The parameters σ_y and σ_z describe which aspect of the plume as it travels from the source?

The parameters σ_y and σ_z describe which aspect of the plume as it travels from the source?

• A. Temporal decay due to oxidation
• B. Spatial spreading in crosswind and vertical directions
• C. Ground deposition rate
• D. Temperature change

Answer: (B)

Plume spread due to turbulence is quantified by σ_y and σ_z, describing how wide the plume becomes in crosswind and vertical directions as it travels from the source. In the Gaussian plume model, the concentration field in the lateral (crosswind) and vertical directions is governed by these standard deviations. A larger σ_y means the plume spreads more across the wind direction, while a larger σ_z means more vertical spreading. Their values grow with distance from the source and depend on atmospheric stability, wind speed, and terrain roughness, reflecting the turbulent mixing that widens the plume. These parameters describe spatial spreading, not chemical decay, ground deposition, or temperature changes, which are governed by other processes.

Plume spread due to turbulence is quantified by σ_y and σ_z, describing how wide the plume becomes in crosswind and vertical directions as it travels from the source. In the Gaussian plume model, the concentration field in the lateral (crosswind) and vertical directions is governed by these standard deviations. A larger σ_y means the plume spreads more across the wind direction, while a larger σ_z means more vertical spreading. Their values grow with distance from the source and depend on atmospheric stability, wind speed, and terrain roughness, reflecting the turbulent mixing that widens the plume. These parameters describe spatial spreading, not chemical decay, ground deposition, or temperature changes, which are governed by other processes.