How do you determine whether a receptor is within the plume envelope?

How do you determine whether a receptor is within the plume envelope?

• A. By comparing receptor coordinates to the predicted plume spread (σ_y, σ_z) at the downwind distance and checking receptor height relative to plume center.
• B. By evaluating the receptor's temperature.
• C. By measuring the receptor's chemical composition.
• D. By guessing from wind direction.

Answer: (A)

Determining whether a receptor lies inside the plume envelope relies on the Gaussian plume geometry: as the plume travels downwind, it spreads crosswind and vertically, with widths described by σ_y(x) and σ_z(x) at that downwind distance x. To decide if the receptor is affected, locate the receptor relative to the plume centerline. Compare its lateral offset y to the predicted crosswind spread σ_y and its vertical offset from the plume centerline z − z_center(x) to the vertical spread σ_z. If the receptor’s coordinates fall within the plume’s crosswind and vertical extents (for example, within a few σ_y and σ_z around the centerline), it is inside the plume envelope and could experience significant concentrations. Temperature or chemical composition don’t determine the envelope’s location, and guessing from wind direction doesn’t provide the spatial match needed.

Determining whether a receptor lies inside the plume envelope relies on the Gaussian plume geometry: as the plume travels downwind, it spreads crosswind and vertically, with widths described by σ_y(x) and σ_z(x) at that downwind distance x. To decide if the receptor is affected, locate the receptor relative to the plume centerline. Compare its lateral offset y to the predicted crosswind spread σ_y and its vertical offset from the plume centerline z − z_center(x) to the vertical spread σ_z. If the receptor’s coordinates fall within the plume’s crosswind and vertical extents (for example, within a few σ_y and σ_z around the centerline), it is inside the plume envelope and could experience significant concentrations. Temperature or chemical composition don’t determine the envelope’s location, and guessing from wind direction doesn’t provide the spatial match needed.