection and dispersion terms (C ∝ Q/(u σ_y σ_z)). If u, σ_y, and σ_z are unchanged, doubling Q simply doubles the concentration everywhere, including the maximum on the plume centerline. The other outcomes would require nonlinear effects or changes in dispersion, which aren’t present here. So the predicted maximum concentrations will approximately double.