EPA

Office of Air Quality

Pla nnin g a nd S ta nd a rds

C Air

lean

United States Office of Air Quality EPA-454/R-00-017

Environmental Protection Planning and Standards April 2000

Agency Research Triangle Park, NC 27711

Air

USER’S GUIDE FOR THE ASSESSMENT SYSTEM

FOR POPULATION EXPOSURE NATIONWIDE

(ASPEN, VERSION 1.1) MODEL
ii

DISCLAIMER

The information in this document has been reviewed in accordance with the U.S. EPA administrative review

policies and approved for publication. Mention of trade names or commercial products does not constitute

endorsement or recommendation for their use.

The following trademarks appear in this document:

UNIX is a registered trademark of AT&T Bell Laboratories.

SUN is a registered trademark of Sun Microsystems, Inc.
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CONTENTS

1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.1 BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.2 MODEL OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.2.1 Input Data Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

1.2.2 Computer Hardware Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

1.3 HOW TO USE THE ASPEN MODEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

1.3.1 Novice Users . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

1.3.2 Experienced Modelers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

1.3.3 Management/Decision Makers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

1.3.4 Programmers/System Analysts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

2.0 ASPENA DISPERSION MODULE DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.1 POINT SOURCE EMISSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.1.1 The Gaussian Sector Average Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.1.2 Wind Speed Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2.1.3 Plume Rise Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2.1.3.1 Stack-tip Downwash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

2.1.3.2 Buoyancy and Momentum Fluxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

2.1.3.3 Unstable or Neutral – Crossover between Momentum and Buoyancy . . . . . . . . . 2-3

2.1.3.4 Unstable or Neutral – Buoyancy Rise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

2.1.3.5 Unstable or Neutral – Momentum Rise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

2.1.3.6 Stability Parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2.1.3.7 Stable – Crossover between Momentum and Buoyancy . . . . . . . . . . . . . . . . . . . . 2-5

2.1.3.8 Stable – Buoyancy Rise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2.1.3.9 Stable – Momentum Rise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2.1.3.10 All Conditions – Distance Less Than Distance to Final Plume Rise . . . . . . . . . 2-6

2.1.4 Dispersion Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

2.1.5 The Vertical Term . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8

2.1.6 The Decay Term . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

2.1.7 Building Wake Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

2.2 AREA SOURCE EMISSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

2.3 DRY DEPOSITION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

2.4 THE WET DEPOSITION MODULE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

2.5 SECONDARY SPECIES FORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

3.0 MAPPING MODULE (ASPENB) DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.1 ASPENB OUTPUT FILE STRUCTURE AND UPDATE PROCEDURE . . . . . . . . . . . . . . . . . 3-1

3.2 INTERPOLATING TO CENSUS TRACT CENTROIDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.2.1 Interpolating to Non-Resident Census Tract Centroids . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

3.2.2 Concentration/Deposition Estimates for the Resident Census Tract . . . . . . . . . . . . . . . . . 3-6

3.2.2.1 Major Point Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
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3.2.2.2 Interpolation for Motor Vehicle and Area Sources . . . . . . . . . . . . . . . . . . . . . . . . 3-8

3.3 DETERMINATION OF IMPACTED CENSUS TRACTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11

4.0 DISPERSION MODULE (ASPENA) USER’S INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.1 MODELING OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4.1.1 Dispersion Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4.1.2 Source Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4.1.3 Receptor Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4.1.4 Meteorological Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4.2 ASPENA INPUTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4.2.1 Emission/Control File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4.2.1.1 Run Information, Species Types and Deposition Options . . . . . . . . . . . . . . . . . . 4-5

4.2.1.2 Reactive Decay Rate Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

4.2.1.3 Source Types and Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

4.2.1.4 Source Release Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

4.2.1.5 Emission Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

4.2.1.6 Secondary Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4.2.1.7 Deposition Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4.2.2 STAR Meteorological Data File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4.2.3 Meteorological Index File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

4.2.3.1 Temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

4.2.3.2 Mixing Heights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

4.2.3.3 Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11

4.2.4 Polar Receptor Grid Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11

4.3 ASPENA OUTPUTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11

4.4 RUNNING ASPENA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12

5.0 ASPENB USER’S INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.1 ASPENB INPUTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

5.1.1 Source Concentration and Deposition File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

5.1.2 Census Tract Data File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

5.1.3 Census Tract Index File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

5.2 ASPENB OUTPUTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6

5.3 RUNNING ASPENB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6

5.4 MODEL RE-START CAPABILITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9

6.0 POST-PROCESSING MODEL OUTPUTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.1 GENERATING CONCENTRATIONS FOR THE SECONDARY

COMPOUNDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

6.2 CALCULATING ANNUAL AVERAGE CONCENTRATIONS . . . . . . . . . . . . . . . . . . . . . . . . 6-3

6.3 EXTRACT AND TABULATE ANNUAL AVERAGE CONCENTRATION . . . . . . . . . . . . . . 6-4

7.0 COMPUTER NOTES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1
v

7.1 MINIMUM HARDWARE REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7.2 COMPILING AND RUNNING ASPEN ON A UNIX WORKSTATION . . . . . . . . . . . . . . . . . 7-1

7.2.1 Modifying the Array Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3

7.3 PORTING THE MODEL TO THE OTHER HARDWARE 

ENVIRONMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4

7.3.1 PC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4

8.0 ASPEN MODEL TUTORIAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

8.1 EXAMPLE 1 – GASEOUS HAPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

8.1.1 Setting up the Emission/Control Input File for Point Sources . . . . . . . . . . . . . . . . . . . . . . 8-1

8.1.2 Setting up the Emission/Control Input File for Mobile Sources . . . . . . . . . . . . . . . . . . . . 8-3

8.1.3 Setting up the Emission/Control Input File for Area Sources . . . . . . . . . . . . . . . . . . . . . . 8-4

8.1.4 Running ASPENA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4

8.1.5 Running ASPENB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-10

8.1.6 Post-Processing Model Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11

8.2 EXAMPLE 2 - PARTICULATE HAPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-15

9.0 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1

APPENDIX A ASPENA SUBROUTINE DESCRIPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

APPENDIX B ASPENA COMMON BLOCKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1

APPENDIX C INPUT AND OUTPUT FILE FORMATS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

C.1 DESCRIPTION OF ASPEN INPUT FILE CONTENT AND FORMAT . . . . . . . . . . . . . . . . . . C-1

C.1.1 Description of Emission/Control File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

C.1.2 Description of Meteorological Index File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2

C.1.3 Description of STAR Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2

C.1.4 Description of Census Tract Index File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-3

C.1.5 Description of Census Tract Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-4

C.2 DESCRIPTION OF ASPEN OUTPUT FILE CONTENT AND FORMAT . . . . . . . . . . . . . . . . C-4

C.2.1 Description of Normalized Source Concentration/Deposition File . . . . . . . . . . . . . . . . . . C-4

C.2.2 Description of Population Concentration/Deposition File . . . . . . . . . . . . . . . . . . . . . . . . . C-5

C.2.3 Description of Source Listing File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-6

C.2.4 Description of the Listing File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-6

C.3 DECAY RATES BY REACTIVITY CLASS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-7

APPENDIX D GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-1
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FIGURES

Figure Page

Figure 1-1 Flow diagram of the ASPEN modeling system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

Figure 3-1 ASPENB receptor grid and census tract centroids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

Figure 3-2 Interpolation to non-resident tract centroids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

Figure 3-3 (a) Resident tract spatial averaging for point sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

Figure 3-3 (b) Resident tract spatial averaging for point sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

Figure 3-4 (a) Resident tract spatial averaging for area and mobile sources . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9

Figure 3-4 (b) Resident tract spatial averaging for area and mobile sources . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10

Figure 4-1 Flow diagram of the ASPENA dispersion module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Figure 4-2 Example ASPENA run stream file (filename: aspena.sys) that creates a testing 

file. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12

Figure 4-3 Example ASPENA run stream file (filename: aspena.sys) that does not create a

testing file. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13

Figure 4-4 Example ASPENA job file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13

Figure 5-1 Flow diagram of the ASPENB mapping module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Figure 5-2 Example MKTRACTS fob file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6

Figure 5-3 Example of ASCII formatted census tract data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6

Figure 5-4 Example ASPENB run stream file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7

Figure 5-5 Example ASPENB run stream file using the rerun feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8

Figure 5-6 Example ASPENB job file that creates intermediate output files . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9

Figure 5-7 Example of an ASPENB re-start job file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10

Figure 6-1 Flow chart of the ASPEN post-processors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

Figure 6-2 Example job file for the SECDAT post-processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

Figure 6-3 Example job file for the post-processor AVGDAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

Figure 6-4 Example 1 job file for the EXTRDAT post-processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

Figure 6-5 Example 2 job file for the EXTRDAT post-processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

Figure 7-1 The commands for compiling ASPENA on a UNIX workstation . . . . . . . . . . . . . . . . . . . . . . . . . 7-2

Figure 7-2 The commands for compiling the ASPENB on a UNIX workstation . . . . . . . . . . . . . . . . . . . . . . . 7-3

Figure 8-1 Example emission/control input file for point sources

(filename: aspena.tri.inp) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

Figure 8-2 Example emission/control input file for on-road mobile sources

(filename: aspena.mv.inp) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3

Figure 8-3 Example emission/control input file for area source

(filename: aspena.ar.inp) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-5

Figure 8-4 Run stream file for the gaseous HAPs ASPENA run

(filename: aspena.ar.sys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-5

Figure 8-5 Run stream file for ASPENA point run (filename: aspena.tri.sys) . . . . . . . . . . . . . . . . . . . . . . . . . 8-6

Figure 8-6 Run stream file for ASPENA mobile run (filename: aspena.mv.sys) . . . . . . . . . . . . . . . . . . . . . . . 8-6

Figure 8-7 Example of ASPENA job file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6

Figure 8-8 ASPENA diagnostic file created by example area source run . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7

Figure 8-9 ASPENA diagnostic file created by example mobile source run . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8
vii

Figure 8-10 ASPENA diagnostic file created by example TRI source run . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9

Figure 8-11 ASPENB example job file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-10

Figure 8-12 Example EXP2ASCI job file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11

Figure 8-13 ASPENB output population concentration/deposition file (in ASCII format)

for example run . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-12

Figure 8-14 Example post-processing job file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-13

Figure 8-15 ASPEN output in ASCII format for the example simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14

Figure 8-16 Example ASPENA input file for point source emits particulate HAPs . . . . . . . . . . . . . . . . . . . . 8-15

Figure 8-17 ASPENA diagnostic file created by example point source run . . . . . . . . . . . . . . . . . . . . . . . . . . 8-16

Figure 8-18 ASPENB output population concentration/deposition file (in ASCII format)

for example point source run (for Saroad code 80141) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-17

Figure 8-19 ASPENB output population concentration/deposition file (in ASCII format)

for example point source run(for Saroad code 80216) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-17
viii

TABLES

Table Page

Table 2-1 Deposition velocities for particulate matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

Table 4-1 ASPENA file descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

Table 4-2 Description of the emission/control file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

Table 4-3 Description of the STAR meteorological data file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

Table 4-4 Description of the meteorological index file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

Table 4-5 Error messages in the ASPENA log file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12

Table 5-1 ASPENB input and output file descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

Table 5-2 Description of census tract data file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

Table 5-3 Description of census tract index file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

Table 5-4 Error messages in the ASPENB log file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8

Table 7-1 ASPEN disk storage requirements for example simulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

Table 8-1 Point source data parameters entered into the emission/control input file . . . . . . . . . . . . . . . . . . . . 8-2

Table C-1 Description of emission/control file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

Table C-2 Description of meteorological index file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2

Table C-3 Description of STAR data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-3

Table C-4 Description of census tract index file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-3

Table C-5 Description of census tract data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-4

Table C-6 Description of normalized source concentration/deposition file . . . . . . . . . . . . . . . . . . . . . . . . . . . C-5

Table C-7 Description of population concentration/deposition file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-6

Table C-8 Description of source listing file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-6
ix

PREFACE

This user’s guide provides documentation for the Assessment System for Population Exposure Nationwide

(ASPEN, Version 1.1), referred to hereafter as ASPEN. It includes a technical description of the ASPEN

algorithms, instructions for running the individual modules and a tutorial for getting started.

Version 1.0 of the ASPEN model was used in the EPA’s Office of Policy’s Cumulative Exposure Project. The

changes to ASPEN in version 1.1, were to make file handling more flexible and easier. None of the technical

algorithms were modified. Therefore, given the same input data, the results from versions 1.0 and versions 1.1

should be identical, although the output files are formatted somewhat differently.
x

ACKNOWLEDGMENTS

The authors would like to acknowledge the many contributions to the development of the ASPEN modeling

system by Systems Applications International. Gerald Anderson and Gary Lundberg developed the original

version of the Human Exposure Model, from which the ASPEN modeling system was derived. Major

contributors to development of ASPEN include the late Dr. Mary Ligocki, Gary Lundberg, Arlene Rosenbaum,

Gerard Mansell, Hans Deuel, and YiHua Wei.

Daniel Axelrad and Tracey Woodruff, both of EPA’s Office of Policy, sponsored the ASPEN development as

part of the Cumulative Exposure Project.
1-1

1.0 INTRODUCTION

The User’s Guide for the Assessment System for Population Exposure Nationwide (ASPEN)

provides the technical description of the ASPEN algorithms. It includes an overview of ASPEN,

a discussion of its features, instructions for running the individual modules, and a tutorial for

getting started.

1.1 BACKGROUND

The Assessment System for Population Exposure Nationwide (ASPEN), a new version of the

Human Exposure Model (HEM), was developed as part of the Cumulative Exposure Project,

sponsored by the US Environmental Protection Agency’s Office of Policy, Planning, and

Evaluation. The Cumulative Exposure Project report (Rosenbaum et al., 1998) includes 

sensitivity analysis of the features of ASPEN. ASPEN was designed to efficiently estimate

outdoor concentrations and depositions of multiple pollutants emitted from a large number of

sources at a large scale (e.g., national), while reporting results at the spatial resolution of census

tracts. The number of emission sources, HAPs, and census tracts included in an analysis are

specified by the user.

As part of the ASPEN development, a number of enhancements were made to HEM. These 

include:

• Modification of plume rise and dispersion parameters and formulations to assure

consistency with those in the Industrial Source Complex - Long Term Model, Version 2

(ISCLT2; EPA, 1992);

• Expansion of HEM’s reactive decay options;

• Incorporation of simple treatment of secondary formation of HAPs;

• Improvement of HEM’s dry deposition algorithm;

• Addition of a wet deposition algorithm;

• Modification of the treatment of locations near point sources;

• Modification of the treatment of area and mobile sources; and

• Improvement of computational procedures to reduce run times.

1.2 OVERVIEW OF THE ASPEN MODEL

The Assessment System for Population Exposure Nationwide (ASPEN) model consists of two

modules, ASPENA and ASPENB, and a series of post-processing programs. ASPENA is a

dispersion module that estimates ambient concentration increments at a set of fixed receptor

locations in the vicinity of an emission source (i.e., the receptor grid). ASPENB is a mapping

module that interpolates ambient concentration increment estimates from the grid receptors to

census tract centroids, and sums contributions from all modeled sources. The post-processing

programs: 
1-2

ASPEN A

(Section 2.0)

ASPEN B

(Section 3.0)

Post-processors

(Section 4.0)

Census 

data

M eteorological 

data

E m issions 

Source data

Annual average H A P 

concentration by 

census tract

• distribute background HAP concentrations by census tract (BCKGRND program),

• generate the secondary compound concentrations and combine the concentrations of the

primary and secondary compounds (SEC_DAT program), 

• calculate the total pollution concentration from all source categories for each HAP from

the ASPENB output files (MRG_DAT program), 

• calculate the annual average HAP concentration (AVG_DAT program), and 

• convert the concentration data files from binary to ASCII format (EXTR_DAT program). 

Together, the ASPEN programs estimate annual average air toxics concentrations (in μg/m3) at

each census tract for each of eight 3-hour time blocks for each HAP/source category

combination. The major processes of the two modules are illustrated in the flow diagram shown

in Figure 1-1.

Figure 1-1 Flow diagram of the ASPEN modeling system

For ease in discussion and application, the ASPEN modeling system can be examined by its two

main components: dispersion module (ASPENA) and mapping module (ASPENB).
1-3

ASPENA - Like its predecessors, the Human Exposure Model (HEM) and the South Coast Risk

and Exposure Assessment Model - Version 2 (SCREAM2), ASPENA uses a Gaussian model

formulation and climatological data to estimate long-term average pollution concentrations. For

each source, the model calculates ground-level concentrations as a function of radial distance and

direction from the source at a set of receptors laid out in a radial grid pattern. These

concentrations represent the steady-state concentrations that would occur with constant emissions

and meteorological parameters. For each grid receptor, concentrations are calculated for each of

a standard set of stability class/wind speed/wind direction combinations. These concentrations

are averaged together using the annual frequency of occurrence of each combination (i.e., the

climatology) as weightings.

These meteorological frequency distributions are typically prepared for the entire simulation

period, usually one or more years. For ASPEN, however, meteorological data are stratified by

time of day into eight 3-hour time blocks, to preserve any characteristic diurnal patterns that

might be important in subsequent estimation of population exposure. In addition to the

climatology, other inputs to ASPEN that are specified by time block include emission rate,

mixing height, and reactive decay rates. The resulting output of ASPENA is a grid of annual

average concentration estimates for each source/pollutant combination by time block.

ASPENB - In ASPENB, the mapping module, annual average concentration estimates from

ASPENA are interpolated from the grid receptors to census tract centroids, and contributions

from all modeled sources are summed to give estimates of cumulative ambient concentration

increments in each census tract. By accounting for all identified source categories (including

background concentrations), the sum of the concentration increments should yield an estimate of

the overall concentration of each HAP within each census tract. These estimates are designed to

represent population-weighted concentration averages (each census tract represents

approximately 4000 people).

1.2.1 Input Data Requirements

The three types of inputs needed to run the ASPEN models are the emission/control file,

meteorological data files, and census tract data files.

• Emission/control file - contains the selected modeling options, source parameter data

(including emission rates), and meteorological station assignments

• Meteorological data - includes the annual frequency of occurrence of each stability/wind

speed/wind direction combination (by time block), temperatures (maximum, minimum

and average), precipitation data, and mixing height (by time block) for meteorological

stations within the modeling region
1-4

• Census tract data - contains the Federal Information Processing Standards (FIPS) code,

location of the tract centroid, hypothetical radius, and urban/rural designation of each

census tract within the modeling region

The emission control file and the meteorological data files are described in detail in Section 4.2

while the census tract data files are described in Section 5.1.

1.2.2 Computer Hardware Requirements

The computer resources required to run an ASPEN application are contingent upon the number

of emission sources and HAPs to be processed. The disk storage requirement to run a simulation

on a UNIX workstation (Sun Ultra Sparc 2 / Solaris 2.5.1), using the emissions from one source

category (on-road mobile), one reactivity class (reactivity class 2 including emissions from 11

HAPs) in a single EPA region (EPA region 9) is approximately 1.3 Mbytes for ASPENA, and 2.7

Mbytes for ASPENB. It takes approximately 6 CPU hours to run both ASPENA and ASPENB

for this simulation run.

1.3 HOW TO USE THE ASPEN MODEL

1.3.1 Novice Users

Novice users are those that are new to the ASPEN model and have limited dispersion modeling

experience. These users should begin with Section 1.2 to gain a conceptual overview of the

model. Section 8 provides a brief tutorial on setting up simple input files under two example

scenarios. Once users have a basic understanding of the model, they will want to review the

ASPENA and ASPENB user’s instructions, respectively, in Sections 4 and 5. Section 2 provides

a complete descriptions of the ASPENA dispersion module. Section 3 provides a detailed

description of the ASPENB mapping module. Section 6 includes a discussion of the software

used to post-process the ASPEN model output. Also, the tutorial provided will help them learn

the structure of the input files and how to review the modeling results.

1.3.2 Experienced Modelers

Modelers that are unfamiliar with the ASPEN models but experienced using dispersion models in

a variety of situations will also benefit from first reviewing the content of Section 1.2 to gain a

basic orientation to the ASPEN model. Sections 4, 5 and 6 can be used as a reference for

learning the overall capabilities of the modeling system’s main components. Finally, the

Appendices provide details of the formats for the ASPEN input and output files. Experienced

modelers may also be interested in reviewing sections 2 and 3, which describe the technical

details of ASPENA and ASPENB.
1-5

1.3.3 Management/Decision Makers

Those involved in air quality management or decision-making capacities related to dispersion

modeling will benefit most from an overview of the model, and a general introduction to the

input data needs and computer hardware requirements for running the model (Section 1.2). Upon

review of this section, managers will understand the basic capabilities of the model well enough

to judge the suitability of the model for particular applications. 

1.3.4 Programmers/Systems Analysts

Programmers and systems analysts, specifically those in charge of maintaining the code or those

involved with installing the ASPEN model code on other computer systems should review

Section 7. Section 7 discusses the minimum hardware requirements to run the model, and how

to port the model to various hardware environments. They may also wish to review Section 1.2

in order to have a basic understanding of the nature and overall capabilities of the model.
2-1

2.0 ASPENA DISPERSION MODULE DESCRIPTION

The ASPEN dispersion module estimates the ambient concentration increments at a set of fixed

receptor locations within the vicinity of the emission source. The steady-state Gaussian plume

equation is used in conjunction with diurnally stratified climatological data, including wind

speed, wind direction, and atmospheric stability, to estimate long-term average ground-level

concentrations at receptor grid locations resulting from elevated point emission sources. The

specific formulation and equations used are described in the following subsections. Unless

otherwise noted, all equations are identical to those in the Industrial Source Complex – Long

Term 2 (ISCLT2) model.

2.1 POINT SOURCE EMISSIONS

2.1.1 The Gaussian Sector Average Equation

The ASPEN modeling system uses the steady-state Gaussian plume equation in order to simulate

elevated point sources with continuous emissions. To reduce computing requirements, ASPEN

utilizes a climatological modeling approach. As with other climatological models (e.g., the

Environmental Protection Agency’s (EPA) Climatological Dispersion Model (CDM) and

ISCLT), the dispersion module is supplied with a STability ARray (STAR) joint probability

matrix. A STAR matrix describes the joint frequency distribution of hourly meteorological

measurements sorted into classes, or bins, by wind speed, wind direction, and atmospheric

stability. The long-term concentration is calculated by simulating the average concentration for

each meteorological bin and summing the averages across bins, weighting each by its frequency

of occurrence.

Normally, a single STAR matrix is prepared for the entire simulation period, usually one or more

years. For ASPEN, meteorological data were prepared in 3-hour time blocks. For example,

there is a STAR matrix for the time period from 3 a.m. to 6 a.m., reflecting the relative long-term

frequency of each meteorological condition for that time of day.

Classification of the wind directions for preparation of the STAR matrix requires partitioning of

the area surrounding each source into sectors of equal angular widths. The mean annual

concentration at each receptor resulting from emissions from a single stack is obtained by

averaging over all wind directions, wind speeds and stability classes according to:

χ

π θ σ = ∑ 1

2

K

R

QfVD

∆ i jk us z ' , ,

where :

χ = concentration (μg/m3

)

K = units scaling coefficient (106

)

Q = pollutant emission rate (g/s)
2-2

f = frequency of occurrence of the ith wind-speed, the j th winddirection, and the kth stability category (unitless)

∆θN = the sector width (radians)

R = radial distance from the point source to receptor (m)

us = mean wind speed at stack height for the ith wind-speed category and

the kth stability category. (m/s)

σz = standard deviation of the vertical concentration distribution for the

kth stability category (m)

V = Vertical Term for the ith wind-speed and kth stability category

(unitless)

D = Decay Term for the ith wind-speed and kth stability category

(unitless)

Each of the terms above are defined and discussed briefly in the following subsections.

2.1.2 Wind Speed Profile

The stack height wind speed, us (m/s), is obtained by adjusting the observed wind speed, uref

(m/s), at a reference height, zref (m), to the stack height, hs (m), through use of the wind power

law. The equation has the form,

us uref

hs

zref

p

=

















Where p is the wind profile exponent which is dependent on both the stability category as well as

whether the source is classified as urban or rural. The default values used in the ASPEN model

are the same as those for the ISCLT2 model and are given below:

Stability Category Rural Exponent Urban Exponent 

A 0.07 0.15

B 0.07 0.15

C 0.10 0.20

D 0.15 0.25

E 0.35 0.30

F 0.55 0.30

The stack height wind speed, us, has a minimum value of 1.0 m/s.

2.1.3 Plume Rise Formulas

The ASPEN model uses all plume rise calculations in the ISCL2 model (EPA, 1992). Prior to

any plume rise calculations, the physical stack height is modified in order to account for stack-tip
2-3

downwash effects. This modified stack height, hsN, is then used in place of the physical stack

height for all subsequent plume rise calculations.

2.1.3.1 Stack-tip Downwash

The physical stack height is modified to account for stack-tip downwash effects following the

treatment of Briggs (1974):

h for sh

s

d

s

v

s

u

s

' . =+ −















 2 15 v u s s < 15.

or

h h for s s ' = v u s s ≥ 15.

where hs is the physical stack height (m), vs is the stack gas exit velocity (m/s), and ds is the stack

tip diameter (m). When stack-tip downwash is not considered, hsN = hs.

2.1.3.2 Buoyancy and Momentum Fluxes

For most calculations involving plume rise, the buoyancy parameter, Fb (m4/s3), as well as the

momentum flux parameter, Fm (m4/s2), are needed. These parameters are calculated as follows:

Where ∆T = Ts - Ta , Ts is the stack gas temperature (K), and Ta is the ambient air temperature

(K).

2.1.3.3 Unstable or Neutral – Crossover between Momentum and Buoyancy

The determination of whether the plume rise is dominated by momentum or buoyancy in the case

where the stack gas temperature is greater than or equal to the ambient air temperature, follows

the procedure of Briggs as outlined in the ISC Users’ Guide, Section 1.1.4.3 ( EPA, 1992). A

crossover temperature difference is calculated using the following equations:

For Fb < 55,















 ∆ =

s

b s s T

T F gv d

4

2

( ) 3

2

3

1

0.0297

s

s

c s

d

v ∆T = T















 =

s

a

m s s T

T

F v d

4

2 2
2-4

And for Fb $ 55,

If the difference between the stack gas and ambient temperature is greater than or equal to the

crossover temperature difference, then the plume rise is assumed to be buoyancy dominated,

otherwise it is momentum dominated.

2.1.3.4 Unstable or Neutral – Buoyancy Rise

When the plume rise is determined to be buoyancy dominated, as described above, then the

distance to final rise, xf (m), is determined as follows:

For Fb < 55:

And for Fb $ 55:

The final effective plume height is then given by:

For Fb < 55:

And for Fb $ 55:

2.1.3.5 Unstable or Neutral – Momentum Rise

When the stack gas temperature is less than or equal to the ambient air temperature, or if ∆T is

less than the crossover temperature, (∆T)c, then the plume rise is assumed to be dominated by

momentum. The effective plume height is then given by:

8

5

49 f Fb x =

s

s

e s s u

v h h 3d ' = +

( ) 3

1

3

2

0.00575

s

s

c s

d

v ∆T = T

5

2

119 f Fb x =

s

b

e s u

F h h 4

3

21.425 ' = +

s

b

e s u

F h h 5

3

38.71 ' = +
2-5

2.1.3.6 Stability Parameter

For stable atmospheric conditions, the stability parameter, s (s-2), is required for plume rise

calculations. In ASPEN, as in the ISCLT2 model, the stability parameter is calculated from the

following equation given by Briggs (1975):

As a default approximation, Mθ'Mz is taken as 0.020 K/m for stability class E, and for class F,

Mθ'Mz is taken as 0.035 K/m.

2.1.3.7 Stable – Crossover between Momentum and Buoyancy

As in the case of unstable conditions, a crossover temperature difference is used to determine

whether the plume rise is buoyancy or momentum dominated for stable atmospheric conditions. 

In this case the crossover temperature difference, (∆T)c, is given by:

If the difference between stack gas temperature and ambient air temperature exceeds or equals

(∆T)c, the plume rise is assumed to be buoyancy dominated; otherwise it is momentum

dominated.

2.1.3.8 Stable – Buoyancy Rise

For buoyancy dominated plume rise, ∆T exceeds (∆T)c as determined above. The distance to

final plume rise, xf, is calculated as 

And the effective plume height, he, is given by the following equation:

2.1.3.9 Stable – Momentum Rise

In stable conditions, if the stack gas temperature is less than or equal to ambient air temperature,

or if ∆T is less than the crossover temperature difference (∆T)c, it is assumed that the plume rise

is momentum dominated. The effective plume height is then given as:

Ts

z s g ∂ ∂

=

θ

( ) T T v s c s s ∆ = 0.019582

s

u

x s

f = 2.0715

3

1

2.6 '















 = +

u s

F h h

s

b

e s
2-6

For this case, the unstable-neutral momentum rise is also evaluated. The smaller of these results

is then used as the resulting plume height.

2.1.3.10 All Conditions – Distance Less Than Distance to Final Plume Rise

When gradual rise is to be estimated and the downwind distance from source to receptor, x, is

less than the distance to final rise, then the effective plume height is given as:

This relation is used only for buoyancy dominated plumes. In addition, if this relation results in a

plume height which exceeds the final plume rise for the appropriate condition, then the final

plume rise is used instead.

For momentum dominated plumes, stable and unstable conditions are treated separately as

follows:

a) Unstable Conditions

h h

F x

u e s

m

j s

= +















 ' 3

2 2

1

3

β

Where x is the downwind distance in meters, with a maximum value, xmax, defined by:

for ( )

x

dv u

v

ss s

sus

max = 4 3 +

2

Fb = 0

= 49 for

5

F 8

b 0 55 < ≤ Fb m s 4 3

= 119 for

5

F 8

b Fb ≥ 55 m s 4 3

3

1

1.5 '















 = +

u s

F h h

s

m

e s















 = +

s

b

e s x

F x h h 3

2 31

1.60 '
2-7

b) Stable Conditions

Here the maximum downwind distance is defined by:

The jet entrainment coefficient, βj

, is given as,

As in the case of buoyant gradual rise, the minimum of the distance-dependent momentum rise,

as calculated above, and the final rise for the appropriate condition is used for the effective plume

rise.

2.1.4 Dispersion Parameters

The standard deviation of the vertical concentration distribution, σz , for point sources is

calculated using a procedure similar to that used in the ISCLT2 model. For a rural point source,

the dispersion parameter, σz , is calculated using equations which approximately fit the PasquillGifford curves (Turner, 1970) and are of the form,

where x, the downwind distance, is in kilometers and σz is in meters. The coefficients a and b are

given as in Table 1-2 of the ISC2 Users’ Guide (EPA, 1992) and are a function of both the

downwind distance as well as stability class.

For urban point sources, the vertical dispersion parameter is computed using the Briggs’

formulas to approximate vertical diffusion data of McElroy and Pooler (1968). Table 1-4 of EPA

(1992) gives the appropriate relations for σz as a function of stability class and downwind

distance from the source. As noted in EPA (1992), although these relations are assumed valid for

downwind distances less than 100m, concentrations calculated at receptor locations within 100m

of a source should be treated as suspect. 

As in the ISCLT2 model, the ASPEN modeling system assumes a uniform lateral distribution

across sector widths and therefore does not make use of the standard deviation of the lateral

dispersion, σy .

( ) 3

1

2

' sin / 3















 = +

u s

x s u h h F

j s

s

e s m

β

s

u

x

π s

max = 0.5

s

s

j v

u = +

3

1 β

b

z σ = ax
2-8

The preceding approximations for dispersion parameters are applicable for ideal point sources. 

In general, a variety of processes can affect the initial growth and evolution point source plume. 

The ISC models use various treatments for consideration of many of these processes including

the initial plume dimensions, building wake and downwash effects, and buoyancy-induced

dispersion. Of these, ASPEN treats only the enhancements to the vertical dispersion parameter

due to buoyancy-induced dispersion. (Treatment of building wake and downwash effects in

ASPEN differs from ISCLT2, and is discussed in Section 2.1.7) 

The current treatment of buoyancy-induced dispersion in the ASPEN modeling system follows

that of Pasquill (1976) as implemented in the ISC2 model. Buoyancy-induced dispersion

enhances the vertical dispersion due to ambient turbulence by taking into account the initial

plume dispersion caused by turbulent motion and turbulent entrainment of ambient air. Then

effective vertical dispersion, σze, is given by the following relation:

where σz is the vertical dispersion due to ambient turbulence, and ∆h is the plume rise due to

momentum and/or buoyancy. Note that ∆h is the distance-dependent plume rise when the

receptor location is between the source and the distance to final plume rise, and is the final plume

rise when the receptor location is beyond the distance to final rise.

2.1.5 The Vertical Term

In general, the vertical term which appears in the Gaussian sector average equation includes the

effects of source elevation, receptor elevation, plume rise, limited mixing in the vertical and the

gravitational settling and dry deposition of larger particles. In the ASPEN dispersion module,

receptor elevation, as well as gravitational settling of large particles, is neglected. In addition,

dry deposition of particles is treated separately, as discussed below. The vertical term is then

given as in the ISC2 model for gases and small particles as follows:































 +

+ − 





























 − = −

2 2

exp 0.5 exp 0.5

z

r e

z

r e z h z h V

σ σ

2

1

2

2

3.5 













 



 



 ∆ = +

h

σ ze σ z

∑

∞

= 













































 − 





























 − 





























 + − 





























 + − 1

2

4

2

3

2

2

2

1 exp 0.5 exp 0.5 exp 0.5 exp 0.5 i z z z z

H H H H

σ σ σ σ
2-9

where:

zr = receptor height above ground (m)

zi

 = mixing height (m)

In the above equation, the infinite series accounts for the effects of restriction on vertical plume

growth at the top of the mixed layer. It should be noted that if the effective stack height, he ,

exceeds the mixing height, zi , then the plume is assumed to fully penetrate the elevated inversion

and the ground-level concentrations are set to zero. At long downwind distances, the vertical

term, as defined above, changes the form of the vertical concentration distribution from Gaussian

to rectangular. Thus, the equation for the vertical term for downwind distances where the ratio of

σz/zi is greater than or equal to 1.6 is changed to the following form:

A more detailed discussion of the Vertical Term, including special treatments for mixing heights

in rural and urban modes under various stability conditions may be found in the ISC2 Users’

Guide (EPA, 1992).

2.1.6 The Decay Term

The decay term is used as a simple means of accounting for the pollutant removal by physical

and/or chemical processes. The decay term takes the following form:

or 

D = 1

h h h e = s + ∆

i

z

z

V

2πσ =















 = − us

x D exp ψ

( ) r i he H4 = z + 2iz +

for

( ) r i e H = z − 2iz + h 3

ψ > 0

( ) r i e H = z + 2iz − h 2

( ) r i e H = z − 2iz − h 1

for ψ = 0
2-10

where:

D = decay term (unitless)

ψ = decay coefficient (s-1)

x = downwind distance (m)

us = wind speed at stack height (m/s)

2.1.7 Building Wake Effects

The procedures used by the ASPENA model to account for the effects of building wakes and

downwash effects are considerably different than those employed in the ISC2 model. Within the

ISC2 model, the effects of building wakes on the plume dispersion coefficients are treated in a

manner following those of Huber and Snyder. Following their suggestions, the vertical

dispersion parameters are adjusted using a vertical virtual distance which is dependent on various

factors including the relative dimensions of nearby buildings, stability class, and urban or rural

classification of the emission source.

ASPENA uses a simpler treatment which also involves adjusting the plume dispersion

parameters for a vertical virtual distance. Within ASPENA, the virtual distances are determined

using an empirical formulation involving the building cross-sectional area and stability class, but

are treated in the same way for both the rural and urban option. The formula used for calculating

the vertical virtual distance, x z, is given by,

where A is the building cross-sectional area and the coefficients b, c, and d are dependent on the

stability class and are given in the following table. This virtual distance is then added to the

physical downwind distance and used through for all plume rise and dispersion parameter

calculations.

Stability Category b c d

A 1.95 0.504 0.754e-08

B 2.72 0.504 0.15799e-07

C 4.05 0.511 0.156395e-06

D 4.95 0.54 0.1039e-05

E 4.95 0.54 0.1039e-05

F 4.95 0.54 0.1039e-05

2.2 AREA SOURCE EMISSIONS

The ASPEN modeling system treats area sources (including motor vehicles) as a pseudo-point

source located within each census tract. Pseudo-point sources are assumed to be vented point

sources with an effective stack height of 5 meters and for which no plume rise calculations are

made. The annual average concentration for area sources are processed within the mapping

( ) c d xz = bA exp A
2-11

module (ASPENB) in one of two ways depending upon the relative area of the census tract with

respect to the location of the receptor grid locations. For large census tracts, five dispersion grids

resulting from the pseudo-point treatment are distributed symmetrically throughout the tract in

order to estimate ambient concentrations due to area source emissions. For small census tracts,

only a single dispersion grid is used, located at the census tract centroid. A more detailed

description of the treatment of area sources may be found in the discussion of the ASPENB

module.

2.3 DRY DEPOSITION

Deposition of pollutants onto surfaces has the effect of reducing the average ambient

concentrations and may be significant for particles. The dry deposition of gaseous HAPs is slow,

so for most of these species, the deposition is less important than chemical reaction as a removal

mechanism. Therefore, neglecting dry deposition for gas phase pollutants has little effect on the

modeled concentrations. The ASPEN model therefore accounts for the deposition of particulate

phase HAPs but does not include deposition of gas phase pollutants.

For particles, dry deposition rates are primarily a function of the particle size, and are thus much

larger for coarse particles than for fine particles. In addition, the deposition of coarse particles is

also highly dependent on gravitational settling. The dry deposition rates are also a function of the

land-use type and vary for urban and rural environments. Deposition velocities, Vd (m/s), for the

fine and coarse particles were obtained for different land-use types using the dry deposition

algorithms of the Variable-grid Urban Airshed Model (UAM-V) photochemical model (SAI,

1992). These values are further parameterized as functions of stability class and wind speed. 

ASPEN’s predicted atmospheric concentrations for particulate matter take into account different

rates of particle deposition on urban and rural lands. The deposition velocities used in ASPENA 

are shown in Table 2.1.

TABLE 2.1 Deposition velocities for particulate matter

Deposition Velocities (m/s) for coarse particles -- Rural*

Stability Wind speed (m/s)

1.5 2.5 4.5 7.0 9.5 12.5

A 1.33E-02 1.98E-02 3.32E-02 5.02E-02 6.73E-02 8.78E-02

B 1.28E-02 1.95E-02 3.30E-02 5.01E-02 6.72E-02 8.78E-02

C 1.25E-02 1.93E-02 3.29E-02 5.01E-02 6.72E-02 8.78E-02

D 1.24E-02 1.92E-02 3.29E-02 5.00E-02 6.72E-02 8.77E-02

E 1.13E-02 1.86E-02 3.25E-02 4.98E-02 6.70E-02 8.76E-02

F 1.04E-02 1.79E-02 3.22E-02 4.96E-02 6.68E-02 8.75E-02
2-12

Deposition velocities (m/s) for coarse particles -- Urban*

Wind speed (m/s)

Stability 1.5 2.5 4.5 7.0 9.5 12.5

A 3.10E-02 4.78E-02 8.27E-02 1.27E-01 1.71E-01 2.24E-01

B 2.99E-02 4.71E-02 8.24E-02 1.27E-01 1.71E-01 2.24E-01

C 2.92E-02 4.68E-02 8.22E-02 1.27E-01 1.71E-01 2.24E-01

D 2.89E-02 4.66E-02 8.22E-02 1.27E-01 1.71E-01 2.24E-01

E 2.64E-02 4.51E-02 8.13E-02 1.26E-01 1.71E-01 2.24E-01

F 2.42E-02 4.37E-02 8.05E-02 1.25E-01 1.70E-01 2.24E-01

Deposition velocities (m/s) for fine particles -- Rural*

Wind speed (m/s)

Stability 1.5 2.5 4.5 7.0 9.2 12.5

A 5.55E-05 8.48E-05 1.45E-04 2.21E-04 2.98E-04 3.89E-04

B 5.39E-05 8.38E-05 1.45E-04 2.21E-04 2.97E-04 3.89E-04

C 5.29E-05 8.32E-05 1.44E-04 2.21E-04 2.97E-04 3.89E-04

D 5.22E-05 8.29E-05 1.44E-04 2.21E-04 2.97E-04 3.89E-04

E 4.86E-05 8.06E-05 1.43E-04 2.20E-04 2.97E-04 3.89E-04

F 4.53E-05 7.85E-05 1.42E-04 2.19E-04 2.96E-04 3.88E-04

Deposition velocities (m/s) for fine particles -- Urban*

Wind speed (m/s)

Stability 1.5 2.5 4.5 7.0 9.5 12.9

A 1.15E-04 1.79E-04 3.13E-04 4.81E-04 6.50E-04 8.53E-04

B 1.11E-04 1.77E-04 3.12E-04 4.81E-04 6.50E-04 8.53E-04

C 1.09E-04 1.76E-04 3.11E-04 4.80E-04 6.49E-04 8.52E-04

D 1.08E-04 1.75E-04 3.11E-04 4.80E-04 6.49E-04 8.52E-04

E 9.98E-05 1.71E-04 3.08E-04 4.78E-04 6.48E-04 8.51E-04

F 9.25E-05 1.66E-04 3.05E-04 4.77E-04 6.47E-04 8.50E-04

*ASPEN computes particulate matter deposition rates for urban and rural lands, and also

incorporates the resulting particle removal rates into predicted air concentrations.

Within the ASPEN dispersion module the deposition of particulate phase pollutants is treated

using an equation similar to the Gaussian sector average equation. To account for dry deposition,

an additional decay term is included in the calculation of ambient concentrations while the

deposition rate, Rd, is given as,

where:

Rd = dry deposition rate (μg/m2-s)

Vd = deposition velocity (m/s)

χ = ground-level concentration (μg/m3)

The decay rate Ψ for dry deposition is determined as a function of the deposition velocity, the

downwind distance from the source and the relative dimensions of the plume with respect to the

Rd = Vd χ
2-13

mixing height. Both the plume dimensions and the mixing height are assumed to be dependent

on the atmospheric stability as well as time of day. The decay term associated with the dry

deposition is given as follows:

D

r

u dep

dep

s

=  −



 

 exp 

* ψ

where:

Ψdep = decay rate for deposition

r

* = 0 if 2σz < h’

s

= (ri - ri-1)/2 where ri is the distance at which 2σz > h’

s

The deposition decay rate, ψdep , is calculated from the deposition velocity and the dimensions of

the plume with respect to the mixing height as follows,

As examination of the above relations reveals, dry deposition, and hence reductions in ambient

concentration, is not considered until the plume dimensions are such that the plume impacts the

surface of the ground.

Separate decay terms are calculated in order to account for plumes which may impact urban or

rural areas, in addition to accounting for whether the pollutant source is classified as urban or

rural.

2.4 WET DEPOSITION

The ASPEN dispersion module uses the wet deposition algorithm from the revised version of the

CAP88-PC model to estimate the wet deposition of particles. The algorithm is based on the

approximate method described by Rodhe (1980, Model3) and uses the fraction of time during

which precipitation is occurring in conjunction with the total annual precipitation to calculate

both the decay rate for the modeled ambient concentrations as well as the deposition fluxes. 

As with the dry deposition calculations, an additional decay term is used to account for the

effects of wet deposition. In this case, the decay rate is a function of the scavenging coefficient,

λ’ (sec-1), where the scavenging coefficient is proportional to the precipitation rate:

where p’

 is the average annual precipitation rate, (cm/yr). Defining fp as the fraction of time that

precipitation actually occurs, then the actual average precipitation rate during periods of

precipitation becomes, 

[ ] ( )() ( ) e z i e z

dep

dep h z h

V

σ σ

ψ min ,2 min ,2 ' ' + − =

' 7 ' 10 p − λ =

p f

p p

'

=
2-14

and the scavenging coefficient is,

The decay term associated with wet deposition is then given as,

While the wet deposition rate is given as,

where:

Rwet = wet deposition rate (μg/m2

-s)

λ = scavenging coefficient (sec-1)

 Q = emission rate (μg/s)

 r = downwind distance from source (m)

 us = windspeed (m/s)

Dwet = decay rate due to precipitation scavenging

2.5 SECONDARY SPECIES FORMATION

Many of the toxic species treated within the ASPEN modeling system are formed through

atmospheric reactions with nontoxic precursor species. The formation of these secondary species

is treated using a post-processing procedure to estimate the annual average concentration

increments. These precursor-product pairs are modeled within the dispersion module using the

appropriate precursor reactive decay rates. ASPEN calculate the secondary product

concentration as the difference between the precursor concentration in an inert model run and the

concentration in the presence of reactive decay. The resulting concentration differences are

adjusted for molar yield and molecular weight to provide an estimate for the concentration of the

secondary species.

As an example, consider the treatment of secondary acrolein production. Since butadiene is the

precursor species, two separate ASPENA runs would be performed, one with the appropriate

decay rate for butadiene (reactive run), and one with a decay rate of zero (inert run). The

concentrations of secondary acrolein are then calculated as:

p f

p'

7 10 − λ =















 =

s

wet u

r D λ

exp

wet

s

wet D

ru

Q R

π

λ

2 =

( ) acrolein butadiene inert butadiene reactive χ = 1.04 χ − χ

-
2-15

where:

χacrolein = ambient concentration of secondary acrolein (μg/m3)

χbutadiene inert = ambient concentration of butadiene for inert run (μg/m3)

χbutadiene reactive = ambient concentration of butadiene for reactive run (μg/m3

)

Other secondary species concentrations are calculated similarly.
3-1

3.0 MAPPING MODULE (ASPENB) DESCRIPTION

3.1 ASPENB OUTPUT FILE STRUCTURE AND UPDATE PROCEDURE

The ASPEN mapping module (ASPENB) produces a separate output file for each HAP/source

category combination. Each of these files contains a record for each census tract with estimates

of annual average concentrations for each of eight 3-hour time blocks. The procedure for

producing these files by ASPENB is as follows:

• As ASPENB processes the an input file of the normalized source

concentrations/depositions (ASPENA output file), each time a HAP is encountered

ASPENB checks the local directory to determine if an output file for that HAP/source

category combination already exists. If not, ASPENB creates the output file, and

initializes it by creating a record for each census tract. An initial tract record contains a

state/county FIPS and tract number, and eight concentration fields (each with a value of

zero), and two deposition fields (each with a value of zero). If an output file already

exists, it is opened.

• ASPENB then proceeds with the processing of the HAP. ASPENB interpolates the

normalized concentrations/depositions of the grid receptors around the emission source to

all the census tracts which fall within the source 50 kilometers impact zone. (See

sections 3.2 and 3.3 for detailed discussions of the interpolation procedures and the

determination of impacted census tracts, respectively.) It then applies the HAP emission

rate to the normalized interpolated concentrations to obtain the population

concentration/deposition estimates. For example, if the normalized concentration from

the emission source for time block 1 at census tract A is 0.5 μg/m3

, and HAP emission

rate is 2 g/sec, the HAP concentration is 1 μg/m3 for time block 1 at census tract A.

• The HAP output file is then updated by incrementing the previous values with the current

estimates, to obtain cumulative estimates for each census tract. After the output file is

updated, it is closed.

3.2 INTERPOLATING TO CENSUS TRACT CENTROIDS

The normalized concentrations/depositions estimated by ASPEN’s dispersion module

(ASPENA) for grid receptors surrounding each emission source are interpolated to the census

tract centroids within the 50 kilometers impact zone in the ASPENB. (See section 3.3 for a

detailed discussion of the determination of impacted census tracts.)
3-2

Figure 3-1. ASPENB receptor grid and census tract centroids

Figure 3-1 illustrates the relationship between the ASPEN model receptor grid and census tract

centroids. The concentric rings represent the inner three rings of the ASPEN receptor array; and

the irregular polygons represent the census tracts. A dark circle within each polygon represents

the centroid of the tract.

The ASPENB designates the tract in which the source is located as the resident tract. Near

sources, where ambient concentration gradients are likely to be steep, the position of a tract

centroid relative to the source may result in a significant over- or underestimate of the

population-weighted average exposure concentration in the tract. The coarser the spatial resolution of the population, the more significant the uncertainty in the average exposure concentration

is likely to be. Therefore, for resident tracts, instead of estimating the ambient concentration

increment at a single point in the tract (i.e., at the centroid), the average concentration increment

over the entire area of the tract is estimated for the resident tract.

Detailed descriptions of the different interpolation procedures for the non-resident and resident

census tract centroids are provided in the following sections.

3.2.1 Interpolating to Non-Resident Census Tract Centroids

The normalized concentrations/depositions for grid receptors are interpolated to the non-resident

census tract (population) centroids with log-log interpolation in the radial direction and linear

interpolation in the azimuthal direction (see Figure 3-2). The estimates are designed to represent

average concentration for the tract. The interpolation to non-resident census tract centroids is

implemented as follows:
3-3

Figure 3-2. Interpolation to non-resident tract centroids

• For each census tract that falls within the 50 kilometer radius of the source impact zone,

calculate the distance between the census tract centroid and the source, d, and its azimuth

az (the clockwise angle measured from north).

• Locate the angular (a1 and a2) and radial indices (r1 and r2) in the receptor grid

surrounding the non-resident census tract. The angular indices are the 2 closest azimuths

of the polar receptor grid to the centroid azimuth. The radial indices are the 2 closet ring

distances of the polar grid to the centroid. For example, the default polar grid has the

following azimuths and ring distances with respect the emission source location:
3-4

 Radial Index Radial Distance (km)

1 0.1

2 0.5

3 1.0

4 2.0

5 5.0

6 10.0

7 15.0

8 20.0

9 25.0

10 30.0

11 40.0

12 50.0

Angular Index Azimuth (Degree)

1 0.0

2 22.5

3 45.0

4 67.5

5 90.0

6 112.5

7 135.0

8 157.5

9 180.0

10 202.5

11 225.0

12 247.5

13 270.0

14 292.5

15 315.0

16 337.5

If a centroid is located at azimuth 110 degrees, and distance 0.65 km with respect to the emission

source, the angular indices are 5 (90 degree) and 6 (112.5 degree), and the radial indices are 2

(0.5 km) and 3 (1.0 km) as shown below.

• Calculate the ratios for log-log interpolation in the radial direction (rratio), and linear

interpolation in the azimuthal direction (aratio)

rratio

d radiir

radiir radiir

=

−

−

ln ln

ln ln

1

2 1
3-5

where:

 d = distance between the census tract centroid and the source

 radiir1 = radial distance in the receptor grid for the radial index r1

 radiir2 = radial distance in the receptor grid for the radial index r2

 rratio = ratio for log-log interpolation in the radial direction

aratio a a = − 1

where:

a = azimuth of the census tract in the receptor scaling

a1 = azimuth for the angular index a1 in the receptor scaling

aratio = ratio for linear interpolation in the azimuthal direction

• Set the logarithm of the concentrations for each time block at the four corners of the

receptor grid surrounding the census tract

c ca r h 1 11 = ln , ,

c ca r h 2 12 = ln , ,

c ca r h 3 21 = ln , ,

c ca r h 4 22 = ln , ,

where:

c1, c2, c3, c4 = the logarithm of the concentrations at the four

corners of the grid for time block h

ca1,r1,h, ca1,r2,h, ca2,r1,h, ca2,r2,h = the concentration for the receptor with indices

(a1,r1), (a1,r2), (a2,r1), and (a2,r2) for time block h

• Log-log interpolation in the radial direction:

ca c c c rratio 11 21 =+ − × ( )

ca c c c rratio 2 3 43 =+ − × ( )

where:

ca1,ca2 = the logarithm of the interpolated concentrations for time block h

c1, c2, c3, c4 = the logarithm of the concentrations at the four “corners” of the grid

for time block h

• Take the exponent of the logarithm of the interpolated concentrations in the radial

direction:

cca ca 1 1) = exp(

cca ca 2 2 = exp( )
3-6

where:

cca1,cca2 = the interpolated concentration for time block h

ca1,ca2 = the logarithm of the interpolated concentrations for time block h

• Finally, linearly interpolate in the azimuthal direction:

where:

tc = concentration at the census tract centroid for time block h

cca1,cca2 = interpolated concentrations at time block h

aratio = ratio for linear interpolation in the azimuthal direction

3.2.2 Concentration/Deposition Estimates for the Resident Census Tract

The procedures for estimating concentration and deposition for the resident census tracts are

different for point sources and pseudo point sources.

3.2.2.1 Major Point Sources

For tracts with centroids close to a major point source, the ambient concentration is estimated in

ASPEN by spatial averaging of the ambient concentrations of receptors estimated to fall within

the bounds of the tracts, instead of by interpolation to the centroid. Figure 3-3 (a,b) illustrates the

spatial averaging procedure. Since inclusion of detailed information on the boundaries of the

census tracts was judged to be excessively resource-intensive, a circle of equal area to the census

tract, centered at the centroid (Figure 3-3a), was used as an estimate of the tract boundary in the

spatial averaging procedure. 

tc = cca1 + (cca2 − cca1) × aratio
3-7

Figure 3-3 (a) Resident tract spatial averaging for point sources.

That procedure is implemented as follows:

• For each point source, the tract with the closest centroid is determined, i.e., the resident

tract is defined.

• An effective or pseudo-radius is calculated for the resident tract based on the known tract

area and the assumption that the shape of the tract is circular.

• Each modeling receptor for the source is evaluated to determine if it falls within the

pseudo-radius of the tract.

• Based on the configuration and spacing of the modeling receptors, an area of

representation is assigned to each receptor.

• The resident tract’s average outdoor concentration is calculated as the area-weighted

average of the modeling receptors that fall within its pseudo-radius (Figure 3-3b). The

calculation is shown as follows:

conck

sci j k ai j

totarea

=

∑ ,, , ×
3-8

Figure 3-3 (b) Resident tract spatial averaging for point sources.

where:

conck = area-weighted average concentration for time block k at the resident tract

sci,j,k = normalized concentration for the receptor at the ith direction, jth distance

within the bound of the resident tract for time block k

ai,j = the area associated with the receptor at the ith direction, and jth distance

totarea = the accumulated area for the receptor grid fall within the bound of the

resident tract

If no receptor fall within the pseudo-radius of the closest tract, then the tract concentration is

estimated with the standard interpolation procedure described in Section 3.2.1.

3.2.2.2 Interpolation for Motor Vehicle and Area Sources

Each motor vehicle and area source is treated as a single pseudo-point source located at the

centroid of each census tract in the ASPEN. Outside of the resident census tract of the pseudopoint source, resulting ambient concentration estimates are interpolated to tract centroids, as is

done for major point sources.

However, the default interpolation approach cannot be implemented within the resident census

tract, since the concentration cannot be estimated at the emission point (the tract centroid) with

the long-term Gaussian formulation. For the resident tract, ASPEN represents motor vehicle and

area sources as multiple pseudo-point sources geographically dispersed throughout the census

tract (see Figure 3-4a). 
3-9

Figure 3-4 (a) Resident tract spatial averaging for area and mobile sources.

For the resident tracts with radius larger than 0.3 kilometers (the average radius of two innermost

modeling receptor rings), ambient concentrations in the resident census tract are estimated on the

basis of five dispersed pseudo- point sources in ASPEN, with spatial averaging of the ambient

concentrations of receptors estimated to fall within the bounds of the tract.

For purposes of the spatial averaging, the tract is assumed to be perfectly round (Figure 3-4a). 

One of the five pseudo-point sources is located at the center of the tract. The others are located

halfway between the center and the hypothetical circumference in each of the four primary

compass directions (Figure 3-4b).
3-10

Figure 3-4 (b). Resident tract spatial averaging for area and mobile sources.

The area-weighted average concentration are estimated for the resident tract for the pseudo point

sources as following:

where:

 ack,m = the cumulative area-weighted concentration associated with the

pseudo point m for time block k at the resident tract

 sci,j,k,m = normalized concentration for the receptor surrounding pseudo point m

at the ith direction, jth distance within the bound of the resident

 tract for time block k

 ai,j,m = the area associated with the receptor surrounding pseudo point m at

 the ith direction, and jth distance

where:

resck = spatially-averaged ambient concentration for time block k

 ack,m = the cumulative area-weighted concentration contributed by

pseudo point m for time block k at the resident tract

∑=

= ×

5

1

,

m

k ack m divm resc

k m = ∑ i j k m × ai j m ac sc , , , , , ,
3-11

divm = the relative size of the receptor grid surrounding pseudo point m

to the total area for the all 5 receptor grids: 1/9 for m=1; 2/9 otherwise.

For the resident tracts smaller than 0.3 kilometers, the concentration/depositions are set to zeros.

3.3 DETERMINATION OF IMPACTED CENSUS TRACTS

The normalized concentrations/depositions estimated by ASPEN’s dispersion module

(ASPENA) for grid receptors surrounding each emission source are interpolated to the census

tract centroids within the 50 kilometers impact zone in the ASPENB. The determination of

which census tracts fall within this zone is facilitated by the structure of the census tract index

and census tract data files.

The tract index file contains the state and county index data. First the state index data are listed

with the following information for each state.

• State FIPS code

• Maximum and minimum longitude and latitude of the state

• Total number of counties in the state

• Pointer to the first county of the state, i.e., the record number of the first county of that

state in the list of all counties (to follow in the tract index file)

Next, the county index data are listed in the tract index file with includes the following

information for each county.

• County FIPS code

• Maximum and minimum longitude and latitude of the county

• Total number of tracts in the county

• Pointer of the first tract of the county, i.e., the record number of the first tract of that

county in the list of all tracts (in the tract data file)

For each census tract, the census tract data file contains the following:

• State/County FIPS code and tract FIPS code

• Location of census tract centroid in longitude and latitude

• Urban/rural designation

• Hypothetical tract radius 

ASPENB finds tract data for the tracts with centroids within the 50 kilometer impact zone of

each emission source as follows:
3-12

• Check the locational parameters of each state to determine if there is a potential overlap

between that state and the 50 km radius circle of grid receptors around the emission

source.

• If there is a potential state overlap, go to the records of the counties in that state and check

each for a potential overlap between the county and the 50 km radius circle of grid

receptors around the emission source.

• If there is a potential county overlap, go to the tract records of the county and for each

tract determine if the centroid falls within the 50 km radius circle of grid receptors around

the emission source.
4-1

Emission/

control file

Meteorological

index

Meteorological

data

Processed

source listing Normalized HAPs

concentraton/ deposition

file

HAP emission rates

ASPEN A

4.0 DISPERSION MODULE (ASPENA) USER’S INSTRUCTION

ASPENA’s required data inputs include HAP emission rates, modeling options, and

meteorological data. Groups of HAPs that are of the same species type (gaseous, fine particulate,

coarse particulate), use the same reactive decay rates, and use the same dry/wet deposition

options may be simulated together in a single run. ASPENA estimates the normalized source

concentration/deposition for the receptor grid surrounding each source. The normalized

concentration/deposition estimates and HAP emission rates are then input to ASPENB, the

mapping module of the modeling system, along with the census tract data. (The HAP emission

rates are carried over from the ASPENA emission/control file to the ASPENA normalized source

concentration/deposition output file.) The final outputs from the ASPEN modeling system are

estimates of annual average concentrations (in μg/m3) at each census tract for each of eight 3-

hour time blocks for each HAP/source category combination.

Figure 4-1 Flow diagram of the ASPENA dispersion module
4-2

A description of the input and output files of the ASPENA module are provided in Table 4-1.

Table 4-1 ASPENA file descriptions

File Name File Type Description Data Contents

Emission/control ASCII ASPENA input file Modeling options; reactive decay rates ;

emission rates for a group of HAPs with

the same species type, reactivity class,

and selections for dry/wet deposition;

Emission rates by stack for point sources

and by census tract for pseudo point

sources (area or mobile sources) for each

of eight 3-hour time blocks; stack

parameters for point sources

Meteorological Index Binary ASPENA input file NWS station ID and location; annual

average temperatures (max, min, and

mean) and precipitation (avg. and

frequency); annual average mixing

heights for eight 3-hour blocks 

STAR meteorological

data

Direct

access

binary

ASPENA input file Joint frequencies of 6 wind speeds, 16

wind directions and 6 stability categories

at each NWS station for each of eight 3-

hour time blocks

SYS file ASCII ASPENA run stream List of ASPENA input and output

filenames

Normalized source

concentration and

deposition file

Binary ASPENA output file

(ASPENB input

file)

Normalized concentration/deposition

estimates for the polar grid receptors

surrounding each emission source for

each of eight 3-hour blocks; emission

rates of the associated HAPs from each

source for each of eight 3-hour time

blocks

Source listing ASCII ASPENA output file List of processed sources used by

ASPENA (used for QA purposes)

4.1 MODELING OPTIONS

ASPEN provides the user with a range of options to meet the needs of a variety of modeling

applications. This section gives an overview of the dispersion, source, receptor and

meteorological options that are available in the ASPENA dispersion module. Section 4.2

discusses the input files in which these modeling parameters are set.
4-3

4.1.1 Dispersion Options

The dispersion parameters in ASPENA are consistent with those in ISCLT2 (EPA, 1992), the

EPA-recommended model(when ASPEN was developed) for estimating long-term average

concentrations resulting from both rural and urban emission sources. ISCLT2 algorithms for

stack-tip downwash, buoyancy-induced dispersion, and final plume rise, and default values for

wind profile exponents and for vertical potential temperature gradients are used for ASPENA

simulations and cannot be overridden by the user.

The user can select either rural or urban dispersion parameters, depending on the characteristics

of the source location. The user also has the option of calculating dry and/or wet deposition flux

values for a simulation of particulate HAPs. Finally, the user may select to invoke ASPENA’s

building downwash algorithms for point sources. However, it should be noted that these

algorithms differ from those in (see Section 2.1.7). 

Note that ASPENA does not treat the effect of terrain elevation on ground-level ambient

concentration estimates, but implicitly assumes flat terrain throughout the modeling domain.

4.1.2 Source Options

ASPENA is capable of modeling three pollutant species types, two types of emission sources,

and up to ten source categories. Each of these source options are listed here.

Species types: (1) gaseous HAPs, (2) fine particulate HAPs, (3) and coarse particulate HAPs

Source types: (1) point/stacked sources and (2) pseudo point/non-stacked sources (area and

mobile sources are treated as pseudo point source in ASPEN). Detailed description of source

types, release parameters, emission rates and multiple sources is given in section 4.2.

Source categories: The emission rates of the emission sources can be aggregated into up to ten

different categories. For example, for the Cumulative Exposure Project, the following emission

source categories were used:

• Metal manufacturing point sources (CAT09)

• Non-metal manufacturing point sources (CAT00)

• Petroleum refineries (CAT02)

• Municipal waste combustors (CAT07)

• Hazardous waste incinerators (CAT08)

• Other point sources (CAT01)

• Manufacturing area sources (CAT05)

• Non-manufacturing area sources (CAT06)

• Onroad mobile sources (CAT03)

• Nonroad mobile sources (CAT04)
4-4

The emission rates of the sources are specified for eight 3-hour time blocks in the model. The

emissions of the sources can be constant or vary by time block.

The modeled HAPs must be assigned a set of reactive decay rates that vary by stability class and

time block. A single ASPENA simulation can include emission rates for a group of HAPs with

the same species type, reactivity class, and selection of dry/wet deposition.

4.1.3 Receptor Options

Surrounding each modeled source, ASPENA uses a default polar receptor grid of 12 concentric

rings in 16 radial directions for a total of 192 receptors. The default ring distances from each

modeled source are 0.1, 0.5, 1.0, 2.0, 5.0, 10.0, 15.0, 20.0, 25.0 30.0, 40.0, and 50.0 km. 

Following the caution of the ISC user’s guide (EPA, 1992) that concentrations at receptors less

than 100 meters from a source may be suspect, the closest receptor distance is 100 meters. Fifty

km is the maximum distance recommended by the EPA for application of a Gaussian model

(EPA, 1992).

ASPENA also allows the user to replace the default distances with user-specified values

(between 100 meters and 50 km) for the 12 rings surrounding the modeled source.

4.1.4 Meteorological Options

ASPENA uses STability Array (STAR) meteorological data which includes joint frequency

distributions of 6 wind speeds, 16 wind directions, and 6 stability categories for each of eight 3-

hour time blocks. The user can select the STAR data to be used for a particular modeled source

by specifying the National Weather Service (NWS) station ID. If no selection is made, ASPENA

will use the STAR data from the NWS station in the data base that is nearest the source.

ASPENA allows the user to customize the meteorological data inputs by excluding specified

stability classes, wind speeds, and wind directions for a certain NWS station. If certain

meteorological parameters are excluded ASPENA will re-normalize the joint frequency

distributions for the station.

4.2 ASPENA INPUTS

The three types of input files needed to run the ASPENA dispersion model are: emission/control

file, a STAR meteorological data file, and a meteorological index file.

4.2.1 Emission/Control File

The emission/control input file allows users of ASPENA to select the appropriate dispersion,

source and receptor options in order to simulate the modeling conditions of interest. The

modeling parameters include specifying species type, source type, source location, source release
4-5

parameters, emissions rates, and decay rates. The format of the emission/control file is provided

in Table 4-2.

4.2.1.1 Run Information, Species Types and Deposition Options

The run information, species type and deposition selections is specified in the first record of the

emissions/control input file. There are three species types in ASPEN: gaseous, fine particles,

and coarse particles. Each emission input file should include only HAPs with the same species

type, reactive decay rates, and dry/wet deposition selection. The syntax, type, and order for

specifying the required information are summarized below.
4-6

Table 4-2 Description of the emission/control file

Record No. Variables Format Description

1 IDRUN A40 Run identification

IDFILE A20 Emission file identifier

ISPTYP I1 Species type (0 = gas; 1 = fine part.; 2 = coarse part.)

IDDEP I1 = 0, include dry deposition; = 1 no dry deposition

IWDEP I1 = 0, include wet deposition; = 1, no wet deposition

2 DK(IC,1) 6F10 Decay rates for 6 stability classes for time block 1

3 DK(IC,2) 6F10 Decay rates for 6 stability classes for time block 2

4 DK(IC,3) 6F10 Decay rates for 6 stability classes for time block 3

5 DK(IC,4) 6F10 Decay rates for 6 stability classes for time block 4

6 DK(IC,5) 6F10 Decay rates for 6 stability classes for time block 5

7 DK(IC,6) 6F10 Decay rates for 6 stability classes for time block 6

8 DK(IC,7) 6F10 Decay rates for 6 stability classes for time block 7

9 DK(IC,8) 6F10 Decay rates for 6 stability classes for time block 8

10 IFIPS I5 State/County FIPS code

IDSRC A10 Plant ID for points; census tract no. for pseudo points

UTMX F10 Longitude (decimal degrees)

UTMY F10 Latitude (decimal degrees)

ITYPE I1 Source type (0 or blank for points; 3 = pseudo points)

IURB I1 Urban/Rural flag (1 = urban; 2 = rural)

11 INWS I5 Star station (NWS) ID (blank or 0 = use nearest station)

NOSC(6) 6I1 Excluded stability classes

NOWS(6) 6I1 Excluded wind speeds

NOWD(6) 6I1 Excluded wind direction

12 RAD (12) 12F5 Polar grid radial distances (km) (blank – use defaults)

13 IDSTK A5 Stack ID for points; FIPS code for pseudo points

RLON F10 Longitude (decimal degrees)

RLAT F10 Latitude (decimal degrees)

STAKH F10 Stack height (m)

STAKD F10 Stack exit diameter (m)

STAKV F10 Stack exit velocity (m/sec)

STAKT F10 Stack exit temperature (Deg K)

IVENT I1 Vent/Stack flag (0 = stacked; 1 = non-stacked)

IBLDG I1 Build flag (0 = no building; 1 = building)

BLDW F10 Width of nearby building (m)

BLDH F10 Height of nearby building (m)

14 SAROAD I5 5-digit Saroad code

IDCAT I1 1-digit source category code

Q 8F10 Emissions (g/sec) for eight 3-hour time blocks

Note that ASPEN treats the SAROAD code/source category code as

a single combined code to refer to a unique chemical and is

therefore technically not separable.

Notes: UTMX/UTMY and RLON/RLAT specify the locations of point sources, or the locations of the

census tract centroid for pseudo point sources (i.e., area and mobile sources).

 Record 14 is repeated for each HAP emitted from the stack or census tract; terminate with blank record.

 Records 13 and 14 are repeated for each source/stack within facility; terminate with blank record. (Last

stack and chemical for each facility will be followed by two blank lines to signal new facility.)

 Records 10 through 14 are repeated for each facility or census tract, terminate with blank record. (Last

facility, stack and chemical in file will be followed by three blank lines to signal no more

facilities.)

 Four blank records are required at the end of file to signal the end of the run.
4-7

Syntax: IDRUN, IDFILE, ISPTYP, IDDEP, IWDEP

Type: Mandatory

Order: 1st record of emission/control input file

IDRUN and IDFILE are the character variables in the header which allow the user to specify the

title and the run information. ISPTYP is the species type: 0 for gaseous, 1 for fine 

particulate and 2 for coarse particulate. IDDEP and IWDEP are the selections for dry and wet

deposition: 0 is the code to include deposition and 1 is the code to exclude deposition. Note that

for the gaseous pollutant species type, ASPENA will not calculate deposition, regardless of how

the deposition selection variables are set.

4.2.1.2 Reactive Decay Rate Inputs

The reactive decay rates are specified in the emission/control input file by stability class and time

block. ASPENA requires that all the HAPs included in a single emission/control input file have

the same decay rates. Therefore, a unique emission/control file is required for each set of HAPs

with different decay rates. The decay rates are specified in the emission/control input file for

each stability class and time block according to the following pattern: decay rates for time block

1 are entered in the second record, for time block 2 in the third record, and so on. The decay rate

for the last time block, time block 8, is entered in the ninth record of the emission input. The

syntax, type, and order for specifying reactive decay rates are summarized below. The reactivity

classes and corresponding decay rates normally used are presented in Appendix C.

Syntax: DK(IC,IH)

Type: Mandatory 

Order: 2nd - 9th record of emission/control input file

4.2.1.3 Source Types and Locations

ASPENA currently handles two source types, identified as point sources and pseudo point

sources. Area and mobile sources are treated as pseudo point source. The location of a source is

indicated by specifying the geodetic coordinates in latitude and longitude. The syntax, type, and

order for identifying source types and locations are as follows.

Syntax: IFIPS, IDSRCE, UTMX, UTMY, ITYPE, IURB

Type: Mandatory, Repeatable

Order: 10th record of emission/control input file

IFIPS is the FIPS code. IDSRCE is the plant ID for a point source, and census tract FIPS code

for pseudo point source. UTMX and UTMY are either the longitude and latitude of a point

source, or the census tract centroid in the case of a pseudo point source. ITYPE is source type: 0

or blank for point source, and 3 for pseudo point source. IURB is urban/rural designation: 1 for

urban and 2 for rural.
4-8

The source locations are also specified along with source parameters in record 13 of the emission

input described in the next section.

Line 11 can be left blank. In this case, the closest meteorological station will be used by

latitude/longitude. Line 12 can be left blank. In this case default receptor grid will be used

4.2.1.4 Source Release Parameters

The input source parameters vary depending on the source type. For a point source, the stack

height, stack exit diameter, stack gas exit temperature, and stack gas exit velocity are required. 

For a pseudo point source, no source parameters are required and ASPENA will use a default

stack height. The syntax, type, and order for specifying source release parameters are

summarized below.

Syntax: IDSTK, RLON, RLAT, STAKH, STAKD, STAKV, STAKT,

IVENT, IBLDG, BLDW, BLDH

Type: Mandatory/Optional, Repeatable 

Order: 13th record of emission/control input file

IDSTK is the stack ID for point source, and census tract FIPS code for pseudo point source.

RLON and RLAT are either the longitude and latitude of a point source or the location of the

census tract centroid, in the case of a pseudo point source. STAKH is the stack release height

above ground (in meters). STAKD is the inside stack diameter (in meters). STAKV is stack gas

exit velocity (in m/sec). STAKT is the stack gas exit temperature (in degrees K). IVENT is the

vent/stack designation: 0 for stacked and 1 for non-stacked. IBLDG is the building flag: 1 to

include consideration of building downwash, 0 otherwise. BLDW and BLDH are the width and

height of nearby buildings (in meters).

4.2.1.5 Emission Rates

The emission rates are specified in ASPENA in eight 3-hour time blocks. The syntax, type and

order for specifying emission rates are summarized below.

Syntax: SAROAD, IDCAT, Q

 Type: Mandatory, Repeatable 

Order: 14th record of emission/control input file

IDCHEM is the 5-digit HAP SAROAD code plus 1-digit source category code. Q is the source

emission rates (in grams/second).

Multiple sources can be repeated as shown in the example in Section 8 (tutorial). In this case

lines 13 and 14 are repeated for each source/stack within facility.
4-9

4.2.1.6 Secondary Compounds

ASPENA models atmospheric transformation processes as first-order reactive decay. Secondary

formation is calculated as the difference between secondary precursor concentrations with and

without reactive decay. This calculation is completed in the post-processing program

SEC_DAT. For a detailed description of the treatment of secondary HAPs see Section 6.1.

4.2.1.7 Deposition Rates

For particles, dry deposition rates are primarily a function of the particle size and land-use type. 

The fine and coarse particle deposition velocities used in ASPENA were obtained for urban and

rural land-use types using the dry deposition algorithms in the Variable-grid Urban Airshed

Model (UAM-V) photochemical model (SAI, 1995). These values were further parameterized as

function of stability class and wind speed.

The ASPENA dispersion module uses the wet deposition algorithm from the revised version of

the CAP88-PC model to estimate the wet deposition of particles. The algorithms are based on

the approximate method described by Rodhe (1980) and use the fraction of time during which

precipitation is occurring in conjunction with the total annual precipitation to calculate both the

decay rate for the modeled ambient concentrations as well as the deposition fluxes.

4.2.2 STAR Meteorological Data File

ASPENA utilizes a climatological modeling approach. As with other climatological models

(e.g., the EPA’s CDM and ISCLT), the dispersion module is supplied with STability Array

(STAR) meteorological data. STAR data include the joint frequencies of 6 wind speeds, 16 wind

directions and 6 stability categories (Pasquill - Gifford: A through F).

For each ASPENA model run, the STAR data is prepared for eight 3-hour time blocks for each

surface station. The station number and time block number are specified at beginning of each

STAR data record. The STAR input file is in binary format. Each record contains the STAR

data for one time block of one star station, and includes the variables shown in Table 4-3.

The STAR data is prepared as follows:

• Split the surface data into eight 3-hour time blocks

• Generate STAR data for each time block

• Combine the eight STAR data sets into one file

The format of the star data is provided in detail in Appendix C.
4-10

Table 4-3 Description of the STAR meteorological data file

Variables Data Type Description

IWB Integer Star (NWS) station ID

IHR Integer Time block number

FSTAR Real STAR data for the time block 

4.2.3 Meteorological Index File

The STAR data file is paired with a binary meteorological index file. The number and ordering

of stations included in both the index file and the STAR data file must be the same. There is one

record for each STAR station containing the following information: station number, station

longitude, station latitude, annual average daily maximum temperature, annual average daily

minimum temperature, annual average temperature, annual average precipitation, annual

frequency of precipitation, and annual average mixing heights for each of eight 3-hour blocks. A

description of the meteorological index file parameters is provided in Table 4-4.

Table 4-4 Description of the meteorological index file

Variables Data Type Description

ISTA Integer Star (NWS) station ID

STAX Real Longitude of the station (decimal degree)

STAY Real Latitude of the station (decimal degree)

ATEMP (1) Real Annual average daily maximum temperature (Deg K)

ATEMP (2) Real Annual average daily minimum temperature (Deg K)

ATEMP (3) Real Annual average temperature (Deg K)

PS Real Annual average precipitation (cm)

FPS Real Fraction of time with precipitation

STAS Real Not used (eight zeros)

HTMI Real Annual average mixing heights for eight 3-hour time blocks

4.2.3.1 Temperatures

For each surface meteorological station included in the STAR data, the annual average daily

minimum, maximum and average temperature (in degrees Kelvin) is specified in the

meteorological index file.

4.2.3.2 Mixing Heights

For each surface meteorological station included in the STAR data, annual average mixing

heights (in meters) are specified for each of eight 3-hour time blocks in the meteorological index

file.
4-11

4.2.3.3 Precipitation

For each surface meteorological station included in the STAR data, annual average precipitation

(cm/year) and fraction of time that precipitation occurs (based on hourly values) are specified in

the meteorological index file.

4.2.4 Polar Receptor Grid Network

Surrounding each modeled source, ASPENA uses a default polar receptor grid of 12 concentric

rings in 16 radial directions for a total of 192 receptors. The ring distances from each modeled

source are 0.1, 0.5, 1.0, 2.0, 5.0, 10.0, 15.0, 20.0, 25.0 30.0, 40.0, and 50.0 km.

Instead using the default concentric distances, the user can specify the distances for the 12 rings

between 100 meters and 50 km surrounding the modeled source.

4.3 ASPENA OUTPUTS

ASPENA creates two output files when it is executed. The first of these is the normalized source

concentration/deposition data file. This binary file contains the source information and the

normalized concentration/deposition for each of eight 3-hour time block at each receptor location

around the source, and the emission rates for each HAP. This file is used as input to the

ASPENB mapping module. The utility program INV2ASCI_CON can be used to convert the

ASPENA output from binary to ASCII format. Converting the file to ASCII allows the user to

review the modeling results of the ASPEN dispersion module. The utility does not convert the

deposition portion of the output, however. Note that a single binary output file is created which

will contain data for all sources and all HAPs specified in the emission/control input file.

The second file created by ASPENA is a listing of all emission sources (source FIPS, ID,

location, type and urban/rural destination) that were processed in the run. This file ends with a

line of zeros. The number of non-zero lines included in the file should equal the total number of

sources included in the emission/control file. This processed source listing file is written to

Fortran unit 88.

The user has the option of creating a third output file that echoes all the information included in

the meteorological index file, the emission/control file and the concentration/deposition output

file. This large file is typically used in the testing stage of the modeling study.

Once ASPENA has been run a log file with a “.como” extension is created. The log file includes

useful information including the input/output filenames and error messages. Table 4-5 presents a

summary of error messages in ASPENA.
4-12

Table 4-5 Error messages in the ASPENA log file

Error Message Module Subroutine Program Aborts

Too many chemicals

Comment: Max number of species is 150

ASPENA SKIP

STACK

Yes

Too many star stations

Comment: Max number of stations is 500

ASPENA STARIN Yes

Bad number in star data

Comment: Errors in star index file

ASPENA STARIN Yes

Can not find star data for station

Comment: Missing star data for stations

specified in the emission/control file

ASPENA STAR Yes

WARNING: iNWS, istar

Comment: The star station IDs specified in

the star data and index file are not in sync

ASPENA STAR Yes

Illegal urban/rural flag

Comment: urban/rural flag must be 1 or 2

ASPENA MAIN Yes

Illegal source type

Comment: Source type must be 0 or 3

ASPENA MAIN Yes

Error ... idummy

Comment:

ASPENA SKIP Yes

4.4 RUNNING ASPENA

ASPENA can be run interactively by simply typing:

aspena aspena.sys

where “aspena.sys” is the run stream filename.

Figures 4-2 and 4-3 show example run stream files used to run ASPENA. The first record in the

file contains the name of the emission/control file, the third record contains the name of the

meteorological index file, the fourth record contains the name of the STAR meteorological data

file, and the fifth record contains the name of the normalized source concentration/deposition

output file. The second record in the file is a placeholder for those that want to create the

optional “echo” output file described above. The creation of the testing file is invoked by

including a file name in record 2, as shown in Figure 4-2. To prevent the creation of the testing

file, “/dev/null” is entered in record 2, as shown in Figure 4-3.

1 aspena.ar.inp

2 aspena.ar.test

3 wtpmix.ind

4 star.dat

5 aspena.ar.con

Figure 4-2. Example ASPENA run stream file (filename: aspena.sys) that creates a testing file.
4-13

1 aspena.ar.inp

2 /dev/null

3 wtpmix.ind

4 star.dat

5 aspena.ar.con

Figure 4-3 Example ASPENA run stream file (filename: aspena.sys) that does not create a testing file.

A job file can be created to run ASPENA multiple times, in sequence, as shown in the 

Figure 4-4. For this example, ASPENA is run 3 times, using 3 different run stream files. The

two statements preceding each run line delete any previously created versions of the ASPENA

output files that will be created by the simulation. The statement after each run line renames the

processed source listing file, so that it will not be overwritten during the subsequent simulation.

rm aspena.tri.lst

rm aspena.tri.con

/bin/time aspena aspena.tri.sys

mv fort.88 aspena.tri.lst

#

rm aspena.ar.lst

rm aspena.ar.con

/bin/time aspena aspena.ar.sys

mv fort.88 aspena.ar.lst

#

rm aspena.mv.lst

rm aspena.mv.con

/bin/time aspena aspena.mv.sys

mv fort.88 aspena.mv.lst

Figure 4-4 Example ASPENA job file

In the above examples, the files with a “*.inp” extension contain the emission/control

information specifying the particular emission source for processing. In general, all chemicals of

the same species type (gas, fine, or coarse particles) with the same reactive decay rates and

deposition options may be processed in a single run, regardless of the source type or location.
5-1

ASPEN B

Census 

Tract Index

Census 

Tract Data

Normalized HAPs 

concentration/ 

deposition file

(ASPEN A output)

Processed source 

concentration file 

listing

Concentration/ 

deposition by 

source category 

and census tract

5.0 ASPENB USER’S INSTRUCTIONS

ASPENB is the mapping module of the ASPEN modeling system. ASPENB takes the diurnallystratified annual average concentration estimates from ASPENA and interpolates the results from

grid receptors to census tract centroids. Further, the contributions from all modeled sources are

summed to give estimates of cumulative ambient concentration increments in each census tract. 

An overview of the inputs and outputs of the ASPENB module is shown in Figure 5-1.

Output from ASPENB is post-processed using a series of programs described in detail in

Section 6. By accounting for all identified source categories (including background

concentrations where available), the sum of the concentration increments should yield an

estimate of the overall concentration of each HAP within each census tract. These estimates are

designed to represent population-weighted concentration averages for each census tract.

Figure 5-1 Flow diagram of the ASPENB mapping module

Several new features have been added to ASPENB (version 1.1). The detailed discussions of

these new features, along with the comparisons to the previous version are as follows:

• Number of output files produced by the model

Each output file produced from version 1.0 of the model contains the tract level

concentration/deposition for a single source category for a particular HAP. If there are ten source

categories for the HAP, there will be ten output files generated by the model. In version 1.1 of

the model there is a single output file or each HAP which contains the tract level
5-2

concentration/deposition for all source categories. Therefore, the number of output files

produced by the model is greatly reduced.

• Output file naming convention

The naming convention for the output file generated by version 1.0 of ASPENB is 5-digit

SAROAD code plus a 1-digit source category code, with a "*.exp" extension. The naming

convention for the version 1.1 of ASPENB output file is simply the 5-digit SAROAD code with

a "*.exp" extension, i.e., the extra digit to identify the source category has been eliminated.

• Number of source categories contained in the ASPENB output file

Flexibility in the number of source categories, which can be included in a modeling simulation,

has been added to the version 1.1 of the ASPENB. The user selects the desired number of source

categories to be included in a particular modeling simulation. A maximum of ten source

categories is allowed.

• Rerun for a single source category

Each output file generated by version 1.0 of the model contains the tract level

concentration/deposition for a single source category for a particular HAP. If there is a need for

rerunning the simulation for that source category, the user can simply delete the output file

generated by the previous simulation, then rerun the model.

The output file generated by version 1.1 of the model contains the tract level

concentration/deposition estimates for all the source categories included in the modeling study. 

If revision is needed for a single source category, that source category alone can be rerun and the

model will replace the previous estimates for that category in the output file. This feature avoids

a requirement to rerun all source categories (i.e., start the output file from scratch) in order to

revise a single source category.

5.1 ASPENB INPUTS

The ASPENB module requires three input files: the normalized concentration/deposition output

file from ASPENA, a census tract data file and a census tract index file. The input data

requirements are the same for both versions of ASPENB. A description of the input and output

files of the ASPENB module are provided in Table 5-1.
5-3

Table 5-1 ASPENB input and output file descriptions

File Name File

Type

Description Data Contents

Normalized source

concentration and

deposition file

Binary ASPENB input file

(ASPENA output

file)

Normalized concentration/deposition

estimates for the polar grid receptors

surrounding each emission source for

each of eight 3-hour blocks; emission

rates of the associated HAPs from

each source for each of eight 3-hour

time blocks

Census tract data Binary ASPENB input file Tract FIPS code, longitude and

latitude of the centroid, urban/rural

flag of the tract, and hypothetical tract

radius

Census tract index Binary ASPENB input file State/county FIPS codes; state/county

max and min longitude/latitude;

pointer to the first county in state and

number of counties in state; pointer to

the first tract in county and number of

tracts in county

Population

concentration and

deposition file 

(naming convention 

{saroad}.EXP)

Direct

access

binary

ASPENB output

file

(AVGDAT input

file)

Estimates of annual average

concentrations (in μg/m3

) at each

census tract for each of eight 3-hour

time blocks, and annual average

deposition fluxes over land and water

(in μg/m2

-day) for each HAP/source

category combination

File listing ASCII ASPENB output

file

List of processed concentration

filenames by ASPENB to prevent

processing an input more than once

5.1.1 Source Concentration and Deposition File

The first input required by the ASPENB module is the normalized source concentration/

deposition data output file from ASPENA. This binary file contains the source information and

the normalized concentration/deposition for each of eight 3-hour time block at each receptor

location around the source, and the emission rates for each HAP. See Appendix C for further

details.
5-4

5.1.2 Census Tract Data File

The second input required by ASPENB is the binary census tract data file. The format of this file

is shown in Table 5-2. For each census tract, the tract data file contains the following:

• State/County FIPS code and tract FIPS code

• Location of census tract centroid in longitude and latitude

• Urban/rural designation

• Hypothetical tract radius

Table 5-2 Description of census tract data file

Variables Data

Type

Description

TRFIPS Integer State/County FIPS code, tract FIPS code

TRLON Real Longitude of the tract centroid (decimal degree)

TRLAT Real Latitude of the tract centroid (decimal degree)

UFLAG Integer Urban/Rural flag of the tract (1 = urban; 2 = rural)

TRRAD Real Hypothetical tract radius (m)

The data in the census file are derived from the 1990 US Census. The longitude and latitude

represent an approximate population weighted census tract centroid. They are calculated as a

population-weighted average of the US Census reported geographic centroids of the constituent

block groups. 

The urban/rural designation was specified based on residential population density: urban if

greater than 750 people/km2. 

Finally, the hypothetical tract radius was derived from the tract area reported in the US Census,

under the assumption of a perfectly round shape:

TRRAD Area = Π

5.1.3 Census Tract Index File

The final input required by ASPENB is the binary census tract index file, containing the state and

county index data. The format of this file is shown in Table 5-3. The state index data are listed

with the following information for each state:

• State FIPS code

• Maximum and minimum longitude and latitude of the state

• Total number of counties in the state
5-5

• Pointer to the first county of the state, i.e., the record number of the first county of that

state in the list of all counties (to follow in the tract index file)

The county index data are listed in the tract index file with includes the following information for

each county:

• County FIPS code

• Maximum and minimum longitude and latitude of the county

• Total number of tracts in the state

• Pointer to the first tract of the state, i.e., the record number of the first tract of that county

in the list of all tracts (in the tract data file)

A utility program, MKTRACTS, generates the census index file utilizing ASCII formatted

census data. Figure 5-2 presents an example MKTRACTS job file.

Table 5-3 Description of census tract index file

Record No. Variables Data Type Description

1 NSTATES Integer Total number of states included in the data

NCOUNTIES Integer Total number of counties included in the

data

NTRACTS Integer Total number of tracts included in the data

2 STFIP Integer State FIPS code

STMNLN Real State minimum longitude (decimal degree)

STMNLT Real State minimum latitude (decimal degree)

STMXLN Real State maximum longitude (decimal degree)

STMXLT Real State maximum latitude (decimal degree)

COPTR Integer Pointer to the first county in the state

NUMCO Integer Total number of counties in the state

3 COFIPS Integer County FIPS code

COMNLN Real County minimum longitude (decimal

degree)

COMNLT Real County minimum latitude (decimal degree)

COMXLN Real County maximum longitude (decimal

degree)

COMXLT Real County maximum latitude (decimal

degree)

TRPTR Integer Pointer to the first tract in the county

NUMTR Integer Total number of tracts in the county

 Record 2 is repeated for all states included in the census tract data file.

 Record 3 is repeated for all counties included in the census tracts data file.
5-6

/bin/time src/mktracts << -eofDATA FILE |smptracts

-eofFigure 5-2 Example MKTRACTS job file

In the above example, the user input the ASCII formatted census tract data SMPTRACTS.ASC,

the utility MKTRACTS generates the corresponding binary formatted census tract data

(SMPTRACTS.DAT) and index file (SMPTRACTS.IND) required by ASPENB.

Figure 5-3 presents an example of ASCII formatted census tract data. Each record contains the

following variables: state FIPS, county FIPS, tract FIPS, longitude, latitude, tract hypothetical

radius, and urban/rural flag.

 9 1 10101-73.679499 41.068223 3.26 2

 9 1 10102-73.633778 41.097472 3.31 2

 9 1 10201-73.623645 41.059098 1.91 2

 9 1 10202-73.588872 41.063468 1.75 2

 9 1 10300-73.637447 41.036887 1.75 2

.......

36119 15000-73.617674 41.334870 4.34 2

Figure 5-3 Example of ASCII formatted census tract data 

5.2 ASPENB OUTPUTS

ASPENB creates two output files when it is executed. The first is the population

concentration/deposition file. This is the binary output file which contains estimated outdoor

concentrations (μg/m3

) and deposition fluxes (μg/m2-day) for each HAP by census tract for each

of eight 3-hour time blocks. The utility EXP2ASCI converts the ASPENB output from binary to

ASCII format. This allows the user to easily view the modeling results of ASPENB. The format

of the binary and ASCII output files are provided in Appendix C.

The second file created by ASPENB is the processed source concentration file. This file contains

a list of all of the normalized source concentration/deposition input file names that have been

processed. This is used to avoid running the same input file twice.

5.3 RUNNING ASPENB

Figure 5-4 shows an example run stream file for ASPENB. As discussed above, there are three

required input files for the ASPENB: the normalized source concentration/deposition file

(output from ASPENA), the census tract data file, and the census tract index file. ASPENB

requires that the tract data and index files be located in the same directory where the job is run. 
5-7

Note that the tract data and index files are specified in record 2 of the run stream file by their

base name only (do not include any extensions). In the directory in which they reside, the two

files should be distinguished by the following extensions: tract data file (*.dat) and index file

(*.ind).

/bin/time aspenb << -ieofONROAD MV FILE |cat3.con

TRACT FILE BASENAME|tracts

FILE LIST FILENAME |filelist.ntl

NO. OF SRC CATEGORY|5

RERUN (Yes/No) |No

-ieofFigure 5-4 Example ASPENB run stream file

The run stream file shown in Figure 5-4 is set up for a modeling simulation that includes total

number of five source categories, and it is not a rerun. Important parameters for the run stream

are as follows:

• Filename for input normalized source concentration/deposition file: cat3.con

• Base name of the census tract data file and index file: tracts

• Filename for output file listing: filelist.ntl

• Number of source categories included in the modeling: 5

• Status of the run, i.e., if it is a rerun: NO

A separate population concentration/deposition output file is created by ASPENB for each HAP. 

The naming convention for the output file is 5-digit SAROAD code with a “*.exp” extension. 

For example, the output file for toluene (with SAROAD code 45202) will be named as

45202.exp. Each time a HAP is encountered during the ASPENB simulation, the local directory

is checked to determine whether an appropriate HAP output file already exists. If not, one is

created. If so, the previous values for the current source category are incremented by the current

estimates to obtain cumulative concentration and deposition estimates for each census tract for

that source category.

In the example shown in Figure 5-4, if the emissions data for the CAT3 are revised, ASPENA

can be rerun for that category to produce revised normalized source concentration/deposition

data. A remodeling for the category can be completed using the rerun feature of ASPENB,

without having to rerun the simulations for other source categories. Figure 5-5 presents the

ASPENB run stream file using the rerun feature. Note that the only difference between the run

stream shown in Figure 5-4 and 5-5 is the selection for the status of the run.
5-8

/bin/time aspenb << -ieofONROAD MV FILE |cat3.rev.con 

TRACT FILE BASENAME|tracts 

FILE LIST FILENAME |filelist.ntl 

NO. OF SRC CATEGORY|5 

RERUN (Yes/No) |Yes

-ieofFigure 5-5 Example ASPENB run stream file using the rerun feature

To successfully execute a rerun for a particular source category, special attention should be paid

to the following:

• Specify "Yes" for rerun status in the ASPENB run stream file

• Use the revised ASPENA output file (as shown in the example cat3.rev.con) as one of the

input files

• Provide the ASPENB output files from the previous modeling runs. Those files contain

results from the previous modeling for all source categories, and the rerun will modify the

results for the single category specified in the input normalized concentration file 

• If the normalized concentrations file name remains unchanged in the rerun from the

previous modeling run (i.e., if cat3.con is the normalized concentrations file name used in

both runs in the examples shown above), then the file name should be removed from

filelist.ntl generated in the previous run, because the model will not allow running a file

with a name included in filelist.ntl.

Once ASPENB has been run a log file with a “.como” extension is created. The log file includes

useful information including the input/output filenames and errors. Table 5-4 presents a

summary of error messages in ASPEN. At the end of a run, the log file displays the following

message: “All done: X sources processed,” where X is the total number of emission sources in

the simulation. The number and type of sources processed by ASPENB should be the same as

those processed in the corresponding ASPENA simulation.

Table 5-4 Error messages in the ASPENB log file

Error Message Module Subroutine Program

Aborts

Error reading source file

Comment: read error or unexpected of in

normalized concentration/deposition file

ASPENB NEXTSOURCE Yes
5-9

5.4 MODEL RE-START CAPABILITY

ASPENA has no direct re-start capability. However, it is possible to re-start ASPENB indirectly

in some cases. For example, for large modeling domains ASPEN input files for the same

HAP/source category combinations may be divided into several files (e.g., stratified by

geographic region). When ASPENB processes the first ASPENA output file, it creates the

appropriate ASPENB HAP output files. When subsequent ASPENA output files are processed

by ASPENB, the previously created ASPENB HAP output files are incremented to accumulate

the concentration increments from all sources for that HAP/source category combination.

To avoid losing output data in the event of ASPENB aborting while processing one of the

multiple files, the user can make an intermediate copy of the ASPENB output files at the

completion of the processing of each ASPENA output file. (See Figure 5-6 for an example job

file.) Then if a run aborts, ASPENB can be re-started at the beginning of the aborted simulation,

using the intermediate ASPENB output files as the starting point. Figure 5-7 presents an

example job file for re-starting the job specified in the Figure 5-6 job file, if it were to abort

during the second ASPENB simulation. First, the partially updated output files are deleted. 

Then the intermediate files are copied back into the local directory. Finally the ASPENB job is

re-started at the beginning of the simulation that aborted. Note that this procedure requires

knowledge of the HAPs that will be processed so that the names of the ASPENB output files are

known.

/bin/time aspenb << -eofON ROAD MV FILE |cat3.epa1.con

TRACT FILE BASENAME|tracts

FILE LIST FILENAME |filelist.ntl

NO. SOURCE CATEGORY|5

RERUN(YES/NO) |NO

-eof-

#

cp -p 45202.exp tmp/45202.exp

cp –p filelist.ntl tmp/filelist.ntl

#

/bin/time aspenb << -eofON ROAD MV FILE |cat3.epa2.con

TRACT FILE BASENAME|tracts

FILE LIST FILENAME |filelist.ntl

NO. SOURCE CATEGORY|5

RERUN (YES/NO) |NO

-eofFigure 5-6 Example ASPENB job file that creates intermediate output files
5-10

rm 45202.exp

rm filelist.ntl

cp –p tmp/45202.exp 452023.exp

cp –p tmp/filelist.ntl filelist.ntl 

/bin/time aspenb << -eofON ROAD MV FILE |cat3.epa2.con

TRACT FILE BASENAME|tracts

FILE LIST FILENAME |filelist.nt

NO. SOURCE CATEGOEY|5

RERUN (YES/NO) |NO

-eofFigure 5-7 Example of an ASPENB re-start job file
6-1

SECDAT

AVGDAT

Secondary HAP 

formation?

Population 

concentration/deposition 

by source category by 

census tract (ASPEN B 

output)

Annual Average HAP 

Concentration by 

Census Tract

Census Data

EXTRDAT

yes

no

6.0 POST-PROCESSING MODEL OUTPUTS

A series of software programs are used to post-process the ASPENB model output. A detailed

descriptions of the post-processors are presented in this section.

There are three post-processors for ASPENB, they are:

• AVGDAT - calculates the annual average HAP concentration for each source

category included in the ASPENB output, calculates the total

annual average concentrations over all categories including the

background value provided by the user

• EXTRDAT - converts the concentration data files from binary to ASCII format

• SECDAT - generates the secondary pollutant concentrations and combines the

concentrations of the primary and secondary components

Note that the processing procedures, which were carried out by two post-processors in version

1.0 of the model (MRG_DAT and BACKGRND), have been incorporated into the post-processor

AVGDAT. Therefore, those two processors are no longer needed for version 1.1 of the model. 

Figure 6-1 presents a flow chart of the relationships among the post-processors.

Figure 6-1 Flow chart of the ASPEN post-processors.
6-2

6.1 GENERATING CONCENTRATIONS FOR THE SECONDARY COMPOUNDS

ASPEN estimates the concentration of the secondary HAPs as the difference between the

precursor concentration in an inert model run and its concentration in the presence of reactive

decay. The resulting concentration differences are adjusted for molar yield and molecular weight

to estimate the concentration of the secondary HAP.

The post-processor SECDAT is used for generating the concentration estimates of the secondary

HAPs, and combining the concentrations of the primary and secondary HAPs. The SECDAT

output file is in the same format as the population concentration/deposition file, so that it can be

further processed by AVGDAT. Figure 6-2 present an example job file for generating secondary

and total concentrations of acrolein.

The job file in Figure 6-2 is formatted as follows:

• Number of source categories included in the ASPENB output file: 5

• Filename of census tract list: ustracts.lst

• SAROAD code for secondary arolein: 80265

• Output filename: 80265.exp

• Scaling factor: -1.04

Note: the negative sign indicates that concentration differences of the HAPs specified

below should be calculated

• The inert concentration filename: 80302.exp (80302 is the SAROAD code for inert 1,3-

butadiene)

• The reactive concentration filename: 43218.exp (43218 is the SAROAD code for 1,3-

butadiene)

To generate the concentrations for the total acrolein, the job file is set up as follows:

• Number of source categories included in the ASPENB output file: 5

• Filename of census tract list: ustracts.lst

• SAROAD code of the total acrolein: 80266

• Output filename: 80266.exp

• Scaling factor: 1.0

Note: the positive sign indicates to calculate the total concentration of the HAPs specified

below

• The primary acrolein concentration filename: 435051.exp (43505 is the SAROAD code

for acrolein)

• The secondary arolein concentration filename: 80265.exp
6-3

#

# Generate secondary species for all source categories

#

rm aspenb/output/80265.exp

/bin/time src/secdat << ieof

5

data/ustracts.lst

80265

aspenb/output/80265.exp

-1.04

aspenb/output/80302.exp

aspenb/output/43218.exp

ieof

#

# Generate total for all categories

#

rm aspenb/output/80266.exp

/bin/time src/secdat << ieof

5

data/ustracts.lst

80266

aspenb/output/80266.exp

1.0

aspenb/output/43505.exp

aspenb/output/80265.exp

ieof

Figure 6-2 Example job file for the SECDAT post-processor

The difference between the post-processor SECDAT and its predecessor SEC_DAT is that the

new version greatly simplifies the processing procedure. In a single run SEC_DAT only treats

the processing for one source category for a particular HAP; but SECDAT can complete the

processing for all the source categories for the HAP included in the ASPENB output. The run

stream set up for SECDAT is the same as the one for SEC_DAT, except that total number of

source categories included in the ASPENB output file needed to be specified, and the file name

will be in the format of 5-digit SAROAD code with ".EXP" extension (i.e., the source category

code digit is no longer needed). 

6.2 CALCULATING ANNUAL AVERAGE CONCENTRATION

The post-processor AVGDAT is used to convert the model results into annual average

concentrations. The input concentration are estimated for eight 3-hour time blocks; the postprocessor calculates the average for the time blocks. The post-processor reads in the

concentrations in eight 3-hour time blocks for all the source categories included in the population

concentration/deposition file. Then it calculates the annual average concentrations for each

source category and total annual average concentration over all source categories, including the

background value provided by the user.
6-4

Figure 6-3 presents an example job file for calculating the average concentration of benzene. 

Important parameters for this run stream are as follows:

• The number of source categories included in the ASPENB output file: 5

• Filename for census tract list: ustracts.lst

• Output filename: 45201.exp.avg

• HAP SAROAD code: 45201 (benzene)

• Path for input concentration file: aspen/

• Background value for the HAP in μg/m3: 0.479

rm 45201.exp.avg

/bin/time avgdat << ieofa

5

ustracts.lst

45201.exp.avg

45202

aspen/

0.479

ieof

Figure 6-3 Example job file for the post-processor AVGDAT

Note that only the path is required for the input concentration files.

6.3 EXTRACT AND TABULATE ANNUAL AVERAGE CONCENTRATION

The output from AVGDAT is in binary format. The EXTRDAT post-processor converts this file

from binary to ASCII format. The post-processor provides the following options to the user:

• Select the concentration units: μg/m3, ppm, pphm, ppb or ppt, input as MGPCM, PPM,

PPHM, PPB or PPT

• Select census tracts:

To convert concentrations for all census tracts: input –1 (see Figure 6-4)

To extract concentrations for the listed tracts only: input total number of tracts, and list

the tracts of interest (see Figure 6-5)

Figure 6-4 presents an example job file for converting benzene concentrations from binary to

ASCII for all tracts (in μg/m3). Important parameters in the job file include:

• Number of source categories included in the ASPENB output: 5

• Name of input file: 45201.exp.avg

• Name of output file: 45201.exp.out

• HAP SAROAD code: 45201 (benzene)

• Filename for census tract list: ustracts.lst
6-5

• HAP name, desired measurement units, molecular weight: BENZENE, MGPCM, 78.11

(format: A10,A8,F10)

• Indicator of census tract selection: -1 (all census tracts)

rm 45201.avg.out

/bin/time extravg << ieofa

5

45201.exp.avg

45201.avg.out

45201

ustracts.lst

BENZ MGPCM 78.11

-1

ieof

Figure 6-4 Example 1 job file for the EXTRDAT post-processor

Figure 6-5 presents an example run stream for converting benzene concentrations from binary to

ASCII for only the 10 listed tracts (units in ppb).

rm 45201.avg.out

/bin/time extravg << ieof

5

45201.exp.avg

45201.avg.out

45201

ustracts.lst

BENZ PPB 78.11

10

 9001 10101 -73.67950 41.06822

 9001 10102 -73.63378 41.09747

 9001 10201 -73.62364 41.05910

 9001 10202 -73.58887 41.06347

 9001 10300 -73.63744 41.03689

 9001 10400 -73.65913 41.02311

 9001 10500 -73.64153 41.01606

 9001 10600 -73.62646 41.02859

 9001 10700 -73.61841 41.02867

 9001 10800 -73.59914 41.04003

ieof

Figure 6-5 Example 2 job file for the post-processor EXTRDAT
7-1

7.0 COMPUTER NOTES

7.1 MINIMUM HARDWARE REQUIREMENTS

The computer resources required to run the ASPEN application are contingent upon the number

of emission sources and HAPs to be processed. The disk storage requirements to run a

simulation on a UNIX workstation (Sun Ultra Sparc 2 / Solaris 2.5.1), using the emissions from

one source category (on-road mobile), one reactivity class (reactivity class 2 including emissions

from 11 HAPs) in a single EPA region (EPA region 9) is approximately 1.3 Mbytes for

ASPENA, and 2.7 Mbytes for ASPENB. It takes 6 CPU hours for both ASPENA and ASPENB

for this simulation. Table 7-1 presents the disk storage requirements.

Table 7-1 ASPEN disk storage requirements for example simulation.

File Disk Storage (Mbytes)

Inputs

Meteorological (214 stations) 4.0

Census tract (48 states, 60,803 tracts) 1.8

Emissions 8.4

Outputs

Normalized source concentration/deposition

(binary)

4.2

Population concentration/deposition (binary) 31.9 (2.9 Mbytes / HAP × 11

HAPs)

Annual average concentration (ASCII) 106.7 (9.7 Mbytes / HAP × 11

HAPs)

Total 157

7.2 COMPILING AND RUNNING ASPEN ON A UNIX WORKSTATION

The commands for compiling ASPEN on a UNIX workstation are presented in Figure 7-1 and

Figure 7-2.
7-2

FLGS = -O2

TARGT = aspena

OBJCTS = \

gauss.o \

gaussz.o \

header.o \

list.o \

notice.o \

opnfil.o \

point.o \

prise.o \

save.o \

aspena.o \

sigmaz.o \

stack.o \

star.o \

starin.o \

szcoef.o \

ddmpr.o \

vert.o \

depos.o \

biddisp.o \

vgausz.o \

blkmet.o \

blkdep.o \

skip.o

$(TARGT): $(OBJCTS)

f77 -o $(TARGT) $(FLGS) $(OBJCTS)

.f.o :

f77 -c $(FLGS) $<

Figure 7-1 The commands for compiling ASPENA on a UNIX workstation
7-3

FLGS = -O2

TARGT = aspenb

OBJCTS = \

addSource.o \

areaAvg1.o \

areaAvg2.o \

aspenb.o \

findResTr.o \

findcloTr.o \

impacted.o \

initSearch.o \

initTarget.o \

inside.o \

interpolate.o \

loadTracts.o \

nextCo.o \

nextSource.o \

nextSt.o \

nextTarget.o \

nextTr.o \

openSource.o \

ptAverage.o \

receploc.o \

setPts.o \

tolog.o \

update.o 

$(TARGT): $(OBJCTS)

f77 -o $(TARGT) $(FLGS) $(OBJCTS)

.f.o :

f77 -c $(FLGS) $<

Figure 7-2 The commands for compiling the ASPENB on a UNIX workstation.

7.2.1 Modifying the Array Limits

In the current version of ASPEN, the array limits are configured as follows:

• Maximum number of meteorological station: 500

• Maximum number of pollutants: 150

• Maximum number of radial distances of the grid: 12 (in ASPENA)

• Maximum number of azimuth direction of the grid: 16

• Maximum number of time blocks: 8

• Maximum number of HAPs emits from a source: 100

• Maximum number of census tracts: 60,803

• Maximum number of the states included in the tracts data: 49
7-4

• Maximum number of counties included in the tracts data: 3,111

• Maximum number of the tracts included in a county: 2,000

• Maximum number of the fields included in the population concentration/population file:

12. The 12 fields are: State/County FIPS code, tract FIPS code, concentrations in eight

3-hour time blocks, deposition over the land and water 

Most of the array limits are specified in PARAMETER statements. Exceptions, which are hard

coded, include the number of receptor grid radial distances (12), the number of receptor grid

azimuthal directions (16), and the number of time blocks (8) in the ASPENA module. 

Depending on the amount of memory available on the particular computer system being used, 

and the needs for a particular modeling application, the other array limits can be easily changed,

and the model can be recompiled.

If the user changes the number of time blocks in the ASPEN model, the ASPENA

emission/control input file, and the number of the fields included in the ASPEN output files

would also need to be changed.

7.3 PORTING THE MODEL TO THE OTHER HARDWARE ENVIRONMENTS

7.3.1 PC

The ASPEN models are designed and coded to allow them to run on most operating

environments, including UNIX and DOS. The current version of the model is written to run on

UNIX. Although the users do not need to make major changes, they may experience some minor

differences between UNIX to PC environments, including the following:

• The suffix .f of all source files should be changed to .for

• The subroutine OPNFIL of ASPENA uses GETARG to read input run stream filename,

which is compiler dependent. GETARG may be available under a different name for

another compiler.
8-1

8.0 ASPEN MODEL TUTORIAL

This section presents examples of the setup and use of ASPEN. Several example applications

are provided to demonstrate how to set up a basic modeling scenario and post-process the model

output. A more detailed discussion of each module is provided in Sections 5, 6, 7 and

Appendix C. Two main example scenarios are presented in this section: a gaseous HAPs and a

particulate HAPs scenario. There are three examples provided for calculating annual average

concentrations for a single gaseous HAP. The final example is for calculating concentrations and

depositions for two particulate HAPs.

8.1 EXAMPLE 1 – GASEOUS HAPS

This example problem is to simulate gaseous toluene concentrations by census tract in one

county (Fairfield, CT). For this example, multiple emission sources (point, area, and on-road

mobile) are modeled. Users must prepare an emission/control input file for each source category. 

A description of the input file parameters required for the emission/control input file for each

source category is provided. The reactivity for toluene for this example is assigned to category 4.

8.1.1 Setting up the Emission/Control Input File for Point Sources

For this example, the input file is prepared to simulate toluene concentrations from two point

sources. The point source emissions data used in this example are from the U.S. EPA’s Toxic

Release Inventory (TRI) database. The emission/control input file for ASPENA is presented in

Figure 8-1. 

1 TRI Point Sources Reactive Catagory 4 011

2 9.870e-07 9.870e-07 9.870e-07 9.870e-07 9.870e-07 9.870e-07

3 9.870e-07 9.870e-07 9.870e-07 9.870e-07 9.870e-07 9.870e-07

4 1.180e-05 7.890e-06 3.950e-06 1.970e-06 9.870e-07 9.870e-07

5 7.890e-05 5.920e-05 3.950e-05 1.970e-05 9.870e-07 9.870e-07

6 6.710e-05 5.130e-05 3.550e-05 1.970e-05 9.870e-07 9.870e-07

7 2.370e-05 1.780e-05 1.180e-05 7.890e-06 9.870e-07 9.870e-07

8 1.970e-06 1.970e-06 1.970e-06 9.870e-07 9.870e-07 9.870e-07

9 9.870e-07 9.870e-07 9.870e-07 9.870e-07 9.870e-07 9.870e-07

10 09001 16269 -73.2694 41.141702

11

12

13 1 -73.2694 41.1417 8.90 0.67 12.00 323.0000 0.00 0.00

14 452020 1.25e-01 1.25e-01 1.25e-01 1.25e-01 1.25e-01 1.25e-01 1.25e-01 1.25e-01

15

16

17 09001 16291 -73.4167 41.366102

18

19

20 1 -73.4167 41.3661 24.00 0.49 20.53 332.0000 0.00 0.00

21 452020 2.62e-03 2.62e-03 2.62e-03 2.62e-03 2.62e-03 2.62e-03 2.62e-03 2.62e-03

23

24

25

26

Figure 8-1 Example emission/control input file for point sources (filename: “aspena.tri.inp”)
8-2

A record by-record description of the input file data requirements is as follows:

• Line 1 (header): The run identifier (title), pollutant species type, and deposition

parameters are specified here. For this example, the parameters are set to: gaseous

species type (= 0); no dry deposition (=1), and no wet deposition (=1).

• Lines 2-9: The decay rates of reactivity category 4 are specified for each of the six

stability classes (A-F) and eight 3-hour time blocks.

• Lines 10-14: For each point source modeled, the source location, emissions, and various

stack parameters must be specified. Detailed information for the two TRI sources

included in this example is provided in Table 8-1. For a description of the input file

format for each of these variables, see Table C-1 in Appendix C.

• Lines 15-16: These lines are left blank to indicate the end of information for the emission

source.

• Lines 17-21: This section contains data for a second point source, analogous to lines 10-

14.

• Lines 22-26: These lines are left blank to indicate the end of the file.

Table 8-1 Point source data parameters entered into the emission/control input file

Variable Source No. 1 Source No. 2 Remarks

FIPS code 09001 09001 Fairfield, CT

Plant ID 16269 16291

Longitude -73.2694 -73.4167

Latitude 41.1417 41.3661

Source type 0 0 Point source

Urban/Rural flag 2 2 Rural

NWS station ID Blank Blank Use nearest station

Stack ID 1 1

Longitude -73.2694 -73.4167

Latitude 41.1417 41.3661

Stack height (m) 8.9 24.0

Stack diameter (m) 0.67 0.49

Stack exit velocity (m/sec) 12.0 20.53

Stack exit temperature (Deg K) 323.0 332.0

Vent/Stack flag 0 0 Stacked

Building flag 0 0 No building

Width of nearby building (m) 0.0 0.0

Height of nearby building (m) 0.0 0.0

HAP Saroad code 45202 45202 Toluene

Source category 0 0 TRI-Nonmetal

Emissions of each time block

(g/sec)

0.125 2.62×10-3 Flat temporal

profile
8-3

8.1.2 Setting up the Emission/Control Input File for Mobile Sources

The example emission/control input file for mobile sources is presented in Figure 8-2. 

1 On-Road MV Sources Reactive Category 4 011

2 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07

3 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07

4 1.18E-05 7.89E-06 3.95E-06 1.97E-06 9.87E-07 9.87E-07

5 7.89E-05 5.92E-05 3.95E-05 1.97E-05 9.87E-07 9.87E-07

6 6.71E-05 5.13E-05 3.55E-05 1.97E-05 9.87E-07 9.87E-07

7 2.37E-05 1.78E-05 1.18E-05 7.89E-06 9.87E-07 9.87E-07

8 1.97E-06 1.97E-06 1.97E-06 9.87E-07 9.87E-07 9.87E-07

9 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07

10 09001 30400 -73.4919 41.0644 31

11 4781

12

13 09001 -73.4919 41.0644 1

14 4520230.1482E+000.1482E+000.1113E+010.9006E+000.9317E+000.1289E+010.5786E+000.1613E+00

15

16

17 09001 30500 -73.5024 41.0780 31

18 4781

19

20 09001 -73.5024 41.0780 1

21 4520230.1168E+000.1168E+000.8744E+000.6927E+000.7138E+000.1005E+010.4522E+000.1257E+00

22

23

24

25

26

Figure 8-2 Example emission/control input file for on-road mobile sources (filename: “aspena.mv.inp”)

Mobile source emissions are specified at the census tract level as pseudo point sources. This

example includes toluene emissions from on-road mobile sources for two census tracts (tracts

30400 and 30500).

• Lines 1-9: These records are identical to the point source emission/control input file

shows in Figure 8-2 (except for the run identifier) because both include emissions for

toluene.

• Lines 10-14: The format of these lines is the same as for the point source example

discussed above. However, some of the variables represent somewhat different

parameters for this case.

Line 10: The census tract FIPS code (30400) is used instead of the plant ID, and

the coordinates (longitude and latitude) of the census tract centroid is specified

instead of the plant location. On-road mobile sources are considered “pseudo

points”, with a source category code of 3.
8-4

Line 11: For this example the NWS station ID for the desired meteorological

station is specified. If left blank, as it was in the point source example, the closest

station in the data base would be assigned. However, for “pseudo points” the

meteorological stations are generally pre-determined so that sources can be

grouped according to meteorological station and urban/rural designation to save

computing time. This is discussed in Appendix C.

Line 13: The source type for mobile sources (and area sources) is designated as

non-stacked (vent/stack flag = 1), and pseudo point source (source type = 3).

Line 14: In contrast to the point source example, for this case the emission rate

varies among the eight time blocks.

• Lines 15-16: These lines are left blank to indicate the end of information for the emission

source.

• Lines 17-21: This section contains data for a second pseudo point source, analogous to

lines 10-14.

• Lines 22-26: These lines are left blank to indicate the end of the file.

8.1.3 Setting up the Emission/Control Input File for Area Sources

Like mobile sources, area sources are specified at the census tract level as pseudo point sources. 

Figure 8-3 shows an emission/control input file for simulating toluene emissions from two area

sources in two census tracts (tract #s 35100 and 42700). The input file for area source emissions

is very similar to the mobile source file discussed in Section 8.1.2. The only difference is that

there are two emissions records in the area source file, corresponding to the two area source

categories: manufacturing emissions (source category code = 5), and non-manufacturing

emissions (source category code = 6). This can be seen in Figure 8-3, where the manufacturing

and non-manufacturing emissions in census tract 35100 are represented by records 14 and 15,

respectively.

8.1.4 Running ASPENA

The two types of input required to run ASPENA are the emission/control file, and the

meteorological files. Procedures for preparing the emission/control file are discussed in Sections

8.1.1 – 8.1.3. The meteorological data input requirements include STAR meteorological data

and a meteorological index file. Versions of the latter two files, containing national 1990 data,

are provided as part of the ASPENA modeling system.
8-5

1 Area Sources Reactive Category 4 011

2 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07

3 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07

4 1.18E-05 7.89E-06 3.95E-06 1.97E-06 9.87E-07 9.87E-07

5 7.89E-05 5.92E-05 3.95E-05 1.97E-05 9.87E-07 9.87E-07

6 6.71E-05 5.13E-05 3.55E-05 1.97E-05 9.87E-07 9.87E-07

7 2.37E-05 1.78E-05 1.18E-05 7.89E-06 9.87E-07 9.87E-07

8 1.97E-06 1.97E-06 1.97E-06 9.87E-07 9.87E-07 9.87E-07

9 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07

10 09001 35100 -73.4919 41.1433 31

11 4781

12

13 09001 -73.4919 41.1433 1

14 4520250.0000E+000.0000E+000.1785E-010.5356E-010.5356E-010.5356E-010.5356E+010.5356E-01

15 4520260.1249E-010.5239E-010.1336E+000.1529E+000.1208E+000.9346E-010.4291E-010.2793E-01

16

17

18 09001 42700 -73.4209 41.1425 31

19 4781

20

21 09001 -73.4209 41.1425 1

22 4520250.0000E+000.0000E+000.8033E010.2410E+000.2410E+000.2410E+000.2410E+000.2410E+00

23 4520260.2810E+010.5116E010.1549E+000.2566E+000.2381E+000.2223E+000.1437E+000.9328E-01

24

25

26

27

28

Figure 8-3 Example emission/control input file for area source (filename: “aspena.ar.inp”)

Once the input files have been prepared and formatted according to the specifications provided in

Appendix C, run stream files need to be created that include the input and output filenames for

the simulation.

Example run stream files for area, point and mobile and gaseous HAPs simulations are shown in

Figures 8-4, 8-5, and 8-6. The filenames shown in the figures correspond to the following:

• aspena.xx.inp - emission/control input file (format: ASCII)

• wtpmix.ind - meteorological index input file (format: binary)

• star.dat - STAR meteorological data file (format: direct access binary)

• aspena.xx.con - ASPENA normalized source concentration/deposition output file

(format: binary)

where, “XX” refers to one of the following source category codes:

ar – area source

tri – point source

mv – mobile source

aspena.ar.inp

/dev/null

wtpmix.ind

star.dat

aspena.ar.con

Figure 8-4 Run stream file for the gaseous HAPs ASPENA run (filename: “aspena.ar.sys”)
aspena.tri.inp

/dev/null

wtpmix.ind

star.dat

aspena.tri.con

Figure 8-5 Run stream file for ASPENA point run (filename: “aspena.tri.sys”)

aspena.mv.inp

/dev/null

wtpmix.ind

star.dat

aspena.mv.con

Figure 8-6 Run stream file for ASPENA mobile run (filename: “aspena.mv.sys”)

In addition to the pollutant concentration output file, ASPENA also creates an output file with

listing all the emission sources processed in Fortran unit 88. It is convenient to rename this file

at the conclusion of each simulation, so that it will no be overwritten by the next simulation in

the job. Figure 8-7 presents an example of a job file for ASPENA simulations made with the

example files discussed above. In the example, the 3 processed source listing files produced for

the three simulations are renamed from “fort.88” to “aspena.tri.lst”, “aspena.ar.lst”, and

“aspena.mv.lst”. 

rm aspena.tri.lst

rm aspena.tri.con

/bin/time aspena aspena.tri.sys

mv fort.88 aspena.tri.lst

#

rm aspena.ar.lst

rm aspena.ar.con

/bin/time aspena aspena.ar.sys

mv fort.88 aspena.ar.lst

#

rm aspena.mv.lst

rm aspena.mv.con

/bin/time aspena aspena.mv.sys

mv fort.88 aspena.mv.lst

Figure 8-7 Example of ASPENA job file
8-7

plant FIPS number: 9001plant ID: 35100 stack type: 3 Long/Lat coordinates : -73.492 41.143 urban/rural 1=urban; Species type : 0 ambient temperatures (k): 289.000 279.000 284.000 meteorological station: 4781 utm coordinates (km): -73.100 40.783 excluded stabilities: 000000 wind speeds: 000000 wind directions: 0000000000000000 Average Precip and freq : 110.2106 0.2067 Stack ID : 09001 Long/Lat coordinates : -73.492 41.143 stack height (m): 0.00 diameter (m): 0.00 exit velocity (m/s): 0.00 exit temperature (k): 0.00 vent/stack class: vent Calculated concentrations for hour 1 from-- chemicals emitted: 452025 452026 emission rate (g/s): 0.00E+00 0.12E-01 receptor grid concentrations (micrograms/cubic meter) resulting from total emissions bearing distance (km) (deg) 0.10 0.50 1.00 2.00 5.00 10.00 15.00 20.00 25.00 30.00 40.00 50 0.0 5.0E+01 2.8E+00 8.4E-01 2.6E-01 6.0E-02 2.2E-02 1.2E-02 8.3E-03 6.1E-03 4.7E-03 3.2E-03 2.4E 22.5 3.8E+01 2.1E+00 6.3E-01 1.9E-01 4.5E-02 1.6E-02 9.4E-03 6.3E-03 4.7E-03 3.7E-03 2.5E-03 1.9E ............... Calculated concentrations for hour 8 from-- chemicals emitted: 452025 452026 emission rate (g/s): 0.54E-01 0.28E-01 receptor grid concentrations (micrograms/cubic meter) resulting from total emissions bearing distance (km) (deg) 0.10 0.50 1.00 2.00 5.00 10.00 15.00 20.00 25.00 30.00 40.00 50 0.0 6.0E+01 3.5E+00 1.0E+00 3.2E-01 7.4E-02 2.7E-02 1.5E-02 9.8E-03 7.1E-03 5.5E-03 3.7E-03 2.7E 22.5 4.7E+01 2.7E+00 7.9E-01 2.4E-01 5.7E-02 2.1E-02 1.2E-02 7.8E-03 5.7E-03 4.5E-03 3.0E-03 2.3E No Deposition Calculations Specified on Input .. ..........Total Plants Processed : 2

Figure 8-8 ASPENA diagnostic file created by example area source run
plant FIPS number: 9001

 plant ID: 30400 stack type: 3 Long/Lat coordinates : -73.492 41.064 urban/rural 1=urban; 2=rural : 1 Species type : 0 ambient temperatures (k): 289.000 279.000 284.000 meteorological station: 4781 utm coordinates (km): -73.100 40.783 excluded stabilities: 000000 wind speeds: 000000 wind directions: 0000000000000000 Average Precip and freq : 110.2106 0.2067 Stack ID : 09001 Long/Lat coordinates : -73.492 41.064 stack height (m): 0.00 diameter (m): 0.00 exit velocity (m/s): 0.00 exit temperature (k): 0.00 vent/stack class: vent Calculated concentrations for hour 1 from-- chemicals emitted: 452023 emission rate (g/s): 0.15E+00 receptor grid concentrations (micrograms/cubic meter) resulting from total emissions bearing distance (km) (deg) 0.10 0.50 1.00 2.00 5.00 10.00 15.00 20.00 25.00 30.00 40.00 50. 0.0 5.0E+01 2.8E+00 8.4E-01 2.6E-01 6.0E-02 2.2E-02 1.2E-02 8.3E-03 6.1E-03 4.7E-03 3.2E-03 2.4E 22.5 3.8E+01 2.1E+00 6.3E-01 1.9E-01 4.5E-02 1.6E-02 9.4E-03 6.3E-03 4.7E-03 3.7E-03 2.5E-03 1.9E ........... Calculated concentrations for hour 8 from-- chemicals emitted: 452023 emission rate (g/s): 0.16E+00 receptor grid concentrations (micrograms/cubic meter) resulting from total emissions bearing distance (km) (deg) 0.10 0.50 1.00 2.00 5.00 10.00 15.00 20.00 25.00 30.00 40.00 50. 0.0 6.0E+01 3.5E+00 1.0E+00 3.2E-01 7.4E-02 2.7E-02 1.5E-02 9.8E-03 7.1E-03 5.5E-03 3.7E-03 2.7E 22.5 4.7E+01 2.7E+00 7.9E-01 2.4E-01 5.7E-02 2.1E-02 1.2E-02 7.8E-03 5.7E-03 4.5E-03 3.0E-03 2.3ENo Deposition Calculations Specified on Input ..

Figure 8-9 ASPENA diagnostic file created by example mobile source run
plant FIPS number: 9001

 plant ID: 16269 stack type: 0 Long/Lat coordinates : -73.269 41.142 urban/rural 1=urban; 2=rural : 2 Species type : 0 ambient temperatures (k): 289.000 279.000 284.000 meteorological station: 4781 utm coordinates (km): -73.100 40.783 excluded stabilities: 000000 wind speeds: 000000 wind directions: 0000000000000000 Average Precip and freq : 110.2106 0.2067 Stack ID : 1 Long/Lat coordinates : -73.269 41.142 stack height (m): 8.90 diameter (m): 0.67 exit velocity (m/s): 12.00 exit temperature (k): 323.00 vent/stack class: stack Calculated concentrations for hour 1 from-- chemicals emitted: 452020 emission rate (g/s): 0.12E+00 receptor grid concentrations (micrograms/cubic meter) resulting from total emissions bearing distance (km) (deg) 0.10 0.50 1.00 2.00 5.00 10.00 15.00 20.00 25.00 30.00 40.00 50. 0.0 1.1E-01 1.1E+00 6.9E-01 4.2E-01 1.6E-01 6.7E-02 3.9E-02 2.7E-02 2.0E-02 1.6E-02 1.1E-02 8.3E 22.5 3.0E-01 1.2E+00 6.5E-01 3.5E-01 1.2E-01 5.0E-02 2.9E-02 2.0E-02 1.5E-02 1.2E-02 8.0E-03 6.0E............. Calculated concentrations for hour 8 from-- chemicals emitted: 452020 emission rate (g/s): 0.12E+00 receptor grid concentrations (micrograms/cubic meter) resulting from total emissions bearing distance (km) (deg) 0.10 0.50 1.00 2.00 5.00 10.00 15.00 20.00 25.00 30.00 40.00 50. 0.0 9.5E-02 9.2E-01 7.3E-01 4.8E-01 1.9E-01 8.0E-02 4.7E-02 3.3E-02 2.4E-02 1.9E-02 1.3E-02 1.0E 22.5 2.0E-01 1.2E+00 7.3E-01 4.2E-01 1.5E-01 6.2E-02 3.6E-02 2.5E-02 1.8E-02 1.4E-02 1.0E-02 7.5E.................No Deposition Calculations Specified on Input .. plant FIPS number: 9001 plant ID: 16291

Figure 8-10 ASPENA diagnostic file created by example TRI source run
8-10

8.1.5 Running ASPENB

Two types of input files are required to run ASPENB. The first is the normalized source

concentration/deposition output file from the ASPENA run. The second contains census tract

information, including tract data (format: binary) and a tract index file (format: binary). For the

purposes of this example, the tract data filenames are: “smptracts.dat” and “smptracts.ind”. Note

that ASPENB requires that the tract data be located in the same directory as where the job is run. 

Also, the tract data files are specified in the job file by their base name only. So, for the example

run, the census tract data file name is entered as smptract, with no suffix at the end. For a

detailed description of how to run ASPENB, see Section 3. The ASPENB job file for the

gaseous HAPs simulations is shown in Figure 8-11.

/bin/time aspenb << -eofPOINT SOURCE FILE |aspena.tri.con

TRACT FILE BASENAME|smptracts

FILE LIST FILENAME |runfile.lst

NO. SOURCE CATEGORY|7

RERUN (YES/NO) |NO

-eof-

#

/bin/time aspenb << -eofON ROAD MV FILE |aspena.mv.con

TRACT FILE BASENAME|smptracts

FILE LIST FILENAME |runfile.lst

NO. SOURCE CATEGORY|7

RERUN (YES/NO) |NO

-eof-

#

/bin/time aspenb << -eofAREA SOURCE FILE |aspena.ar.con

TRACT FILE BASENAME|smptracts

FILE LIST FILENAME |runfile.lst

NO. SOURCE CATEGORY|7

RERUN (YES/NO) |NO

-eofFigure 8-11 ASPENB example job file

ASEPENB creates a separate population concentration/deposition output file (format: binary) for

each HAP encountered in the ASPENA output file. The naming convention for the output file is

the 5-digit pollutant SAROAD code with an *.exp extension. For example, the ASPENB output

filename for toluene (SAROAD code = 45202) is 45202.exp.

The ASPENB module also provides an output file containing a list of all the names of processed

input ASPENA files. In the Figure 8-11 example, the name for the listing file is "runfile.lst"
8-11

 which contains the input normalized source concentration filenames (“aspena.tri.con”,

“aspena.mv.con” and “aspena.ar.con” for the example).

Utility “exp2asci” converts the binary formatted ASPENB population concentration/deposition

file into ASCII format. Figure 8-12 presents an example of the binary to ASCII conversion using

“exp2asci”. In the example, 45202.exp is the binary formatted ASPENB output, “smptracts” is

the census tract data file, and 7 is the number of source categories included in “45202.exp”. The

utility generates the ASCII formatted output file named as “45202.txt”.

rm 45202.txt/bin/time

exp2asci << -eof7

*.EXP FILENAME |45202.exp

TRACTS DATA FILE |smptracts

-eofFigure 8-12 Example EXP2ASCI job file

The ASCII formatted ASPENB output population concentration/deposition file generated by the

utility “exp2asci” for the example is presented in Figure 8-13.

8.1.6 Post-Processing Model Output

The ASPENB output files are in binary format and contain pollutant concentration estimates for

each of eight 3-hour time blocks for each source category. A series of software programs are

available to post-process the model output. Detailed descriptions of these programs are provided

in Section 4. (Deposition estimates are also contained in the ASPENB output files, but are not

treated by the post-processors.) For this example the following two post-processors are used:

• AVGDAT - calculates the annual average HAP concentration for each source category,

and calculates the total annual average concentration over all categories

• EXTRDAT - converts the concentration data files from binary to ASCII format 

Figure 8-14 presents an example job file for post-processing the example model output.

The ASPEN ASCII output for the example simulations is shown in Figure 8-15. It contains the

concentrations of toluene (in μg/m3

) by source category and census tract. The first two columns

are the state and county FIPS codes and tract FIPS code. The output displays annual average

concentrations for TRI, on-road mobile, manufacturing and non-manufacturing area sources,

under the CAT00, CAT03, CAT05 and CAT06 columns, respectively.
8-12

9001 10101 0.632475E-03 0.602951E-03 0.385393E-03 0.154866E-03 0.142112E-03 0.224468E-03 0.419884E-03 0.60.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.964551E-03 0.123733E-02 0.632815E-02 0.20.331155E-02 0.298845E-02 0.196255E-02 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+00 0.000000E+00 0.000000E+00 0.308918E-03 0.297286E-03 0.244506E-03 0.311125E-03 0.648992E-03 0.90.422919E-03 0.102578E-02 0.456361E-03 0.317639E-03 0.346642E-03 0.415487E-03 0.396137E-03 0.000000E+00 0.00.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+009001 10102 0.653247E-03 0.731114E-03 0.435314E-03 0.185383E-03 0.165064E-03 0.268752E-03 0.468903E-03 0.80.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.631174E-03 0.153372E-02 0.709802E-02 0.20.361774E-02 0.521225E-02 0.149818E-02 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+00 0.000000E+00 0.000000E+00 0.369893E-03 0.388875E-03 0.317510E-03 0.415000E-03 0.892116E-03 0.10.545520E-03 0.126443E-02 0.596893E-03 0.431510E-03 0.475560E-03 0.582221E-03 0.591870E-03 0.000000E+00 0.00.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+009001 10201 0.844332E-03 0.706242E-03 0.493527E-03 0.200628E-03 0.188866E-03 0.277834E-03 0.530698E-03 0.70.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.184324E-02 0.203914E-02 0.104112E-01 0.30.579354E-02 0.496717E-02 0.297403E-02 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+00 0.000000E+00 0.000000E+00 0.441517E-03 0.455559E-03 0.322872E-03 0.383767E-03 0.658951E-03 0.90.670122E-03 0.151366E-02 0.722135E-03 0.421889E-03 0.428519E-03 0.415162E-03 0.405331E-03 0.000000E+00 0.00.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+009001 10202 0.988371E-03 0.806748E-03 0.578435E-03 0.239344E-03 0.226871E-03 0.325602E-03 0.615040E-03 0.80.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.272014E-02 0.315319E-02 0.154034E-01 0.60.952190E-02 0.766703E-02 0.463139E-02 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+00 0.000000E+00 0.000000E+00 0.566090E-03 0.604773E-03 0.404266E-03 0.467594E-03 0.699876E-03 0.10.929373E-03 0.199587E-02 0.971293E-03 0.533134E-03 0.526697E-03 0.438111E-03 0.454870E-03 0.000000E+00 0.00.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+00.......................................36119 15000 0.164685E-03 0.494377E-03 0.249541E-03 0.138755E-03 0.129794E-03 0.256117E-03 0.936136E-03 0.0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.759098E-03 0.277467E-03 0.10.112701E-02 0.303295E-02 0.317063E-02 0.582770E-03 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.845961E-04 0.227843E-03 0.196333E-03 0.389976E-03 0.10.924682E-04 0.128902E-03 0.229063E-03 0.316118E-03 0.242534E-03 0.420564E-03 0.713992E-03 0.288280E-03 0.00.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.00.000000E+00 0.000000E+00 0 0 45202

Figure 8-13 ASPENB output population concentration/deposition file (in ASCII format) for the example 
8-13

rm 45202.exp.avg

/bin/time avgdat << ieof

7

smptracts.lst

45202.exp.avg

45202

samples/

0.0

ieof

#

rm 45202.avg.out

/bin/time extravg << ieof

7

45202.exp.avg

45202.avg.out

45202

smptracts.lst

TOLUENE MGPCM 92.14

-1

ieof

Figure 8-14. Example post-processing job file
8-14

Average Concentrations SAROAD Code 45202; Species TOLUENE MGPCM --------------------------------------------------------------------------------------------------------- FIPS Code Cat00 Cat01 Cat02 Cat03 Cat04 Cat05 Cat06 Bk--------------------- ----------------------------------------------------------------------------------- 9001 10101 0.4071E-03 0.0000E+00 0.0000E+00 0.2574E-02 0.0000E+00 0.3456E-03 0.4447E-03 0.000 9001 10102 0.4756E-03 0.0000E+00 0.0000E+00 0.2959E-02 0.0000E+00 0.4748E-03 0.5900E-03 0.000 9001 10201 0.5009E-03 0.0000E+00 0.0000E+00 0.4329E-02 0.0000E+00 0.4058E-03 0.5989E-03 0.000 9001 10202 0.5803E-03 0.0000E+00 0.0000E+00 0.6715E-02 0.0000E+00 0.4805E-03 0.7638E-03 0.000 9001 10300 0.4722E-03 0.0000E+00 0.0000E+00 0.4025E-02 0.0000E+00 0.3379E-03 0.5220E-03 0.000 9001 10400 0.4340E-03 0.0000E+00 0.0000E+00 0.3371E-02 0.0000E+00 0.2958E-03 0.4549E-03 0.000 9001 10500 0.4515E-03 0.0000E+00 0.0000E+00 0.3839E-02 0.0000E+00 0.3007E-03 0.4812E-03 0.000 9001 10600 0.4881E-03 0.0000E+00 0.0000E+00 0.4443E-02 0.0000E+00 0.3357E-03 0.5370E-03 0.000 9001 10700 0.5008E-03 0.0000E+00 0.0000E+00 0.4796E-02 0.0000E+00 0.3451E-03 0.5588E-03 0.000 9001 10800 0.5491E-03 0.0000E+00 0.0000E+00 0.6050E-02 0.0000E+00 0.3952E-03 0.6474E-03 0.000 9001 10900 0.6123E-03 0.0000E+00 0.0000E+00 0.8710E-02 0.0000E+00 0.4629E-03 0.7809E-03 0.000 9001 11000 0.5987E-03 0.0000E+00 0.0000E+00 0.8919E-02 0.0000E+00 0.4178E-03 0.7315E-03 0.000 9001 11100 0.5683E-03 0.0000E+00 0.0000E+00 0.7246E-02 0.0000E+00 0.3946E-03 0.6777E-03 0.000 9001 11200 0.4728E-03 0.0000E+00 0.0000E+00 0.4386E-02 0.0000E+00 0.3135E-03 0.5156E-03 0.000 9001 11300 0.4201E-03 0.0000E+00 0.0000E+00 0.3389E-02 0.0000E+00 0.2720E-03 0.4376E-03 0.000 9001 20100 0.7148E-03 0.0000E+00 0.0000E+00 0.1865E-01 0.0000E+00 0.5490E-03 0.1004E-02 0.000 9001 20200 0.5568E-03 0.0000E+00 0.0000E+00 0.5354E-02 0.0000E+00 0.7085E-03 0.8610E-03 0.000 9001 20300 0.5863E-03 0.0000E+00 0.0000E+00 0.5123E-02 0.0000E+00 0.8751E-03 0.1036E-02 0.000 9001 20400 0.6764E-03 0.0000E+00 0.0000E+00 0.9716E-02 0.0000E+00 0.1051E-02 0.1486E-02 0.000 9001 20500 0.6369E-03 0.0000E+00 0.0000E+00 0.7910E-02 0.0000E+00 0.6095E-03 0.9718E-03 0.000 9001 20600 0.6852E-03 0.0000E+00 0.0000E+00 0.9828E-02 0.0000E+00 0.7735E-03 0.1250E-02 0.000 9001 20700 0.7898E-03 0.0000E+00 0.0000E+00 0.1841E-01 0.0000E+00 0.1179E-02 0.2108E-02 0.000 9001 20800 0.7328E-03 0.0000E+00 0.0000E+00 0.1478E-01 0.0000E+00 0.8390E-03 0.1434E-02 0.000 9001 20900 0.8289E-03 0.0000E+00 0.0000E+00 0.3388E-01 0.0000E+00 0.1113E-02 0.2069E-02 0.000 9001 21000 0.8012E-03 0.0000E+00 0.0000E+00 0.3328E-01 0.0000E+00 0.8739E-03 0.1602E-02 0.000 9001 21100 0.8043E-03 0.0000E+00 0.0000E+00 0.4475E-01 0.0000E+00 0.7977E-03 0.1536E-02 0.000 9001 21200 0.7407E-03 0.0000E+00 0.0000E+00 0.1967E-01 0.0000E+00 0.7066E-03 0.1251E-02 0.000 9001 21300 0.6920E-03 0.0000E+00 0.0000E+00 0.1452E-01 0.0000E+00 0.5808E-03 0.1012E-02 0.000 9001 21400 0.6660E-03 0.0000E+00 0.0000E+00 0.1225E-01 0.0000E+00 0.5077E-03 0.8898E-03 0.000 9001 21500 0.6845E-03 0.0000E+00 0.0000E+00 0.1453E-01 0.0000E+00 0.5155E-03 0.9262E-03 0.000 9001 21600 0.7361E-03 0.0000E+00 0.0000E+00 0.2144E-01 0.0000E+00 0.6121E-03 0.1105E-02 0.000 9001 21700 0.7567E-03 0.0000E+00 0.0000E+00 0.2774E-01 0.0000E+00 0.6457E-03 0.1225E-02 0.000 9001 21800 0.8116E-03 0.0000E+00 0.0000E+00 0.4962E-01 0.0000E+00 0.7827E-03 0.1540E-02 0.000 9001 21900 0.8084E-03 0.0000E+00 0.0000E+00 0.6120E-01 0.0000E+00 0.8278E-03 0.1607E-02 0.000

..............................................

..............................................

Figure 8-15 ASPEN output in ASCII format for the example simulation
8-15

8.2 EXAMPLE 2 - PARTICULATE HAPS

Figure 8-16 presents an emission/control input file for an example simulation to calculate ambient

concentrations of particulate HAPs from point source emissions. The input includes emissions of

chromium (fine) and nickel (fine) from a TRI source. Differences between this file and the example for

gaseous emissions from point sources are as follows:

7. Line 1: Both dry and wet depositions are selected in the example (= 0) for the fine particulate

HAPs (species type=1)

8. Lines 2-9: Reactive decay rates for particulate HAPs are all set to 0.

1 TRI Point Sources Reactive Category 2 100

2 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00

3 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00

4 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00

5 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00

6 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00

7 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00

8 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00

9 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00

10 9001 13777 -73.1483 41.185301

11

12

13 1 -73.1483 41.1853 6.10 0.15 5.00 308.0000 0.00 0.00

14 801410 7.19e-05 7.19e-05 7.19e-05 7.19e-05 7.19e-05 7.19e-05 7.19e-05 7.19e-05

15 802160 7.19e-05 7.19e-05 7.19e-05 7.19e-05 7.19e-05 7.19e-05 7.19e-05 7.19e-05

16

17

18

19

20

Figure 8-16 Example ASPENA input file for point source emits particulate HAPs

The other ASPEN model simulation and post-processing procedures for this example are the same as

those described for gaseous HAPs starting in Section 8.1.1.
plant FIPS number: 9001 plant ID: 13777 stack type: 0 Long/Lat coordinates : -73.14

urban/rural 1=urban; 2=rural : 1 Species type : 1 ambient temperatures (k): 289.000 279.000 284.000 meteorological station: 4781 utm coodinates (km): -73.100 40.783 excluded stabilities: 000000 wind speeds: 000000 wind directions: 0000000000000000 Average Precip and freq : 110.2106 0.2067 Stack ID : 1 Long/Lat coordinates : -73.148 41.185 stack height (m): 6.10 diameter (m): 0.15 exit velocity (m/s): 5.00 exit temperature (k): 308.00 vent/stack class: stack Calculated concentations for hour 1 from-- chemicals emitted: 801410 802160 emission rate (g/s): 0.72E-04 0.72E-04 receptor grid concentrations (micrograms/cubic meter) resulting from total emissions bearing distance (km) (deg) 0.10 0.50 1.00 2.00 5.00 10.00 15.00 20.00 25.00 30.00 40.00 50 0.0 2.0E+01 2.1E+00 6.5E-01 2.0E-01 4.8E-02 1.7E-02 9.9E-03 6.6E-03 4.9E-03 3.8E-03 2.6E-03 1.9E 22.5 1.8E+01 1.6E+00 4.9E-01 1.5E-01 3.5E-02 1.3E-02 7.5E-03 5.1E-03 3.7E-03 2.9E-03 2.0E-03 1.5E ........... Calculated concentations for hour 8 from-- chemicals emitted: 801410 802160 emission rate (g/s): 0.72E-04 0.72E-04 receptor grid concentrations (micrograms/cubic meter) resulting from total emissions bearing distance (km) (deg) 0.10 0.50 1.00 2.00 5.00 10.00 15.00 20.00 25.00 30.00 40.00 50 0.0 2.3E+01 2.6E+00 7.9E-01 2.5E-01 5.9E-02 2.1E-02 1.2E-02 7.8E-03 5.7E-03 4.4E-03 3.0E-03 2.2E 22.5 2.1E+01 2.0E+00 6.1E-01 1.9E-01 4.5E-02 1.6E-02 9.3E-03 6.2E-03 4.6E-03 3.6E-03 2.4E-03 1.8E Total Deposition 1 from-- (deg) 0.10 0.50 1.00 2.00 5.00 10.00 15.00 20.00 25.00 30.00 40.00 50 0.0 3.1E+03 2.0E+02 5.6E+01 1.6E+01 3.7E+00 1.4E+00 8.0E-01 5.6E-01 4.3E-01 3.4E-01 2.4E-01 1.9E 22.5 3.5E+03 2.1E+02 5.9E+01 1.7E+01 3.9E+00 1.4E+00 8.5E-01 5.9E-01 4.5E-01 3.6E-01 2.6E-01 2.0E

Figure 8-17 ASPENA diagnostic file created by example point source run
8-17

9001 10101 0.887709E-07 0.774276E-07 0.779782E-07 0.336689E-07 0.245561E-07 0.273105E-07 0.490938E-07 0.840.954688E-06 9001 10102 0.936549E-07 0.847418E-07 0.825023E-07 0.381454E-07 0.256891E-07 0.294738E-07 0.546769E-07 0.90.104341E-05 9001 10201 0.106153E-06 0.891512E-07 0.903393E-07 0.360951E-07 0.286658E-07 0.312934E-07 0.561904E-07 0.90.108410E-05 9001 10202 0.117312E-06 0.974810E-07 0.983083E-07 0.385422E-07 0.312283E-07 0.340161E-07 0.617253E-07 0.90.117850E-05 9001 10300 0.106110E-06 0.868497E-07 0.897928E-07 0.338026E-07 0.287059E-07 0.307150E-07 0.539455E-07 0.80.105309E-05 .......... 0 080141

Figure 8-18 ASPENB output population concentration/deposition file (in ASCII format) for example point source run (for 

9001 10101 0.887709E-07 0.774276E-07 0.779782E-07 0.336689E-07 0.245561E-07 0.273105E-07 0.490938E-07 0.840.954688E-06 9001 10102 0.936549E-07 0.847418E-07 0.825023E-07 0.381454E-07 0.256891E-07 0.294738E-07 0.546769E-07 0.90.104341E-05 9001 10201 0.106153E-06 0.891512E-07 0.903393E-07 0.360951E-07 0.286658E-07 0.312934E-07 0.561904E-07 0.90.108410E-05 9001 10202 0.117312E-06 0.974810E-07 0.983083E-07 0.385422E-07 0.312283E-07 0.340161E-07 0.617253E-07 0.90.117850E-05 9001 10300 0.106110E-06 0.868497E-07 0.897928E-07 0.338026E-07 0.287059E-07 0.307150E-07 0.539455E-07 0.80.105309E-05......... 0 080216

Figure 8-19 ASPENB output population concentration/deposition file (in ASCII format) for example point source run (for 
9-1

9.0 REFERENCES

Briggs, G.A.,1974. Diffusion Estimates for Small Emissions. In ERL, ARL USAEC Report

ATDL-106. U.S. Atomic Energy Commission, Oak Ridge, Tennessee.

Briggs, G.A.,1975. Plume Rise Predictions. In Lectures on Air Pollution and Environmental 

Impact Analyses, American Meteorological Society, Boston, Massachusetts.

EPA, 1992. User’s Guide for the Industrial Source Complex (ISC2) Dispersion Models. Volume

II - Description of the Model Algorithms. EPA-450/4-92-008b. U.S. Environmental

Protection Agency, Research Triangle Park, North Carolina.

McElroy, J.L. and Pooler, F., 1968. The St. Louis Dispersion Study. U.S. Public Health Service,

National Air Pollution Control Administration, Report AP-53.

Pasquill, F., 1976. Atmospheric Dispersion parameters in Gaussian Plume Modeling. Part II.

Possible Requirements for Change in the Turner Workbook Values. EPA-600/4-76/030b,

U.S. Environmental Protection Agency, Research Triangle Park, North Carolina.

Rodhe, H., 1980. “Estimate of Wet Deposition Pollutants Around a Point Source,” Atmospheric 

Environment, 14, 1197-1199.

Rosenbaum, A.S., Ligocki, M.P., Wei, Y.H., 1998. Modeling Cumulative Outdoor

Concentrations of Hazardous Air Pollutants. Prepared for U.S. EPA Office of Policy,

Planning, and Evaluation. Prepared by, Systems Applications International, a division of

ICF Kaiser International (SYSAPP-98-96/33R1). Available on the World Wide Web at:

http://www.epa.gov/CumulativeExposure. 

SAI, 1995. User’s Guide to the Variable-Grid Urban Airshed Model (UAM-V). SYSAPP95/027. Systems Applications International, San Rafael, California.

Turner, D.G., 1970. Workbook of Atmospheric Dispersion Estimates. PHS Publication No. 999-

AP-26. U.S. Department of Health, Education, and Welfare, National Pollution Control

Administration, Cincinnati, Ohio.
A-1

APPENDIX A ASPENA SUBROUTINE DESCRIPTIONS

ASPENA

Main driving routine for ASPENA model.

Called by: None

Calls to: HEADER, OPNFIL, POINT, STARIN

BID_DISP

Adjusts dispersion parameters to account for buoyancy-induced dispersion.

Called by: GAUSS

Calls to: None

DDMPR

Calculates the distance dependent momentum plume rise.

Called by: PRISE

Calls to: None

DEPOS

Retrieves deposition velocities for specified wind speed and stability class

Called by: GAUSS

Calls to: None

GAUSS

Performs Gaussian plume computations for each point source.

Called by: STACK

Calls to: BID_DISP, DEPOS, PRISE, VERTF, VGAUSZ

GAUSSZ

Calculates vertical dispersion parameters at each radial distance for each stability class

assuming no wake effects.

Called by: POINT

Calls to: SIGMAZ

HEADER

Writes header information to output files.

Called by: ASPENA

Calls to: None

LIST

Writes point source data to output files.

Called by: POINT, STACK

Calls to: None
A-2

OPNFIL

Opens and reads user input files.

Called by: ASPENA

Calls to: GETARG (System function)

POINT

Main routine to set up and process a single point source.

Called by: ASPENA

Calls to: GAUSSZ, LIST, SAVE, SKIP, STACK, STAR

PRISE

Calculates the plume rise for each type of plume ( buoyant/momentum) and for each

atmospheric stability class (unstable/neutral/stable).

Called by: GAUSS

Calls to: DDMPR

SAVE

Updates and saves concentration and deposition grids for each point source and time

block

Called by: POINT, STACK

Calls to: None

SIGMAZ

Calculates the vertical dispersion parameter, σz, from dispersion curves as a function of

downwind distance, stability class, and rural/urban classification.

Called by: GAUSSZ, VGAUSZ

Calls to: SZCOEF

SKIP

Routine to read point and stack parameters for “skipped” points. “Skipped” points are

those for which the STAR data from previously processed point is used.

Called by: POINT

Calls to: None

STACK

Main routine to process individual point sources.

Called by: POINT

Calls to: GAUSS, LIST, SAVE

STAR

Sets up STAR data for current plant.

Called by: POINT

Calls to: None
A-3

STARIN

Reads STAR data file and creates index of STAR stations.

Called by: ASPENA

Calls to: None

SZCOEF

Determines coefficients and ranges for calculation of rural dispersion 

parameter.

Called by: SIGMAZ

Calls to: None

VERT

Computes the Vertical Term for use in Gaussian plume equation.

Called by: GAUSS

Calls to: None

VGAUSZ

Calculates vertical dispersion parameter with wake effects using virtual distances.

Called by: GAUSS

Calls to: SIGMAZ
B-1

APPENDIX B ASPENA COMMON BLOCKS

Parameters : MXSTA = 500 – maximum number of met stations

MXSPEC = 150 – maximum number of species in run

common/srcblk/ : information concerning sources

ifips INTEGER plant FIPS code

utmx,utmy REAL plant location

itype INTEGER source type

iurb INTEGER urban/rural flag

isptyp INTEGER species type

idsrce CHAR source ID

common/metblk/ : information concerning STAR met data

istar INTEGER INWS index

nosc(6) INTEGER array of excluded stability classes

nows(6) INTEGER array of excluded wind speeds

nowd(16) INTEGER array of excluded wind directions

atemp(6) REAL array of temperatures

fp REAL frequency of precipitation

p REAL annual average precipitation

common/grdblk/ : information concerning radial receptor grid locations

nr INTEGER number of radial grid locations

rad(12) REAL radial distance to receptor locations

common/stkblk/ : information concerning stacks

rlon,rlat REAL stack location

stakh REAL stack height

stakd REAL stack diameter

stakv REAL stack exit gas velocity

stakt REAL stack exit gas temperature

ivent INTEGER stack/vent flag

ibldg INTEGER building downwash flag

bldw REAL building width

bldh REAL building height

idstk CHAR stack ID

common/chmblk/ : information concerning chemical species

nchem INTEGER number of chemical species

idchem INTEGER chemical ID

q(mxspec,8) REAL emission rates

dk(6,8) REAL reactive decay rates
B-2

common/oldblk/ : information concerning building downwash

olda REAL area of nearby building at last stack

comon/sigblk/ : information concerning vertical dispersion parameters

sigz(12,6) REAL vertical dispersion without wake effects

vsigz(12,6) REAL vertical dispersion with wake effects

delta(6) REAL contribution to vertical distance due to building

common/conblk/ : information concerning ambient concentrations

c(16,12) REAL ambient concentrations

common/dep/ : information concerning depositions

dep1(16,12) REAL dry deposition flux to land

dep2(16,12) REAL dry deposition flux to agricultural land

dep3(16,12) REAL dry deposition flux to water

depw(16,12) REAL wet deposition flux 

iddep INTEGER dry deposition flag

iwdep INTEGER wet deposition flag

common/runblc/ : information concerning run ID

idrun CHAR run ID

idfile CHAR run filename

common/runblk/ :

inps(10) LOGICAL

invers INTERGER

common/stablk/ : information concerning met data

nsta INTEGER number of met stations

ista(mxsta) INTEGER met station ID

stax,stay(mxsta)REAL met station location

stas(8, mxsta) REAL average wind speeds

htmi(8, mxsta)REAL mixing heights

atmp(3, mxsta)REAL average temperatures

fps(mxsta) REAL precipitation frequencies

p(mxsta) REAL precipitation amounts

common/lmet/ : information concerning various options

lpsuedo LOGICAL flag indicating pseudo-point

lstrec INTEGER index of last record processed

lskp LOGICAL flag indicating that station is skipped

irec INTEGER index of current record

iurblst INTEGER urban/rural flag of last processed source
B-3

common/maxcon/ : information concerning concentrations

xc(16,12) REAL array of maximum concentrations

xcavg(16,12) REAL array of average concentrations

common/totdep/ : information concerning total depositions

deptot(16,12,3)REAL array of total depositions
C-1

APPENDIX C INPUT AND OUTPUT FILE FORMATS

C.1 DESCRIPTION OF ASPEN INPUT FILE CONTENT AND FORMAT

C.1.1 Description of Emission/Control File

Table C-1 Description of Emission/Control File

Record No. Variables Format Description

1 IDRUN A40 Run identification

IDFILE A20 Emission file identifier

ISPTYP I1 Species type (0 = gas; 1 = fine part.; 2 = coarse part.)

IDDEP I1 = 0, include dry deposition; = 1, no dry deposition

IWDEP I1 = 0, include wet deposition; = 1, no wet deposition

2 DK(IC,1) 6F10 Decay rates for 6 stability classes for time block 1

3 DK(IC,2) 6F10 Decay rates for 6 stability classes for time block 2

4 DK(IC,3) 6F10 Decay rates for 6 stability classes for time block 3

5 DK(IC,4) 6F10 Decay rates for 6 stability classes for time block 4

6 DK(IC,5) 6F10 Decay rates for 6 stability classes for time block 5

7 DK(IC,6) 6F10 Decay rates for 6 stability classes for time block 6

8 DK(IC,7) 6F10 Decay rates for 6 stability classes for time block 7

9 DK(IC,8) 6F10 Decay rates for 6 stability classes for time block 8

10 IFIPS I5 State/County FIPS

IDSRC A10 Plant ID for points; census tract no. for pseudo points

UTMX F10 Longitude (decimal degrees)

UTMY F10 Latitude (decimal degrees)

ITYPE I1 Source type (0 or blank for points; 3 = pseudo points)

IURB I1 Urban/Rural flag (1 = urban; 2 = rural)

11 INWS I5 Star station (NWS) ID (blank or 0 = use nearest station)

NOSC(6) 6I1 Excluded stability classes

NOWS(6) 6I1 Excluded wind speeds

NOWD(6) 6I1 Excluded wind direction

12 RAD (12) 12F5 Polar grid radial distances (km) (blank – use defaults)

13 IDSTK A5 Stack ID for points; FIPS code for pseudo points

RLON F10 Longitude (decimal degrees)

RLAT F10 Latitude (decimal degrees)

STAKH F10 Stack height (m)

STAKD F10 Stack exit diameter (m)

STAKV F10 Stack exit velocity (m/sec)

STAKT F10 Stack exit temperature (Deg K)

IVENT I1 Vent/Stack flag (0 = stacked; 1 = non-stacked)

IBLDG I1 Build flag (0 = no building; 1 = building)

BLDW F10 Width of nearby building (m)

BLDH F10 Height of nearby building (m)

14 IDCHEM I6 5-digit Saroad code plus 1-digit source category code

Q 8F10 Emissions (g/sec) for eight 3-hour time blocks
C-2

Note:

• UTMX/UTMY and RLON/RLAT specify the locations of point sources, or the locations

of the census tract centroid for pseudo point sources (i.e., area and mobile sources).

• Record 14 is repeated for each HAP emitted from the stack or census tract.

• Records 10 through 14 are repeated for each facility or census tract, followed by two

blank lines to indicate the end of the data record for the facility or census tract

• The emission record of the last facility or census tract will be followed by five blank lines

to indicate the end of the file.

• For multiple pseudo point sources that use meteorological data from the same STAR

station, and that have the same urban/rural designation, ASPEN will calculate the same

normalized concentration/deposition receptor grid. To save computing time, the emission

records for pseudo point sources should be entered so that all sources that will use the

same meteorological station ID (NWS ID) and urban/rural designation are grouped

together. ASPEN checks for this grouping, and omits redundant calculations. This is the

preferred method for treating pseudo-point since the code will not need to re-search the

STAR data for the appropriate station since the data will already be stored in memory.

C.1.2 Description of Meteorological Index File

The meteorological index file is in binary format. There is one record for each STAR station

containing the following information.

Table C-2 Description of meteorological index file

Variables Data Type Description

ISTA Integer Star (NWS) station ID

STAX Real Longitude of the station (decimal degree)

STAY Real Latitude of the station (decimal degree)

ATEMP (1) Real Annual average daily maximum temperature (Deg K)

ATEMP (2) Real Annual average daily minimum temperature (Deg K)

ATEMP (3) Real Annual average temperature (Deg K)

PS Real Annual average precipitation (cm)

FPS Real Fraction of time with precipitation

STAS Real Not used (eight zeros)

HTMI Real Annual average mixing heights for eight 3-hour time

blocks

C.1.3 Description of STAR Data

The STAR input file is in binary format Each record contains the STAR data for one time block

of one star station, and includes the following variables.
C-3

Table C-3 Description of STAR Data

Variables Data Type Description

IWB Integer Star (NWS) station ID

IHR Integer Time block number

FSTAR (nd, ns, nc) Real STAR data for the time block

 nd = number of wind directions (16)

 ns: = number of stability classes (6)

 nc = number of wind speed categories (6)

C.1.4 Description of Census Tract Index File 

The census tract index file is in binary format, and it contains the following variables.

Table C-4 Description of census tract index file

Record No. Variables Data Type Description

1 NSTATES Integer Total number of states included in the data

NCOUNTIES Integer Total number of counties included in the

data

NTRACTS Integer Total number of tracts included in the data

2 STFIP Integer State FIPS code

STMNLN Real State minimum longitude (decimal degree)

STMNLT Real State minimum latitude (decimal degree)

STMXLN Real State maximum longitude (decimal degree)

STMXLT Real State maximum latitude (decimal degree)

COPTR Integer Pointer to the first county in the state

NUMCO Integer Total number of counties in the state

3 COFIPS Integer County FIPS code

COMNLN Real County minimum longitude (decimal

degree)

COMNLT Real County minimum latitude (decimal degree)

COMXLN Real County maximum longitude (decimal

degree)

COMXLT Real County maximum latitude (decimal

degree)

TRPTR Integer Pointer to the first tract in the county

NUMTR Integer Total number of tracts in the county

Note:

Record 2 is repeated for all states included in the census tract data file.

Record 3 is repeated for all counties included in the census tracts data file.
C-4

C.1.5 Description of Census Tract Data 

The census tract data is in binary format. There is one record for each census tract containing the

following variables.

Table C-5 Description of census tract data

Variables Data

Type

Description

TRFIPS Integer State/County FIPS code, tract FIPS code

TRLON Real Longitude of the tract centroid (decimal degree)

TRLAT Real Latitude of the tract centroid (decimal degree)

UFLAG Integer Urban/Rural flag of the tract (1 = urban; 2 = rural)

TRRAD Real Hypothetical tract radius (m)

C.2 DESCRIPTION OF ASPEN OUTPUT FILE CONTENT AND FORMAT

C.2.1 Description of Normalized Source Concentration/Deposition File

The normalized source concentration/deposition file is the output of the ASPEN dispersion

module (ASPENA) and input to the ASPEN mapping module (ASPENB). It is in binary format.
C-5

Table C-6 Description of Normalized Source Concentration/Deposition File

Record

No.

Variables Data Type Description

1 ID Character Emission file identifier

VERSION Integer Version number

2 IDSRC Character Plant ID for points; census tract no. for pseudo points

IDSTAK Character Stack ID for points; FIPS code for pseudo points

ITYPE Integer Source type

RLON Real Longitude (decimal degree)

RLAT Real Latitude (decimal degree)

IURB Integer Urban/Rural flag

NCHEM Integer Number of HAPs with emissions

ICHEM(I),(RATE

(I,J),J=1,NUMGR

D),I=1,NCHEM)

Integer

Real

5-digit HAP SAROAD code plus 1-digit source

category code,

emission rates for eight 3-hour time blocks

NC Integer Number of radial distances

R(I),I=1,NC Real Polar grid radial distances (km)

NL Integer Number of azimuth direction

F Real Start bearing (0 degree)

4 (C(I,J,K),I=1,NL),

J=1,NC

Real Normalized concentration for the receptor grid

5 (DUL(I,J),I=1,NL)

,J=1,NC

Real Normalized urban land deposition for the receptor grid

6 (DRL(I,J),I=1,NL)

,J=1,NC

Real Normalized rural land deposition for the receptor grid

7 (DW(I,J),I=1,NL),

J=1,NC

Real Normalized wet deposition for the receptor grid

Note:

Record 4 is repeated for each of eight 3-hour time blocks.

Record 2 through record 7 is repeated for each facility or census tract.

C.2.2 Description of Population Concentration/Deposition File

The population concentration/deposition file is the output of the ASPEN mapping module

(ASPENB). It is in binary format. There is one record for each census tract containing the

following information.
C-6

Table C-7 Description of Population Concentration/Deposition File

Variables Data Type Description

STCO Integer State/County FIPS code

TRACT Integer Census tract FIPS code

CONC Real concentration in eight 3-hour time blocks (μg/m3

) for each source

category

DLAND Real deposition flux on land (μg/m2

-day) for each source category

DWATER Real deposition flux on water (μg/m2

-day) for each source category

An empty record with zeros for the first two fields, followed by the 5-digit HAP SAROAD code

and zeros for the rest of nine fields, indicates the end of the file.

C.2.3 Description of Source Listing File

The source listing file is the output of the ASPEN dispersion module (ASPENA) used for

purpose of quality assurance. It is in ASCII format. There is one record for each emission

source processed by ASPENA, containing the following variables.

Table C-8 Description of source listing file

Variables Data Type Description

IFIPS Integer State/County FIPS code

IDSRCE Character Plant ID for points; census tract no. for pseudo points

UTMX Real Longitude (decimal degrees)

UTMY Real Latitude (decimal degrees)

ITYPE Integer Source type (0 or blank for points; 3 = pseudo points)

IURB Integer Urban/Rural flag (1 = urban; 2 = rural)

The last record of the source listing contains zeros for the variables to indicate the end of the file.

C.2.4 Description of the Listing File

The listing file is an output file of the ASPEN mapping module (ASPENB). It lists the

normalized source concentration/deposition input filenames processed by ASPENB. ASPENB

checks this file each time a simulation is started to prevent processing a file twice.
C-7

C.3 DECAY RATES BY REACTIVITY CLASS

Reactivity Class 1 - non reactive

Stability Class A B C D E F

Time Block 1 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 2 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 3 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 4 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 5 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 6 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 7 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 8 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Reactivity Class 2 - particulate matter (five)

Stability Class A B C D E F

Time Block 1 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 2 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 3 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 4 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 5 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 6 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 7 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 8 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Reactivity Class 3 - particulate matter (coarse)

Stability Class A B C D E F

Time Block 1 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 2 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 3 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 4 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 5 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 6 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 7 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Time Block 8 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01 0.00E+01

Each pollutant is assigned a reactivity class (Rosenbaum, et al., 1998)
C-8

Reactivity Class 4 - medium low reactivity

Stability Class A B C D E F

Time Block 1 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07

Time Block 2 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07

Time Block 3 1.18E-05 7.89E-06 3.95E-06 1.97E-06 9.87E-07 9.87E-07

Time Block 4 7.89E-05 5.92E-05 3.95E-05 1.97E-05 9.87E-07 9.87E-07

Time Block 5 6.71E-05 5.13E-05 3.55E-05 1.97E-05 9.87E-07 9.87E-07

Time Block 6 2.37E-05 1.78E-05 1.18E-05 7.89E-06 9.87E-07 9.87E-07

Time Block 7 1.97E-06 1.97E-06 1.97E-06 9.87E-07 9.87E-07 9.87E-07

Time Block 8 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07 9.87E-07

Reactivity Class 5 - medium reactivity

Stability Class A B C D E F

Time Block 1 2.47E-06 2.47E-06 2.47E-06 2.47E-06 2.47E-06 2.47E-06

Time Block 2 2.47E-06 2.47E-06 2.47E-06 2.47E-06 2.47E-06 2.47E-06

Time Block 3 2.96E-05 1.97E-05 9.87E-06 4.93E-06 2.47E-06 2.47E-06

Time Block 4 1.97E-04 1.48E-04 9.87E-05 4.93E-05 2.47E-06 2.47E-06

Time Block 5 1.68E-04 1.28E-04 8.88E-05 4.93E-05 2.47E-06 2.47E-06

Time Block 6 5.92E-05 4.44E-05 2.96E-05 1.97E-05 2.47E-06 2.47E-06

Time Block 7 4.93E-06 4.93E-06 4.93E-06 2.47E-06 2.47E-06 2.47E-06

Time Block 8 2.47E-06 2.47E-06 2.47E-06 2.47E-06 2.47E-06 2.47E-06

Reactivity Class 6 - medium high reactivity

Stability Class A B C D E F

Time Block 1 4.93E-06 4.93E-06 4.93E-06 4.93E-06 4.93E-06 4.93E-06

Time Block 2 4.93E-06 4.93E-06 4.93E-06 4.93E-06 4.93E-06 4.93E-06

Time Block 3 5.92E-05 3.95E-05 1.97E-05 9.87E-06 4.93E-06 4.93E-06

Time Block 4 3.95E-04 2.96E-04 1.97E-04 9.87E-05 4.93E-06 4.93E-06

Time Block 5 3.35E-04 2.57E-04 1.78E-04 9.87E-05 4.93E-06 4.93E-06

Time Block 6 1.18E-04 8.88E-05 5.92E-05 3.95E-05 4.93E-06 4.93E-06

Time Block 7 9.87E-06 9.87E-06 9.87E-06 4.93E-06 4.93E-06 4.93E-06

Time Block 8 4.93E-06 4.93E-06 4.93E-06 4.93E-06 4.93E-06 4.93E-06
C-9

Reactivity Class 7 - very high reactivity

Stability Class A B C D E F

Time Block 1 5.01E-04 5.01E-04 5.01E-04 5.01E-04 5.01E-04 5.01E-04

Time Block 2 3.21E-05 3.21E-05 3.21E-05 3.21E-05 5.01E-04 5.01E-04

Time Block 3 9.00E-05 6.04E-05 3.08E-05 1.60E-05 5.01E-04 5.01E-04

Time Block 4 5.93E-04 4.45E-04 2.97E-04 1.49E-04 8.14E-06 8.14E-06

Time Block 5 5.04E-04 3.86E-04 2.67E-04 1.49E-04 8.14E-06 8.14E-06

Time Block 6 1.79E-04 1.34E-04 9.00E-05 5.99E-05 8.14E-06 8.14E-06

Time Block 7 3.95E-05 3.95E-05 3.95E-05 3.21E-05 5.01E-04 5.01E-04

Time Block 8 5.01E-04 5.01E-04 5.01E-04 5.01E-04 5.01E-04 5.01E-04

Reactivity Class 8 - high reactivity

Stability Class A B C D E F

Time Block 1 1.23E-05 1.23E-05 1.23E-05 1.23E-05 1.23E-05 1.23E-05

Time Block 2 1.23E-05 1.23E-05 1.23E-05 1.23E-05 1.23E-05 1.23E-05

Time Block 3 1.48E-04 9.87E-05 4.93E-05 2.47E-05 1.23E-05 1.23E-05

Time Block 4 9.87E-04 7.40E-04 4.93E-04 2.47E-04 1.23E-05 1.23E-05

Time Block 5 8.39E-04 6.41E-04 4.44E-04 2.47E-04 1.23E-05 1.23E-05

Time Block 6 2.96E-04 2.22E-04 1.48E-04 9.87E-05 1.23E-05 1.23E-05

Time Block 7 2.47E-05 2.47E-05 2.47E-05 1.23E-05 1.23E-05 1.23E-05

Time Block 8 1.23E-05 1.23E-05 1.23E-05 1.23E-05 1.23E-05 1.23E-05

Reactivity Class 9 - low reactivity

Stability Class A B C D E F

Time Block 1 4.94E-07 4.94E-07 4.94E-07 4.94E-07 4.94E-07 4.94E-07

Time Block 2 4.94E-07 4.94E-07 4.94E-07 4.94E-07 4.94E-07 4.94E-07

Time Block 3 5.90E-06 3.95E-06 1.98E-06 9.85E-07 4.94E-07 4.94E-07

Time Block 4 3.94E-05 2.96E-05 1.97E-05 9.85E-06 4.94E-07 4.94E-07

Time Block 5 3.36E-05 2.57E-05 1.78E-05 9.85E-06 4.94E-07 4.94E-07

Time Block 6 1.19E-05 8.90E-06 5.90E-06 3.95E-06 4.94E-07 4.94E-07

Time Block 7 9.85E-07 9.85E-07 9.85E-07 4.94E-07 4.94E-07 4.94E-07

Time Block 8 4.94E-07 4.94E-07 4.94E-07 4.94E-07 4.94E-07 4.94E-07
D-1

APPENDIX D GLOSSARY

ASPEN -- Assessment System for Population Exposure Nationwide

ASCII -- American Standard Code for Information Interchange, a standard set of codes used by

computers and communication devices. Sometimes used to refer to files containing only such

standard codes, without any application-specific codes such as might be present in a document

file from a word processor program.

Binary File -- A file written without the use of a FORTRAN FORMAT statement.

Directory -- A logical subdivision of a disk used to organize files stored on a disk.

Dispersion Model -- A group of related mathematical algorithms used to estimate (model) the

dispersion of pollutants in the atmosphere due to transport by the mean (average) wind and small

scale turbulence.

DOS -- Disk Operating System. Software that manages applications software and provides an

interface between applications and the system hardware components, such as the disk drive,

terminal, and keyboard.

EPA -- U. S. Environmental Protection Agency.

Error message -- A message written by the model to the error/message file whenever an error is

encountered that will inhibit data processing.

ISCLT -- Industrial Source Complex - Long Term Dispersion Model.

Joint Frequency Distribution -- The joint frequency of wind direction sector, wind speed class

and stability category (see also STAR).

Mixing Height -- The depth through which atmospheric pollutants are typically mixed by

dispersive processes.

Pasquill Stability Categories -- A classification of the dispersive capacity of the atmosphere,

originally defined using surface wind speed, solar insulation (daytime) and cloudiness

(nighttime). They have since been reinterpreted using various other meteorological variables.

STAR -- STability ARray, a joint frequency distribution summary of stability category, wind

speed and wind direction. The STAR data are used as input for the ISC Long Term dispersion

model.
D-2

Station Identification -- An integer or character string used to uniquely identify a station or site as

provided in the upper air (TD-5600 and TD-6201), mixing height (TD-9689), and surface

weather (CD-144 and TD-3280) data formats available from NCDC. 

Syntax -- The order, structure and arrangement of the inputs that make of the input runstream

file, specifically, the rules governing the placement of the various input elements including

pathway IDs, keywords, and parameters.

Wind Profile Exponent -- The value of the exponent used to specify the profile of wind speed

with height according to the power law (see Section 1.1.3 of Volume II).
TECHNICAL REPORT DATA

(Please read Instructions on reverse before completing)

1. REPORT NO.

 EPA-454/R-00-017 2. 3. RECIPIENT'S ACCESSION NO.

4. TITLE AND SUBTITLE

USER’S GUIDE for the ASSESSMENT SYSTEM FOR POPULATION

EXPOSURE NATIONWIDE MODEL (ASPEN, VERSION 1.1) 

5. REPORT DATE

 April 2000 

6. PERFORMING ORGANIZATION CODE

7. AUTHOR(S)

 8. PERFORMING ORGANIZATION REPORT NO.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

 

 

10. PROGRAM ELEMENT NO.

11. CONTRACT/GRANT NO. 

 EPA Contract No. 68D98006

12. SPONSORING AGENCY NAME AND ADDRESS

 U.S. Environmental Protection Agency

 Office of Air Quality Planning and Standards

 Emissions, Monitoring & Analysis Division

 Research Triangle Park, NC 27711

13. TYPE OF REPORT AND PERIOD COVERED

 Final Report

14. SPONSORING AGENCY CODE

15. SUPPLEMENTARY NOTES

 EPA Work Assignment Manager: Jawad S. Touma 

16. ABSTRACT

This user’s guide provides documentation for the Assessment System for Population

Exposure Nationwide (ASPEN, Version 1.1), referred to hereafter as ASPEN. It includes

a technical description of the ASPEN algorithms, user instructions for running the

model and a tutorial for getting started. The ASPEN model consists of a dispersion and

mapping module. The dispersion module is a Guassian formulation for estimating ambient

annual average concentrations at a set of fixed receptors within the vicinity of the

emission source. The mapping module produces a concentration at each census tract.

Input data needed are emissions data, meteorological data and census tract data.

17. KEY WORDS AND DOCUMENT ANALYSIS

a. DESCRIPTORS b. IDENTIFIERS/OPEN ENDED TERMS c. COSATI Field/Group

 Air Pollution

 Air Quality Dispersion Models 

 Meteorology 

 Air Toxics 

 

18. DISTRIBUTION STATEMENT

 Release Unlimited

19. SECURITY CLASS (Report)

 Unclassified 21. NO. OF PAGES 109

20. SECURITY CLASS (Page)

 Unclassified 22. PRICE

 EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION IS OBSOLETE