The Pasquill-Gifford puff model predicts that doubling the total airborne mass doubles the COTA concentration at a fixed downwind distance.

The Pasquill-Gifford puff model predicts that doubling the total airborne mass doubles the COTA concentration at a fixed downwind distance.

• A. True
• B. False
• C. Cannot be determined
• D. Depends on wind speed

Answer: (A)

The key idea is linear scaling with source strength. In the Pasquill-Gifford puff model, the concentration at a receptor is proportional to the released mass M, divided by the spreading of the puff (described by dispersion terms) and modulated by wind. If you keep wind speed and atmospheric dispersion conditions fixed and simply increase the mass released, every point in the concentration field scales proportionally with M. So at a fixed downwind distance, doubling the total airborne mass doubles the concentration reported at that location (the COTA concentration), provided there are no processes that remove or transform the pollutant (like chemical decay, deposition, or phase changes).

The key idea is linear scaling with source strength. In the Pasquill-Gifford puff model, the concentration at a receptor is proportional to the released mass M, divided by the spreading of the puff (described by dispersion terms) and modulated by wind. If you keep wind speed and atmospheric dispersion conditions fixed and simply increase the mass released, every point in the concentration field scales proportionally with M. So at a fixed downwind distance, doubling the total airborne mass doubles the concentration reported at that location (the COTA concentration), provided there are no processes that remove or transform the pollutant (like chemical decay, deposition, or phase changes).