PB87-232641
SENSITIVITY ANALYSIS FOR APPLICATION OF INHALATION
EXPOSURE METHODOLOGY (IEM) TO STUDIES OF HAZARDOUS
WASTE MANAGEMENT FACILITIES
Oak Ridge National Laboratory
Oak Ridge, TN
Aug 87
U.S. DEPARTMENT OF COMMERCE
National Technical Information Service
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PB87-232641
EPA/600/2-87/071
August 1987
SENSITIVITY ANALYSIS FOR APPLICATION OF THE INHALATION EXPOSURE
METHODOLOGY (IEM) TO STUDIES OF HAZARDOUS WASTE MANAGEMENT FACILITIES
by
F. R. O'Donnell
Health and Safety Research Division
and
C. C. Gilmore
Energy Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee 37830
LAG No. DW14930265-01-1
Project Officer
Benjamin L. Blaney
Thermal Destruction Branch
Hazardous Waste Engineering Research Laboratory
Cincinnati, Ohio 45268
This research was conducted in cooperation with the
U.S. Department of Energy under Martin Marietta
Energy Systems, Inc. contract DE-AC05-840R21400
HAZARDOUS WASTE ENGINEERING RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
REPRODUCED BY
NATIONAL TECHNICAL •
INFORMATION SERVICE:
U.S. DEPARTMENT OF COMMERCE
SPRINGFIELD, VA. 22161
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'' EPA/600/2-87/071 . I
«. TITlt ANO SUSTITLI
Sensitivity Analysis for Application of Inhalation
Exposure Methodology (IEM) to Studies of Hazardous
Waste Management Facilities
T. AVTMORIS)
F. R. O'Donnell and C. C. Gilmore
1 PtRFORMINC ORGANIZATION NAMf ANO AODRfSS
Oak Ridge National Laboratory
P.O. Box X
Oak Ridge, Tennessee 37830
12. SPONSORING A6INCT NAM( ANO AOORtSS
Hazardous Waste Engineering Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
1 RICi'UNT-S ACCtSS'Q* *A. .
PB87 23264
August 1987
1 *••* ORMING ORGANIZATION C
10 PROGRAM tkiMINf N6. ' '
DW14930265-01-1
1/1/84 - 12/31/84
1« SPONSORING AGtKC* COO(
EPA/ 12/600
I/AS
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COVIRIO
TECHNICAL REPORT DATA
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NOTtt
The Inhalation Exposure Methodology (IEM) is an integrated system of
computer programs that simulates the atmospheric transport of and the resulting
human exposures to pollutants released from one or more sources at an industrial
complex. This study was undertaken to determine the sensitivity of IEM pre-
dictions of pollution concentrations and population exposures to (1) variations
of selected, user-supplied source, meteorological, climatologies!, and pollutant
parameter values and (2) use of the three available source modeling options to
represent emission sources found at hazardous waste management facilities (HWMFs).
These sources include incinerators and associated structures, storage, and treat-
ment tanks, drum stacks, process buildings, surface impoundments, waste piles,
and land treatment areas.
7.
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U. OlSTRiSUTlON STATEMINT
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-------
NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
ii
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FOREWORD
Today's rapidly developing and changing technologies and Industrial
products and practices frequently carry with them Increased generation
of solid and hazardous wastes. These materials, if improperly dealt
with, can threaten both public health and the environment. Abandoned
waste sites and accidental releases of toxic and hazardous substances to
the environment also have important environmental and public health
implications. The Hazardous Waste Engineering Research Laboratory
assists in providing an authoritative and defensible engineering basis
for assessing and solving these problems. Its products support the
policies, programs and regulations of the Environmental Protection
Agency, the permitting and other responsibilities of state and local
governments and the needs of both large and small businesses in handling
their wastes responsibly and economically.
This report discusses the sensitivity of predictions made by the
Inhalation Exposure Methodology (IEM) to the more Important, user-
controlled input parameters and modeling options that are applicable to
low-level emission sources found at hazardous waste management
facilities. It is intended to provide additional information on the use
of IEM to staff and contractors of EFA interested in modeling releases
of pollutants from industrial complexes and in estimating associated
population exposures. For further information, please contact the
Alternative Technologies Division of the Hazardous Waste Engineering
Research Laboratory.
Thomas R. Hauser, Director
Hazardous Waste Engineering Research Laboratory
iii
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ABSTRACT
The Inhalation Exposure Methodology (IEM) is an integrated system
of computer programs that simulates the atmospheric transport of and the
resulting human exposures to pollutants released from one or more
sources at an industrial complex. This study was undertaken to
determine the sensitivity of IEM predictions of pollutant concentrations
and population exposures to (1) variations of selected, user-supplied
source, climatological, and pollutant parameter values and (2) use of
the three available source modeling options to represent emission
sources found at hazardous waste management facilities (HWMFs). These
sources include incinerators and associated structures, storage and
treatment tanks, drum stacks, process buildings, surface impoundments,
landfills, waste piles, and land treatment areas.
This report was submitted by the Oak Ridge National Laboratory in
partial fulfillment of IAG No. DW14930265-01-1 under sponsorship of the
U.S. Environmental Protection Agency. This report covers the period
January 1, 1984, to December 31, 1984, and work was completed in January
1986.
IV
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CONTENTS
Page
Foreword iii
Abstract iv
Figures vii
Tables x
Acknowledgements xii
1. Introduction 1
Background 1
Purpose and Structure of this Report 3
General Overview of the IEH System 3
2. Summary 9
3. Discussion of the Exposure Estimation Procedure 11
Sector-Segment Concentrations 12
Sector-Segment Populations 14
Exposure Estimation 15
4. Method Used for the Sensitivity Analysis . 17
5. Discussion of Parameters that Affect Concentration Estimates ... 21
Meteorological and Climatological Parameters 21
Source Related Parameters 47
Pollutant Related Parameters 53
Receptor Location 59
6. Discussion of Source Representation Options 63
Stacks vs. Stacks with Buiding Wake Effects 69
Stacks vs. Areas 69
Stacks vs. Volumes 69
Area vs. Areas 73
Areas vs. Volumes 73
Volume vs. Volumes 73
References . 75
Appendixes
A. PGPC (X/Q) Profiles by Stability Category for
Several Release Heights and Each Source 79
B. TGRC (X/Q) Profiles by Stability Category for
Several Release Heights and Each Source 95
C. PGPC (X/Q) Profiles by Release Height for Each
Stability Category and Each Source 108
D. TGRC (X/Q) Profiles by Release Height for Each
Stability Category and Each Source 124
E. PGPC (X/Q) Profiles by Source Width for Each
Stability Category and Release Height 137
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F. TGRC (X/Q) Profiles by Source Width for Each
Stability Category and Release Height. . 153
Glossary. 169
List of Abbreviations and Symbols 171
vi
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FIGURES
Number Page
1 Schematic representation of program group interactions in
the IBM and their use of executive (EXEC) programs 5
2 Orientation of the grid and centroid coordinate systems
used in the IEM (see explanation in text) 7
3 Comparison of grid-point and sector-segment concentrations
for releases from 0- and 20-m high stack sources with no
plume rise under F stability conditions 13
4 The wind-speed scaling factor (equals 1.0 for 0.75 m/s) ... 25
5 FGFC profiles for releases from a 6.1-m high tank farm
represented as four stack sources with adjacent structures 50
6 TGRC profiles for releases from a 6.1-m high tank farm
represented as four stack sources with adjacent structures 51
7 Illustration of decay term behavior 54
8 Effects of deposition on concentration predictions for
releases from a 20-m high stack source 56
9 TGRC profiles for releases from a 5-m high process building 64
10 TGRC profiles for releases from a 10-m high process building 65
11 TGRC profiles for releases from a 6.1-m high tank farm 67
12 TGRC profiles for releases from a 3.05-m high tank farm 68
13 PGFC (X/Q) profiles by stability category for several
release heights from the stack source 80
14 PGPC (X/Q) profiles by stability category for several
release heights from the 14.1-m square source 83
15 PGPC (X/Q) profiles by stability category for several
release heights from the 80.6-m square source 86
VI1
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16 PGPC (X/Q) profiles by stability category for several
release heights from the 316.2-m square source 89
17 PGPC (X/Q) profiles by stability category for several
release heights from the 2236.1-m square source 92
]
18 TGRC (X/Q) profiles by stability category for several
release heights from the 14.1-m square source 96
19 TGRC (X/Q) profiles by stability category for several
release heights from the 80.6-m square source . . 99
20 TGRC (X/Q) profiles by stability category for several
release heights from the 316.2-m square source 102
21 TGRC (X/Q) profiles by stability category for several
release heights from the 2236.1-m square source 105
22 PGPC (X/Q) profiles by release height for each stability
class from the stack source 109
23 PGPC (X/Q) profiles by release height for each stability
class from the 14.1-m square source 112
24 PGPC (X/Q) profiles by release height for each stability
class from the 80.6-m square source 115
25 PGFC (X/Q) profiles by release height for each stability
class from the 316.2-m square source 118
26 PGPC (X/Q) profiles by release height for each stability
class from the 2236.1-m square source 121
27 TGRC (X/Q) profiles by release height for each stability
class from the 14.1-m square source 125
28 TGRC (X/Q) profiles by release height for each stability
class from the 80.6-m square source • 128
29 TGRC (X/Q) profiles by release height for each stability
class from the 316.2-m square source 131
30 TGRC (X/Q) profiles by release height for each stability
class from the 2236.1-m square source 134
31 PGPC (X/Q) profiles by source width for each stability
class and 0-m-high releases 138
32 PGPC (X/Q) profiles by source width for each stability
class and 5-m-high releases 141
viii
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33 PGPC (X/Q) profiles by source width for each stability
class and 10-m-high releases 144
34 PGPC (X/Q) profiles by source width for each stability
class and 15-m-high releases 147
35 PGPC (X/Q) profiles by source width for each stability
class and 20-m-high releases 150
36 TGRC (X/Q) profiles by source width for each stability
class and 0-m-high releases 154
37 TGRC (X/Q) profiles by source width for each stability
class and 5-m-high releases 157
38 TGRC (X/Q) profiles by source width for each stability
class and 10-m-high releases 160
39 TGRC (X/Q) profiles by source width for each stability
class and 15-m-high releases 163
40 TGRC (X/Q) profiles by source width for each stability
class and 20-m-high releases 166
ix
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TABLES
Number Page
1 Typical source dimensions at HWMFs 4
2 Total exposure and exposed population estimates produced by
the IEM and the HEM within 20 km of six sites 16
3 Composite of stability and wind-speed class frequencies as
reported for eight scattered weather stations 23
4 Summary of maximum concentrations and exposures, stack 26
5 Summary of maximum concentrations and exposures, 200-m2 area 27
6 Summary of maximum concentrations and exposures, 6500-m2 area 28
7 Summary of maximum concentrations and exposures, 100,000-m2 area. ... 29
8 Summary of maximum concentrations and exposures, 5,000,000-m2 area. . . 30
9 Values (pg/m3) and locations (km) of maximum FGFCs for
receptors beginning at 0.15 km downwind 32
10 Values (jug/m3) and locations (km) of maximum TGRCs for
receptors beginning at 0.15 km downwind 33
11 Values (pg/m3) and locations (km) of maximum FGFCs for
receptors beginning at 0.30 km downwind 34
12 Values (/jg/m3) and locations (km) of maximum TGRCs for
receptors beginning at 0.30 km downwind 35
13 Values (pg/m3) and locations (km) of maximum PGPCs for
receptors beginning at 1.25 km downwind 36
14 Values (/jg/m3) and locations (km) of maximum TGRCs for
receptors beginning at 1.25 km downwind 37
15 Stability category sequences, in order of increasing maximum
concentration, for each source, release height, and first
receptor location 38
16 PSEFs (108 person-/ig/m3) for first receptor at 0.15 km 39
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17 TEPs (108 person-/ig/m3) for first receptor at 0.15 tan 40
18 PSEPs (108 person-^g/m3) for first receptor at 0.30 km 41
19 TEPs (108 person-jig/m3) for first receptor at 0.30 km 42
20 PSEPs (108 person-^g/m3) for first receptor at 1.25 km 43
21 TEPs <108 person-/*g/m3) for first receptor at 1.25 km 44
22 Stability categories giving maximum PGFCs and TGRCs for
each source, release height, and first receptor location 46
23 Summary of maximum concentrations and exposures for the
building wake effects study 52
24 Summary of maximum concentrations and exposures for the
deposition effects study 60
25 Effects of several receptor array choices on maximum
concentration and total exposure potential predictions 61
26 Summary of maximum concentrations and exposures for the
process building simulation calculations 66
27 Summary of maximum concentrations and exposures for the
tank-farm simulation calculations 70
28 Percent differences in predicted maximum TGRC values between the
first and second source representations of the indicated pairs. ... 71
29 Percent differences in predicted TEP values between the first
and second source representations of the indicated pairs 72
xi
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ACKNOWLEDGEMENTS
It is a pleasure to acknowledge the assistance of
Dr. Benjamin L. Blaney, Dr. David E. Layland, and Dr. William B. Peterson
of the U.S. Environmental Protection Agency and of Dr. Brian D. Murphy and
Dr. Frank C. Koraegay of the Oak Ridge National Laboratory. Their comments
and insights during the review of this document were most helpful.
XII
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SECTION 1
INTRODUCTION
BACKGROUND
The Inhalation Exposure Methodology (IEM) is an integrated system of
computer programs that simulates the atmospheric transport of and the
resulting human exposures to pollutants released from one or more sources at
an industrial complex.1 The IEM uses a Gaussian-plume atmospheric dispersion
model to calculate annual-average, sector-averaged, centerline, ground-level,
air concentrations of released pollutants at user-selected receptor points.
It uses these concentrations to calculate average concentrations over each
sector segment of a user-specified polar grid. Finally, it multiplies the
sector-segment-averaged concentrations and their corresponding sector-segment
populations to give estimates of human exposures to the released pollutants.
Although applicable to a variety of problems, the IEM was developed as a tool
for estimating pollutant concentrations and associated human exposures in the
vicinity of hazardous waste management facilities (HWMFs).
An interactive version of the IEM system has been installed, for use by
contractors and staff of the U. S. Environmental Protection Agency, on the IBM
system at the National Computer Center, Research Triangle Park, North
Carolina.1 This version provides automatic access to and linkage of on-line
(1) meteorological data, (2) population data, (3) a slightly modified version
(called ISCLTM) of the long-term version of the Industrial Source Complex
(ISCLT) Dispersion Model,* and (4) a concentration-exposure estimation program
(CONEX). Persons wishing to use this version of the IEM should contact their
Project Officers to arrange access to the IBM system and the IEM programs and
data files. These persons also should consult the IEM user's guide1 and its
addendum,2 and the ISCLT user's guide3 and revisions.4
Whenever a computer simulation of reality, such as the IEM, is used to
predict the impacts of an activity, concern arises about the accuracy
(validity) of the predictions. This accuracy is dependent on both the
accuracy of the computing algorithms (how well the model calculations match
reality) and the certainty of the values assigned to the required input
* The calculations performed by the ISCLTM are identical to those performed
by the ISCLT; the only differences between the two codes are in sections
that control the flow of input and output data.
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parameters (although the best available values are used, they may be
approximations or may be selected from a range of possible values). Ideally,
the accuracy of the predictions could be determined by comparing the
predictions to environmental measurements taken under conditions similar to
those used to make the predictions. Unfortunately, such comparisons require a
large observational data base. In the case of the IEM, the data base should
contain measured annual-average, ground-level air concentrations of and
corresponding exposures to gaseous and particulate pollutants released from a
variety of sources under a variety of meteorological conditions. Such a data
base is difficult and expensive to obtain and, to our knowledge, does not
exist. Therefore, we did not attempt to validate IEM predictions in this
study. However, some general comments can be made concerning the accuracy of
the IEM algorithms.
Previous studies indicate that Gaussian plume models, such as the ISCLTM,
give reasonably accurate, but often slightly high, predictions of annual-
average, centerline, ground-level, air concentrations of pollutants released
from various sources under well-behaved meteorological conditions over flat
terrain.5 For example, most predicted concentrations at receptor points
located within 10 km of the sources were between 0.5 and 2 times the measured
concentrations.6-10 Predicted concentrations at receptor points located
between 10 and 150 km from the sources were between 0.25 and 4 times the
measured concentrations.11-16 (The use of a simple Gaussian plume model to
predict concentrations beyond 50 km from the source usually is not
recommended.)17 Heron, et al.18 used the ISCLT to study particulates released
from a steel processing complex located in "relatively" flat terrain and found
predicted concentrations to be between 0.7 and 1.3 (mean -0.9) times
concentrations measured at six sampling stations, after correcting for
background. For releases under complex meteorological conditions (e.g., sea
breezes) or over complex terrain, predicted concentrations were found to be
between 0.1 and 10 times the measured concentrations.19-21 (If complex
meteorological and terrain conditions are present, the use of models other
than simple Gaussian plume models should be considered.)17 The presence of
structures near release points or other conditions that cause turbulence also
affect predictions adversely. Use of the building wake effects and stack-tip
downwash algorithms available in the ISCLTM dispersion model should improve
the agreement between predicted and measured values when such structures or
conditions are present, but the wake effects algorithm tends to underpredict
concentrations in the building wake region.22
The accuracy of the sector-segment-averaged concentrations calculated by
CONEX (see Sect. 3) is approximately the same as the accuracy of the
concentrations calculated by ISCLTM. However, the accuracies of the
procedures used in the IEM to estimate the number of persons residing in the
sector segments and to estimate human exposures are unknown. As discussed in
Section 3, the IEM results are similar to those obtained using the Human
Exposure Model (HEM).23
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PURPOSE AND STRUCTURE OF THIS REPORT
This study was undertaken to illustrate the sensitivity of IEM
predictions to (1) variations of selected, user-supplied source,
meteorological, climatological, and pollutant parameter values and (2) use of
the three available source modeling options to represent emission sources
found at hazardous waste management facilities (HWMFs). These sources include
incinerators and associated structures, storage and treatment tanks, drum
stacks, process buildings, surface impoundments, landfills, waste piles, and
land treatment areas. Several sources may be found at one HWMF.
Table 1 is a summary of source dimensions found at several HWMFs.24,25
The area covered by these sources ranges from very small (essentially a point)
to very large (up to 400 x. 106 m2). The height at which these sources release
pollutants generally is low (between ground level and 20 m); even the
incinerator stacks have low release heights (i.e., <30 m). Modeling the
sources found at a HWMF could present problems because they may be located
close together, be near buildings and structures that could influence
pollutant dispersion, and have ill-defined pollutant release rates. In some
cases, source-specific pollutant release rates may be unavailable, thus
forcing the modeler to represent several sources as a single source.
The remainder of this section contains a brief overview of the IEM
system. Section 2 is a summary of our findings. Section 3 contains
descriptions and discussions of the IEM algorithms for calculating sector-
segment concentrations and populations, and exposures. The methods used to
conduct the sensitivity analysis of the atmospheric dispersion algorithms are
discussed in Section 4. The effects of varying meteorological, source, and
pollutant parameter values and of using different receptor layouts are
discussed in Section 5. This discussion complements the work of Eldridge and
Gschwandtner.26 Finally, the effects on predictions due to using the three
source representation options (point, area, and volume) to model typical HWMF
sources are demonstrated in Section 6. Many of the results of the sensitivity
analysis runs are presented in the Appendixes as normalized concentration
profiles, plots of X/Q [(pg/m3)/(g/s)] as a function of downwind distance. A
glossary and a list of symbols and acronyms are given also.
GENERAL OVERVIEW OF THE IEM*
The IEM consists of four groups of computer programs called MET, POP,
ISCLTM, and CONEX. Each group consists of one or more computational and one
or more EXEC programs (Fig. 1). The EXEC programs control the flow of the IEM
because they contain the programming needed to access system-stored data files
and programs, to direct the user in preparation of problem-specific input data
files for the main programs, to submit the programs and data files to the IBM
operating system, and to process program outputs.
* The reader should consult reference 1 for details of the IEM and reference
2 for a discussion of procedures for manually creating and editing input
data files.
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Table 1. Typical source dimensions at HWMFs
Type
Surface Impoundments
Land treatment areas
Landfills
Waste piles
Process buildings
Drum stacks
Storage tanks
Incinerator structures
Incinerator stacks
Area, m
20 - 75 x 103
<1900>a
4000 - 4 x 108
<3.3 x 10 >
930 - 9.3 x 107
<6500>
30 - 4 x 105
<280>
75 - 300
<150>
-1300
50 - 1400
<320>
125 - 315
<220>
Release height, m
0
0
0
<3.1>
3 - 18
<9.4>
-6.1
2-10
<6.7>
4-20
<12>
9-27
<22>
Mean values are enclosed by < >.
Sources:
The MITRE Corporation, Air Emission Control Practices at Hazardous Waste
Management Facilities, Working Paper WP-83-W00048 (1983).
B. L. Blaney, U.S. Environmental Protection Agency, Cincinnati, OH,
Personal Communication, 1984.
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MET GROUP
USE EXECO. EXEC1.
AND EXEC2
1
ISCLTM
USE EXEC6 AND
EXEC7
POP GROUP
USE EXEC3 AND
EXEC4
I
CONEX
USE EXECS AND
EXEC7
I
OUTPUT TABLES
USE EXEC7
Figure 1. Schematic representation of program group interactions
in the IEM and their use of executive (EXEC) programs.
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The MET group Is a series of three main programs (SERCH, DIREC, and STAR)
that uses EXECO, EXEC1, and EXEC2 to guide the user in identifying
meteorological stations near the facility; in selecting an appropriate
meteorological data set; and in naming and formatting the data set as required
for compatability with the atmospheric dispersion code.
The FOP group is a series of two main programs (RD80 and APORT) that uses
EXEC3 and EXEC4 to guide the user in creating, naming, and formatting a
population data set for use by the concentration-exposure program (CONEX).
The ISCLTM group uses EXECS to direct the user in creating, naming, and
formatting an input data file for use by ISCLTM. Similarly, the CONEX group
uses EXECS to direct the user in creating, naming, and formatting the input
data file needed to run the concentration-exposure program (CONEX).
A final executive program, EXEC7, runs the two main computational
programs, ISCLTM and CONEX. This EXEC program collects all output files
prepared by the various program groups and feeds them, in proper order, to
ISCLTM and CONEX.
The IEM uses two polar coordinate systems, called the "grid system" and
the "centroid system". The orientations of the two coordinate systems are
shown in Figure 2. Both systems are centered on a common origin and use the
same set of 16 equally spaced (22.5° apart) direction vectors (Di, where i is
the direction index). Vector Dl points to the North, D5 to the East, D9 to
the South, D13 to the West, etc. Each direction vector lies along the center
of a 22.5° wide sector. The rings of the centroid system (RCk, where k is the
ring index) are located at radial distances XCk (in meters) from the origin.
The centroid rings are positioned midway between successive rings of the grid
system (RGj, where j is the ring index), which are located distances XGj from
the origin. For example, RC1 is midway between RG1 and RG2, and RC2 is midway
between RG2 and RG3. Thus, there always must be one more grid ring (maximum
of 20) than there are centroid rings (maximum of 19). Also note that the area
inside RG1, which is usually the source (plant) boundary, is excluded from the
centroid system.
The points at which the direction vectors and grid rings intersect,
FG(i,j), are the points at which ISCLTM calculates "grid-point concentrations"
[GPC(i.j)]. The GPC(i.j) are annual-average, sector-averaged, centerline,
ground-level, air concentrations. (See Reference 3 for details of the
calculations.)
The points at which the direction vectors and centroid rings intersect,
FC(i,k), are the geometric centroids of the sector segments [SS(i,k)], or the
areas, over which CONEX calculates (see Sect. 3) "sector-segment
concentrations" [SSC(i.k)]. Each sector segment is bounded by its two nearest
grid rings and the limits of its associated sector (i.e., two imaginary lines
located ±11.25° from its direction vector). The shaded area in Figure 2 shows
sector segment SS(9,2), which is centered on centroid point PC..,2). This
point is located at the intersection of direction vector D9 (180° from North)
and centroid ring RC2 (distance XC2 from the origin). This sector segment
occupies the area bounded by directions 168.75° and 191.25° and grid rings RG2
and RG3 (distances XG2 and XG3 from origin).
-------
ORNL-DWG 82-19021
D13
Figure 2. Orientation of the grid and centroid coordinate
systems used in the IEM (see explanation in text).
-------
SECTION 2
SUMMARY
A study was made of the sensitivity of IEM predictions to variations of
the more important user-supplied input parameter values and to the use of some
of the available modeling options to represent emission sources found at
HWMFs. These sources have relatively low pollutant release heights, may be
located near structures that influence pollutant dispersion, and, except for
incinerator stacks, may have essentially no associated plume rise. Parameters
affecting plume rise, which have been studied elsewhere, were not included in
this study. The parameters studied in detail include atmospheric stability
class, release height, and source area. Effects due to wind speed and
direction, adjacent buildings, pollutant decay and deposition, the arrangement
of receptor points, the use of different source geometries, and the method
used to estimate exposures also are discussed. In most cases, the study
assumed a unit (1 g/s) total pollutant release rate, a wind blowing from one
direction, and a wind speed of 0.75 m/s (see Sect. 4). The more important
findings of this study include:
(1) The IEM method for estimating the total exposed population is as
accurate as any other general method. However, the accuracy of the
method used to link exposed persons to specific pollutant
concentrations (i.e., to calculate exposures) is unknown, but likely
is comparable to the accuracy of other existing methods (Sect. 3).
(2) For the sources considered in this study, wind speed acted as an
inverse, linear scaling factor on concentration and population
exposure predictions, except when pollutant decay and deposition
were considered. Linear scaling also would not be found for stack
sources that produce plume rise, which were not part of this study
(Sect. 5).
(3) Variations in atmospheric stability, pollutant release height, and
source area had interdependent and strong influences on predicted
concentrations and exposures. Therefore, every effort should be
made to evaluate these parameters accurately (Sect. 5).
Preceding page blank
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(4) Increasing stability increased exposure predictions but, depending
largely on the release height, either increased or decreased maximum
concentration predictions (Sect. 5).
(5) Increasing release height decreased both exposure and concentration
predictions (Sect. 5).
(6) Increasing source area had little effect on exposure predictions,
for the same receptor array. Maximum concentration predictions
varied by as much as 60% for the source areas considered in this
study (Sect. 5).
(7) Use of the building wake effects option increased concentration
predictions within 200 m of the source center but had little effect
on more distant concentration predictions and on population exposure
predictions (Sect. 5).
(8) For pollutants that have half-lives of a few days or less, decay
could reduce significantly airborne concentrations at receptors
beyond 1 km. For longer-lived pollutants, decay would be
unimportant (Sect. 5).
(9) Pollutant deposition affected significantly both concentration and
exposure predictions, especially at sites characterized by stable
atmospheric conditions and low wind speeds (Sect. 5). The IEM
pollutant deposition option should be used if the emitted pollutants
are particles or can form particles that can be characterized.
(10) The choice of a receptor array can bias predictions significantly.
For the sources considered in this study, an array with receptors
concentrated between the first allowed distance and 2 km should
produce the most accurate predictions (in terms of the model's
predictive capability) of maximum concentration and exposures
(Sect. 5).
(11) Use of the various available emission source modeling options
produced essentially the same predictions of population exposures
and of airborne concentrations at receptors beyond -1 km. At the
closer receptors, use of the stack and the area source
representations produced very similar concentration predictions.
For the more stable atmospheric conditions, use of volume source
representations resulted in predictions of close-in concentrations
that were higher than those predicted using stack and area source
representations. For the less stable conditions, use of volume
source representations resulted in concentration predictions that
generally were lower than those predicted using the other options
(Sect. 6).
10
-------
SECTION 3
DISCUSSION OF THE EXPOSURE ESTIMATION PROCEDURE
Exposure is defined as the product of an average airborne pollutant
concentration and the number of persons immersed in that concentration over a
specified time interval. In the IEM, the time interval is one year and the
unit of exposure is person-/jg/m3. Three types of exposure estimates usually
are of interest: the maximum individual exposure, the total population
exposure, and the population exposures attributable to selected concentration
levels.
The maximum individual exposure is numerically equal to the maximum
grid-point concentration at an occupied grid point. Thus, the parameters that
affect calculation of the maximum individual exposure are the same as those
that affect calculation of the maximum grid-point air concentration. These
parameters are discussed in Section 5. The remainder of this section deals
with factors affecting population exposure estimates.
An accurate population exposure estimate requires (1) accurate estimates
of the total number of persons involved, (2) accurate estimates of the air
concentrations to which the persons are exposed, and (3) an accurate method
for linking the air concentrations and the exposed persons. Reasonably
accurate estimates of air concentrations at selected receptor locations can be
obtained using an atmospheric dispersion model such as the ISCLTM. Similar
estimates of the total exposed population can be obtained from census data or
from specially prepared, site-specific data. However, the accuracies of
methods for linking exposed persons and concentrations are unknown, but likely
are poor. The method used in the IEM involves (1) using the grid-point
concentrations to calculate an average concentration over each sector segment
(area) of the centroid system, (2) manipulating the census data to give the
number of persons residing in each sector segment, and (3) multiplying
corresponding sector-segment concentrations and populations to give sector-
segment population exposures. The sector-segment exposures then are added to
give a total population exposure estimate. The sector-segment exposures also
are used to determine the exposures associated with various concentration
levels.
11
-------
SECTOR-SEGMENT CONCENTRATIONS
The IBM calculates SSC(l,k), the average concentration (jig/m3) over
sector segment SS(i.k) of the centroid system, from the grid-point
concentrations at grid points PG(i,j) and PG(i,j+l) as follows:
SSC(i.k) - exp[Cl + (C2 - Cl) x RTEMP],
where, using the IEM orientation of coordinate systems (see Fig. 2),
k - j,
Cl - In GPC(i.j),
GPC(i.j) - grid-point concentration (/jg/m3) at PG(i,j),
C2 - In GPC(i,j+l),
GPC(i,j+l) - grid-point concentration (/jg/m3) at PG(i,j+l),
RTEMP - [ ln(XCk/XGj ) ]/[ ln(XGj+l/XGj ) ],
XCk - distance (m) from the origin to centroid point PC(i,k),
XGj - distance (m) from the origin to grid point PG(i.j), and
XGj+1 - distance (m) from the origin to grid point PG(i,j+l).
In general, the accuracy of the averaging process is as good as the
accuracy of the grid-point concentration calculations. For pollutants
released at heights above -10 m under stable atmospheric conditions (e.g.,
stability classes E and F), grid-point concentration profiles rise sharply to
their maximums. Under these conditions, sector-segment concentrations within
-1 km of the source may represent a large (one or two orders of magnitude)
range of grid-point concentrations, depending also on the grid-point spacing
used. (Increases in grid-point spacings increase the range of concentrations
represented by the sector-segment averages.) Figure 3 illustrates the
relationship between grid-point and sector-segment concentration profiles for
releases from stack sources (with no plume rise) with heights of 0 and 20 m
under stable (F) conditions. (As shown in the Appendixes, grid-point
concentration profiles exhibit the most curvature under F stability
conditions.) The receptor array described in Section 4 was used. For the 0-m
release height, the grid-point concentration profile is essentially a straight
line. The ranges of grid-point concentrations included in the sector-segment
concentrations is small (less than a factor of 3) out to 2 km, beyond which
the larger spread between grid points causes the ranges to increase to about a
factor of 5. For the 20-m release height, the grid-point concentration
profile rises rapidly to near its maximum value, peaks smoothly, and becomes
linear beyond -2 km. In this case, the first visible sector-segment
concentration, centered at 225 m, is the average of grid-point concentrations
that span two orders of magnitude. Subsequent segment-average concentrations
are obtained from decreasing ranges of grid-point concentrations until the 2-
km point is reached. Beyond 2 km, the relationship between the grid-point and
sector-segment concentration profiles is similar to the relationship for the
0-m release. Because the sector segments nearest the source are the smallest
and usually contain few people, they account for only a small fraction of the
12
-------
10000 £
1000 -
100 -
100 p
10
0.1
0.01
0.1
Distance from origin, km
(a) Release height = 0 m
Distance from origin, km
(b) Release height = 20 m
10
Figure 3. Comparison of grid-point and sector-segment concentrations
for releases from 0- and 20-m high stack sources with no plume rise
under F stability conditions.
13
-------
total exposure. Thus, any significant distortions caused by the averaging
process should have very little effect on the total exposure predictions. As
shown in Section 5, any reasonable choice of a receptor array will produce
acceptable total exposure estimates.
SECTOR-SEGMENT POPULATIONS
The population data provided with the IEM consists of 55 data sets that
were prepared using 1980 census data, which lists the number of persons
residing in census enumeration districts that are located at specific
latitude-longitude points. One of the IEM data sets contains estimates of the
number of persons in each cell of a coarse-grid (0.1" latitude by 0.1°
longitude) rectangular matrix that covers the contiguous United States. At
36° latitude, such a cell would have dimensions of -11 by -9 km. (These
dimensions would change slightly with latitude due to the curvature of the
Earth). Each of the remaining 54 data sets contain estimates of the number of
persons in each cell of a fine-grid (2' latitude by 2' longitude or -3.7 by
-3.0 km at 36° latitude) rectangular matrix that encompasses a specific
metropolitan area. The cell populations were obtained by assuming that all
persons assigned to census enumeration districts located within the latitude-
longitude window of a cell reside in and are distributed uniformly over the
cell.
To estimate the number of persons residing in the sector segments of the
centroid coordinate system, the IEM superimposes the array of sector segments
(see Fig. 2) on the array of rectangular cells and calculates the areal
fraction of each cell that is intersected by each sector segment. Then
SSP(i,k), the population in sector segment SS(i,k), is calculated using
N
SSP(i.k) - S f (i,k) x P ,
- c c
c-1
where N - number of cells intersected by SS(i,k),
f (i.k) - areal fraction of cell c that lies within SS(i,k), and
P - total number of persons assigned to cell c.
The accuracy of the population assignment procedure used by the IEM is
unknown. The procedure can produce a distorted population distribution if a
particular site is characterized by a grossly nonuniform population distribu-
tion. For example, at a site located near a large body of water, or any other
uninhabited area, the IEM may assign persons to sector segments in which no
one resides. Similar distortions could arise at sites characterized by iso-
lated, small-sized, but densely populated areas. The IEM procedure also may
offer some advantages. The census data have two shortcomings: (1) they locate
an entire enumeration-district population at a point, and (2) they do not
account for the daily movement of persons about their "point" of residence.
Since the area encompassed by an enumeration district depends, to some extent,
on the surrounding population density, the census data condense populations in
areas of variable size to populations at points. The IEM procedure may
14
-------
compensate to some degree for these shortcomings by spreading the census popu-
lation over the area covered by the sector segment to which it is assigned.
(We know of no good method to model in a general way the daily movement of
people about their point of residence.)
A user of the IEM may, of course, supply an alternate population data set
using the procedures outlined in the addendum to the IEM user's guide.2 This
option is useful if site-specific population data are available.
EXPOSURE ESTIMATION
The IEM calculates sector-segment exposures, SSE(i,k), from their
corresponding sector-segment concentrations and populations using
SSE(i.k) - SSC(i.k) x SSP(i.k).
The sector-segment exposures are combined to give exposures in:
(1) each sector, SE(i) - Z SSE(i.k),
k
16
(2) each radial band, RBE(k) - S SSE(i,k), and
i-1
16
(3) the entire assessment area, TE - 2 2 SSE(i.k).
i-1 k
There are other methods for locating exposed persons and linking them to
air concentrations. One such method is used in the Human Exposure Model
(HEM).23 This method does not manipulate the census data. Rather, it calcu-
lates an average concentration at the location of each census enumeration dis-
trict. The averaging calculation is similar to the one used in the IEM, but
it uses the grid-point concentrations at the four grid points nearest to and
surrounding the point at which the enumeration district is located.
A comparison was made of the exposure estimates produced by the IEM and
the HEM methods for maleic anhydride plants located at six different sites.27
Table 2 summarizes the results of the comparison. Total exposures calculated
using HEM differed by between -36 and +35% from those calculated using IEM.
These differences may be due to two factors: (1) the different methods used to
link exposed persons and air concentrations and (2) the fact that IEM results
were based on 1980 census data and the HEM results, on 1970 data extrapolated
to 1980. As shown in Table 2, differences (-13 to +7%) in the total popula-
tions used do not account for the exposure differences. A combination of the
details of the population distributions and the methods of linking concentra-
tions and exposed persons is the likely explanation for the total exposure
differences. These differences are not large in the context of the overall
uncertainties inherent in this type of calculation. .
15
-------
Table 2. Total exposure and exposed population estimates produced
by the IEM and the HEM within 20 km of six sites
% HEM
Site IEM HEM difference
. _
Total exposure (person-ug/m )
West Virginia 25,700* 33,600 30.7
Missouri 46,100 47,300 2.6
Indiana 79,500a 50,900 -36.0
Illinois 28,600* 38,700 35.3
New Jersey 12,500? 9,540 -23.7
Pennsylvania 270,000 267,000 -1.1
Total exposed population (thousands of persons)
West Virginia 56* 52 -7.3
Missouri 1,248 1,338 7.2
Indiana 110a 108 -2.1
Illinois 154* 160 4.1
New Jersey 1'470h 1«277 -13-1
Pennsylvania 1,063 1,090 2.6
*Coarse-grid population data were used.
Fine-grid population data were used.
Source: Reference 27.
16
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SECTION 4
METHOD USED FOR THE SENSITIVITY ANALYSIS
Emission sources found at HWMFs have relatively low pollutant release
heights, may be located near structures that influence pollutant dispersion,
and except for incinerator stacks, may have essentially no associated plume
rise. Previous studies have examined the sensitivity of ISCLTM predictions to
typical hazardous waste incinerator stack parameters.28-30 Based on these
studies and the fact that all stack parameters except the physical stack
height affect only plume rise, which merely modifies the release height (or
the effective stack height), we did not study these parameters in detail.
Some general statements about the effects of stack parameters are given in
Section 5. The remaining, important, user-supplied input parameters include
meteorological parameters (wind speed, wind direction, and stability class),
source parameters (release height, source area, and adjacent building cross
sections), pollutant parameters (decay coefficient, settling velocity, and
reflection coefficient), and the array of grid points chosen. The effects of
varying these parameters are illustrated in Section 5. The effects of using
the three source representation options to model two typical HWMF sources are
illustrated in Section 6.
Several typical HWMF sources were selected for detailed study: a stack
with essentially no plume rise, a 14.1-m square (200 m2) area, an 80.6-m
square (6500 m2) area, a 316.2-m square (100,000 m2) area, and a 2236.1-m
square (5,000,000 m2) area. Since the ISCLTM algorithm will not accept zero
values for a stack diameter or gas exit velocity, our stack source was assumed
to have a diameter of 1.0 m and a gas exit velocity of 1 x 10-s m/s, the
ISCLTM default value. Source (release) heights of 0, 5, 10, 15, and 20 m were
considered for these sources. Limited evaluations were made of the effects of
representing a 200-m2 process building by one stack source, by two area
sources, and by two volume sources; two release heights, 5 and 10 m, were
considered for each representation. Similar evaluations were made for a 200-
m2 tank farm containing four tanks that were represented by four point sources
with and without building wake effects, by one area source, by four area
sources, by one volume source, and by four volume sources. Two release
heights, 3 and 6 m, were considered for each representation.
These sources were studied using, unless otherwise indicated, the ISCLTM
default parameter values and the following simplifying conditions:
17
-------
(1) Source-specific pollutant emission rates were chosen to give a total
emission rate of 1 g/s. This simplification makes the calculated
concentrations (pg/m3) equivalent to concentrations per unit release
[(A*g/m3)/(g/s)], which are called X/Q values.
(2) The wind was assumed to blow only in one direction, from North to
South. This simplification causes the highest concentrations to
occur on direction vector D9 (South), which we call the "primary
direction".
(3) Only one wigd speed (0.75 m/s, the ISCLTM default for class 1) was
considered.
These conditions were used only if they acted as scaling factors (i.e., if
they affected the magnitude but not the shape of the concentration profiles).
Conditions 1 and 2 were used throughout this study; condition 3 was not used
when considering the effects of pollutant decay and deposition. (Condition 3
also would not have been used if parameters that affect plume rise had been
studied.)
The above simplifications were chosen to minimize the number of computer
runs required and to isolate the effects of meteorological parameter values on
the IEM predictions. Although the results of this study, if used properly,
could be used to estimate concentrations and exposures from a real facility
under real meteorological conditions, making an IEM run for the facility would
be much easier and more reliable. Use of the results of this study in a real
application would involve scaling the concentrations and exposures to account
for (1) actual pollutant release rates; (2) actual combinations of wind speed,
stability class, and wind direction; and (3) the actual population
distribution. Step 1 could be accomplished easily, but accomplishment of
steps 2 and 3 would be very difficult and time consuming.
Measures used to study the behavior of IEM predictions under the above
conditions included:
(1) Primary Grid-Point Concentration [PGPC(j) - GPC(9,j)] profiles:
plots of primary-direction grid-point concentrations vs. downwind
distance (XGj),
(2) Value and location of the maximum PGPC,
(3) Primary Sector Exposure Potential [PSEP - SEP(9)]: the total
exposure in the primary sector [SE(9) in Sect. 3] for a uniform site
population density of 1 person/m2,
16
(4) Total Grid-Ring Concentration [TGRC(j) - Z GPC(i.j)] profiles:
plots of the sums of all grid-point concentrations on the jth grid
ring vs. downwind distance (XGj),
* The EPA recommends using 1.5 m/s for wind speed class I.31
18
-------
(5) Value and location of the maximum TGRC, and
16
(6) Total Exposure Potential [TEP - Z SEP(i)]: the sum of all sector
exposure potentials, or the totat~population exposure for a uniform
site population density of 1 person/m2.
The TGRC and TEP measures were included because the dimensions of some of the
area sources were large enough to cause substantial air concentrations to
occur at grid points that lie outside the primary sector. Ignoring these
concentrations would give a false impression of the importance of area size
(see Sect. 5). These measures also give a better picture of IEM predictions
under real meteorological conditions. They are equivalent to the PGPC and
FSEP values that would be obtained if the wind was assumed to blow equally in
all directions and if the pollutant release rate was 16 g/s. For the stack
source, which essentially is a point source, PGPC and TGRC values are equal,
as are the PSEP and TEF values. As source size increases, differences between
the PGPC and TGRC values and between the PSEP and TEP values also increase.
One concern of this study, and indeed of any atmospheric modeling effort,
was optimum receptor location. Concentrations at receptor locations are the
output predictions of the atmospheric dispersion program, and it is important
that the output reflects accurately the calculational capability of the
program. To satisfy this concern, a detailed preliminary study was made of
concentrations due to releases from a 30-m-high stack source, with no plume
rise, under all combinations of stability and wind-speed classes. Good plume
profiles and output maximum concentrations that were within a few percent of
those actually calculated by the ISCLTM were obtained by locating receptors on
grid rings at 50-m intervals between 100 m and 2 km, and at 5, 10, 20, 30, and
50 km. Except for location of the first grid ring, this receptor array was
used throughout this study. The ISCLTM algorithms (see Ref. 4 for details)
did not allow the first grid ring to be closer than 100 m for the stack, 150 m
for the 200- and 6500-m2 areas, 300 m for the 100,000-m2 area, and 1250 m for
the 5,000,000-m2 area. Since the maximum number of grid rings used in this
study (44) exceeds the number (20) normally allowed in the IEM, suggested
receptor arrays are discussed in Section 5.
19
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SECTION 5
DISCUSSION OF PARAMETERS THAT AFFECT CONCENTRATION ESTIMATES
The IEM uses a Gaussian-plume atmospheric dispersion model, ISCLTM, to
calculate GPCs (annual-average, sector-averaged, centerline, ground-level, air
concentrations of pollutants at user-specified receptor' locations). As the
name implies, a Gaussian-plume dispersion model assumes that pollutants
released from a source are transported downwind in well-defined plumes.
Sixteen such plumes are assumed in the IEM, one lying along and filling each
of the sixteen direction vectors. Each plume is characterized by a line
connecting the points of maximum concentration at each downwind (x) distance
and a crosswind (y,z) distribution of pollutant concentration about the line.
A maximum concentration line is an imaginary line drawn parallel to a
direction vector at an elevation that, for most sources considered in this
study, is determined largely by the pollutant release height. The crosswind
distribution tends to be least uniform (high maximum concentration relative to
concentrations at other locations) near the source and to become more uniform
with increasing downwind distance. The lateral (y) component of this
distribution is treated by the sector averaging procedure. Our concern is
with evaluation of the distribution at the ground surface, at z - 0, where the
ISCLTM calculates GPC values. These values are affected by the
meteorological, climatological, source, and pollutant parameters and by the
choice of a receptor array (the locations of the grid points at which the GPCs
are calculated).
METEOROLOGICAL AND CLIMATOLOGICAL PARAMETERS
Selection of a representative meteorological data set is very important.
Consultation with a professional meteorologist is recommended, especially when
site-specific data are not available, when the site has complex topographic
features, or when the site features differ from those at the nearest weather
station.
The meteorological data supplied with the IEM consists of National
Oceanic and Atmospheric Administration Stability Array (STAR) data sets for
weather stations located throughout the contiguous United States. Each data
set contains a time-averaged joint frequency distribution of wind direction,
wind-speed class, and atmospheric (Pasquill) stability category. (An annual
meteorological data set contains 576 entries. Each entry is the fraction of
the year during which one of six Pasquill stability categories occurs in
21
Preceding page blank
-------
combination with winds blowing into one of the sixteen 22.5°-wide sectors at
speeds within the range of speeds assigned to one of six wind-speed classes.)
For this study, the components of the joint frequency distribution were
treated separately. Each stability category was studied, but only one wind
speed and one wind direction were considered. The wind was assumed to blow
only from North to South, thus, the fraction of the time that the wind blows
from direction 1 toward direction 9, the primary direction, was set equal to
1.0. The fractions for all other directions were set to zero. This
simplification makes the results of this study applicable to all directions.
Also only one wind speed was considered in detail. Except for the situations
discussed below, this simplification also allows the results of this study to
be applied to other wind speeds. In principle, the results of this limited
study could be applied to a real case simply by multiplying the results for a
given stability category by the appropriate wind-speed scaling factors (see
below) and joint frequency distributions. In practice, it would be much
simpler and less error-prone to run the IEM for the problem of interest.
To illustrate the relative occurrence of each stability category and
wind-speed class in real meteorological data sets, data from eight scattered
weather stations were analyzed. The results of this analysis are presented in
Table 3. (These results should not be used in studies of specific sites.)
Stability category D tended to occur most often, while categories A and B
occurred infrequently. In some STAR data sets, categories E and F are
combined and listed under category E. These data sets contain either no
entries or all zeros for stability category F. (This is why the minimum
frequency of occurrence is zero for category F in Table 3.) Wind speed
classes 2 (2.5 m/s) and 3 (4.3 m/s) occurred most often; classes 1 (0.75 m/s)
and 4 (6.8 m/s) also were important; and classes 5 (9.5 m/s) and 6 (12.5 m/s)
were relatively rare.
Wind Direction
The fraction of the time that the wind blows in a given direction (i.e.,
within ± 11.25" of a given direction vector) is an important parameter in
concentration calculations using a real meteorological data set. It
determines the fraction of the total pollutant release that is directed into
the plume centered on the given direction. This parameter enters the
atmospheric dispersion calculations, which are performed separately for each
direction, as a linear, multiplicative, scaling factor. Thus, this parameter
affects the magnitude of the calculated GPCs but not the shape of their
profiles. For example, if the wind is assumed to blow from North to South
only 10% of the time, the resulting concentrations and exposures will be 0.1
times those given in this study.
Wind Speed
Wind speed determines both the- length of time it takes for a pollutant to
be transported from the emission point to>stme downwind distance and the
volume per unit time of ambient air passing the emission point. This volume
flow determines the initial total quantity of pollutant contained per unit
length of the plume and, thus, determines the total quantity of pollutant that
can be distributed across a given plume cross section. For the sources
considered in this study, wind speed and downwind GPCs were related inversely,
22
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Table 3. Composite of stability and wind-speed class
frequencies for eight scattered weather stations
Class Minimum Mean Maximum
A
B
C
D
E
F
1
2
3
4
5
6
0.00286
0.02669
0.08606
0.25820
0.06127
0.0
0.06822
0.19485
0.25863
0.13032
0.00913
0.00186
Stability class
0.01089
0.06022
0.10267
0.46934
0.17335
0.18358
Wind- speed class
0.19650
0.25887
0.29737
0.19881
0.03881
0.01026
0.03329
0.10239
0.14081
0.62780
0.30483
0.28043
0.36065
0.32479
0.38707
0.26425
0.08517
0.03808
Annual average data, based on five years of observation, from the
following weather stations: Elythe/Riverside, CA
Eau Claire, VI
Kansas City, MO
Williamsport/Lyco, PA
Bismarck, ND
Sheridan County, WY
Morgantown, W
Louisville, KY
23
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except when pollutant decay and deposition were considered. (Wind speed is a
linear, multiplicative, scaling factor in the denominator of the dispersion
equation.) Figure 4 depicts the scaling factor (the straight line) as a
function of wind speed for a reference speed of 0.75 m/s, the base speed used
throughout this study. Multiplication of the concentrations and exposures
presented in this study by the appropriate scaling factor will generate
concentrations and exposures for any desired wind speed. For example, if the
desired wind speed is 2.5 m/s, multiply the results of this study by 0.3.
(Dividing by the ratio of the new and old wind speeds, 2.5/0.75 - 3.3, yields
the same result.)
For sources having an associated plume rise, the linear relationship will
not hold. In fact, increasing wind speed may lead to higher concentration and
exposure predictions for these sources.30 This reversal occurs because
increasing the wind speed reduces plume rise and, thus, lowers the effective
pollutant release height.
Uncertainties that could be introduced into IEM predictions due to the
use of discrete (mean) wind speeds to represent ranges of values are
illustrated by the stepped curve in Figure 4. For example, for wind speed
class 2, with an average wind speed of 2.5 m/s and limits of 1.5 and 3.4 m/s,
the calculated concentrations and exposures could be between a factor of 1.7
low and a factor of 1.4 high. Largest uncertainties would occur in wind speed
classes 1 and 6, which are open ended. In practice, these potential
uncertainties may not be realized. Bowman and Crowder ran the ISCLT using
either mean wind speeds or true hourly average wind speeds and found less than
a 3% difference between the two sets of concentration predictions.30
Stabilty Class
A stability class is a measure of atmospheric turbulence; it determines
the rapidity with which emitted pollutants mix with the available ambient air.
Thus, this parameter affects the crosswind distribution of pollutant
concentration. The rapid mixing that occurs under unstable (e.g, A)
conditions causes the distribution to become uniform sooner (nearer to the
source) than does the slower mixing that occurs under stable (e.g., F)
conditions. The effects of stability on concentration and exposure
predictions also are affected by the pollutant release height, the source
area, and the location of the first receptor.
The effects of stability class on PGPC and TGRC profiles are illustrated,
respectively, in Appendix A (Figs. 13-17) and Appendix B (Figs. 18-21). For
ground-level (0-m) releases, increasing stability (from A to F) increased the
concentration at every receptor location. Maximum concentrations always
occurred under F stability, at the first allowed receptor location for the
source being considered (see Tables 4-8). Increasing stability in combination
with increasing release height caused concentrations at receptors near the
source to decrease faster than concentrations at more distant locations, moved
the locations of the maximum concentrations farther downwind, and.caused the
maxima to occur under less stable conditions. This effect was most pronounced
for stack (0-m2 area) source releases (Table 4). For ground-level releases,
maximum concentrations always occurred at 100 m and increased with the
following stability-class sequence: A B C D E F. For 10-m releases, maximum
24
-------
10
o
o
(ft
0.1
0.03
0.1
r
Class 1: 0.75
Class 2: 2.5 ^
Class 3: 4.3
Class
Class S:
Class 6: 12.S
i i i i i I
10
Wind speed, m/s
Figure 4. The wind-speed scaling factor (equals 1.0 for 0.75 m/s)
25
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Table 4. Summary of maximum concentrations and exposures, stack
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
0
Values
1938(0. 10)a
2550(0.10)
3634(0.10)
5814(0.10)
7650(0.10)
11630(0.10)
0.79
0.98
1.35
3.63
6.26
10.80
Values
1938(0. 10)a
2550(0.10)
3634(0.10)
5814(0.10)
7650(0.10)
11630(0.10)
0.79
0.98
1.35
3.63
6.26
10.80
Release height, m
5
10 15
and locations of maximum FGFCs , /ig/m3
1818(0.10)
2282(0.10)
2900(0.10)
3263(0.10)
2813(0.10)
1688(0.15)
FSEPs ,
0.79
0.98
1.34
3.55
6.08
10.27
1499(0.10) 1044(0.10)
1635(0.10) 883(0.10)
1473(0.10) 586(0.15)
869(0.15) 329(0.25)
600(0.20) 216(0.35)
352(0.35) 124(0.60)
108 person-/ig/m3
0.78 0.74
0.96 0.88
1.29 1.15
3.40 2.96
5.78 4.90
9.63 8.04
and locations of maximum TGRCs, pg/m3
1818(0.10)
2282(0.10)
2900(0.10)
3263(0.10)
2813(0.10)
1688(0.15)
TEPs,
0.79
0.98
1.34
3.55
6.08
10.27
1499(0.10) 1044(0.10)
1635(0.10) 883(0.10)
1473(0.10) 586(0.15)
869(0.15) 329(0.25)
600(0.20) 216(0.35)
352(0.35) 124(0.60)
108 person-/ig/m3
0.78 0.74
0.96 0.88
1.29 1.15
3.40 2.96
5.78 4.90
9.63 8.04
20
(km)
647(0.10)
455(0.15)
304(0.20)
164(0.35)
101(0.50)
57(0.85)
0.71
0.83
1.04
2.66
4.32
6.94
(km)
647(0.10)
455(0.15)
304(0.20)
164(0.35)
101(0.50)
57(0.90)
0.71
0.83
1.04
2.66
4.32
6.94
The closest distance allowed for this source.
26
-------
Table 5. Summary of maximum concentrations and exposures, 200-m2 area
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
Release height, m
0
Values
602(0. 15)a
845(0.15)
1214(0.15)
1986(0.15)
2679(0.15)
4081(0.15)
0.74
0.91
1.25
3.44
6.00
10.42
Values
878(0. 15)a
1227(0.15)
1763(0.15)
2882(0.15)
3883(0.15)
5913(0.15)
5
and locations
589(0.15)
808(0.15)
1108(0.15)
1556(0.15)
1719(0.15)
1457(0.15)
PSEPs ,
0.74
0.91
1.24
3.41
5.91
10.11
and locations
858(0.15)
1172(0.15)
1603(0.15)
2235(0.15)
2449(0.15)
2032(0.15)
10
15
20
of maximum PGPCs , ^g/m3 (km)
551(0.15)
708(0.15)
843(0.15)
748(0.15)
541(0.20)
330(0.35)
108 person-^g/m3
0.74
0.90
1.22
3.33
5.71
9.56
473(0.15)
534(0.15)
493(0.15)
298(0.25)
201(0.35)
119(0.60)
0.70
0.84
1.10
2.92
4.86
8.00
392(0.15)
376(0.15)
267(0.20)
152(0.35)
97(0.50)
56(0.85)
0.68
0.79
1.02
2.63
4.29
6.92
Of ma^imim TGRCs , /Jg/m3 (km)
799(0.15)
1021(0.15)
1205(0.15)
1045(0.15)
706(0.20)
392(0.35)
682(0.15)
763(0.15)
691(0.15)
375(0.25)
239(0.35)
133(0.60)
562(0.15)
530(0.15)
351(0.20)
181(0.30)
110(0.50)
60(0.85)
TEPs, 108 person-^g/m3
A
B
C
D
E
F
0.76
0.95
1.32
3.58
6.19
10.72
0.76
0.95
1.31
3.53
6.08
10.34
0.76
0.94
1.28
3.43
5.83
9.71
0.73
0.88
1.15
2.99
4.94
8.09
0.70
0.83
1.06
2.68
4.35
6.98
The closest distance allowed for this source.
27
-------
Table 6. Summary of maximum concentrations and exposures, 6500-m2 area
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
Release height, m
0
Values
208(0. 15)a
307(0.15)
447(0.15)
743(0.15)
1020(0.15)
1562(0.15)
0.69
0.82
1.10
3.17
5.61
9.80
Values
603(0. 15)a
883(0.15)
1282(0.15)
2123(0.15)
2903(0.15)
4439(0.15)
0.75
0.94
1.30
3.57
6.21
10.76
5
10 15
20
and locations of maximum FGFCs, /ig/m3(km)
206(0.15)
300(0.15)
426(0.15)
649(0.15)
791(0.15)
860(0.15)
FSEFs ,
0.69
0.82
1.10
3.16
5.56
9.63
199(0.15) 181(0.15)
280(0.15) 235(0.15)
368(0.15) 266(0.15)
433(0.15) 211(0.20)
369(0.15) 154(0.30)
256(0.35) 101(0.60)
10 8 person- jzg/m3
0.69 0.66
0.82 0.77
1.09 1.00
3.12 2.76
5.45 4.69
9.25 7.80
164(0.15)
191(0.15)
178(0.15)
116(0.30)
80(0.50)
49(0.85)
0.64
0.73
0.93
2.52
4.16
6.77
and locations of maximum TGRCs, /jg/m3(km)
596(0.15)
860(0.15)
1212(0.15)
1823(0.15)
2185(0.15)
2289(0.15)
TEFs,
0.75
0.94
1.29
3.55
6.13
10.47
574(0.15) 518(0.15)
795(0.15) 655(0.15)
1026(0.15) 718(0.15)
1157(0.15) 494(0.15)
939(0.15) 283(0.30)
465(0.30) 156(0.55)
108 person-jug/m3
0.75 0.72
0.93 0.87
1.28 1.16
3.47 3.05
5.93 5.05
9.90 8.24
462(0.15)
522(0.15)
462(0.15)
216(0.25)
130(0.45)
70(0.80)
0.69
0.83
1.07
2.75
4.44
7.10
The closest distance allowed for this source.
28
-------
Table 7. Summary of maximum concentrations and exposures, 100,000-m2 area
Stability
class
A
B
C
D
E
F
Release height, m
0
14(0
35(0
58(0
104(0
151(0
229(0
Values
• 30)a
.30)
.30)
.30)
.30)
.30)
5
10
15
20
and locations of maximum PGFCs, jjg/m3(km)
14(0
35(0
57(0
102(0
143(0
201(0
.30)
.30)
.30)
.30)
.30)
.30)
PSEPs,
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
0.62
0.69
0.89
2.72
4.92
8.70
98(0
207(0
328(0
581(0
831(0
1267(0
0.71
0.85
1.16
3.39
5.99
10.45
Values
• 30)a
.30)
.30)
.30)
.30)
.30)
0.62
0.69
0.89
2.71
4.90
8.63
14(0.
35(0.
56(0.
94(0.
121(0.
137(0.
30)
30)
30)
30)
30)
30)
13(0
32(0
49(0
74(0
81(0
67(0
.30)
.30)
.30)
.30)
.30)
.40)
13(0.
30(0.
44(0.
57(0.
50(0.
36(0.
30)
30)
30)
30)
30)
70)
108 person-/ig/m3
0.62
0.69
0.89
2.70
4.86
8.45
0.60
0.65
0.82
2.42
4.24
7.23
0.58
0.62
0.77
2.23
3.81
6.35
and locations of maximum TGRCs, /*g/m3(km)
98(0
206(0
323(0
559(0
768(0
1054(0
0.71
0.85
1.16
3.38
5.96
10.32
.30)
.30)
.30)
.30)
.30)
.30)
TEPs,
98(0.
203(0.
311(0.
497(0.
609(0.
625(0.
30)
30)
30)
30)
30)
30)
93(0
186(0
269(0
372(0
372(0
248(0
.30)
.30)
.30)
.30)
.30)
.30)
89(0.
171(0.
233(0.
268(0.
208(0.
91(0.
30)
30)
30)
30)
30)
45)
108 person-jig/m3
0.71
0.85
1.16
3.35
5.87
9.99
0.68
0.80
1.07
2.99
5.08
8.44
0.66
0.76
1.00
2.74
4.52
7.32
The closest distance allowed for this source.
29
-------
Table 8. Summary of maximum concentrations and exposures, 5,000,000-m2 area
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
0
Values
-------
concentrations occurred between 100 and 350 m and increased in the sequence
F E D C A B. For 20-m releases, maximum concentrations occurred between 100
and 850 m and increased in the sequence F E D C B A, the reverse of the
ground-level sequence.
As source area was increased, the distance to the first allowed receptor
increased and the above effects of stability class were, at least apparently,
mitigated. For the 5,000,000-m2 area source (Table 8), maximum concentrations
always occurred at the first allowed receptor (at 1250 m) and always increased
in the same sequence, A B C D E F. This consistency is due largely to the
fact that the first allowed receptor was beyond the range of distances that
are affected strongly by the joint interaction of stability and release
height. There was also a small mitigation of the stability/release height
effects with increasing area for the other sources considered. Tables 9-14
present the values and locations of of maximum FGPCs and TGRCs that were
obtained when the first receptors were located at 150, 300, or 1250 m. Table
15 is a summary of the stability-class sequences (in order of increasing
stability) given in Tables 9-14. Note that the larger areas tend to slow the
release-height-dependent reversal of sequences.
The effects of stability class on the concentration profiles are related
directly to the degree of mixing associated with the stabilities. For
ground-level releases, the maximum concentration line is always at ground
level. Therefore, ground-level releases always predicted the highest GPCs.
Also, since the line concentration decreases with distance from the source,
the maximum GPC always occurred at the first receptor. Concentrations
decrease with increasing distance from the source due to dispersion, which
distributes the pollutants throughout the plume cross section by depleting the
line concentration. Increasing the release height raises the maximum
concentration line and leads to an overall reduction in ground-level
concentrations. As release height is increased, the slower mixing associated
with stable conditions does not allow significant concentrations of pollutants
to reach ground level at the close-in receptors. As the plume travels
downwind, dispersion spreads the plume, and maximum GPCs occur when the plume
reaches ground level, at more distant receptors. As stability is decreased,
maximum GPCs tend to occur at closer receptors. In fact, for the sources
studied, the maximum GPCs always occurred at the closest receptor under A
stability conditions.
Tables 4-8 and 16-21 list PSEPs and TEPs for each source, stability
class, and release height studied. These exposure measures always increased
with increasing stability. This effect is expected because (1) sector-segment
areas and, in this case, their populations increase with distance from the
origin and (2) sector-segment concentrations in segments beyond -1250 m
downwind always increase with increasing stability. This relationship is
likely to hold for real population distributions.
The behavior of IEM predictions with changes in stability are important
when modeling low-level releases. Using either urban stability mode option to
model a ground-level release may result in concentration and exposure
predictions that are lower than those obtained when using the rural mode
option. (Both urban mode options move stabilities E and F to D, and urban
mode 2 moves D to C; C to B; and B to A.) For a ground-level release, the
31
-------
Table 9. Values (/jg/m3) and locations (1m) of maximum
PGPCs for receptors beginning at 0.15 km downwind
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
Release height, m
0
842(0.15)
1164(0.15)
1671(0.15)
2723(0.15)
3656(0.15)
5566(0.15)
602(0.15)
845(0.15)
1214(0.15)
1986(0.15)
2679(0.15)
4081(0.15)
208(0.15)
307(0.15)
447(0.15)
743(0.15)
1020(0.15)
1562(0.15)
5
820(0.15)
1105(0.15)
1501(0.15)
2047(0.15)
2185(0.15)
1688(0.15)
589(0.15)
808(0.15)
1108(0.15)
1556(0.15)
1719(0.15)
1457(0.15)
\
206(0.15)
300(0.15)
426(0.15)
649(0.15)
791(0.15)
860(0.15)
10
Stack source
755(0.15)
945(0.15)
1087(0.15)
869(0.15)
600(0.20)
352(0.35)
200 -m2 source
551(0.15)
708(0.15)
843(0.15)
748(0.15)
541(0.20)
330(0.35)
6500-m2 source
199(0.15)
280(0.15)
368(0.15)
433(0.15)
369(0.15)
256(0.35)
15
633(0.15)
685(0.15)
586(0.15)
329(0.25)
216(0.35)
124(0.60)
473(0.15)
534(0.15)
493(0.15)
298(0.25)
201(0.35)
119(0.60)
181(0.15)
235(0.15)
266(0.15)
211(0.20)
154(0.30)
101(0.60)
20
508(0.15)
455(0.15)
304(0.20)
164(0.35)
101(0.50)
57(0.85)
392(0.15)
376(0.15)
267(0.20)
152(0.35)
97(0.50)
56(0.85)
164(0.15)
191(0.15)
178(0.15)
116(0.30)
80(0.50)
49(0.85)
Distances are given in parentheses ().
32
-------
Table 10. Values (pg/m3) and locations (km) of maximum
TGRCs for receptors beginning at 0.15 km downwind
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
Release height, m
0
842(0.15)
1164(0.15)
1671(0.15)
2723(0.15)
3656(0.15)
5566(0.15)
878(0.15)
1227(0.15)
1763(0.15)
2882(0.15)
3883(0.15)
5913(0.15)
603(0.15)
883(0.15)
1282(0.15)
2123(0.15)
2903(0.15)
4439(0.15)
5
820(0.15)
1105(0.15)
1501(0.15)
2047(0.15)
2185(0.15)
1688(0.15)
858(0.15)
1172(0.15)
1603(0.15)
2235(0.15)
2449(0.15)
2032(0.15)
596(0.15)
860(0.15)
1212(0.15)
1823(0.15)
2185(0.15)
2289(0.15)
10
Stack source
755(0.15)
945(0.15)
1087(0.15)
869(0.15)
600(0.20)
352(0.35)
200 -m2 source
799(0.15)
1021(0.15)
1205(0.15)
1045(0.15)
706(0.20)
392(0.35)
6500-m2 source
574(0.15)
795(0.15)
1026(0.15)
1157(0.15)
939(0.15)
465(0.30)
15
633(0.15)
685(0.15)
586(0.15)
329(0.25)
216(0.35)
124(0.60)
682(0.15)
763(0.15)
691(0.15)
375(0.25)
239(0.35)
133(0.60)
518(0.15)
655(0.15)
718(0.15)
494(0.15)
283(0.30)
156(0.55)
20
508(0.15)
455(0.15)
304(0.20)
164(0.35)
101(0.50)
57(0.85)
562(0.15)
530(0.15)
351(0.20)
181(0.30)
110(0.50)
60(0.85)
462(0.15)
522(0.15)
462(0.15)
216(0.25)
130(0.45)
70(0.80)
Distances are given in parentheses ().
33
-------
Table 11. Values (jig/m3) and locations (km) of maximum
PGPCs for receptors beginning at 0.3 km downwind
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
Release height, m
0
190(0.30)
299(0.30)
444(0.30)
746(0.30)
1037(0.30)
1604(0.30)
157(0.30)
252(0.30)
375(0.30)
634(0.30)
883(0.30)
1364(0.30)
77(0.30)
134(0.30)
203(0.30)
349(0.30)
492(0.30)
755(0.30)
5
189(0.30)
295(0.30)
431(0.30)
685(0.30)
879(0.30)
1080(0.30)
156(0.30)
249(0.30)
365(0.30)
585(0.30)
757(0.30)
945(0.30)
77(0.30)
133(0.30)
199(0.30)
329(0.30)
438(0.30)
575(0.30)
10
Stack source
186(0.30)
283(0.30)
393(0.30)
530(0.30)
534(0.30)
352(0.35)
200 -m2 source
154(0.30)
240(0.30)
336(0.30)
461(0.30)
477(0.30)
330(0.35)
6500-m2 source
76(0.30)
130(0.30)
187(0.30)
277(0.30)
310(0.30)
256(0.35)
15
174(0.30)
249(0.30)
312(0.30)
312(0.30)
216(0.35)
124(0.60)
144(0.30)
212(0.30)
269(0.30)
280(0.30)
201(0.35)
119(0.60)
72(0.30)
117(0.30)
157(0.30)
187(0.30)
154(0.30)
101(0.60)
20
162(0.30)
217(0.30)
238(0.30)
164(0.35)
101(0.50)
57(0.85)
136(0.30)
186(0.30)
209(0.30)
152(0.35)
97(0.50)
56(0.85)
69(0.30)
106(0.30)
129(0.30)
116(0.30)
80(0.50)
49(0.85)
100, 000 -m2 source
A
B
C
D
E
F
14(0.30)
35(0.30)
58(0.30)
104(0.30)
151(0.30)
229(0.30)
14(0.30)
35(0.30)
57(0.30)
102(0.30)
143(0.30)
201(0.30)
14(0.30)
35(0.30)
56(0.30)
94(0.30)
121(0.30)
137(0.30)
13(0.30)
32(0.30)
49(0.30)
74(0.30)
81(0.30)
67(0.40)
13(0.30)
30(0.30)
44(0.30)
57(0.30)
50(0.30)
36(0.70)
Distances are given in parentheses ().
34
-------
Table 12. Values (/jg/m3) and locations* (Ion) of maximum
TGRCs for receptors beginning at 0.3 km downwind
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
0
190(0.30)
299(0.30)
444(0.30)
746(0.30)
1037(0.30)
1604(0.30)
198(0.30)
316(0.30)
469(0.30)
792(0.30)
1102(0.30)
1703(0.30)
151(0.30)
260(0.30)
391(0.30)
672(0.30)
945(0.30)
1453(0.30)
98(0.30)
207(0.30)
328(0.30)
581(0.30)
831(0.30)
1267(0.30)
5
189(0.30)
295(0.30)
431(0.30)
685(0.30)
879(0.30)
1080(0.30)
197(0.30)
312(0.30)
456(0.30)
730(0.30)
941(0.30)
1168(0.30)
151(0.30)
258(0.30)
383(0.30)
632(0.30)
838(0.30)
1093(0.30)
98(0.30)
206(0.30)
323(0.30)
559(0.30)
768(0.30)
1054(0.30)
Release height, m
10
Stack source
186(0.30)
283(0.30)
393(0.30)
530(0.30)
536(0.30)
352(0.35)
200 -m2 source
194(0.30)
300(0.30)
419(0.30)
572(0.30)
586(0.30)
392(0.35)
6500-m2 source
149(0.30)
251(0.30)
360(0.30)
527(0.30)
583(0.30)
465(0.30)
100,000-m2 source
98(0.30)
203(0.30)
311(0.30)
497(0.30)
609(0.30)
625(0.30)
15
174(0.30)
249(0.30)
312(0.30)
312(0.30)
216(0.35)
124(0.60)
182(0.30)
264(0.30)
334(0.30)
344(0.30)
239(0.35)
133(0.60)
141(0.30)
225(0.30)
300(0.30)
351(0.30)
283(0.30)
156(0.55)
93(0.30)
186(0.30)
269(0.30)
372(0.30)
372(0.30)
248(0.30)
20
162(0.30)
217(0.30)
238(0.30)
164(0.35)
101(0.50)
57(0.85)
170(0.30)
231(0.30)
259(0.30)
181(0.30)
110(0.50)
60(0.85)
134(0.30)
203(0.30)
245(0.30)
213(0.30)
130(0.45)
70(0.80)
89(0.30)
171(0.30)
233(0.30)
268(0.30)
208(0.30)
91(0.45)
Distances are given in parentheses ().
35
-------
Table 13. Values (jig/m3) and locations (km) of maximum
PGFCs for receptors beginning at 1.25 km downwind
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
Release height, m
0
3.1(1.25)
15.5(1.25)
28.8(1.25)
58.4(1.25)
86.9(1.25)
134.6(1.25)
3.0(1.25)
14.8(1.25)
27.7(1.25)
56.2(1.25)
83.7(1.25)
129.6(1.25)
2.4(1.25)
12.3(1.25)
23.1(1.25)
47.5(1.25)
70.7(1.25)
109.6(1.25)
1.6(1.25)
7.0(1.25)
13.7(1.25)
29.4(1.25)
43.9(1.25)
67.9(1.25)
0.4(1.25)
0.8(1.25)
1.9(1.25)
5.0(1.25)
7.7(1.25)
12.3(1.25)
5
3.1(1.25)
15.5(1.25)
28.8(1.25)
57.8(1.25)
85.1(1.25)
128.3(1.25)
3.0(1.25)
14.8(1.25)
27.6(1.25)
55.7(1.25)
82.0(1.25)
123.6(1.25)
2.4(1.25)
12.3(1.25)
23.0(1.25)
47.1(1.25)
69.4(1.25)
104.8(1.25)
1.6(1.25)
7.0(1.25)
13.6(1.25)
29.2(1.25)
43.2(1.25)
65.5(1.25)
5
0.4(1.25)
0.8(1.25)
1.9(1.25)
5.0(1.25)
7.7(1.25)
12.1(1.25)
10
Stack source
3.1(1.25)
15.5(1.25)
28.6(1.25)
56.3(1.25)
80.1(1.25)
110.9(1.25)
200-m2 source
3.0(1.25)
14.8(1.25)
27.5(1.25)
54.2(1.25)
77.3(1.25)
107.1(1.25)
6500-m2 source
2.4(1.25)
12.2(1.25)
22.9(1.25)
45.9(1.25)
65.7(1.25)
91.6(1.25)
100, 000 -m2 source
1.6(1.25)
7.0(1.25)
13.6(1.25)
28.6(1.25)
41.3(1.25)
58.7(1.25)
15
3.0(1.25)
14.5(1.25)
26.1(1.25)
48.6(1.25)
64.2(1.25)
77.1(1.25)
2.8(1.25)
13.9(1.25)
25.0(1.25)
46.8(1.25)
61.9(1.25)
74.7(1.25)
2.4(1.25)
11.5(1.25)
20.9(1.25)
39.8(1.25)
53.0(1.25)
64.9(1.25)
1.5(1.25)
6.6(1.25)
12.4(1.25)
25.0(1.25)
33.9(1.25)
43.4(1.25)
20
2.9(1.25)
13.8(1.25)
24.2(1.25)
42.4(1.25)
51.1(1.25)
50.4(1.25)
2.8(1.25)
13.2(1.25)
23.3(1.25)
40.9(1.25)
49.4(1.25)
49.1(1.25)
2.3(1.25)
10.9(1.25)
19.5(1.25)
34.9(1.25)
42.7(1.25)
43.5(1.25)
1.5(1.25)
6.3(1.25)
11.6(1.25)
22.2(1.25)
28.0(1.25)
30.8(1.25)
,000,000-m2 source
0.4(1.25)
0.8(1.25)
1.9(1.25)
5.0(1.25)
7.6(1.25)
11.6(1.25)
0.4(1.25)
0.8(1.25)
1.7(1.25)
4.4(1.25)
6.5(1.25)
9.5(1.25)
0.4(1.25)
0.7(1.25)
1.6(1.25)
4.0(1.25)
5.7(1.25)
7.9(1.25)
'stances are given in parentheses ().
36
-------
Table 14. Values (/jg/m3) and locationsa (km) of maximum
TGRCs for receptors "beginning at 1.25 km downwind
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
0
E
F
0
3.1(1.25)
15.5(1.25)
28.8(1.25)
58.4(1.25)
86.9(1.25)
134.6(1.25)
3.2(1.25)
15.8(1.25)
29.5(1.25)
59.8(1.25)
89.0(1.25)
138.0(1.25)
3.3(1.25)
16.3(1.25)
30.7(1.25)
62.8(1.25)
93.6(1.25)
145.0(1.25)
2.9(1.25)
13.5(1.25)
26.0(1.25)
55.4(1.25)
82.7(1.25)
128.1(1.25)
2.9(1.25)
6.6(1.25)
14.3(1.25)
36.5(1.25)
56.1(1.25)
88.1(1.25)
5
3.1(1.25)
15.5(1.25)
28.8(1.25)
57.8(1.25)
85.1(1.25)
128.3(1.25)
3.2(1.25)
15.8(1.25)
29.4(1.25)
59.3(1.25)
87.3(1.25)
131.5(1.25)
3.3(1.25)
16.3(1.25)
30.6(1.25)
62.3(1.25)
91.8(1.25)
138.5(1.25)
2.9(1.25)
13.5(1.25)
25.9(1.25)
55.0(1.25)
81.4(1.25)
123.4(1.25)
5
2.9(1.25)
6.6(1.25)
14.3(1.25)
36.4(1.25)
55.7(1.25)
86.6(1.25)
Release height, m
10
Stack source
3.1(1.25)
15.5(1.25)
28.6(1.25)
56.3(1.25)
80.1(1.25)
110.9(1.25)
200 -m2 source
3.2(1.25)
15.8(1.25)
29.3(1.25)
57.7(1.25)
82.2(1.25)
113.8(1.25)
6500-m2 source
3.3(1.25)
16.3(1.25)
30.4(1.25)
60.7(1.25)
86.7(1.25)
120.7(1.25)
100,000-m2 source
2.9(1.25)
13.4(1.25)
25.8(1.25)
53.9(1.25)
77.7(1.25)
110.1(1.25)
,000,000-m2 source
2.9(1.25)
6.6(1.25)
14.3(1.25)
36.1(1.25)
54.5(1.25)
82.0(1.25)
15
3.0(1.25)
14.5(1.25)
26.1(1.25)
48.6(1.25)
64.2(1.25)
77.1(1.25)
3.0(1.25)
14.8(1.25)
26.7(1.25)
49.8(1.25)
65.8(1.25)
79.3(1.25)
3.1(1.25)
15.3(1.25)
27.8(1.25)
52.5(1.25)
69.8(1.25)
85.0(1.25)
2.8(1.25)
12.6(1.25)
23.6(1.25)
47.0(1.25)
63.6(1.25)
80.7(1.25)
2.8(1.25)
6.2(1.25)
13.1(1.25)
32.1(1.25)
46.5(1.25)
66.4(1.25)
20
2.9(1.25)
13.8(1.25)
24.2(1.25)
42.4(1.25)
51.1(1.25)
50.4(1.25)
3.0(1.25)
14.1(1.25)
24.8(1.25)
43.5(1.25)
52.5(1.25)
52.0(1.25)
3.1(1.25)
14.6(1.25)
25.8(1.25)
46.0(1.25)
56.0(1.25)
56.6(1.25)
2.7(1.25)
12.0(1.25)
22.1(1.25)
41.6(1.25)
52.2(1.25)
56.8(1.25)
2.7(1.25)
5.9(1.25)
12.4(1.25)
29.2(1.25)
40.5(1.25)
53.7(1.25)
Distances are given in parentheses ().
37
-------
Table 15. Stability category sequences, In order of increasing maximum
concentration, for each source, release height, and first receptor location
Source Release height, m
area,
6
6
100
m2
0
200
,500
0
200 ,
,500
,000
A B
A B
A B
A B
A B
A B
A B
0
C D E
C D E
C D E
C D E
C D E
C D E
ODE
F
F
F
F
F
F
F
First
F
F
A
First
A
A
A
A
10
recptor
E A D
E A B
F B C
B
C
E
recptor
B F C
B F C
B C F
BCD
D
D
D
E
at 150 m
C
D
D
at 300 m
E
E
E
F
F E
F E
F E
F E
F E
F A
A B
20
D C B
DOB
D A C
A D B
A D B
E B D
F C E
A
A
B
C
C
C
D
First recptor at 1250 m
0 ABCDEF ABCDEF ABCDFE
200 ABCDEF ABCDEF ABCDFE
6,500 ABCDEF ABCDEF ABCDEF
100,000 ABCDEF ABCDEF ABCDEF
5,000,000 ABCDEF ABCDEF ABCDEF
38
-------
Table 16. FSEFs (10s person-/jg/m3) for first receptor at 0.15 km
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
0
0.76
0.94
1.30
3.53
6.13
10.61
0.74
0.91
1.25
3.44
6.00
10.42
0.69
0.82
1.10
3.17
5.61
9.80
5
0.76
0.94
1.29
3.49
6.02
10.24
0.74
0.91
1.24
3.41
5.91
10.11
0.69
0.82
1.10
3.16
5.56
9.63
Release height, m
10
Stack source
0.75
0.93
1.26
3.39
5.78
9.63
200-m2 source
0.74
0.90
1.22
3.33
5.71
9.56
6500-m2 source
0.69
0.82
1.09
3.12
5.45
9.25
15
0.72
0.86
1.13
2.95
4.90
8.04
0.70
0.84
1.10
2.92
4.86
8.00
0.66
0.77
1.00
2.76
4.69
7.80
20
0.70
0.82
1.04
2.66
4.32
6.94
0.68
0.79
1.02
2.63
4.29
6.92
0.64
0.73
0.93
2.52
4.16
6.77
39
-------
Table 17. TEPs (108 person-/jg/m3) for first receptor at 0.15 km
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
0
0.76
0.94
1.30
3.53
6.13
10.61
0.76
0.95
1.32
3.58
6.19
10.72
0.75
0.94
1.30
3.57
6.21
10.76
5
0.76
0.94
1.29
3.49
6.02
10.24
0.76
0.95
1.31
3.53
6.08
10.34
0.75
0.94
1.29
3.55
6.13
10.47
Release height, m
10
Stack source
0.75
0.93
1.26
3.39
5.78
9.63
200 -m2 source
0.76
0.94
1.28
3.43
5.83
9.71
6500-m2 source
0.75
0.93
1.28
3.47
5.93
9.90
15
0.72
0.86
1.13
2.95
4.90
8.04
0.73
0.88
1.15
2.99
4.94
8.09
0.72
0.87
1.16
3.05
5.05
8.24
20
0.70
0.82
1.04
2.66
4.32
6.94
0.70
0.83
1.06
2.68
4.35
6.98
0.69
0.83
1.07
2.75
4.44
7.10
40
-------
Table 18. PSEPs (108 person-/jg/m3) for first receptor at 0.30 km
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
0
0.71
0.87
1.19
3.36
5.89
10.25
0.70
0.85
1.16
3.31
5.81
10.13
0.67
0.79
1.07
3.11
5.52
9.66
0.62
0.69
0.89
2.72
4.92
8.70
5
0.71
0.87
1.19
3.34
5.84
10.06
0.70
0.85
1.16
3.29
5.77
9.95
0.67
0.79
1.07
3.10
5.49
9.54
0.62
0.69
0.89
2.71
4.90
8.63
Release height, m
10
Stack source
0.71
0.87
1.18
3.29
5.70
9.60
200 -m2 source
0 . 70
0.85
1.15
3.25
5.64
9.53
6500-m2 source
0.67
0.79
1.06
3.07
5.40
9.22
100 , 000 -m2 source
0.62
0.69
0.89
2.70
4.86
8.45
15
0.68
0.81
1.08
2.91
4.88
8.04
0.67
0.80
1.05
2.88
4.84
7.99
0.64
0.74
0.97
2.74
4.67
7.79
0.60
0.65
0.82
2.42
4.24
7.23
20
0.66
0.77
1.00
2.64
4.31
6.94
0.65
0.76
0.98
2.62
4.29
6.92
0.62
0.71
0.91
2.50
4.16
6.77
0.58
0.62
0.77
2.23
3.81
6.35
41
-------
Table 19. TEPs <108 person-/ig/m3) for first receptor at 0.30 km
Stability
class
A
B
C
D
E
F
A
B
C
0
E
F
A
B
C
D
E
F
A
B
C
D
E
F
0
0.71
0.87
1.19
3.36
5.89
10.25
0.71
0.88
1.20
3.39
5.94
10.33
0.71
0.88
1.21
3.43
6.01
10.45
0.71
0.85
1.16
3.39
5.99
10.45
5
0.71
0.87
1.19
3.34
5.84
10.06
0.71
0.88
1.20
3.37
5.89
10.13
0.71
0.88
1.21
3.42
5.97
10.28
0.71
0.85
1.16
3.38
5.96
10.32
Release height, m
10
Stack source
0.71
0.87
1.18
3.29
5.70
9.60
200 -m2 source
0.71
0.87
1.19
3.33
5.75
9.67
6500-m2 source
0.71
0.88
1.20
3.37
5.84
9.84
100,000-m2 source
0.71
0.85
1.16
3.35
5.87
9.99
15
0.68
0.81
1.08
2.91
4.88
8.04
0.68
0.82
1.09
2.94
4.92
8.08
0.68
0.82
1.10
2.99
5.01
8.23
0.68
0.80
1.07
2.99
5.08
8.44
20
0.66
0.77
1.00
2.64
4.31
6.94
0.66
0.78
1.01
2.67
4.34
6.98
0.66
0.79
1.03
2.72
4.43
7.10
0.66
0.76
1.00
2.74
4.52
7.32
42
-------
Table 20. FSEFs (108 person-^g/m3) for first receptor at 1.25 km
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
0
0.65
0.72
0.95
2.93
5.27
9.29
0.65
0.72
0.95
2.91
5.24
9.24
0.64
0.70
0.91
2.82
5.10
9.02
0.61
0.65
0.82
2.58
4.72
8.39
0.48
0.48
0.54
1.71
3.27
5.94
5
0.65
0.72
0.95
2.92
5.25
9.23
0.65
0.72
0.95
2.90
5.22
9.18
0.64
0.70
0.91
2.82
5.09
8.97
0.61
0.65
0.82
2.58
4.71
8.34
0.48
0.48
0.54
1.71
3.27
5.92
Release height, m
10
Stack source
0.65
0.72
0.95
2.91
5.21
9.04
200 -m2 source
0.65
0.72
0.94
2.89
5.18
9.00
6500-m2 source
0.64
0.70
0.91
2.81
5.05
8.80
100,000-m2 source
0.61
0.65
0.82
2.57
4.68
8.21
5,000,000-m2 source
0.48
0.48
0.54
1.71
3.25
5.86
15
0.62
0.68
0.88
2.62
4.55
7.75
0.62
0.68
0.87
2.60
4.53
7.72
0.61
0.66
0.84
2.53
4.42
7.55
0.59
0.61
0.76
2.31
4.10
7.07
0.46
0.45
0.50
1.54
2.86
5.10
20
0.61
0.65
0.83
2.41
4.10
6.80
0.60
0.65
0.82
2.40
4.08
6.78
0.60
0.63
0.79
2.33
3.98
6.65
0.57
0.59
0.72
2.14
3.71
6.26
0.45
0.44
0.47
1.43
2.61
4.56
43
-------
Table 21. TEPs (108 person-jig/m3) for first receptor at 1.25 km
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
0
E
F
0
0.65
0.72
0.95
2.93
5.27
9.29
0.65
0.73
0.96
2.94
5.29
9.33
0.66
0.74
0.97
2.99
5.37
9.46
0.68
0.74
0.98
3.04
5.47
9.65
0.72
0.74
0.91
2.91
5.38
9.60
5
0.65
0.72
0.95
2.92
5.25
9.23
0.65
0.73
0.96
2.94
5.28
9.27
0.66
0.74
0.97
2.98
5.35
9.40
0.68
0.74
0.98
3.03
5.45
9.59
0.72
0.74
0.91
2.91
5.37
9.56
Release height, m
10
Stack source
0.65
0.72
0.95
2.91
5.21
9.04
200 -m2 source
0.65
0.73
0.96
2.93
5.23
9.08
6500-m2 source
0.66
0.74
0.97
2.97
5.31
9.21
100,000-m2 source
0.68
0.74
0.98
3.02
5.41
9.40
5,000,000-m2 source
0.72
0.74
0.91
2.90
5.34
9.43
15
0.62
0.68
0.88
2.62
4.55
7.75
0.63
0.68
0.88
2.63
4.57
7.78
0.63
0.69
0.89
2.67
4.64
7.89
0.65
0.70
0.90
2.72
4.74
8.08
0.69
0.70
0.84
2.62
4.69
8.16
20
0.61
0.65
0.83
2.41
4.10
6.80
0.61
0.65
0.83
2.43
4.12
6.83
0.61
0.66
0.84
2.46
4.18
6.93
0.63
0.67
0.85
2.51
4.27
7.11
0.67
0.67
0.79
2.42
4.25
7.25
44
-------
maximum concentration, which might correspond to the maximum individual
exposure, always occurred under F stability conditions. (Stability class F
always produced the worst case, or the highest, population exposure
predictions.) Table 22 gives the stability class under which the maximum
concentration occurred for each release height, source area, and first
receptor location studied. For most combinations, use of an urban mode option
will predict lower maximum concentrations than will use of the rural mode
option.
Other Parameters
Other meteorological and climatological parameters used by the ISCLT that
may be specified by the modeler include: ambient air temperatures, mixing
layer heights, vertical gradient of potential temperature, height above ground
at which the wind speed was measured, air entrainment coefficients for
unstable and stable atmospheres, and acceleration due to gravity. Default
values are supplied for several of the parameters. The default values of the
vertical gradient of potential temperature should be used unless site-specific
measurements are available for each stability class. These values are used in
the calculation of buoyant plume rise. The default values for air entrainment
coefficients and the acceleration due to gravity also should be used.
Ambient air temperatures must be supplied for each stability category and
each season. These temperatures can be obtained from a variety of sources,
including publications by the U.S. Department of Commerce32 and by Ruffner,33
and various climatological atlases. Ambient air temperature affects only the
calculation of buoyant plume rise. The developers of the ISCLT suggest using
the average seasonal daily maximum temperature for stability classes A, B, and
C; the average seasonal temperature for stability class D; and the average
seasonal daily minimum temperature for stability classes E and F.
Mixing heights also must be supplied by the user for each wind-speed
class, stability class, and season. The ISCLTM automatically sets mixing
heights for stability classes E and F to 10 km if the rural mode stability
class option is chosen. Annual-average and seasonal morning and afternoon
mixing heights may be found in Holzworth's publication.34 This parameter is
not very important for low-level releases; small errors in mixing height
specification, except possibly under very unstable conditions, likely will
have little or no effect on GPC calculations within 50 km of the source.
Specification of the height at which the wind speed measurements used to
define the meteorological data were taken is very important. The modeler
should confirm this height with the supplier of the data. An inaccurate
height may cause an incorrect wind speed to be calculated at the pollutant
release height (see following discussion of release height effects). The
default height supplied by the ISCLTM is 10 m; it applies to the STAR data
supplied with the IEM.
45
-------
Table 22. Stability categories giving maximum PGPCs and TGRCs for
each source, release height, and first receptor location
Source Release height, m
area, m2 0 5 10 15 20
First receptor at 100 m
OF D B A A
First recptor at 150 m
OF E C B A
200 F E C B A
6,500 F F D C B
First recptor at 300 m
OF F E C,D C
200 F F E DC
6,500 F F E DC
100,000 F F F ED
First recptor at 1250 m
OF F F F E
200 F F F F E
6,500 F F F F F
100,000 F F F F F
5,000,000 F F F F F
46
-------
SOURCE RELATED PARAMETERS
Source related parameters studied in detail were release height and area.
In general, the effects of these parameters on the IEM predictions were
influenced by stability class and allowed receptor locations. Enhanced ground
level turbulence due to structures near the sources was considered by using
the building wake effects option to model a hypothetical tank farm. Some
general comments are given regarding parameters affecting plume rise, which
affects only emissions from incinerator stacks, not those from the other
sources commonly found at HWMFs.
Release Height
The effects of release height on PGPC and TGRC profiles are illustrated,
respectively, in Appendixes C (Figs. 23-27) and D (Figs. 28-31). In all
cases, predicted concentrations decreased with increasing release height. In
general, the decreases were largest nearest the source and diminished as
downwind distance increased. Increasing atmospheric stability magnified the
decreases at close-in receptors; increasing source area lessened the effects
slightly, even after correcting for effects due to first receptor location.
Note that concentration profiles for releases at or below 10 m (the height at
which the wind speed measurements were made) converged as downwind distance
increased. Concentration profiles for releases above 10 m did not converge.
Tables 4-14 illustrate release-height related changes in maximum PGPCs
and TGRCs for each stability class, source, and first receptor location.
These changes followed the pattern noted above for the overall concentration
profiles. Under the conditions of this study, increasing the release height
from 0 to 20 m reduced maximum concentration predictions by between -7%
(Table 14, all sources under A stability) and ~99.5% (Table 4, stack source
under F stability). The magnitude of the reductions depended strongly on
stability class and first receptor location, and to a lesser extent on source
area. Note also that increasing release height tended to increase the
distance to the maximum concentration.
Exposure predictions also decreased with increasing release height
(Tables 4-8 and 16-21). However, the effects of release height changes on
exposure predictions were smaller than the effects on maximum concentration
predictions. Increasing the release height from 0 to 20 m decreased exposure
predictions by between -6% (Table 21, all sources under A stability) and -36%
(Table 4, stack source under F stability). The decreases depended strongly on
stability class, moderately on first receptor location, and weakly on source
area. The relative insensitivity of exposure predictions to changes in
release height is explained by the tendency of concentration profiles for
different release heights to merge at downwind distances of a few kilometers
and by the large fraction of the total study area affected by the merged
concentrations.
Source Area
The effects of source area on PGPC and TGRC profiles are illustrated,
respectively, in Appendixes E (Figs. 32-36) and F (Figs. 37-41). Except at
47
-------
close-in receptors for the higher release heights under the more stable
conditions, increasing source size always lowered the PGPC curves out to
-10 km, where the profiles for the three smaller sources tended to merge. The
TGRC curves exhibited the same trend but (1) differences due to increasing
release height were smaller; (2) the stack (0-m wide) and 200-m2 (14.1-m wide)
area source profiles were very similar but reversed, the area source curves
were slightly higher than the stack curves; and (3) all profiles tended to
merge and, in fact, to cross over so that increasing source size always
increased concentrations beyond 10 km (not shown in Figs. 37-41). The
differences between the PGPC and TGRC profiles are explained by the fact that
the TGRC curves account for GPCs in sectors other than the primary one. These
GPCs become more important as source size increases and, thus, allows
pollutants to be spread over a larger area. As noted in Section 4, TGRCs
represent concentrations that would arise under conditions corresponding to
the wind blowing equally in all directions with a pollutant release rate of 16
g/s. Therefore, we prefer to use TGRCs when discussing source-size effects.
Also, source-size effects should be compared using receptor arrays that have
the same starting point.
Tables 10, 12, and 14 show the effects of source size on maximum TGRCs.
Increasing area tended to reduce the distance to the maximum TGRC. Except for
the stack source, which always predicts maximum TGRCs that are lower than
those predicted by the 200-m2 area source, increasing source area decreased
maximum TGRCs for ground-level releases and for releases under A stability
conditions. For the other release heights and stabilities, area-size effects
depended on the combination of release height, stability class, and first
receptor location. Increasing the distance to the first receptor always
decreased maximum TGRC values, regardless of the actual source area.
Three sources can have their first receptors at 150 m. For this receptor
array, the largest source-size related difference in maximum TGRC values
occurred for a 10-m release under E stability conditions; the maximum TGRC
predicted by the stack source was -36% lower than the one predicted by the
6500-m2 area source (Table 10). The 200-m2 area always predicted the highest
TGRCs for ground-level releases and for releases under stability classes A and
B. As stability and release height were increased, the 6500-m2 source tended
to predict the highest TGRCs.
Four sources can have their first receptors at 300 m. For this array,
the largest source-size related difference in maximum TGRC values occurred for
a 20-m release under E stability conditions; the maximum TGRC predicted by the
stack source was -51% lower than the one predicted by the 100,000-m2 area
source (Table 12). The 200-m2 area always yielded the highest TGRCs for
ground-level and 5-m releases, and for releases under stability classes A
through C. Except for 10-m releases under D stability, the 100,000-m2 source
predicted the highest TGRCs for releases at or above 10 m under stabilities D
through F.
All five sources can have their first receptors at 1250 m. For this
array, the largest source-size related difference in maximum TGRC values
occurred for a ground-level release under B stability conditions; the maximum
TGRC predicted by the 5,000,000-m2 area source was -60% lower than the one
predicted by the 6500-m2 area source (Table 14). The 6500-m2 area always
48
-------
yielded the highest TGRCs, except for 20-m releases under stability class F.
Tables 17, 19, and 21 show that source size had little effect on
predicted TEPs. Increasing the distance to the first receptor always
decreased TEPs, regardless of the actual source area. For each receptor
array, TEPs tended to increase with increasing source area, but the increases
were small. For the array beginning at 150 m, the maximum increase was -3%
and occurred for 10-m releases under F stability (Table 17). For the
remaining arrays, maximum increases occurred for 20-m releases under F
stability. The increases were -5% for the 300-m array (Table 19) and -7% for
the 1250-m array (Table 21). These increases were due largely to the tendency
for the larger areas to predict higher concentrations at the more distant
receptor locations.
Building Wake Effects
The building wake effects option attempts to simulate the increased
atmospheric turbulence caused by air flowing over and around structures
adjacent to or near the source. This option is invoked by specifying the
height and the crosswind width of a building adjacent to a stack source.
Provision is also made to account for squat buildings (see Reference 3).
To study how use of the building wake effects option affects the IEM
predictions for low release heights, a tank farm containing four 6.1-m high
tanks was modeled as four 6.1-m high stack sources with no plume rise. Each
tank was assumed to have an adjacent structure (i.e., a tank) with a crosswind
width of 7.1 m. Four structure heights were studied, 0 (no building), 3, 4.5,
and 6.0 m. As shown in Figure 5a, PGPC profiles were similar for all building
heights under A stability conditions. The same was true under B stability
conditions. The already high turbulence associated with these stabilities
apparently masked the effects of the building wake. As stability was
increased, the 0-m profile (no building) began to show the characteristic
close-in dip (see Fig. 13). Profiles for the 3- and 4.5-m high buildings do
not exhibit the characteristic close-in dip, while those for the 6-m high
building show increasingly lower concentrations relative to the other building
heights. These effects were greatest under F stability conditions (Fig. 5b).
One explanation for the effects of the 6-m building is that it produces the
most turbulence and directs much of the emissions into sectors other than the
primary one. This explanation is supported by the TGRC profiles (Fig. 6),
which essentially are identical except for the characteristic close-in dip
exhibited for the 0-m high adjacent building under F stability conditions
(Fig. 6b). Thus, it appears that use of the building wake effects option will
maximize concentration predictions at receptors very near the source.
Maximum TGRCs were identical for all building heights under A stability
conditions (Table 23). As stability was increased, differences between the
maximum TGRCs remained small (<12%), except for the 0-m building under F
stability conditions (-39% less than the 3-m building maximum). Note that the
maximum TGRCs always occurred on the first allowed (150 m) ring, except for
the 0-m structure under F stability conditions, which occurred on the 200-m
ring.
49
-------
1000
100
10
0.1
Profile labels indicate
adjacent building height.
3,4.5,6
I i i i
0.1
10
Distance from origin, km
(a) Stability class A
1000
o
x
100
10
0.1
Profile labels indicate
adjacent building height, m
• •
Distance from origin, km
(b) Stability class F
10
Figure 5. FGFC profiles for releases from a 6.1-m high tank farm
represented as four stack sources with adjacent structures.
50
-------
1000
100
10
0.1
Profile labels indicate
adjacent building height, m
3.4.5.6
0.1
1
Distance from origin, km
(a) Stability class A
10
1000
o
\
x
100
10
0.1
Profile labels indicate
adjacent building height,
10
Distance from origin, km
(b) Stability class F
Figure 6. TGRC profiles for releases from a 6.1-m high tank farm
represented as four stack sources with adjacent structures.
51
-------
Table 23. Summary of maximum concentrations and
exposures for building wake effects study
Building
height, m
0.0
3.0
4.5
6.0
0.0
3.0
4.5
6.0
0.0
3.0
4.5
6.0
0.0
3.0
4.5
6.0
0.0
3.0
4.5
6.0
0.0
3.0
4.5
6.0
Maximum
PGPC, X/Q
762
762
762
762
1016
1009
998
977
1342
1261
1211
930
1677
1562
1466
850
1600
1670
1583
749
1040
1667
1664
569
Maximum
TGRC, X/Q
Stability class A
811
811
811
811
Stability class B
1079
1072
1060
1047
Stability class C
1425
1339
1285
1356
Stability class D
1777
1656
1555
1571
Stability class E
1691
1769
1678
1610
Stability class F
1082
1764
1763
1755
PSEP
(xlO-8)
0.77
0.76
0.76
0.76
0.96
0.95
0.95
0.95
1.31
1.29
1.28
1.24
3.49
3.47
3.44
3.29
5.98
5.95
5.91
5.61
10.10
10.08
10.01
9.39
TEP
(xlO-8)
0.78
0.77
0.77
0.77
0.96
0.96
0.96
0.95
1.32
1.30
1.29
1.31
3.51
3.48
3.46
3.52
6.01
5.97
5.93
6.04
10.13
10.11
10.04
10.26
a
All maximums occur at 150 m, except those for the 0-m release under F
stability, which occur at 200 m.
52
-------
TEP predictions were not affected significantly by building wake effects
for low sources because most of the effects occurred close to the source.
Variations on the order of 2% or less were found for changes in adjacent
building height under the same stability conditions.
From the above observations, one could conclude that use of the building
wake effects option makes little difference in IEM predictions for low-level
releases. It would be desirable to confirm the findings of this limited
analysis by investigating the effects of other building geometries and release
heights.
Plume Rise
The importance of plume rise is that it increases the release height,
with all the attendant ramifications thereof. In the ISCLTM, plume rise may
be momentum- or buoyancy-driven, or both. Parameters affecting plume rise
include the stack exit gas velocity and temperature, the stack diameter, the
ambient air temperature, the mixing layer height, the acceleration due to
gravity, and the wind speed. As noted above, increasing wind speed may
decrease plume rise. Of the source parameters in this group, exit gas
velocity and temperature have the greatest effects. Stack diameter is
relatively unimportant. Ambient air temperature can be important, but, for
low sources, the mixing layer height is unlikely to be important. The
acceleration due to gravity is a constant. Since others have studied the
sensitivity of the ISCLT predictions to variations in the parameters affecting
plume rise,28-30 the above brief description is all that we attempted in this
regard.
POLLUTANT RELATED PARAMETERS
Pollutant parameters considered were the decay coefficient and the
deposition related parameters, particle size and reflection coefficient. Only
brief consideration was given to deposition since its use is not recommended
for small particles.
Decay Coefficient
The decay coefficient is defined by A - ln(2)/t.. .„, where t- .„ is the
pollutant half-life. %This coefficient enters the concentration calculations
through a multiplicative decay term defined by:
Decay term - exp[-Ax/u(h)],
where x is the downwind distance (m) and u(h) is the mean wind speed (m/s) at
release height h (m). Typical degradation (decay) half-lives for reactive
pollutants that might be released from HWMFs range from 0.41 day (for
Resorcinol) to 27 days (for CO).36 Nonreactive pollutants, including trace
metals, have essentially infinite half-lives.
Figure 7 illustrates the effect of the decay term for pollutants with
half-lives of one hour and one day as functions of wind speed and downwind
53
-------
o>
c
0.9
o
* 0.8
u
o
0.7
0.6
Profile labels indicate
wind speed class
i 1—i—i i i i 11—
0.1
1 10
Distance from origin, km
(b) t,/2 = 1 day
0.8
o>
c
•5 0.6
c
o
= 0.4
o
0.2
Profile labels indicate
wind speed class
0.1
1 10
Distance from origin, km
(a) t,2 = 1 hour
Figure 7. Illustration of decay term behavior.
54
-------
distance. For pollutants having half-lives greater than a few days, decay
should have negligible effect on IEM predictions. For half-lives less than
one day, under real meteorological conditions, the decay term could reduce
exposures appreciably because concentrations at the farther downwind distances
will be substantially reduced. Effects on maximum concentrations, which
usually occur within 1 km, will not be greatly affected, unless very short
half-lives are involved. For example, less than 10% of a pollutant with a
one-hour half-life will decay by the time it travels 1 km downwind under all
but the lowest wind-speed class, for which about 30% would decay.
Deposition Parameters
The ISCLTM contains an algorithm to account for deposition of airborne
particles onto the ground surface. To use this option, the modeler must
specify the number of particle-size categories to be considered (i.e., enter a
positive integer for NVS on card 17 of the input data file). Subsequent input
cards must specify, for each particle-size category, a settling velocity
(m/s), the fraction of the total particulate mass in that category, and a
surface reflection coefficient. Guidance is given in the ISCLT user's guide
for calculating settling velocities and determining reflection coefficients.3
Use of this option to model particles with diameters smaller than -20 ^m
should be undertaken cautiously.3!22
To indicate the effects of using the ISCLTM deposition option, we
considered releases of 5-pm-diameter, stable (nondecaying) particles from a
20-m high stack source. Particles of this size are respirable and could be
formed during HWMF operations or after emission of smaller-sized particulate
or gaseous pollutants that attach to ambient air particles. These particles
were assigned a settling velocity of 0.0072 m/s and a reflection coefficient
of 0.8. The releases were studied under the following combinations of wind
speed and stability: wind-speed class 1 (0.75 m/s), stability classes B, D,
and F; wind-speed class 3 (4.3 m/s), stability classes B and D; and wind-speed
class 6 (12.5 m/s), stability class D. The results of this study are
summarized in Figure. 8 and Table 24.
Figure 8 illustrates PGPC and TGRC profiles obtained with and without
deposition. (Recall that PGPC and TGRC concentrations, and PSEPs and TEPs are
identical for stack sources of small diameter.) For the lowest wind speed
(Figs. 8a-c), accounting for deposition produced close-in concentrations that
equaled or exceeded those obtained when not accounting for deposition. At
some downwind distance, the profiles crossed and concentrations predicted
without considering deposition exceeded those obtained with deposition.
Increasing stability magnified the differences between the concentrations and
lengthened the distance to the crossover point. Under the least stable
conditions (A and B), concentrations with and without deposition were equal at
the first few receptors; at subsequent receptors, concentrations with no
deposition exceeded those with deposition. Increasing wind speed (Figs. 8a,
8d, and 8e), in addition to lowering all concentrations, moved the crossover
point to the first receptor location, thus causing concentrations without
deposition to exceed those with deposition at all downwind receptor locations.
Thus, increasing wind speed reduced concentrations obtained when accounting
for deposition more than it did when deposition was ignored. This means that
wind speed is not a linear scaling factor when deposition is considered.
55
-------
1000 p
100 r
0.1 1
Distance from origin, km
(a) Stability class B, wind-speed class 1
1000 P
100
.10
0.1
DEPOSITION
KO
DEPOSITION
0.1 1
Distance from origin, km
(b) Stability class D, wind—speed class 1
10
Figure 8. Effects of deposition on concentration predictions
for releases from a 20-m high stack source.
56
-------
1000 p
100
10
0.1
0.1 1
Distance from origin, km
(c) Stability class F, wind-speed class 1
10
100 p
0.01
O.t 1
Distance from origin, km
(d) Stability class D, wind—speed class 3
Figure 8. Continued.
57
-------
100 p
0.01
0.1 1
Distance from origin, km
(e) Stability class D, wind-speed class 6
10
Figure 8. Continued.
58
-------
Table 24 summarizes the behavior of maximum concentration and exposure
potential predictions with and without deposition. Accounting for deposition
tended to shorten the distance to the location of the maximum. Also, for the
lowest wind speed and the stabilities considered, accounting for deposition
gave maximum concentrations that were 0-87% higher than those obtained without
accounting for deposition. At higher wind speeds, accounting for deposition
produced maximum concentrations that were 5-8% lower. Estimates of exposure
potential were always lower when deposition was considered, by 9-70% for the
conditions considered. Differences in the exposure predictions tended to
increase with increasing stability. This effect is explained largely by
differences between the concentration profiles at the farther downwind
distances.
Based on the above limited observations, one could conclude that the
deposition option should be used if well-characterized particles are emitted
from the sources. Ignoring deposition likely will maximize predicted
concentrations and exposures under real meteorological conditions. However,
at sites characterized by substantial time periods of calm winds and stable .
conditions, failure to account for deposition could lead to substantial
underestimates of maximum concentrations and, therefore, of maximum individual
exposures and to substantial overestimates of population exposures.
RECEPTOR LOCATION
As noted in Section 4, careful receptor location will ensure that the
predictive capabilities of any atmospheric model are fully reflected in its
output. Predictions obtained using four alternate receptor arrays were
compared with predictions obtained using our base receptor array. The
following arrays were compared:
* Base array, receptors at 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5,
0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 ,1.0, 1.05, 1.1, 1.15,
1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8,
20.0,
* Array
30.
* Array
* Array
1,
0,
2,
3,
receptors
40.0, and
receptors
receptors
at 0
50.0
at 0
at 0
.1, 0
km;
.1, 0
.1, 1
1 ^'
.3,
5
.0,
0.5,
1 0
10.0
*** • ~ »
0.7,
S 0
, and
i.o,
10.0
50.0
1.5,
, and
km; i
2.0,
50.0
ind
5.0, 10.0,
km;
* Array 4, receptors at 0.1 and 50.0 km.
Table 25 summarizes the comparison results for a 0-m (ground-level) and a
20-m high release from a stack source, without plume rise, under D stability
conditions and a wind speed of 0.75 m/s. For a ground level release, all
receptor arrays gave the same maximum concentration, because it occurs at the
first allowed receptor location, which was the same in all the arrays. As the
receptor arrays become more open, predicted exposure potentials diverged
downward from the base case. However, even the most open array (4), which
contains only the first and last receptors of the base case, predicted an
exposure potential that was only -28% lower than the one predicted by the base
case.
59
-------
Table 24. Summary of maximum concentrations and
exposures for the deposition effects study
Stability
class
Wind
speed, m/s
Deposition
No deposition
% difference,
Dep./No dep.
B
B
0
D
D
F
B
B
D
D
D
F
Maximum FGFCs and TGRCs, X/Q(location in km)
455 (0.15) 455 (0.15)
73 (0.15) 79 (0.15)
196 (0.30) 164 (0.35)
27 (0.35) 29 (0.35)
9 (0.35) 10 (0.35)
107 (0.75) 57 (0.90)
0.75
4.3
0.75
4.3
12.5
0.75
0.75
4.3
0.75
4.3
12.5
0.75
FSEPs and TEFs (xlO-8)
0.65 0.83
0.11 0.14
2.03 2.66
0.42 0.46
0.14 0.16
2.11 6.94
-0
-8
20
-5
-8
87
-22
-22
-24
-9
-10
-70
60
-------
Table 25. Effects of several receptor array choices on
concentration and total exposure predictions
Receptor
array
- 1
2
3
4
1
2
3
4
Maximum
Value ,
X/Q
5814b
5814?
5814?
5814b
5814b
1 fi^ AC
159. 8d
136.8®
58. 4r
0.5g
FGFCs and TGRCs
% difference
from base
Ground-level release
0
0
0
0
20-m release
-2.3
-16.4
-64.3
-99.7
PEPs
Value ,
xlO8
3 gQ
3.60
3.42
3.24
2.61
266
2.64
2.48
2.29
0.78
and TEPs
% difference
from base
-0.6
-5.6
-10.5
-28.2
-0.6
-6.8
-13.8
-70.6
«
See text for receptor array descriptions.
Occurs at 0.1 km.
Occurs at 0.35 km.
Predicted at 0.3 km instead of at 0.35 km.
6Predicted at 0.5 km instead of at 0.35 km.
Predicted at 1.0 km instead of at 0.35 km.
^Predicted at 0.1 km instead of at 0.35 km.
61
-------
For a 20-m release, maximum concentration predictions dropped rapidly as
receptor separation increased. Arrays 3 and 4 yielded predictions of maximum
concentration and, therefore, of maximum individual exposure that are
unacceptably lower than the base case predictions. Array 2 produced
marginally acceptable values. Except for Array 4, which gave an unacceptably
low (-71% or a factor of 3.3) prediction, exposure potential predictions
behaved like those for the ground-level release.
Based on this study, alternate receptor Array 1 would be a reasonable
choice for modeling releases from HWMF sources. Since this array contains
only 13 receptors and the IEM allows specification of up to 20 receptors,
additional receptors could be included. For example, Tables 4-14 could be
used to locate the receptors giving the maximum concentrations for the
particular sources being considered. These receptors could be added, as
necessary to Array 1. (Note that, for some sources, it might be necessary to
move the location of the first receptor beyond 0.1 km.) Also, for the higher
release heights, for stack sources with plume rise, or for sources that cover
a large area, it might be appropriate to include more receptors between the
first one and the one at 2 km.
62
-------
SECTION 6
DISCUSSION OF SOURCE REPRESENTATION OPTIONS
Many of the sources commonly found at HWMFs can be modeled using one of
the source-representation options available in the ISCLTM. The source area
discussion in Section 5 illustrates the effects of representing a source by a
stack (essentially a point) and by one or more different-sized area sources.
These representation options normally are not considered when modeling an
actual source. Rather, one tries to match the area of the model source with
the area of the actual source. In this section, we discuss differences in
concentration and exposure potential predictions due to modeling two typical
HWMF components, a process building and a small tank farm, using source
representations that, except for the stack representations, keep the source
area constant. The results summarized in this section merely show differences
in predictions due to use of the various source representations; they do not
address the question of which representation gives the most accurate results.
This question can be answered only by comparing the various predictions with
measurements made under similar conditions.
The process building was assumed to be 10-m high, to cover 200 m2, and to
release pollutants either from a rooftop or a midheight vent. The building
was modeled as one stack source, as one 14.1-m square area source, as two 10-m
square area sources, and as two volume sources having standard deviations of
2.33 for their crosswind source distributions and 4.65 for their vertical
source distributions (see Ref. 3 for an explanation of these terms).
Figures 9 and 10 illustrate the TGRC profiles obtained for the source
representations used to model the 5- and 10-m releases, respectively. Only
profiles for A and F stability conditions are given because they bound the
effects due to stability. Maximum TGRCs and TEPs are given in Table 26 for
each source representation and stability class.
The tank farm was assumed to contain four 6.1-m high tanks, to cover 200
m2, and to release pollutants from vents located on top of the tanks. The
tanks were modeled as four stack sources, as four stack sources with adjacent
6.0-m high structures, as one 14.1-m square area source, as four 7.07-m square
area sources, as one volume source having standard deviations of 3.29 for its
crosswind source distribution and 2.84 for its vertical source distribution,
and as four volume sources having standard deviations of 1.64 for their
crosswind source distributions and 2.84 for their vertical source
distributions. Midheight (3.05-m) releases were considered only for the
single area and and volume source representations. Figures 11 and 12
illustrate the TGRC profiles obtained for the source representations used to
63
-------
1000
100
10
0.1
Profile labels indicate
source representation
2 VOLUMES
J 1 1 L.
0.1
1
Distance from origin, km
(a) Stability class A
10
1000
o
x
100
10
0.1
Profile labels indicate
source representation
J 1
Distance from origin, km
(b) Stability class F
10
Figure 9. TGRC profiles for releases from a 5-m high process building.
64
-------
1000
100
10
0.1
Profile labels indicate
source representation
0.1
10
Distance from origin, km
(a) Stability class A
1000
o
x
100
10
Profile labels indicate
source representation
2 VOLUMES
t i i i
i i i
0.1
10
Distance from origin, km
(b) Stability class F
Figure 10. TGRC profiles for releases from a 10-m high process building.
65
-------
Table 26. Summary of maximum concentrations and exposures
for the process building simulation calculations
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
Source representation
1 stack
820
1105
1501
2047
2185
1688
0.76
0.94
1.29
3.49
6.02
10.24
755
945
1087
869
600
352
0.75
0.93
1.26
3.39
5.78
9.63
1 area
TGRCs, X/Q (5-m
858
1172
1603
2235
2449
2032
TEPs xlO-8 (5-m
0.76
0.95
1.31
3.53
6.08
10.34
TGRCs, X/Q (10-m
799
1021
1205
1045
706
392
TEPs xlO-8 (10-m
0.76
0.94
1.28
3.43
5.83
9.71
2 areas
release)
822
1119
1527
2113
2295
1861
release)
0.76
0.94
1.29
3.51
6.04
10.29
release)
763
968
1134
957
653
371
release)
0.76
0.94
1.27
3.41
5.80
9.67
2 volumes
653
900
1182
1632
1918
2195
0.73
0.91
1.25
3.43
5.95
10.19
620
813
989
1139
1123
972
0.73
0.91
1.23
3.37
5.79
9.76
66
-------
1000
100
10
0.1
E4 STAC
'4ST;
. 1 VOLUME^ 4
Profile labels indicate
source representation
VOLUMES
0.1
10
Distance from origin, km
(a) Stability class A
1000 -
o
x
100 r
Profile labels indicate
source representation
Distance from origin, km
(b) Stability class F
Figure 11. TGRC profiles for releases from a 6.1-m high tank farm.
67
-------
1000
100
10
0.1
0.1
1 VOLUME
Profile labels indicate
source representation
1
Distance from origin, km
(a) Stability class A
10
1000
o
x
100
10
1 VOLUME
0.1
Profile labels indicate
source representation
10
Distance from origin, km
(b) Stability class F
Figure 12. TGRC profiles for releases from a 3.05-m high tank farm.
68
-------
model the 6.1- and 3.05-m releases, respectively. Again, only profiles for A
and F stability conditions are given. Maximum TGRCs and TEPs are given in
Table 27 for each source representation and stability class.
Differences between predictions made using the various source
representations were small and generally occurred within 1 km of the origin.
As illustrated in Table 28, differences between maximum TGRC predictions
rarely exceeded a factor of two. (A factor of two difference corresponds to
percentage differences of -50% and +100% in Tables 28 and 29. As noted in
Section 1, the expected accuracy of Gaussian-plume model predictions under
favorable conditions is a factor of two.) As shown in Table 29, differences
between TEP predictions never exceeded 5%.
STACKS VS. STACKS WITH BUILDING WAKE EFFECTS
In agreement with the discussion of building wake effects in Section 5,
stack sources with and without building wake effects gave the same maximum
concentration under A stability. For stabilities B through E, stacks without
wake effects gave slightly (3-13%) higher maximum concentrations. Considering
wake effects produced higher (38%) maximum concentrations under F stability,
because use of this option did not produce the characteristic close-in dip in
the TGRC profile. Using the building wake effects option produced slightly
(0.8-1.3%) lower TEP predictions under stabilities A through C and slightly
(0.3-1.3%) higher predictions for the remaining stabilities. These
differences are not significant.
STACKS VS. AREAS
All stack and area source representations of a given source produced
similar TGRC profiles. The curves essentially are superimposed, except near
the first receptor, where the effects of increasing stability and release
height caused the curves to deviate slightly. In this region, the area source
profiles tended to be slightly higher than the the stack source profiles,
except for stacks affected by building wakes under F stability conditions.
Maximum TGRC predictions confirmed this trend. Maximums due to stack
representations were always lower (0.2-20%) than those due to corresponding
area source representations, except for stacks with building wake effects
under F stability, whose maximums were 39-53% higher than those predicted
using area source representations. Total exposure potential predictions for
stack vs. area source representations differed by between -1.6 and 2.6%.
Again, the TEP predictions are not significantly different.
STACKS VS. VOLUMES
Stack source representations produced higher close-in concentrations than
did corresponding volume source representations for the lower stability
classes. As stability and release height increased, this situation reversed,
and volume sources tended to predict higher concentrations. This effect is
especially noticeable for 10-m releases under F stability (Fig. lOb). Volume
sources even outpredicted point sources with building wake effects under F
stability (Fig. 12b). Maximum TGRC predictions confirmed the above
observations. Under the less stable conditions, stack sources produced higher
(2-27%) concentrations. Under the more stable conditions, stack source
69
-------
Table 27. Summary of maximum concentrations and exposures
for the tank-farm simulation calculations
Stability
class
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
Source representation
Stacks
4
811
1079
1425
1777
1691
1082
0.78
0.96
1.32
3.51
6.01
10.13
4w/BW
TGRCs, X/Q
811
1047
1356
1571
1610
1755
TEPs xlO-8
0.77
0.95
1.31
3.52
6.04
10.26
TGRCs, X/Q
TEPs xlO-8
Areas
1
(6.1-m
848
1147
1531
1976
1957
1261
(6.1-m
0.76
0.95
1.30
3.51
6.03
10.21
4
release)
818
1097
1457
1848
1794
1151
release)
0.76
0.94
1.29
3.48
5.99
10.15
Volumes
1
738
1030
1371
1824
1998
1936
0.74
0.93
1.28
3.48
6.01
10.25
4
699
961
1257
1678
1868
1887
0.74
0.92
1.26
3.45
5.95
10.17
(3.05-m release)
871
1207
1703
2624
3273
3975
755
1077
1492
2201
2699
3251
(3.05-m release)
0.76
0.95
1.31
3.56
6.15
10.61
0.74
0.93
1.28
3.52
6.09
10.51
70
-------
Table 28. Percent differences in predicted maximum TGRC values between
the first and second source representations of the indicated pairs
Source pair,
release height
4 stacks: 4 stacks w/BW, 6.
Stability class
A
Stacks vs .
1 m 0.0
B C
Stacks w/BW
3.1 5.1
D
13.1
E
5.0
F
-38.3
Stacks vs. areas
4 stacks:! area, 6.1m
4 stacks : 4 areas , 6.1m
1 stack:! area, 5 m
1 stack:! area, 10 m
1 stack: 2 areas, 5 m
1 stack: 2 areas, 10 m
4 stacks w/BW:l area, 6.1
4 stacks w/BW: 4 areas, 6.1
4 stacks : 1 volume , 6.1m
4 stacks : 4 volumes , 6.1m
1 stack: 2 volumes, 5 m
1 stack: 2 volumes, 10 m
4 stacks w/BW:l volume, 6.
4 stacks w/BW: 4 volumes, 6
1 area: 4 areas, 6.1m
1 area: 2 areas, 5 m
1 area: 2 areas, 10 m
1 area:l volume, 3.05 m
1 area : 1 volume , 6.1m
1 area : 4 volumes , 6.1m
1 area: 2 volumes, 5 m
1 area: 2 volumes, 10 m
2 areas : 2 volumes , 5 m
2 areas: 2 volumes, 10 m
-4.4
-0.9
-4.4
-5.5
-0.2
-1.1
m -4.4
m -0.9
Stacks vs
9.9
16.0
25.6
21.8
1 m 9.9
.1 m 16.0
Area vs
3.7
4.4
4.7
Areas vs
15.4
14.9
21.3
31.4
28.9
25.9
23.1
-5.9 -6.9
-1.6 -2.2
-5.7 -6.4
-7.4 -9.8
-1.3 -1.7
-2.4 -4.1
-8.7 -11.4
-4.6 -6.9
. volumes
4.8 3.9
12.3 13.4
22.8 27.0
16.2 9.9
1.7 -1.1
8.9 7.9
. areas
4.6 5.1
4.7 5.0
5.5 6.3
. volumes
12.1 14.1
11.4 11.7
19.4 21.8
30.2 35.6
25.6 21.8
24.3 29.2
19.1 14.7
-10.1
-3.8
-8.4
-16.8
-3.1
-9.2
-20.5
-15.0
-2.6
5.9
25.4
-23.7
-13.9
-6.4
6.9
5.8
9.2
19.2
8.3
17.8
37.0
-8.3
29.5
-16.0
-13.6
-5.7
-10.8
-15.0
-4.8
-8.1
-17.7
-10.3
-15.4
-9.5
13.9
-46.6
-19.4
-13.8
9.1
6.7
8.1
21.3
-2.1
4.8
27.7
-37.1
19.7
-41.9
-14.2
-6.0
-16.9
-10.2
-9.3
-5.1
39.2
52.5
-44.1
-42.7
-23.1
-63.8
-9.3
-7.0
9.6
9.2
5.7
22.3
-34.9
-33.2
-7.4
-59.7
-15.2
-61.8
1 volume:4 volumes, 6.1m
Volume vs. volumes
5.6 7.2 9.1
8.7
7.0
2.6
71
-------
Table 29. Percent differences in predicted TEP values between the
first and second source representations of the indicated pairs
Source pair,
release height
4 stacks: 4 stacks w/BW, 6
Stability class
A
Stacks vs.
.1 m 1.3
B
C
D
E
F
Stacks w/BW
1.1
0.8
-0.3
-0.5
-1.3
Stacks vs. areas
4 stacks:! area, 6.1 m
4 stacks : 4 areas , 6.1m
1 stack:! area, 5 m
1 stack:! area, 10 m
1 stack: 2 areas, 5 m
1 stack: 2 areas, 10 m
4 stacks w/BW:l area, 6.1
4 stacks w/BW: 4 areas, 6.
4 stacks : 1 volume , 6.1m
2.6
2.6
0.0
-1.3
0.0
-1.3
m 1.3
1 m 1.3
Stacks vs
5.4
4 stacks : 4 volumes ,6.1m 5.4
1 stack: 2 volumes, 5 m
1 stack: 2 volumes, 10 m
4 stacks w/BW : 1 volume , 6
4 stacks w/BW: 4 volumes,
1 area : 4 areas , 6.1m
1 area: 2 areas, 5 m
1 area: 2 areas, 10 m
1 area:l volume, 3.05 m
1 area : 1 volume , 6.1m
1 area: 4 volumes, 6.1m
1 area: 2 volumes, 5 m
1 area: 2 volumes, 10 m
2 areas : 2 volumes , 5 m
2 areas : 2 volumes , 10 m
4.1
2.7
.1 m 4.1
6.1 m 4.1
Area vs
• 0.0
0.0
0.0
Areas vs.
2.7
2.7
2.7
4.1
4.1
4.1
4.1
1.1
2.1
-1.1
-1.1
0.0
-1.1
0.0
1.1
. volumes
3.2
4.3
3.3
2.2
2.2
3.3
. areas
1.1
1.1
0.0
volumes
2.2
2.2
3.3
4.4
3.3
3.3
3.3
1.5
2.3
-1.5
-1.6
0.0
-0.8
0.8
1.6
3.1
4.8
3.2
2.4
2.3
4.0
0.8
1.6
0.8
2.3
1.6
3.2
4.8
4.1
3.2
3.3
0.0
0.9
-1.1
-1.2
-0.6
-0.6
0.3
1.1
0.9
1.7
1.8
0.6
1.1
2.0
0.9
0.6
0.6
1.1
0.9
1.7
2.9
1.8
2.3
1.2
-0.3
0.3
-1.0
-0.9
-0.3
-0.3
0.2
0.8
0.0
1.0
1.2
-0.2
0.5
1.5
0.7
0.7
0.5
1.0
0.3
1.3
2.2
0.7
1.5
0.2
-0.8
-0.2
-1.0
-0.8
-0.5
-0.4
0.5
1.1
-1.2
-0.4
0.5
-1.3
0.1
0.9
0.6
0.5
0.4
1.0
-0.4
0.4
1.5
-0.5
-1.0
-0.8
1 volume:4 volumes, 6.1m
Volume vs. volumes
0.0 1.1
1.6
0.9
1.0
0.8
72
-------
predictions were between 1 and 64% lower than the corresponding volume source
predictions. Note that the 1 stack vs. 2 volumes comparison in Table 28 shows
that the stack predicted higher maximum.concentrations under all stability
classes except F. Total exposure predictions made using stack source
representations generally were higher (^5%) than those made using volume
source representations. Under the more stable conditions, a few stack source
representations yielded slightly lower (<1.5%) TEPs.
AREA VS. AREAS
Using one area source to represent an emission area always produced
slightly higher concentrations and exposures than did using more than one area
source. Maximum TGRC predictions were between 4 and 10% higher, and TEF
predictions ranged from equal to 1.6% higher.
AREAS VS. VOLUMES
Differences between predictions made using area and volume source
representations were similar to the differences between stack and volume
source representations. Under the less stable conditions, area sources
produced higher (<37%) maximum TGRCs. Under the more stable conditions, some
area source predictions were between 2 and 62% lower than the corresponding
volume source predictions. Total exposure predictions made using area source
representations generally were higher (<5%) than those made using volume
source representations. Under the more stable conditions, a few area source
representations yielded slightly lower (sl%) TEPs.
VOLUME VS. VOLUMES
Using one volume source to represent an emission source always produced
slightly higher concentrations and exposures than did using more than one
volume source. Maximum TGRC predictions were between 2 and 9% higher, and TEP
predictions ranged from equal to 1.6% higher. These relationships are similar
to those found in the one area vs. multiple areas comparison.
73
-------
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Computing Ground-Level Air Concentration of S02 and Suspended Particulates
for Both Point and Dispersed Sources, pp. 321-326 in Preprint Volume,
Joint Conference on Applications of Air Pollution Meteorology, American
Meteorological Society, Boston (1977).
20. Smith, D. B., and R. B. Ruch, Jr., Comparative Performance in Complex
Terrain of Several Air Quality Impact Assessment Models Based on
Aerometric Program Data, pp. 225-228 in Preprints, Fourth Symposium on
Turbulence, Diffusion, and Air Pollution, American Meteorological Society,
Boston (1979).
21. Wilson, A. D., H. E. Cramer, J. F. Bowers, Jr., and H. V. Geary, Jr.,
Detailed Diffusion Modeling As a Method of Interpreting and Supplementing
Air Quality Data, pp. 315-320 in Preprint Volume, Joint Conference on
Applications of Air Pollution Meteorology. American Meteorological
Society, Boston (1977).
22. Bowers, J. F., and A. J. Anderson, An Evaluation Study for the Industrial
Source Complex (ISC) Dispersion Model. EPA-450/4-81-002 (1981).
76
-------
23. Anderson, G. E., C. S. Lin, J. Y. Holman, and J. P. Killus, Human Exposure
to Atmospheric Concentrations of Selected Chemicals, Volumes I and II,
EPA-2/250-1 and EPA-2/250-2 (1980).
24. The MITRE Corporation, Air Emission Control Practices at Hazardous Waste
Management Facilities, Vorking Paper WP-83-W00048, Produced under Contact
Number 68-01-6092 with the Office of Solid Waste, U.S. Environmental
Protection Agency, Washington, D.C. (1983).
25. B. L. Blaney, U.S. Environmental Protection Agency, Cincinnati, Ohio,
Personal Communication, 1984.
26. Eldridge, K., and G. Gschwandtner, Applicationf of CDM, ISC-LT, and TCM-2
to Point and Area Sources. Pacific Environmental Services, Inc., Final
Report on Task Assignment No. 29, EPA Contract No. 68-02-3511 with the
U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina (1983).
27. O'Donnell, F. R., and G. A. Holton, "Automated Methodology for Assessing
Inhalation Exposure to Hazardous Waste Incinerator Emissions," pp. 225-234
in Incineration and Treatment of Hazardous Waste: Proceedings of the Ninth
Annual Research. Symposium at Ft. Mitchell, Kentucky. May 2-4, 1983, EPA-
600/9-84-015, (July 1984).
28. Holton, G. A., C. A. Little, F. R. O'Donnell, E. L. Etnier, and
C. C. Travis, Initial Atmospheric Dispersion Modeling in Support of the
Multiple-Site Incineration Study. ORNL/TM-8181 (1982).
29. Gunthorpe, P., and C. Maxwell, Inhalation Exposure Methodology (IEM)
Modeling of Hazardous Waste Incinerators, Midwest Research Institute,
Final Report under EPA Contract No. 68-01-6322 with the U.S. Environmental
Protection Agency, Washington, D.C. (1983).
30. Bowman, J. T., and J. W. Crowder, "A Comparison of the Short-Term and
Long-Term Dispersion Algorithms for the Industrial Source Complex Model,"
presented at the 76th Annual Meeting of the Air Pollution Control
Association, Atlanta, Georgia, June 19-24, 1983.
31. D. E. Layland, U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina, Personal Communication, August 30, 1984.
32. U.S. Department of Commerce, Comparative Climatic Data for the United
States Through 1981, National Oceanic and Atmospheric Administration,
National Climatic Center, Asheville, North Carolina (August 1982).
33. Ruffner, J. A., Climates of the States, Volumes 1 and 2, Gayle Research
Company, Detroit, Michigan (1978). -
34. Holzworth, G. C., Mixing Heights, Wind Speeds, and Potential for Urban Air
Pollution Throughout the Contiguous United States, Office of Air Programs
Publication No. AP-101, U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina (January 1972).
77
-------
35. Oak Ridge National Laboratory, Health and Environmental Effects Document
on Coal Liquefication - 1982, Volume2. Appendices, ORNL/TM-8624/V2
(September 1983).
78
-------
APPENDIX A
PGPC (X/Q) PROFILES BY STABILITY CATEGORY FOR
SEVERAL RELEASE HEIGHTS AND EACH SOURCE
79
-------
o
\
x
1000
100
10
0.1
Profile labels indicate
stability class
0.1
1
Distance from origin, km
(a) Release height = 0 m
10
O
\
x
1000
100
10
0.1
Profile labels indicate
stability class
-1 1 ' i i i i i I
l I 1 1 1—!_]_
0.1 1
Distance from origin, km
(b) Release height = 5 m
Figure 13. PGPC (X/Q) profiles by stability category
for several release heights from the stack source.
10
80
-------
O
\
X
1000
100
10
Profile labels indicate
stability class
0.1
0.1
1
Distance from origin, km
(c) Release height = 10 m
10
O
\
X
1000
100
10
0.1
0.1
Profile labels indicate
stability class
1
Distance from origin, km
(d) Release height = 15 m
i i t i i
10
Figure 13. Continued.
81
-------
o
\
X
1000
100
10
0.1
0.1
Profile labels indicate
stability class
1
Distance from origin, km
(e) Release height = 20 m
10
Figure 13. Continued.
82
-------
1000 -
100 -
o
\
X
Profile labels indicate
stability class
O
\
X
1000
100
10
0.1
Distance from origin, km
(a) Release height = 0 m
i i I
Profile labels indicate
stability class
0.1 1 10
Distance from origin, km
(b) Release height = 5 m
Figure 14. PGPC (X/Q) profiles by stability category for
several release heights from the 14.1-m square source.
83
-------
o
X:
X
1000
100
10
0.1
0.1
Profile labels indicate
stability class
1
Distance from origin, km
(c) Release height = 10 m
i 1111
10
i T r i i
1000
100
10
0.1
Profile labels indicate
stability class
0.1
1
Distance from origin, km
(d) Release height = 15 m
10
Figure 14. Continued.
84
-------
1000
T I I I I I
Profile labels indicate
stability class
O
x
100
10
0.1
0.1
1
Distance from origin, km
(e) Release height = 20 m
10
Figure 14. Continued.
85
-------
o
X
1000
100
10
0.1
I T I
0.1
Profile labels indicate
stability class
_j i i i i i i
1
Distance from origin, km
(a) Release height = 0 m
10
1000 -
a
\
X
Profile labels indicate
stability class
Distance from origin, km
(b) Release height = 5 m
Figure 15. PGPC (X/Q) profiles by stability category for
several release heights from the 80.6-m square source.
86
-------
o
\
x
1000
100
10
Profile labels indicate
stability class
0.1
0.1
1
Distance from origin, km
(c) Release height = 10 m
10
1000
I I I I I I
Profile labels indicate
stability class
O
x
100 T
10
0.1
I I I 1
I 1 III!
0.1
1
Distance from origin, km
(d) Release height = 15 m
Figure 15. Continued.
10
87
-------
1000
I 1 I I 1 I
Profile labels indicate
stability class
100
10
0.1
0.1
1
Distance from origin, km
(e) Release height = 20 m
Figure 15. Continued.
10
88
-------
1000 -
100
o
\
X
10
0.1
-IIII I I
0.1
Profile labels indicate
stability class
i i i i I
1
Distance from origin, km
(a) Release height = 0 m
10
1000
100
o
X
10
0.1
1I I i
Profile labels indicate
stability class
-I JL.
i i
i i i
0.1 1 10
Distance from origin, km
(b) Release height = 5 m
Figure 16. PGPC (X/Q) profiles by stability category for
several release heights from the 316.2-m square source.
89
-------
1000 r
100 r
O
X
Profile labels indicate
stability class
1000 -
O
V.
X
0.1
Distance from origin, km
(c) Release height = 10 m
Profile labels indicate
stability class
Distance from origin, km
(d) Release height = 15 m
Figure 16. Continued.
90
-------
1000 r
Profile labels indicate
stability class
O
\
x
100 -
10
0.1
0.1
1
Distance from origin, km
(e) Release height = 20 m
10
Figure 16. Continued.
91
-------
o
\
x
1000
100
10
0.1
0.1
Profile labels indicate
stability class
1
Distance from origin, km
(a) Release height = 0 m
i i i i i i
10
O
\
x
1000
100
10
0.1
I I I I I 1
Profile labels indicate
stability class
0.1 1
Distance from origin, km
(b) Release ht „. I = 5 m
Figure 17. PGPC (X/Q) profiles by stability category for
several release heights from the 2236.1-m square source
10
92
-------
1000
I I F I ( I I \
II I
Profile labels indicate
stability class
O
x
100
10
0.1
0.1
J I I
1
Distance from origin, km
(c) Release height = 10 m
10
1000
Profile labels indicate
stability class
O
x
100
10
0.1
0.1
I I 1 lilt
1
Distance from origin, km
(d) Release height = 15 m
i i iii
10
Figure 17. Continued.
93
-------
1000
T i i r i
Profile labels indicate
stability class
100
O
\
x
10
0.1
0.1
J 1 I
1
Distance from origin, km
(e) Release height = 20 m
i i
10
Figure 17. Continued.
-------
APPENDIX B
TGRC (X/Q) PROFILES BY STABILITY CATEGORY FOR
SEVERAL RELEASE HEIGHTS AND EACH SOURCE
95
-------
o
x
1000
100
10
0.1
r i i i r
I I I I I
0.1
Profile labels indicate
stability class
_J 1 1 1 I I I
1
Distance from origin, km
(a) Release height = 0 m
10
O
\
x
1000
100
10
0.1
T I TIT
ProfIIe IabeIs indicate
stability class
i i i i i i i
i t i i
0.1 1 10
Distance from origin, km
(b) Release height = 5 m
Figure 18. TGRC (X/Q) profiles by stability category for
several release heights from the 14.1-m square source.
96
-------
o
\
x
1000
100
10
Profile labels indicate
stability class
0.1
I I I I I I I I
0.1
1
Distance from origin, km
(c) Release height = 10 m
10
1000
100
10
Profile labels indicate
stability class
0.1
_J I I
0.1
1
Distance from origin, km
(d) Release height = 15 m
10
Figure 18. Continued.
97
-------
II I I I I I I
o
\
X
1000
100
10
0.1
0.1
Profile labels indicate
stability class
1
Distance from origin, km
(e) Release height = 20 m
i i i i
10
Figure 18. Continued.
98
-------
1000
100
a
\
x
10
0.1
Profile labels indicate
stability class
i t
0.1
1
Distance from origin, km
(a) Release height = 0 m
10
o
\
x
1000
100
10
0.1
Profile labels indicate
stability class
0.1 1
Distance from origin, km
(b) Release height = 5 m
Figure 19. TGRC (X/Q) profiles by stability category for
several release heights from the 80.6-m square source.
10
99
-------
1000
100
o
\
X
10
Profile lobals indicate
stability class
0.1
0.1
1
Distance from origin, km
(c) Release height = 10 rn
10
I I I I 7 |
o
\
x
1000
100
10
0.1
0.1
Profile labels indicate
stability class
' i i i i i I
1
Distance from origin, km
(d) Release height = 15 m
Figure 19. Continued.
100
10
-------
I I I I I I I I \
i I r r i r i _
1000
100
o
\
X
10
0.1
0.1
Profile labels indicate
stability class
I I
1
Distance from origin, km
(•) Release height = 20 m
10
Figure 19. Continued.
101
-------
o
X
1000
100
10
0.1
i I I I 1 ' _
0.1
Profile labels indicate
stability class
1
Distance from origin, km
(a) Release height = 0 m
10
1000
100
o
\
x
10
0.1
Profile labels indicate
stability class
0.1 1 10
Distance from origin, km
(b) Release height = 5 m
Figure 20. TGRC (X/Q) profiles by stability category for
several release heights from the 316.2-m square source.
102
-------
1000
100
o
\
X
10
Profile labels indicate
stability class
0.1
I I I
0.1
1
Distance from origin, km
(c) Release height = 10 m
10
O
\
x
1000
100
10
Profile labels indicate
stability class
0.1
0.1
1
Distance from origin, km
(d) Release height = 15 m
10
Figure 20. Continued.
103
-------
1000
Profile labels indicate
stability class
O
\
x
100
10
0.1
t 1 I t I
0.1
1
Distance from origin, km
(e) Release height = 20 m
10
Figure 20. Continued.
104
-------
o
\
X
1000
100
10
0.1
I I I I
0.1
Profile labels indicate
stability class
1
Distance from origin, km
(a) Release height = 0 m
10
1000 =-
100 -
O
\
x
Profile labels indicate
stability class
_l 1_
Distance from origin, km
(b) Release height = 5 m
Figure 21. TGRC (X/Q) profiles by stability category for
several release heights from the 2236.1-m square source
105
-------
I I I I T T I j
1000
100
o
x
10
0.1
0.1
Profile labels indicate
stability class
I
Distance from origin, km
(c) Release height = 10 m
i i i i i i
10
1000
Profile labels indicate
stability class
O
x
100
10
0.1
(111
0.1
1
Distance from origin, km
(d) Release height = 15 m
Figure 21. Continued.
10
106
-------
1000
I \
Profile labels indicate
stability class
O
\
x
100
10
0.1
0.1
1
Distance from origin, km
(e) Release height = 20 m
10
Figure 21. Continued.
107
-------
APPENDIX C
PGPC (X/Q) PROFILES BY RELEASE HEIGHT FOR
EACH STABILITY CATEGORY AND EACH SOURCE
108
-------
o
\
x
1000
100
10
0.1
0.1
Profile labels indicate
release height in meters
1
Distance from origin, km
(a) Stability class A
10
o
\
X
1000
100
10
. 5
0.1
T I I I I ]
Profile labels indicate
release height in meters
0.1 1
Distance from origin, km
(b) Stability class B
10
Figure 22. PGPC (X/Q) profiles by release height
for each stability class from the stack source.
109
-------
o
X
1000
100
10
Profile labels indicate
release height in meters
0.1
0.1
1
Distance from origin, km
(c) Stability class C
10
o
\
x
1000
100
10
Profile labels indicate
release height in meters
0.1
0.1
1
Distance from origin, km
(d) Stability class D
10
Figure 22. Continued.
110
-------
o
x
1000
100
10
0.1
0.1
Profile labels indicate
release height in meters
I L L I I I I
Distance from origin, km
(e) Stability class E
10
T 1 I (I ~
o
\
x
1000
100
10
0.1
0.1
Profile labels indicate
release height in meters
1
Distance from origin, km
(f) Stability class F
Figure 22. Continued.
Ill
I I I j
10
-------
o
\
x
1000
100
10
0.1
0.1
Profile labels indicate
release height in meters
Distance from origin, km
(a) Stability class A
10
o
\
X
1000
100
10
0.1
Profile labels indicate
release height in meters
0.1 1
Distance from origin, km
(b) Stability class B
Figure 23. PGPC (X/Q) profiles by release height for
each stability class from the 14.1-m square source.
10
112
-------
I 1 I
o
\
X
1000
100
10
Profile labels indicate
release height in meters
0.1
0.1
o
\
x
1000
100
10
0.1
0.1
1
Distance from origin, km
(c) Stability class C
10
I I V
Profile labels indicate
release height in meters
Distance from origin, km
(d) Stability class D
Figure 23. Continued.
10
113
-------
o
X
1000
100
10
Profile labels indicate
release height in meters
0.1
I til
I I I I
0.1
1
Distance from origin, km
(e) Stability class E
10
o
\
X
1000
100
10
0.1
0.1
Profile labels indicate
release height in meters
Distance from origin, km
(f) Stability class F
10
Figure 23. Continued.
114
-------
o
\
x
1000
100
10
0.1
i T i i r
0.1
I I I r—i—r-r-r_|
Profile labels indicate
release height in meters
1
Distance from origin, km
(a) Stability class A
10
O
\
x
1000
100
10
0.1
I I I I I I I
I I T
Profile IabeIs indicate
release height in meters
0.1 1
Distance from origin, km
(b) Stability class B
Figure 24. PGPC (X/Q) profiles by release height for
each stability class from the 80.6-m square source.
10
115
-------
o
x
1000 r
100 -
10
0.1
0.1
Profile labels indicate
release height in meters
1
Distance from origin, km
(c) Stability class C
10
o
x
1000
100
10
15
Profile labels indicate
release height in meters
0.1
j - 1
i i i i i i
0.1
Distance from origin, km
(d) Stability class D
Figure 24. Continued.
10
116
-------
o
\
x
1000 -
100
10
Profile labels indicate
release height in meters
0.1
0.1
1
Distance from origin, km
(e) Stability class E
10
o
\
X
1000
100
10
0.1
0.1
Profile labels indicate
release height in meters
Distance from origin, km
(f) Stability class F
10
Figure 24. Continued.
117
-------
o
\
X
1000
100
10
0.1
0.1
Profile labels indicate
release height in meters
J I I I I 1—L.
1
Distance from origin, km
(a) Stability class A
10
1000
100
10
0.1
Profile labels indicate
release height in meters
0.1 1
Distance from origin, km
(b) Stability class B
Figure 25. PGPC (X/Q) profiles by release height for
each stability class from the 316.2-m square source.
10
118
-------
1000
Profile labels indicate
release height in meters
o
\
x
100
10
0.1
J I I I I I I I
I I—I—I—I
0.1
1
Distance from origin, km
(c) Stability class C
10
1000
Profile labels indicate
release height in meters
O
\
x
100
10
0.1
_! 1 1 1 1 L I I I
_1 1 1—I—I—[_
0.1
Distance from origin, km
(d) Stability class D
10
Figure 25. Continued.
119
-------
1000
Profile labels indicate
release height in meters
o
x
100
10
0.1
0.1
Distance from origin, km
(e) Stability class E
10
1000
Profile labels indicate
release height in meters
o
\
X
100
10
0.1
1 I
0.1
1
Distance from origin, km
(f) Stability class F
10
Figure 25. Continued.
120
-------
O
\
X
1000 -
100 r
10
0.1
0.1
Profile labels indicate
release height in meters
0,5,10
Distance from origin, km
(a) Stability class A
H
1000
100
10
0.1
I I I I I I I |
Profile IabeIs indicate
release height in meters
0.1 1
Distance from origin, km
(b) Stability class B
10
Figure 26. PGPC (X/Q) profiles by release height for
each stability class from the 2236.1-m square source.
121
-------
1000
Profile labels indicate
release height in meters
o
X
100
10
0.1
0,5.10
0.1
1
Distance from origin, km
(c) Stability class C
10
1000
I I I I I
Profile labels indicate
release height in meters
o
x
100
10
_0.3.10
0.1
0.1
Distance from origin, km
(d) Stability class 0
10
Figure 26. Continued.
122
-------
1000
Profile labels indicate
release height in meters
o
x
100
10
0.5,10
0.1
0.1
1
Distance from origin, km
(e) Stability class C
10
1000
Profile labels indicate
release height in meters
O
-x
X
100
10
0.1
0.1
Distance from origin, km
(f) Stability class F
10
Figure 26. Continued.
123
-------
APPENDIX D
TGRC (X/Q) PROFILES BY RELEASE HEIGHT FOR
EACH STABILITY CATEGORY AND EACH SOURCE
124
-------
o
\
X
1000
100
10
0.1
0.1
1000
100 r
a
\
x
Profile labels indicate
release height in meters
10
Distance from origin, km
(a) Stability class A
ii r i
Profile labels indicate
release height in meters
Distance from origin, km
(b) Stability class B
Figure 27. TGRC (X/Q) profiles by release height for
each stability class from the 14.1-m square source.
125
-------
o
X
1000
100
10
Profile labels indicate
release height in meters
0.1
I I t I
0.1
Distance from origin, km
(c) Stability class C
10
I T I I
o
\
x
1000
100
10
Profile labels indicate
release height in meters
0.1
0.1
1
Distance from origin, km
(d) Stability class D
10
Figure 27. Continued.
126
-------
1000 i-
o
v.
X
Profile labels indicate
release height in meters
Distance from origin, km
(e) Stability class E
o
\
X
1000
100
10
t -
0.1
0.1
Profile labels indicate
release height in meters
1
Distance from origin, km
(f) Stability class F
Figure 27. Continued.
10
127
-------
1000 r
100
o
\
X
10
0.1
I I I
0.1
Profile labels indicate
release height in meters
1
Distance from origin, km
(a) Stability class A
10
o
\
X
1000
100
10
0.1
1 I I
Profile labels indicate
release height in meters
0.1 1
Distance from origin, km
(b) Stability class B
10
Figure 28. TGRC (X/Q) profiles by release height for
each stability class from the 80.6-m square source.
128
-------
O
x
1000
100
10
Profile labels indicate
release height in meters
0.1
0.1
1
Distance from origin, km
(c) Stability class C
10
o
x
1000
100
10
Profile labels indicate
release height in meters
0.1
I I I 1 1 I 1
0.1
Distance from origin, km
(d) Stability class D
Figure 28. Continued.
10
129
-------
I T i
1000 r
: 10
15
100
o
x
10
Profile labels indicate
release height in meters
0.1
j I | [ i I I I
0.1
1
Distance from origin, km
(e) Stability class E
10
1000
100
o
\
x
10
0.1
0.1
Profile labels indicate
release height in meters
1
Distance from origin, km
(f, ,'.t ability class F
10
Figure 28. Continued.
130
-------
o
X
1000
100
10
0.1
0.1
Profile labels indicate
release height in meters
^0,5,10
I I i
1
Distance from origin, km
(a) Stability class A
10
o
x
1000
100
10
0.1
Profile labels indicate
release height in meters
i
i i
0.1 1
Distance from origin, km
(b) Stability class B
10
Figure 29. TGRC (X/Q) profiles by release height for
each stability class from the 316.2-m square source.
131
-------
1000 r
100 r
O
\
x
10 r
Profile labels indicate
release height in meters
0.1
till
0.1
1
Distance from origin, km
(c) Stability class C
10
i r i i
1000 -
100
O
\
X
10
Profile labels indicate
release height in meters
0.1
i 1—i
_! i ' I 1 '
0.1
Distance from origin, km
(d) Stability class D
Figure 29. Continued.
132
10
-------
1000
100
o
\
X
10
Profile labels indicate
release height in meters
0.1
i I I I I
0.1
1
Distance from origin, km
(e) Stability class E
10
o
\
x
1000
100
10
Profile labels indicate
release height in meters
0.1
0.1
1
Distance from origin, km
(f) Stability class F
10
Figure 29. Continued.
133
-------
1000 -
100 =•
o
X
10
0.1
1 I 1
0.1
Profile labels indicate
release height in meters
Distance from origin, km
(a) Stability class A
1 1 111
10
1000 -
100
o
\
X
10
0.1
Profile labels indicate
release height in meters
0.1 1
Distance from origin, km
(b) Stability class B
10
Figure 30. TGRC (X/Q) profiles by release height for
each stability class from the 2236.1-m square source.
134
-------
1000
Profile labels indicate
release height in meters
100
o
\
X
10
0.1
I i IIL i__.!_
0.1
Distance from origin, km
(c) Stability class C
10
1000
Profile labels indicate
release height in meters
100
o
\
X
10
0.1
0.1
1
Distance from origin, km
(d) Stability class D
10
Figure 30. Continued.
135
-------
1000
\ I I
I I I I _
Profile labels indicate
release height in meters
o
x
100
10
0.1
I I I I I ..J__
0.1
1
Distance from origin, km
(e) Stability class E
10
1000
Profile labels indicate
release height in meters
o
\
x
100
10
0.1
0.1
Distance from origin, km
(f) Stability class F
10
Figure 30. Continued.
136
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APPENDIX E
PGPC (X/Q) PROFILES BY SOURCE WIDTH FOR EACH
STABILITY CATEGORY AND RELEASE HEIGHT
137
-------
o
\
x
1000
100
10
- 14.1 .
0.1
1 i 1—i—i—i i
Profile labels indicate
source width in meters
2236
0.1
10
Distance from origin, km
(a) Stability class A
1000 b
100 -
Profile labels indicate
source width in meters
o
\
X
Distance from origin, km
(b) Stability class B
Figure 31. PGPC (X/Q) profiles by source width for
each stability class and 0-m-high releases.
138
-------
1000 -
100
10
, -j
Profile labels indicate
source width in meters
0.1
0.1
O
\
X
1000
100
10
10
Distance from origin, km
(c) Stability class C
Profile labels indicate -|
source width in meters
0.1
_J I I
0.1
10
Distance from origin, km
(d) Stability class D
Figure 31. Continued.
139
-------
o
\
x
1000
100
10
0.1
0.1
o
\
X
1000
100
10
0.1
Profile labels indicate J
source width in meters
10
Distance from origin, km
(e) Stability class E
Profile labels indicate
source width in meters
Distance from origin, km
(f) Stability class F
Figure 31. Continued.
140
-------
1000 r
100 -
o
\
X
10
0.1
I I I
0.1
Profile labels indicate
source width in meters
i—i—i i I
1
Distance from origin, km
(a) Stability class A
10
o
\
x
1000
100
10
0.1
I I I I
\ I I I I
80.6
316.2
Profile labels indicate
source width in meters
0.1 1
Distance from origin, km
(b) Stability class B
Figure 32. PGPC (X/Q) profiles by source width for
each stability class and 5-m-high releases.
10
141
-------
o
\
X
1000
100
10
80.6
0.1
0.1
316.2
Profile labels indicate
source width in meters
2236.1
1
Distance from origin, km
(c) Stability class C
10
o
\
x
1000
100
10
Profile labels indicate
source width in meters
0.1
0.1
1
Distance from origin, km
(d) Stability class D
Figure 32. Continued.
10
142
-------
O
x
1000
100
10
Profile labels indicate
source width in meters
0.1
0.1
1
Distance from origin, km
(e) Stability class E
10
r i i \
a
\
X
1000
100
10
316.2
Profile labels indicate
source width in meters
0.1
0.1
Distance from origin, km
(f) Stability class F
10
Figure 32. Continued.
143
-------
1000 -
a
\
x
o
\
X
1000
100
10
0.1
0.1
Profile labels indicate
source width in meters
Distance from origin, km
(a) Stability class A
Profile labels indicate
source width in meters
-1 1, I L.
1 1—I—I_J_
10
Distance from origin, km
(b) Stability class B
Figure 33. PGPC (X/Q) profiles by source width for
each stability class and 10-m-high releases.
144
-------
1000
100
o
\
X
10
Profile labels indicate
source width in meters
0.1
I I I l t 1 I I I
0.1
1
Distance from origin, km
(e) Stability class E
10
1000
100
o
\
x
10
Profile labels indicate
source width in meters
0.1
0.1
1
Distance from origin, km
(f) Stability class F
10
Figure 33. Continued.
145
-------
o
X
1000
100
10
0.1
0.1
Profile labels indicate
source width in meters
1
Distance from origin, km
(c) Stability class C
i 11111
10
1000
100
o
x
10
Profile labels indicate
source width in meters
0.1
0.1
1
Distance from origin, km
(d) Stability class D
10
Figure 33. Continued.
146
-------
1000
100
o
X
10
0.1
0.1
Profile labels indicate
source width in meters
Distance from origin, km
(a) Stability class A
10
1000
100
o
X
10
0.1
I I I
0.1
Profile labels indicate
source width in meters
1
Distance from origin, km
(b) Stabilit-y- class B
10
Figure 34. PGPC (X/Q) profiles by source width for
each stability class and 15-m-high releases.
147
-------
1000
100
o
\
X
10
0.1
0.1
316.2
1 I
I t I I I T I
Profile labels indicate
source width in meters
1
Distance from origin, km
(c) Stability class C
10
o
\
X
1000
100
10
0.1
0.1
I I
Profile labels indicate
source width in meters
2236.1
1
Distance from origin, km
(d) Stability class D
Figure 34. Continued.
10
148
-------
1000
100
o
X
10
0.1
0.1
o
\
x
1000
100
10
0.1
0.1
Profile labels indicate
source width in meters
10
Distance from origin, km
(e) Stability class E
Profile labels indicate
source width in meters '
10
Distance from origin, km
(f) Stability class F
Figure 34. Continued.
149
-------
1000
100
o
x
10
0.1
0.1
Profile labels indicate
source width in meters
1
Distance from origin, km
(a) Stability class A
10
1000 -
o
\
x
Profile labels indicate
source width in meters
Distance from origin, km
(b) Stability class B
Figure 35. PGPC (X/Q) profiles by source width for
each stability class and 20-m-high releases.
150
-------
1000
Profile labels indicate
source width in meters
o
x
100
10
0.1
0.1
_] I 1 I I 1 I
1
Distance from origin, km
(c) Stability class C
10
1000
Profile labels indicate
source width in meters
o
\
X
100
10
0.1
_l I II III
0.1
10
Distance from origin, km
(d) Stability class D
Figure 35. Continued.
151
-------
1000
i r
Profile labels indicate
source width in meters
100
o
\
X
10
_ 80.6
0.1
0.1
I I
1
Distance from origin, km
(e) Stability class E
10
1000
Profile labels indicate
source width in meters
o
\
X
100
10
0.1
0.1
316.2
1
Distance from origin, km
(f) Stability class F
I I III
10
Figure 35. Continued.
152
-------
APPENDIX F
TGRC (X/Q) PROFILES BY SOURCE WIDTH FOR EACH
STABILITY CATEGORY AND RELEASE HEIGHT
153
-------
1000 -
100 r
o
X
Profile labels indicate
source width in meters
Distance from origin, km
(a) Stability class A
O
\
x
1000
100
10
0.1
Profile labels indicate
source width in meters
i i
0.1 i
Distance from origin, km
(b) Stability class B
Figure 36. TGRC (X/Q) profiles by source width for
each stability class and 0-m-high releases.
10
154
-------
I II I I I
1000
100
Profile labels indicate
source width in meters
O
x
10
' 1
0.1
1 I [.._. 11 I 111
I II II
0.1
1000
100
1
Distance from origin, km
(c) Stability class C
10
o
\
x
10
Profile labels indicate
source width in meters
0.1
_] I I I I 1 1
0.1
10
Distance from origin, km
(d) Stability class D
Figure 36. Continued.
155
-------
1000 -
O
X
Profile lobels indicote
source width in meters
Distance from origin, km
(e) Stability class E
I I I
o
\
X
1000 r
100
10
Profile labels indicate
source width in meters
0.1
J I I I 1 1—L.
0.1
10
Distance from origin, km
(f) Stability class F
Figure 36. Continued.
156
-------
1000 r
100 r
O
\
X
Profile labels indicate
source width in meters
Distance from origin, km
(a) Stability class A
o
\
x
1000
100
10
0.1
Profile labels indicate
source width in meters
0.1 1
Distance from origin, km
(b) Stability class B
Figure 37. TGRC (X/Q) profiles by source width for
each stability class and 5-m-high releases.
10
157
-------
o
x
1000
100
10
Profile labels indicate
source width in meters
0.1
0.1
1
Distance from origin, km
(c) Stability class C
10
1000
100
o
\
x
10
316.2
Profile labels indicate
source width in meters
0.1
0.1
1
Distance from origin, km
(d) Stability class D
10
Figure 37. Continued.
158
-------
o
x
1000
100
10
Profile labels indicate
source width in meters
0.1
0.1
1
Distance from origin, km
(e) Stability class E
10
o
\
x
1000
100
10
Profile labels indicate
source width in meters
0.1
0.1
Distance from origin, km
(f) Stability class F
10
Figure 37. Continued.
159
-------
o
x
1000
100
10
0.1
Profile labels indicate
source width in meters
0.1
I I 1 I I
1
Distance from origin, km
(a) Stability class A
10
o
\
x
Profile labels indicate
source width in meters
Distance from origin, km
(b) Stability class B
Figure 38. TGRC (X/Q) profiles by source width for
each stability class and 10-m-high releases.
160
-------
I I
o
\
X
1000
100
10
Profile labels indicate
source width in meters
0.1
0.1
1
Distance from origin, km
(c) Stability class C
10
o
\
x
1000
100
10
Profile labels indicate
source width in meters
0.1
0.1
1
Distance from origin, km
(d) Stability class D
10
Figure 38. Continued.
161
-------
1000 -
o
x
Profile labels indicate
source width in meters
Distance from origin, km
(e) Stability class E
o
X
1000
100
10
r i T i i i i
Profile labels indicate
source width in meters
0.1
j 1 1 1
i—i
0.1
Distance from origin, km
(f) Stability class F
10
Figure 38. Continued.
162
-------
o
X
1000
100
10
0.1
I I I I I
0.1
1 I I
Profile labels indicate
source width in meters
1
Distance from origin, km
(a) Stability class A
10
o
X
1000
100
10
0.1
0.1
Profile labels indicate
source width in meters
10
Distance from origin, km
(b) Stability class B
Figure 39. TGRC (X/Q) profiles by source width for
each stability class and 15-m-high releases.
163
-------
1000 r
O
X
Profile labels indicate
source width in meters
1000 =•
o
\
x
Distance from origin, km
(c) Stability class C
Profile labels indicate
source width in meters
Distance from origin, km
(d) Stability class 0
Figure 39. Continued.
164
-------
1 I I I
1000
100
: u.i
o
X
10
316.2
Profile labels indicate
source width in meters
0.1
_J I
0.1
1
Distance from origin, km
(e) Stability class E
10
1000
Profile labels indicate
source width in meters
o
\
X
100
10
0.1
0.1
Distance from origin, km
(f) Stability class F
Figure 39. Continued.
165
10
-------
o
\
x
1000
100
10
0.1
i I I I r
Profile labels indicate
source width in meters
0.1
o
X
1000
100
10
0.1
0.1
2236.1
I I I 1
10
Distance from origin, km
(a) Stability class A
I I
Profile labels indicate
source width in meters
10
Distance from origin, km
(b) Stability class B
Figure 40. TGRC (X/Q) profiles by source width for
each stability class and 20-m-high releases.
166
-------
1000 r
O
X
Profile labels indicate
source width in meters
Distance from origin, km
(c) Stability class C
1000
Profile labels indicate
source width in meters
o
\
x
100
10
0.1
_l 1 1—I—I I I I I
I I
0.1
1
Distance from origin, km
(d) Stability class D
10
Figure 40. Continued.
167
-------
1000 -
Profile labels indicate
source width in meters
o
\
x
100 r
10
0.1
0.1
1
Distance from origin, km
(e) Stability class E
10
1000
Profile labels indicate
source width in meters
o
\
x
100
10
316.2
0.1
0.1
1
Distance from origin, km
(f) Stability class F
Figure 40. Continued.
10
168
-------
GLOSSARY
Centerline: the line that bisects a sector of one of the coordinate systems
Centroid distance, XCk: the distance (m) from the origin to the kth centroid
ring
Centroid point, PC(i,k): the intersection of the ith direction vector and the
kth centroid ring
Centroid radius: same as centroid distance
Centroid ring, RCk: an imaginary circle of radius XCk drawn about the origin
Centroid system: the polar coordinate system used by CONEX
Direction vector, Di: the ith of 16 imaginary, equally spaced (22.5° apart),
radial lines emanating from the origin of both the grid and the centroid
systems, where, for example, Dl, at 0°, points to the North; D5, at 90°,
to the East; D9, at 180°, to the South; D13, at 270°, to the West; and
D16, at 337.5°, to the North Northwest
Exposure: the product of a time-averaged airborne pollutant concentration and
the number of persons immersed in that concentration over the time
averaging interval (person-/ig/m3)
Exposure potential: an artificial measure of the exposure that would occur if
the study area was occupied by a uniformly distributed population with a
density of 1 person/m2.
Grid distance, XGj: the distance (m) from the origin to the jth grid ring
Grid point, PG(i,j): the intersection of the ith direction vector and the jth
grid ring
Grid-point concentration, GPC(i.j): the annual-average, sector-averaged,
centerline, ground-level, air concentration (jtg/m3) calculated by ISCLTM
at grid point PG(i,j)
Grid radius: same as grid distance
Grid ring, RGj: an imaginary circle of radius XGj drawn about the origin
169
-------
Grid system: the polar coordinate system used by ISCLTM
Point concentration: same as grid-point concentration
Primary direction: the direction toward which the wind was assumed to blow in
this study, D9 or South
Primary grid-point concentration, PGPC(j): the grid-point concentration at
grid point PG(9,j), which lies on the primary direction
Primary sector: S(9), the sector centered on the primary direction
Primary sector exposure potential, PSEP: the sum of the sector-segment
exposure potentials in the primary sector
Primary sector-segment concentration, PSSC(k): the sector-segment
concentration in sector segment SS(9,k)
Sector, S(i): the 22.5° wide sector centered on the ith direction vector
Sector exposure potential, SEP(i): the sum of the sector-segment exposure
potentials' in sector S(i)
Sector segment, SS(i.k): the area centered on centroid point PC(i,k), which
is bounded by grid rings RGj and RGj+1 and imaginary radii that are
±11.25° from the ith direction vector
Sector-segment area, SSA(i.k): the area (m2) covered by sector segment
SS(i.k)
Sector-segment concentration, SSC(i.k): the average concentration (/jg/m3)
over sector segment SS(i,k)
Sector-segment exposure potential, SSEP(i,k): the exposure potential
associated with sector segment SS(i,k), defined as SSC(i.k) x SSA(k)
Total exposure potential (TEP) - the sum of all sector-segment exposure
potentials
170
-------
LIST OF ABBREVIATIONS AND SYMBOLS
Cl - In GPC(i.j)
C2 - In GPC(i,j+l)
CONEX - Concentration-Exposure Program used in the IEM
Di - ith direction vector
f1(i,k) - areal fraction of the 1th rectangular population cell that is
intersected by sector segment SS(i,k)
GPC(i.j) - grid-point concentration at PG(i,j)
i - direction index for both the grid and centroid coordinate systems
HEM - Human Exposure Model
IEM - Inhalation Exposure Methodology
ISCLT - the long-term version of the Industrial Source Complex Dispersion
Model
ISCLTM - the modified version of the ISCLT used in the IEM system; its
results are identical to those of the ISCLT
j - distance index for the grid coordinate system
k - distance index for the centroid coordinate system
1 - index for the population cells contained in the population data
file
F^ - total number of persons in the 1th rectangular cell of the
population data file
PC(i.k) - centroid point located at the intersection of the ith direction
vector and the kth centroid ring
PSSC(k) - primary-sector segment concentration, equal to SSC(9,k)
PGPC(j) - primary grid-point concentration, equal to GPC(9,j)
PG(i.j) - grid point located at the intersection of the ith direction vector
and the jth grid ring
PSEP - primary-sector exposure potential
RBE(k) - total exposure in the radial band centered on the kth centroid ring
RCk - kth centroid ring
171
-------
RGj - jth grid ring
RTEMP - [ln(XCk/XGj)]/[ln(XGj+l/XGj)l
S(i) - 22.5"-wide sector that lies along the ith direction vector
SE(i) - total exposure (person-/ig/m3) in sector S(i)
SEF(i) - exposure potential in sector S(i)
SS(i,k) - sector segment centered on centroid point PC(i,k)
SSA(k) - area (m2) of all sector segments centered on the kth centroid ring
SSC(i.k) - average concentration (/ig/m3) over sector segment SS(i,k)
SSE(i.k) - total exposure (person-pg/m3) in sector segment SS(i,k)
SSP(i.k) - number of persons assigned to sector segment SS(i,k)
TE - total exposure in the assessment area
TEF - total exposure potential
TGRC(j) - sum of all grid-point concentrations on the jth grid ring
XCk - distance (m) from the origin to the kth centroid ring
XGj - distance (m) from the origin to the jth grid ring
X/Q - grid-point or sector-segment concentration [(/ig/m3)/(g/s)] due to a
unit (1 g/s) pollutant release rate
172
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