AQS Air Dispersion Modeling 3

Question 1

The AERMAP terrain preprocessor in the AERMOD modeling system is used to:

Accepted Answer

Extract terrain elevation data and compute hill height scales for sources and receptors

Answer

Process hourly meteorological observations into boundary layer parameters

Answer

Generate automated emission inventories from facility source databases

Answer

Create receptor grids and determine maximum impact receptor locations

Question 2

Under stable atmospheric conditions (Pasquill-Gifford Class E or F), which plume behavior pattern is most commonly observed?

Accepted Answer

Fanning — wide horizontal spread with minimal vertical mixing

Answer

Looping — large irregular vertical oscillations driven by convective cells

Answer

Coning — symmetric moderate dispersion in both horizontal and vertical directions

Answer

Fumigation — rapid downward mixing bringing high concentrations to ground level

Question 3

For regulatory modeling to compare with the 24-hour PM2.5 National Ambient Air Quality Standard, the model output should be analyzed using which averaging period?

Accepted Answer

24-hour average concentrations

Answer

1-hour average concentrations

Answer

Annual average concentrations

Answer

8-hour average concentrations

Question 4

A wind rose diagram is primarily used to display:

Accepted Answer

The frequency distribution and speed of winds from different compass directions at a monitoring site

Answer

The vertical temperature profile of the atmosphere at a sounding station

Answer

The spatial distribution of modeled pollutant concentration isopleths

Answer

The diurnal variation of mixing height over a monitoring period

Question 5

The 'critical wind speed' for maximum ground-level concentration from a buoyant stack plume is the wind speed at which:

Accepted Answer

The reduction in plume rise from stronger winds exactly offsets the increased horizontal dilution, yielding the highest ground concentration

Answer

Atmospheric stability transitions from unstable Class B to neutral Class D

Answer

Stack exit velocity equals ambient wind speed at stack tip elevation

Answer

Plume centerline height equals the atmospheric mixing layer height

Question 6

In AERMOD, when modeling in complex terrain, using the 'ELEV' terrain option rather than the 'FLAT' option means that the model will:

Accepted Answer

Incorporate actual receptor terrain elevations and hill height scales into dispersion calculations

Answer

Assume all receptors lie at sea-level elevation regardless of location

Answer

Model area sources instead of point sources at elevated terrain locations

Answer

Use annually averaged meteorology rather than hourly data

Question 7

Which EPA document provides the primary regulatory framework specifying preferred air dispersion models and procedures for permit applications such as PSD and NSR reviews?

Accepted Answer

EPA Guideline on Air Quality Models (Appendix W to 40 CFR Part 51)

Answer

40 CFR Part 50 — National Primary and Secondary Ambient Air Quality Standards

Answer

EPA Method 9 — Visual Determination of the Opacity of Emissions

Answer

40 CFR Part 60 — Standards of Performance for New Stationary Sources