Air Pollution Module Based on SCREEN3 Model

Scope of the Module

SCREEN3 is a version of the USEPA Industrial Source Complex (ICS) model. This model is based on the steady state Gaussian Model of plume dispersion as described earlier. This model is recommended for the following applications:

• Industrial Source Complexes
• Rural or urban areas
• Flat or rolling terrain
• Transport distances less than 50 kilometers
• 1-hour to annual averaging times; continuous toxic emissions
• Default options of the model include:
• Stack tip downwash
• Final plume rise
• Buoyancy induced dispersion
• The vertical potential temperature gradient
• Treatment for calms
• Appropriate wind profile exponents
• Basic inputs required by the model are emission rate, physical stack height, stack gas exit velocity and stack gas temperature. This model is based on ICS3 and an upgrade of ICS2 which was used in the commercial software AIRSCAPE described in air pollution notes and modelling.

Software and Manual

Windows based model. The output should be saved by the user as an output (filename.out) file which can be utilized by typical Spreadsheet applications as Excel.

Example Problem

A sample run of the SCREEN3 simulation is presented below. The sample inputs are provided by user on the screen. For example, in this run a point source with building downwash in an urban setting was selected and the values of chosen input variables are shown in Table 1. The standard output of the model is shown in Table 2. Other options chosen were as specified as default options although user can specify and alter these conditions (e.g., default option of wind speed anemometers were at 10 meter).

Table 1: SCREEN3 Input Parameters
 *** SCREEN3 MODEL RUN *** *** VERSION DATED 96043 *** POINT SOURCE EXAMPLE WITH BUILDING DOWNWASH  SIMPLE TERRAIN INPUTS: SOURCE TYPE = POINT EMISSION RATE (G/S) = 100.000  STACK HEIGHT (M) = 100.0000 STK INSIDE DIAM (M) = 2.0000 STK EXIT VELOCITY (M/S)= 15.0000 STK GAS EXIT TEMP (K) = 450.0000 AMBIENT AIR TEMP (K) = 293.0000 RECEPTOR HEIGHT (M) = .0000 URBAN/RURAL OPTION = URBAN BUILDING HEIGHT (M) = 80.0000 MIN HORIZ BLDG DIM (M) = 80.0000 MAX HORIZ BLDG DIM (M) = 100.0000 THE REGULATORY (DEFAULT) MIXING HEIGHT OPTION WAS SELECTED. THE REGULATORY (DEFAULT) ANEMOMETER HEIGHT OF 10.0 METERS WAS ENTERED. BUOY. FLUX = 51.319 M**4/S**3; MOM. FLUX = 146.500 M**4/S**2. *** FULL METEOROLOGY ***

Table 2: SCREEN3 Standard Output
 *** SCREEN AUTOMATED DISTANCES *** *** TERRAIN HEIGHT OF 0. M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES *** DIST CONC U10M USTK MIX HT PLUME SIGMA SIGMA (M) (UG/M**3) STAB (M/S) (M/S) (M) HT(M) Y(M) Z(M) DWASH ------- ---------- ---- ----- ----- ------ ------ ------ ------  100. .0000 0 .0 .0 .0 .00 .00 .00 NA 200. .0000 0 .0 .0 .0 .00 .00 .00 NA 300. 631.6 1 1.5 2.1 480.0 125.11 90.71 82.09 SS 400. 517.4 1 1.5 2.1 480.0 140.59 118.85 113.59 SS 500. 494.6 6 1.0 2.0 10000.0 113.08 50.21 50.05 SS 600. 578.0 6 1.0 2.0 10000.0 113.08 59.27 54.62 SS 700. 638.4 6 1.0 2.0 10000.0 113.08 68.06 59.18 SS 800. 715.3 6 1.0 2.0 10000.0 113.08 76.59 65.44 SS 900. 699.4 6 1.0 2.0 10000.0 113.08 84.89 68.33 SS 1000. 681.9 6 1.0 2.0 10000.0 113.08 92.97 71.13 SS  MAXIMUM 1-HR CONCENTRATION AT OR BEYOND 100. M: 800. 715.3 6 1.0 2.0 10000.0 113.08 76.59 65.44 SS DWASH= MEANS NO CALC MADE (CONC = 0.0) DWASH=NO MEANS NO BUILDING DOWNWASH USED DWASH=HS MEANS HUBER-SNYDER DOWNWASH USED DWASH=SS MEANS SCHULMAN-SCIRE DOWNWASH USED " DWASH=NA MEANS DOWNWASH NOT APPLICABLE, X<3*LB" **************************************** *** REGULATORY (Default) ***  PERFORMING CAVITY CALCULATIONS  WITH ORIGINAL SCREEN CAVITY MODEL " (BRODE, 1988) " **************************************** *** CAVITY CALCULATION - 1 *** *** CAVITY CALCULATION - 2 *** CONC (UG/M**3) = 3168. CONC (UG/M**3) = 1691. CRIT WS @10M (M/S) = 3.32 CRIT WS @10M (M/S) = 7.77 CRIT WS @ HS (M/S) = 5.26 CRIT WS @ HS (M/S) = 12.32 DILUTION WS (M/S) = 2.63 DILUTION WS (M/S) = 6.16 CAVITY HT (M) = 114.88 CAVITY HT (M) = 105.20 CAVITY LENGTH (M) = 142.41 CAVITY LENGTH (M) = 101.30 ALONGWIND DIM (M) = 80.00 ALONGWIND DIM (M) = 100.00 **************************************** END OF CAVITY CALCULATIONS  **************************************** **************************************** *** SUMMARY OF SCREEN MODEL RESULTS **** **************************************** CALCULATION MAX CONC DIST TO TERRAIN PROCEDURE (UG/M**3) MAX (M) HT (M) -------------- ----------- ------- ------- SIMPLE TERRAIN 715.3 800. 0. BLDG. CAVITY-1 3168. 142. --(DIST = CAVITY LENGTH) BLDG. CAVITY-2 1691. 101. --(DIST = CAVITY LENGTH) *************************************************** ** REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS ** ***************************************************
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