Air Dispersion Modeling Flashcards

Which EPA-approved air dispersion model is the preferred regulatory model for most near-field (within ~50 km) stationary source applications?

Answer: AERMOD

AERMOD (American Meteorological Society/EPA Regulatory Model) is the EPA's preferred regulatory model for near-field dispersion from stationary sources.

In the Pasquill-Gifford atmospheric stability classification system, which stability class represents the most unstable atmospheric conditions?

Answer: Class A

Class A is the most unstable Pasquill-Gifford stability class, occurring under strong solar radiation and light surface winds.

The Gaussian plume model assumes that pollutant concentrations follow what type of statistical distribution in both the horizontal and vertical directions from the plume centerline?

Answer: Normal (Gaussian) distribution

The Gaussian plume model assumes a normal (bell-curve) distribution of pollutant concentrations both crosswind and vertically from the plume centerline.

The AERMET meteorological preprocessor is used to prepare which type of data for input into AERMOD?

Answer: Surface meteorological and upper-air sounding data

AERMET processes surface meteorological observations and upper-air soundings to derive planetary boundary layer parameters required by AERMOD.

In air dispersion modeling, 'effective stack height' is defined as the sum of the physical stack height plus:

Answer: Plume rise due to momentum and buoyancy of exhaust gases

Effective stack height equals physical stack height plus plume rise, which results from the upward momentum and buoyancy of hot exhaust gases.

In the Gaussian dispersion equation, sigma-z (σz) represents the standard deviation of pollutant concentration in which direction?

Answer: Vertical direction

Sigma-z (σz) is the standard deviation of vertical concentration distribution, quantifying the degree of vertical plume spreading with distance from the source.

Building downwash in air dispersion modeling occurs when stack emissions are captured by the aerodynamic wake created by:

Answer: The source building or nearby structures

Building downwash occurs when the aerodynamic recirculation zone behind a building or structure captures and pulls the plume downward toward ground level.