SEPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 2771 1
EPA 600 7-80-036
February 1980
Investigation of
IMO2/NOx Ratios in
Point Source Plumes
Interagency
Energy/Environment
R&D Program Report
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EPA-600/7-80-036
February 1980
Investigation of IMO2/NOX Ratios
in Point Source Plumes
by
J.P. Blanks, E.P. Hamilton III,
B.R. Eppright, and N.A. Nielsen
Radian Corporation
P.O. Box 9948
Austin, Texas 78766
Contract No. 68-02-2608
Task No. 63
Program Element No. INE624
EPA Project Officer: J. David Mobley
Industrial Environmental Research Laboratory
Office of Environmental Engineering and Technology
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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ABSTRACT
The report gives results of a study to relate ground level NO2 concen-
trations to NOx emissions (N02/N0x ratio) in plumes from six large power
plants in the Chicago area, using a photostationary state reactive Gaussian
plume model. The aim of the study was to assess the level of NOx control
required to meet a probable short-term N02 national ambient air quality
standard (NAAQS). The major uncertainty of an earlier study (EPA-600/7-78-212)
was its assumption of uniform, fixed N02/N0x ratios of 0.5 (summer) and 0.25
(winter). The reactive model used in this study predicted significantly
higher N02/N0x ratios at the point of maximum plume impact (0.93 for worst
case) with high ambient ozone levels (0.2 ppm). Average N02/N0x ratios for
all high ozone cases studied were 0.76-0.9. The reactive model predicts sig-
nificantly higher ground level NOx impacts from the six plants. These results
indicate that the threshold short-term N02 NAAQS level requiring NOx flue
gas treatment technology could increase by 40%. The previous study indicated
that most of the six plants could meet a 500 microgram/cu m short-term N02
standard using NOx combustion modification techniques (50% NOx control) ; this
study indicates NOx flue gas treatment technology (90% control) may be re-
quired on these plants to meet a 750 microgram/cu m standard, and most
certainly for 500 micrograms/cu m.
ii
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EXECUTIVE SUMMARY
The 1977 Amendments to the Clean Air Act required the
Environmental Protection Agency (EPA) to establish a short-term
National Ambient Air Quality Standard for N02 or to show that
such a standard is unnecessary. If a short term N02 ambient
standard is established, it is uncertain what level of NO emis-
sion controls would be required from stationary combustion
sources to attain and/or maintain compliance with the ambient
standard. EPA s Industrial Environmental Research Laboratory
at" R AC t* *a*-r»>» T*-**^ Avu -.1 — n i_ i___ . ..... . J
In the previous study, the major uncertainty was the
extent of conversion of NO emissions (which are primarily NO)
f° 22xTAt/i«ound level- The assumption was made of uniform,
fixed N02/NOX ratios of 0.5 for summer and 0.25 for winter. In
the tollow-on study, a reactive Gaussian plume model using the
photostationary state approach was developed and used to deter-
mine the relationship of ground level N02 to NO emissions in
fi!^HS^r°\S1X large power plants in the Chicago AQCR. It was
aSSJ f?e 7? assumptions of uniform N02/N0x ratios were not
M£££ in /S?lxcab?-e to la*8e scale P«>blein8.x Significantly
higher N02/N0x ratios at the point of maximum plume impact can
wSJ* m%*$l"mt "^conditions. Plume NO./NO^ ratios as
high as 0.93 were found for the summer AM case (6 stability
5 m/sec wind speed - worst case in previous study) with hieh
ambient ozone levels. Average N02/NOX ratios for all high ozone
?£?Vt?dicd«an8?d froml°-76 to 0.9? Ozone is the most impor"-
X2 *?? * aff?c5inS N02/NOX ratios. Other factors influencing
the ratio are wind speed and stability class. iJ-uencing
TQQC -.If th,e ,hiSher summer AM ratios were applied to the
1985 results of the previous study, significantly higher maxi-
S^tfSOUn£hleVeliN°2 ^Pacts from^the ^x Plantsywou!d be p?e-
dicted. These plant impacts are as follows:
Maximum Ground Level N02 Impact Due to Plant
(Vtg/m3)
Previous Reactive
Study Model
Bailly (Northern Indiana Public Service) 754 1357
Will County (Commonwealth Edison) 710 1Q78
Waukegan (Commonwealth Edison) 524 922
Joliet (Commonwealth Edison) 993 1497
Fisk (Commonwealth Edison) 379 £52
Bethlehem Steel 1182 U82
iii
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The new results indicate that, for these conditions,
the threshold short-term N02 standard level where N0x flue gas
treatment becomes necessary could increase by at least 40 per-
cent. For the above plants, the previous study indicated that
most'could meet a 500 yg/m3 short-term N02 standard with com-
bustion modification techniques for NOX control (50 percent NOX
reduction). The reactive study indicates that combustion modi-
fication may be insufficient to meet a 750 yg/m3 standard and
that NO flue gas treatment technology (90 percent NOX control)
would almost certainly be required on these units to meet a
500 yg/m3 standard. Cases of interaction of several power
plant plumes were also studied with similar results and conclu-
sions Thus, it appears that a short-term N02 ambient air
quality standard could require stringent N0x controls on new
and existing stationary combustion sources.
iv
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TABLE OF CONTENTS
Page
EXECUTIVE SUMMARY .
CONTENTS - v
FIGURES _ __ vii
TABLES _
1.0 INTRODUCTION i
2.0 CONCLUSIONS 3
3.0 RECOMMENDATIONS 9
4.0 TECHNICAL DISCUSSION u
4.1 An Adapted Gaussian Model n
4.2 The Reactive Gaussian Model H
4.2.1 Background H
4.2.2 Application of NO 14
4.2.3 The Equilibrium Hypothesis 16
4.3 Reactive Model Results 19
4.3.1 Interactions Between NO, N02, 03 In a
Plume 19
4.3.2 Power Plant Reactive Plume Modeling 23
4.3.2.1 Meteorology 24
4.3.2.2 Power Plants 25
4.3.3 Model Results—Individual Plants 26
4.3.4 Model Results — Interaction Case 30
REFERENCES 34
APPENDICES
A. SELECTED CONVERSION FACTORS ' 35
B. SUMMARY OF METEOROLOGICAL CONDITIONS FOR CASE
DAYS STUDIED - 37
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TABLE OF CONTENTS (continued)
Page
C. PREDICTED 1975 NO AND NO LEVELS FOR SIX
CHICAGO AREA POWER PLANTS - PREVIOUS
STUDY (NON-REACTIVE PLUME MODEL) 42
D. PREDICTED NO AND NO CONCENTRATIONS FOR
SIX CHICAGO-AREA POWER PLANTS--REACTIVE
PLUME MODEL 49
E. PREDICTED NO CONCENTRATION FOR INTERACTION
OF EIGHT CHICAGO-AREA POWER PLANTS--REACTIVE
PLUME MODEL — 56
VI
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LIST OF FIGURES
Number Page
1 PROCEDURE FOR COMPUTING SHORT-TERM CONCENTRA-
TIONS OF NO, N02, AND 03 18
2 SPECIES CONCENTRATIONS OF NO, N02, AND 03 VERSUS
N0x CONCENTRATIONS — 20
3 TYPICAL SURFACE CONCENTRATIONS OF NO, N02, AND
03 DOWNWIND FROM STACK 21
4 TYPICAL SPECIES CONCENTRATIONS ACROSS WIDTH OF
PLUME 22
5 POWER PLANTS IN CHICAGO AQCR-- 27
6 NO 2 CONCENTRATIONS AND N02/NO RATIO FOR AN
EXAMPLE INTERACTION CASE 32
vii
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LIST OF TABLES
Number Page
1 OVERALL PLUME N02/NOV RATIOS AT POINT OF PEAK
X
CONCENTRATION OBTAINED FROM REACTIVE MODEL -
HIGH OZONE CASE--
2 EFFECT OF NEW N02/NOV RATIOS ON RESULTS OF
X
PREVIOUS STUDY - SUMMER A.M., COINCIDENT
HIGH OZONE CASE
3 1975 ESTIMATED NO FROM SIX POWER PLANTS
x
STUDIED (NOX AS N02) 28
MODEL RESULTS FOR WILL COUNTY PLANT 29
viii
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1.0 INTRODUCTION
Nitrogen oxides react with numerous chemical pollutants
in the atmosphere. Consequently, simulation of NOX reactions is
an important and complicated problem. The most important reactions
im most photochemical situations concern NO, N02, 03, and hydro-
carbons in the presence of sunlight. Sunlight causes N02 to break
down to an NO molecule and an oxygen atom. This oxygen atom
combines with an 02 molecule to form ozone, which then combines
with NO to form N02 and 02. Thus, oxygen atoms tend to "trade
off" between NO and 02.
The process becomes much more complicated when hydro-
carbons are considered. The mechanism here seems to be that HC
molecules present reaction "paths" for the production of N02 from
NO which do not involve the breakdown of 03. Thus, a surplus of
03 builds up from the dissociation of N02 and the subsequent
reformation of 0 atoms with 02 molecules. This explains the heavy
buildup of ozone in the presence of large hydrocarbon concentra-
tions .
All of these mechanisms (and many others) enter into
the modeling of NOX in the atmosphere. In addition, the chemical
pollutants are being advected and diffused by wind and turbulence
in the atmosphere. In general, large numerical computer models
are required to simulate atmospheric chemistry. However, these
models are generally very expensive and difficult to use.
One recourse available to the modeler is to utilize
the simpler and less expensive Gaussian plume model. This type
of model has enjoyed great success in modeling the advection and
diffusion of pollutants in the past. It offers an analytical
closed-form solution to the diffusion equation often used to model
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advection and diffusion of inert pollutants. As long as the
ground surface in the area to be modeled is not too irregular,
and the wind field is homogenous and wind shear is not too large,
the Gaussian model is usually adequate for inert chemical species.
However, the diffusion equation for which the Gaussian formulae
are derived are not valid when the species are reactive. The
chemical reactions introduce nonlinearities into the diffusion
equation which make analytical solutions impossible.
In modeling NOX, the nitrogen atoms are usually assumed
to be present only in NO or N02. Consequently, it is permissible
to consider the sum of these concentrations, or identically the
concentration of NOX, to be inert. Thus, NOX may be modeled by
a Gaussian plume formula. This was done by Radian in a previous
study for EPA, Eppright et al, Impact of Point Source Control
Strategies on N02 Levels, EPA-600/7-78-212, November 1978.l
In this case, the difficulty is assessing the proper
ratio of NO to N02 or, identically, the ratio of NO or N02 con-
centrations to total NOV concentrations. In the above previous
X
study a constant ratio was assumed for all parts of the plume,
meaning essentially that both NO and N02 concentrations were
described by Gaussian formulae. Moreover, the ratio of N02 to
NOX in the plume was assumed based on ambient data to be either
1/2 (0.5) in summer or 1/4 (0.25) in winter. The purpose of this
study was to develop a more sophisticated treatment of the photo-
chemistry in order to investigate the applicability of these ratios.
In this study, several of the cases in the previous report
were analyzed using the reactive model described in this report.
Days with high ozone concentrations were identified and meteoro-
logical conditions and ambient NO, N02, and ozone concentrations
were developed. The cases were modeled using the above data for
both high (0.2 ppm) and low (0.1 ppm) ozone concentrations. Also,
interaction of sources was studied to a limited extent.
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2.0 CONCLUSIONS
The reactive model was run for several cases involving
six power plants in the Chicago AQCR. A range of meteorological
conditions was identified for days with high ambient ozone con-
centrations. Meteorological conditions were varied in order to
study the surface N02/NOX ratios due to the power plants under
conditions when a short-term N02 standard might be violated. Re-
sults for individual power plants are shown in Appendix D and are
discussed in Section 4.3.3. From these results the following
conclusions concerning the cases studied were drawn:
• N02/NOX ratio for the plume at the point of highest
ground level concentration increases as the back-
ground ozone concentration increases. Ozone pro-
bably has the most influence on the ratio because
for higher ozone levels, larger fractions of NO
are converted to N02. According to the theory used
in the modeling approach, the total NOV concentration
f\
(NO + N02) is independent of background ozone con-
centration.
• For a given wind speed, as the atmosphere becomes
more stable over the range of stabilities studied,
the N02/NOV ratio increases.
For a given stability class studied, the N02/NOX
ratio decreases as wind speed increases.
For a given stability class, the distance of the
NOX peak from the stack decreases as wind speed
increases. This is a general characteristic of
Gaussian dispersion models.
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It should be noted that these conclusions are valid
only for peak concentrations. At other locations within the plume,
different N02/NOX ratios will occur. For example, the N02/NOX
ratio increases as cross wind distance from the plume centerline
increases although the total concentration of NOX is reduced over
the same distance.
It is also worthwhile to mention that most of those
conclusions can be anticipated from the knowledge that (a) as NOX
increases, with a given 03 background, less conversion of total
NO to N02 occurs, meaning the ratio of N02/NOX decreases, and
(b) given a fixed total NOX value, as 03 increases so does the
N02/N0x ratio. Given these facts, which are derived from the re-
sults of the Technical Discussion (Part 4.0), the major conclu-
sion which might not be expected is that, for a given stability
class, the N02/N0 ratio decreases as wind speed increases. This
is probably due to the fact that an increasing wind speed will
lower the plume height, so that the maximum NOX concentration
will be raised, and thus the N02/NOX ratio will be decreased.
It was also found that plant plume interactions are
still potentially significant contributors to high ambient N02
concentrations. The reactive model predicts that plume inter-
actions may indeed occur over reasonably long distances, depending
upon meteorological conditions. Results for power plant interac-
tion cases are shown in Appendix E and are discussed in Section
4.3.4.
For individual plants, ratios of N02/NOX in the plumes
at points of peak concentration were found to vary between 0.19
and 0.80 for low backgound ozone concentrations and from 0.46 to
0.93 for high ozone concentrations. Results for the latter case
are shown in Table 1. They are considerably higher than the ratio
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of 0.5 assumed for summer conditions in the previous study.
The results of the earlier study, shown in Appendix D, indicate
that previous worst cases occurred for summer A.M., C stability,
5 m/sec wind speed. These conditions are very similar to those
used in the present study (C stability, 4.5 m/sec) except for
mixing height.* Thus, for coincident high ozone and NOX, it
appears that the N02/NOX ratio in the plume can be significantly
higher than 0.5.
For the six plants studied using the reactive model (1985
emissions levels), the summer A.M. NOa concentrations from the pre-
vious study (ratio of 0.5) were reapportioned using the new N02/
N0x ratios. Non-power-plant ratios were assumed to remain at 0.5.
The results are shown in Table 2. These are the short-term results
which would have been obtained in the previous study had higher
N02/NOX ratios for the power plants been used as appears to be
warranted by the results of the latest reactive study.
The new results indicate that, for these conditions
with concurrent high ozone levels, the threshold short-term N02
standard level where flue gas treatment (FGT) for NO becomes
necessary could increase by at least 40 percent, i.e., if 500
Ug/m3 were the threshold level under the old study, 750 yg/m3
could be the new threshold level. For the above plants, the
previous study indicated that most could meet a 400 yg/m3 short-
term standard with combustion modification techniques for NO
control. The reactive sutyd indicates that combustion modifica-
may be insufficient to meet a 750 yg/m3 standard and that NO
flue gas treatment technology would almost certainly be required
* The theoretical analysis in Section 4.2 indicates, however, that
increased NOX concentrations due to reduced mixing heights will
still result in plume N02/N0 ratios significantly higher than
0.5 under high ozone conditions (e.g. 0.2 ppm) .
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TABLE 1.
OVERALL PLUME N02/NOX RATIOS AT POINT
OF PEAK CONCENTRATION OBTAINED FROM
REACTIVE MODEL - HIGH OZONE CASE
Stability
B
C
D
Range In
Wind Speed
Studied
1-3 m/sec
3-6 m/sec
6-8 m/sec
N02/NOX Ratio
Min Max
.46
.45
.77
90
91
93
Avg.
.76
.78
.90
(Note: Bethlehem Steel showed consistently lower ratios than
all other power plants and thus tended to reduce the
average ratio.)
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TABLE 2. EFFECT OF NEW N02/NOV RATIOS ON RESULTS OF
Ps
PREVIOUS STUDY - SUMMER A.M., COINCIDENT HIGH OZONE.CASE
As Modified Based on
As Reported in Previous
Plant
Bailly **
Will Cty +
Waukegan +
Jollet +
Fisk+
Both Stl
Plant Plume
N0s/N0x Ratio
0.5
0.5
0.5
0.5
0.5
0.5
Total
NOX
1696
1648
1588
2336
1531
2554
Study
Plant
NO 2
754
710
524
998
379
1182
Total
NO 2
849
824
794
1168
766
1277
Results
riant Plume
N02/N0x Ratio
0.90
0.76
0.88
0.75
0.82
0.50
of Latest Study
Total
N0y
1696
1648
1588
2336
1531
2554
Plant
NOX
1357
1078
922
1497
652
1182
Total
NOZ*
1451
1193
1372
1667
1039
1277
* Total N02 assumes 50 percent conversion of non-power plant NOX to N02.
** Northern Indiana Public Service
+ Commonwealth Edison
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on these units to meet a 500 yg/m3 standard. These effects
might be further amplified if non-power plant plumes also had
higher N02/N0x ratios.
Results of the interaction cases indicate the same
effect, namely that NOX flue gas treatment most probably will
be required to meet higher short-term ambient N02 standards if
plume reactivity is considered. Thus, it appears that a short-
term N02 ambient air quality standard could require stringent
N0x conctrols on new and existing stationary combustion sources,
8
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3.0 RECOMMENDATIONS
Further study of the application of NOX control tech-
nology to large point sources should be undertaken. While this
study essentially agrees with the previous study that large point
sources may dominate high short-term N02 levels based upon
reactive plume modeling, several factors merit further investiga-
tion. First, the stack emissions in Ib/hr* from each plant were
assumed to consist entirely of NO. The effects of NO/NOX ratio
and ozone concentration in the stack upon N02/N0x ratio downwind
should be investigated in detail as N02 can constitute a signi-
ficant portion of the effluent from some sources. Second, this
study has shown that the downwind N02/N0x ratio is highly depen-
dent upon background ozone concentration and meteorological con-
ditions. In the case of the plants studied, site-specific meteor-
ological conditions related to the lake breeze effect were not
considered, although the lake breeze is thought to have contri-
buted significantly to high ozone concentrations on several days
during the period studied. More defensible results could be ob-
tained if the meteorological conditions were investigated more
thoroughly or if another AQCR without these specific conditions
were investigated. Third, a large scale study of plant inter-
actions similar to the previous study should be considered in
order to further clarify the extent of power plant N02 impact.
Fourth, the new reactive model should be investigated with respect
to applicability, especially with regard to variations in diffu-
sivity and advection coefficients. Finally, a large scale photo-
chemical model should be used to investigate the effects of point
source NOX control strategies on levels of NO, N02, ozone, and
other pollutants on an AQCR basis.
* Government policy is to stress the use of SI units in technical
reports. However, for this report, commonly used units will be
given. Conversion factors are shown in Appendix A
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Furthermore, cost and performance characteristics of
full-scale NOX flue gas treatment (FGT) control devices should
continue to be studied. The effects of these devices on air
quality, economics, and system performance should be investi-
gated.
10
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4.0 TECHNICAL DISCUSSION
4.1 An Adapted Gaussian Model
The reactive plume model developed and used in this
study will be discussed. This model was an adapted form of the
Gaussian dispersion formula. It was found that, although the
species NO, N02, and 03 are not inert, some linear combinations of
these species' concentrations act as they were inert2' 3' "*. in
addition, reactions between these particular species are generally
fast enough to assume they are in equilibrium. This phenomenon
will be discussed in greater detail in Section 4.2. The impor-
tance of these two observations is that they allow the determina-
tion of closed form solutions rather than requiring numerical
solutions for the concentrations of these three species when they
are the only three pollutants present.
Of course, this last condition is not usually fulfilled.
The presence of hydrocarbons in the atmosphere causes a slow
buildup of ozone which interacts with NO to form N02, as mentioned
before. Thus the (NO, N02, 03) system is not closed. However,
the ozone buildup is so gradual that for a given short-term ob-
servation, the 03 acts as a background concentration. Thus, when
03 background concentrations are available, the simulation mecha-
nism described here will be a reasonable approximation for short-
term analyses.
4.2 The Reactive Gaussian Model
4.2.1 Background
The reactive Gaussian computer model used was a modi-
fied version of a Gaussian dispersion model. Whereas most Gaussian
11
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models are non-reactive, the version used in this study reflects
three of the major photochemical reactions known to occur in the
atmosphere. These three reactions are described as follows:
N02 + hy -*• NO -f 0; ki (depends on sunlight), (1)
0 + 02 -»• 03; k2 = 2.33 x 10"5ppm"2 min"1 (2)
NO 4- 03 + N02 4- 02;k3 = 2.95 x 10 ppm"l min"1 (3)
Since the reaction in equation (2) occurs quite rapidly, equations
(1) and (3) dominate the chemistry.
These equations are by no means the only photochemical
processes which occur in the atmosphere. Certainly reactions
involving hydrocarbons, C02, and H20 contribute heavily to the
photochemical problem. However, these three reactions, when
incorporated into an atmospheric dispersion model, can be used to
show short-term trends in the major photochemical species in NO,
N02, and 03.
The use of Gaussian model to predict dispersion and
advection processes involves other difficulties apart from not
dealing with hydrocarbons. Modern numerical models are better
equipped to describe the complex structure of the lower atmo-
sphere, and in addition, are better predictors of atmospheric
mechanisms in complex terrain. Moreover, the major advantage of
numerical models is their ability to simulate the chemical mech-
anisms which occur in the atmosphere because the concentrations
of chemical species at any point in space and time are functions
of the reactions which took place prior to the time considered.
Thus, in order to find the concentration of N02 at a given time
and place in the atmosphere, one must solve for the concentra-
tions of all three species, NO, N02 and 03 for all times prior
to that considered, and for all locations in space from which
12
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pollutants may diffuse or advect to the point in question. This
methodology is ideally suited for numerical cell models, since
they already employ a reiterative scheme in determining the wind
flow. The major difficulty with numerical models is their ex-
tremely long solution time and attendant expense. In addition,
the complexity of the numerical approach makes it difficult to
get any insight into the physical mechanisms which can be applied
generally.
The model developed for this study uses the photosta-
tionary state relationship ^ 3 to obtain an analytical solution to
the species concentrations, while largely incorporating the chem-
ical processes described in reactions (1) to (3). The analytical
nature of the model allows a very fast computation time, and also
allows some fairly general statements to be made concerning the
chemical processes.
As was previously mentioned, the reason that a Gaussian
model is not directly applicable to the species NO, N02, and 03
is that they are not inert. Their reactions introduce nonlineari-
ties into the diffusion equations for the concentrations which
prohibit their expansions as Gaussian curves.
However, consider the case of a closed volume with
interacting species which are not in equilibrium. Though the
molecular concentrations change, the atomic concentrations
(obtained by adding the distributions from different species) will
not, as a consequence of the conservation of mass. Following
Peters and Richards3 this fact can be exploited to decouple the
differential equations which describe the NO, N02 and 03 reactions.
Inherent to this decoupling process is the assumption that atomic
concentrations are diffused independently of the molecular form
in which they are bound. In the case of a single nitrogen atom,
13
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this assumption implies that its movement due to diffusion and
turbulence is, for the practical purposes, independent of whether
the atom is bound up with a single oxygen atom as NO or two oxygen
atoms (NOa)• In other words, given the position of the nitrogen
atom at a certain time, its position at a later time will be gov-
erned by a distribution law which is independent of the other atoms
with which it is bonded. Although this assumption seems question-
able on a microscopic level (because of the different molecular
weights and different molecular diffusion rates), on a macroscopic
level the atmospheric turbulence dominates the diffusion and
differences due to molecular type are inconsequential. This prin-
ciple is generally assumed in modeling any airborne pollutant.
4.2.2 Application to NOX
Consider the nitrogen atoms in the equations (1), (2),
and (3). They can exist either in the form NO or N02. Thus,
the concentration of nitrogen atoms is given by
i|»i = [NO] + [N02] <4>
Now, by the preceding arguments, in the case of a con-
tinuous point source at point (0, 0, H) of the coordinate system,
in a steady wind u in the x direction it may be seen that
_ i TJ\ 2 t — u\ 2\ t c\
z T tij _ (z - n.) \ v->;
where iho is the background level of [NO] + [NO2] and Qi is the
source strength of [NOj + lN02]- Other forms of the Gaussian
formula are available, but this is sufficient for explanation.
14
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Thus, the nitrogen atomic concentration is given. One
might ask if there are any other "composites" of this type. One
such group is the "floating" oxygen atoms which may either be
"free" (that is, 0 atoms) or bound up on N02 or 03. These atoms
are driven by turbulence and diffusion mechanisms identical to
those which influence the nitrogen atoms, so the quantity
[N02] + [03] + [0] is determined by an equation analogous to that
for the nitrogen atoms, if it is assumed that equations (1), (2),
and (3) are all that apply (i.e., other photochemical processes
are ignored). Since [0] is small, due to the reaction speed of
equation (2), the combination considered is as follows:
$2 » [03] + [N02] (6)
with a distribution of the form,
1^2 = ^20
where i|»2o is the background level of [N02] + [03] and Qa is the
source strength of [N02] + [ 03].
It is anticipated that in many cases of interest involv-
ing equations (5) and (7), one will have 4>io = Qz = 0 since the
background level of [NO] + [NO2] will be zero and all the pollu-
tant emitted from the stack will be NO, meaning Qa = 0. However,
equations (5) and (7) will be maintained in their present form
for symmetry and generality. Nonzero background levels were
used in this analysis.
15
-------
4.2.3 The Equilibrium Hypothesis
Since ^i and ^2 are given in closed form, equations (4)
and (6) give two equations in three unknowns. The concentrations
[NO], [N02J, and [03] cannot be found without more assumptions.
If the assumption is made that the species [NO],
and [03] are in equilibrium, then there exist three equations in
three unknowns allowing a solution. Choosing [NO] as the species
in question,
d| [NO] = k, [N02] - k3[NO][03] (8)
and for equilibrium to hold, this must equal zero, so
(9)
Combining equations (4) , (6) , and (9) gives
(10)
[N02] -'.
*i - *2 - Tp- V(*i + ^2 + rr) - 4*i*2 (ID
[NO] - £i
[Oj]
Thus, the species concentrations are available in closed
form for a short-term solution.
16
-------
These are the solutions for the NO, N02 and 03 concen-
trations given the assumption of equilibrium. There are some
difficulties with this assumption, as are discussed in references
(2), (3), and (4). In general, non-homogeneities in the plume
and background concentrations seem to cause some departures from
equilibrium, but it is thought that this is largely a result of
o
concentration measurements which are averaged over time. Until
more is known about these processes, the equilibrium assumption
still appears to be a very reasonable and practical approach.
It should be mentioned here that in applying equations
(10) through (12), it is not necessary to actually calculate the
new composite functions i|>i or i|>2. Instead, it is sufficient to
observe that by the arguments of the preceding section the same
results were obtained for the atomic concentrations regardless of
whether the species was considered inert. Thus, the existing
Gaussian model can be modified and used to calculate the "inert"
species concentrations at any given point in space, and then these
quantities transformed to get the new equilibrium concentrations.
Thus, if the existing model gives [NO] , [N02] , and
o o
[03] as the "inert" concentrations at a point (x, y, z) , then
from equations (4) and (6)
*i - CNO]0 + [N02]Q
[N02]
o (14)
Equations (10) through (12) may then be applied directly to
i|>i, ^2 to transform the "inert" concentrations to actual concen-
trations. This procedure, shown in Figure 1, was used in the
present study.
17
-------
Input Data
Meteorological Conditions
Oi, NOX Background Values
Plant Data--N0 Emission Rates
Points for Computation
Compute vi - [NOX] at Each
Ambient Point Using Standard
Gaussian Dispersion Formulae
Compute *2 " [NO2] + [Oj]
Using Background Ozone
and NO j Levels
Apply Equilibrium
Hypothesis to tf>i and vz
to Compute [NO], [N02]
and [03] at Each Point
FIGURE 1. PROCEDURE FOR COMPUTING SHORT-
TERM CONCENTRATIONS OF NO, N02, AND 03
18
-------
4.3 Reactive Model Results
In the previous section it was shown that an analytic
solution to the short-term reactive plume problem could be reached.
The methodology developed was tested both theoretically and prac-
tically. These results will now be discussed.
4.3.1 Interactions Between NO, N02 , Oa In a Plume
It is useful to consider the relative concentrations
of NO, N02, and Oa which exist in a plume when these species are
in equilibrium. Using the equilibrium relation previously derived,
INO][03] = kj. = k (15)
[N02] k3
and the above methods it is possible to obtain the short-term
concentrations of NO, N02, and 03 as a function of [NO ]. Assum-
ing an initial background concentration of 0.1 ppm for ozone, and
assuming k=0.01, Figure 2 shows these concentrations. Notice
that if K is changed to 0.005 the curves are virtually unchanged,
so exact values of k are not crucial.
Another informative way of viewing the NO, N02, Oa inter-
actions is by considering a typical plume. Figure 3 shows the
three species' surface concentrations at various points downwind
from a stack. Figure 4 shows the concentrations as a function of
crosswind distance from the plume centerline.
A third observation about the relative NO, N02,and NO
X
concentrations is that there is usually some ambiguity about the
proportions of these species emitted from the stack. Thus, often
19
-------
Concen-
tration
(ppm)
equilibrium const. - .01
equilibrium const. « .005
.1
.2 .3
(NO,) (ppoi)
/ (N0x= NO + N02)
.5
02-4241-1
FIGURE 2. SPECIES CONCENTRATIONS OF NO,
N02, AND Os versus NO CONCENTRATIONS
20
-------
Increasing Distance •*•
02-4242-1
FIGURE 3. TYPICAL SURFACE CONCENTRATIONS OF
NO, NO2, AND 03 DOWNWIND FROM STACK
21
-------
(0,)
Increasing Distance from Centerline of Flume -*•
02-4243-1
FIGURE 4. TYPICAL SPECIES CONCENTRATIONS
ACROSS WIDTH OF PLUME
22
-------
measurements of NOX emissions do not discriminate between NO and
N02. However, with the huge concentrations of NOX within the stack,
Figure 2 shows that NO will prevail. Indeed, NO is generally
assumed to comprise 95 percent or more of the NOX present in stack
emissions. This is important because it allows the simplifying
assumption that plant NOX emissions are comprised entirely of NO.
4.3.2 Power Plant Reactive Plume Modeling
Computer runs using the new reactive model were made for
six power plants in the Chicago AQCR under a large variety of
meteorological conditions to determine the ratios of N02 to NO
concentrations. Three types of cases were investigated, all of
which were based on concentrations downwind from the stacks.
(1) First, the total NOX concentration was
calculated, assuming a constant background
concentration of NOX of 0.05 ppm, which
is a representative value.
(2) A low-ozone situation was simulated.
This run used the same background value
of NOX as (1), but the ratio of background
NOz to NOX was adjusted to give equilibrium.
The ozone level was set at 0.1 ppm.
(3) A high-ozone background was simulated.
Here the ozone level was set at 0.2 ppm.
The NOX level was kept at 0.05 ppm, but
again the background N0-N02 split was
adjusted for equilibrium.
23
-------
In each case the following results were obtained:
Downwind distance of N02 and N0x peaks
• NO2 and NOX concentrations
Ratio of NO2 to NO for the plume only
These cases were evaluated for given meteorological
conditions and power plant outputs.
4.3.2.1 Meteorology
Ambient atmospheric conditions were developed from
actual 1975 Chicago data. Seven days with extremely high ambient
Oa levels at up to seven continuous monitor sites were identified.*
Ambient ozone maximum levels on these days ranged from slightly
over 0.1 ppm to nearly 0.25 ppm. A synopsis of Chicago meteoro-
logical conditions for these days is given in Appendix B. In
general, meteorological conditons associated with these days were
as follows:
Sunny and warm with no cloud cover, haze,
or thin high clouds
High pressure and/or presence of a cool front
Temperature in high 80's or low 90's
• Wind speeds about 10 mph or less
B or C stability
Unlimited mixing or high mixing heights*
*It was assumed that high ambient 03 levels would result in high
N02 levels for power plants.
24
-------
The "stability" of the atmosphere refers to its ability to dis-
perse pollutants. Mixing height in the thickness of a ground-
gased layer through which pollutant mixing and dispersion occurs.
In addition, on several days conditions were favorable
for onshore penetration by the lake breeze or lake breeze enhance-
ment of meteorological conditions in the areas with the highest
ambient concentrations.
For each of the above three case types (representative
low 03, high 03), nine meteorological situations were simulated.
Type B stability was run with wind speeds of 1, 2, and 3 m/sec.
Type C wind speeds considered were 3, 4.5, and 6 m/sec. Type D
stabilities had wind speeds of 6, 7, and 8 m/sec. The temperature
was 80°F, and there was unlimited mixing. As previously stated,
these conditions appear to be conducive to high ambient ozone
levels in Chicago, although further investigations should also
address lake breeze effects.
4.3.2.2 Power Plants
The following six Chicago-area coal-fired power plants
were investigated in this study:
Bailly (Northern Indiana Public Service)
Will County (Commonwealth Edison)
Waukegan (Commonwealth Edison
Joliet (Commonwealth Edison)
• Fisk (Commonwealth Edison)
• Bethlehem Steel
*In the previous study results (Appendix C), mixing heights
ranged from 200-800 meters. Theoretically, these lower mixing
heights are usually conducive to high ozone formation. The
ozone incident studied may have resulted from other factors (such
as lake breeze effect) despite unlimited mixing or high mixing
heights.
25
-------
The locations of these plants are shown in Figure 5.
In the previous Chicago study, these six plants had high ambient
NOX and N02 levels predicted; these levels are shown for 1975 in
Appendix C.
NOX emissions for 1975 for these six plants were esti-
mated in the previous study and are shown in Table 3. These emis-
sions were assumed to be entirely NO at the stack orifice; the
values in Table 3 were converted to reflect the change in atomic
weight. It was also assumed that no ozone was emitted from the
stacks.
A.3.3 Model Results--Individual Plants
Detailed model results for the six plants studied are
shown in Appendix D. Ratios of N02/NOX at the point of highest
ground level concentration ranged from 0.19 to 0.80 for low back-
ground ozone concentrations and from 0.46 to 0.93 for high ozone
concentrations. As an example, results for the Will County plant
are shown in Table 4. From the results, the following conclusions
concerning the cases studied were drawn:
• the N02/N0xratio for the plume at the point
of highest ground level concentration is
related to background ozone concentration.
Ozone probably has more influence on the
ratio than any other factor.
• for a given wind speed, as the atmosphere
becomes more stable over the range of sta-
bilities studied, the ratio of N02/NOX
increases.
26
-------
•<530
<560 -
GRUNDY
r
i
i KAMKAKEH
^/
3SO
380
— AQCR BOUNDARY
EI3 INCORPORATED A« = A BOUNDARY
-- COUNTY BOUNDARIES
O UTILITY FOSSIL-FLTLED STEAM PLANT
+ UTILITY COMBUSTION TURBINE PLANT
A NON-UTILITY FOSSIL-FUELED STEAM PLANT
UTW EASTING
FIGURE 5. POWER PLANTS IN CHICAGO AQCR
(Plants Used Are Identified)
27
-------
TABLE 3. 1975 ESTIMATED NOX
FROM SIX POWER PLANTS STUDIED
(N0y AS NO 2)
Plant NOX as N02*
(Ib/hr)
Bailly 14,960
Will County 15,126
Waukegan 13 > 414
Joliet 24,606
Fisk 7>298
Bethlehem Steel 10,135
"Full Load.
28
-------
TABLE 4.
MODEL RESULTS FOR WILL COUNTY PLANT
LOW OZONE BACKGROUND
HIGH OZONE BACKGROUND
ro
so
STABILITY
B
B
B
C
C
C
D
D
D
WIND SPEED
METERS /SEC
1
2
3
3
4.5
6
6
7
8
DISTANCE OF NO
PEAK FROM 1ST
STACK (m)
11600
4000
2800
6400
4800
4000
16800
14400
12800
NOX IN EXCESS
OF BACKGROUND
NOX (ppm)
.152
.220
.257
.184
.214
.229
.082
.088
.093
N02 IN EXCESS OF
BACKGROUND NO,
yg/m3
133
144
147
140
143
145
102
106
109
ppm
.072
.078
.080
.076
.078
.078
.055
.058
.059
EXCESS N02
EXCESS NOX
(ppm)
.48
.35
.31
.41
.36
.34
.66
.65
.64
N02 IN EXCESS OF
BACKGROUND N02
Ug/m*
240
305
325
275
301
311
138
148
155
ppm
.130
.165
.180
.150
.160
.170
.075
.080
.080
EXCESS N02
EXCESS N0x
(ppm)
.85
.75
.69
.81
.76
.74
.91
.91
.90
Background Concentrations*
Low Ozone Case:
f03] - .1 ppm, [NOX1 - .05 ppm, [NO] - .00455 ppm, fN02J - .0455
High Ozone Case:
[Oi] - .2 ppm, [NOJ • .05 ppm, [NO] - .00238 ppm, [N02] - .0476 ppm
ppm
-------
• for a given stability class, the distance
of the NO peak from the stack decreases
as wind speed increases. This is a general
characteristic of Gaussian dispersion mo-
dels.
It should also be noted that the total [NOX] value is
independent of the concentration of background ozone, so one
value of [N0x] is given for both cases. Also, the NO, N02, and
NO concentrations all peak at the same point in the modeling
results, which is again the result of the monotonic dependence
of [NO] and [N02] on [NOX] in the model theory, as illustrated
earlier in Figure 2.
It also appears that the short-term N02 impact of power
plants will be significant in many cases. Moreover, it should be
noted that, for the cases studied, the net percentage of N02 at
the point of greatest impact may be greater than the value
assumed in the previous study, depending on background ozone con-
centration. This would result-in greater power plant impacts and,
thus, a greater need for flue gas treatment to meet a given short-
term N02 standard.
4.3.4 Model Results — Interaction Case
The interaction of plumes from eight power plants along
the Chicago Sanitary and Barge Canal was also studied. Resulting
ground-level N02 concentrations along a line from Collins to Fisk
for the meteorological conditions discussed in Section 4.3.2.1
are shown in Appendix E. The case studied which resulted in the
highest N02 concentrations was B stability, high ozone; these re-
sults are shown in Figure 6 along with the N02/N0 ratio for a
X
wind speed of 1 m/sec.
30
-------
When NO concentrations from a given plume are calcu-
lated in a Gaussian model the predictions are questionable beyond
50 km, and since the total distance modeled in this study was of
the order of 100 km, this might cause some concern. However, the
figures clearly show that the most important interactive effects
occur within 50 km of each stack (where the Gaussian approach is
reasonable).
Comparison of these results with others in Appendix E
indicates that strong plume interactions may indeed occur. The
degree of interaction and the resulting ground level N02 concen-
trations at any point was found to be a result of the following
factors:
• background ozone concentration
• stability class
wind speed (and direction)
In addition, the degree of interaction is highly depen-
dent upon power plant loading; this was not investigated in this
study although it was addressed to some degree for "typical" cases
in the previous study. The cases investigated in this study
assumed that all plants were operating at full load, a case which
amy not occur during most of the year. However, this case is
more likely to occur during the meteorological conditions addressed
in this study, since high ozone conditions are generally associated
with hot weather and strongly correlate with summer peak loads
caused by high air-conditioning demand. For example, the Common-
wealth Edison 1975 summer peak load of 12,305 megawatts occurred
on August 1 between 1 and 2 pm; August 1 was one of the days
studied because of high ozone levels. Moreover, the Commonwealth
31
-------
10.000-f
10.000
o
Will
COIIIll*
LIKE Of IKICRACIIO* STUDIED
o HIM.O
QJOIIET 7.8
OjOUtT 2.1.6
ORIOMUKO
I«/SK
JW5*C
)•/$«
0.80
•
0.70
10.000
-^^ ^OOO *0.000 70.000 W.OOO
sunct IHflers)
6 N02 CONCENTRATIONS AND N02/N0x RATIO
FOR AN EXAMPLE INTERACTION CASE
32
-------
Edison summer peak period in 1975 was from 14 July to 30 August,
a period including all but two of the days with very high ozone
levels. Hence, it is not unreasonable for generalized analysis
to consider cases with power plants at full load or nearly full
load, especially if the system peak correlates well with high
measured ambient ozone levels.*
* Because of its general nature, this analysis did not attempt to
include actual plant loadings. More specific analysis of actual
case days should include actual loadings and emission rates.
33
-------
REFERENCES
1. B. R. Eppright, et al, Impact of Point Source Control
Strategies in N02 Levels. EPA-RJO/7-78-212, Novem^
her 1978.
2. Bilger, R. W. (1978) "The effect of admixing fresh
emissions on the photostationary state relationship
in photochemical smog." Atmospheric Environment 12,
1109-1118.
3. Peters, L. K. and Richards, L. W. (1977) "Extension
of atmospheric dispersion models to incorporate fast
reversible reactions." Atmospheric Environment 11,
101-108.
4. Kewley, D. J. (1978) "Atmospheric Dispersion of a
Chemically Reacting Plume." Atmospheric Environment
Vol. 12 pp. 1895-1900.
5. Seinfeld, J. H. (1975) Air Pollution: Physical and
Chemical Fundamentals. McUraw-Hill, Inc.
34
-------
APPENDIX A
SELECTED CONVERSION FACTORS
35
-------
APPENDIX A
SELECTED CONVERSION FACTORS
New Units
Joules
Metric Tons/
Year
Equal
Old Units
Million BTU
(MMBTU)
Tons/Year
Multiplied By
1.054 x 109
0.907
m/sec
knots
0.514
g/sec
Ib/hour
0.125
nr
Thousand Cubic
Feet (MCF)
28.3
m/sec
inph
0.447
kilometer
mile
1.609
g/joule
lb/MMBTU
4.304 x 10"7
kPa
psia
0.143
36
-------
APPENDIX B
SUMMARY OF METEOROLOGICAL CONDITIONS
FOR CASE DAYS STUDIED
37
-------
APPENDIX B
07/01/75
SUMMARY OF METEOROLOGICAL CONDITIONS
FOR CASE DAYS STUDIED
Sunny; warm; no precipitation in area.
Weak pressure gradient, on west part of broad
high pressure system.
Southeasterly to southerly gradient flow over
area. Wind speed 3-12 mph.
Favorable for lake breeze from Lake Michigan to
reach well into Chicago.
C stability; temperature mid-80's.
Mixing heights 6700-6800 ft.
07/02/75
Mostly sunny, with mostly high, thin clouds;
warm; and no precipitation in area.
Weak pressure gradient in morning, becoming some-
what stronger in afternoon, as broad high pressure
system shifted slowly to position southwest through
southeast of Chicago.
Southwesterly to westerly gradient flow over area.
Wind speed 3-9 mph.
Not very favorable for lake breeze to extend
onshore on west side of Lake Michigan.
B stability; temperature upper 80's.
Mixing heights 6500-6800 ft.
38
-------
07/30/75
Sunny; warm; no precipitation; hazy.
High pressure ridge over area, with center in
northeastern U.S.
Easterly gradient wind over most of area. Wind
speed 3-13 mph.
Favorable for lake breeze enhancement of easterly
winds to occur well into Chicago.
C stability; temperature lower 90's.
Mixing heights 500-5800 ft.
07/31/75
08/01/75
Sunny; warm; no precipitation; hazy.
High pressure over area, with one center over
northern lower Michigan and one in the Middle
Atlantic States.
Easterly gradient flow, in general, over the area,
with a northeast tendency. Wind speed 0-13 mph.
C stability; temperature lower 90's.
Mixing heights 500-5700 ft.
Partly sunny in morning, mostly cloudy in afternoon
and night; warm; thundershowers and showers in
latter part of afternoon and in evening; hazy in
early morning, before thundershowers began in after-
noon, and between showers.
39
-------
-- Cold front moving east from Central and Northern
Plains and weak disturbance moving north from
lower Mississippi Valley; high pressure shifting
slowly southeastward.
-- Generally southerly to southeasterly gradient
winds over area, but variable and gusty with
disturbed conditions in afternoon. Wind speeds
0-13 mph.
-- Marginal situation for significant penetration of
lake breeze into Chicago, but conditions apparently
rather complicated during course of day.
-- B to D stability; temperature in lower 90's.
-- Mixing height 4700-5900 ft.
-- NOTE: Cold front did not move through Chicago
until the afternoon of 08/02.
08/04/75 -- Sunny; warm; no precipitation.
— Between two cold fronts, one from Lower Great Lakes
to lower Mississippi Valley and one Upper Great
Lakes to Central Plains; weak high pressure,
centered over northern Missouri.
-- Westerly gradient wind in day, followed by westerly
to southwesterly gradient flow in evening and night
as second cold front approached from the north.
Wind speeds 5-9 mph.
-- Not favorable for lake breeze penetration into
Chicago.
40
-------
-- B to C stability; temperature in upper 80's to
lower 90's.
-- Nearly unlimited mixing.
— NOTE: Cold front passed through Chicago in the
morning on 08/05, accompanied by showers and
followed by a large, cool high pressure system.
08/11/75 -- Day began clear and very hazy, with increasing
high, thin cloudiness in late morning; overcast in
afternoon, with thunderstorm activity; warm until
mid afternoon.
-- Quasi-stationary front in area, on east-west
alignment just north of Chicago; weak pressure
gradient, with weak lows in southeast Canada and in
Nebraska and a weak high center in northern
Wisconsin-Michigan area.
-- Winds variable, but mostly with westerly component;
high wind gusts with thunderstorms in mid afternoon.
Wind speeds 0-23 mph.
-- Not favorable for lake breeze penetration very far
into Chicago or for much duration.
-- B and D stability; temperature high 80's.
-- Mixing heights 8800-9000 ft.
-- NOTE: Front and disturbed, showery weather remained
in Chicago area for next four days.
41
-------
APPENDIX C
PREDICTED 1975 NOX AND N02
LEVELS FOR SIX CHICAGO AREA
POWER PLANTS - PREVIOUS STUDY1
(NON-REACTIVE PLUME MODEL)
42
-------
NOX Concentrations
Year: 1975
Study Conditions
(pg/m ) at Power Plant Worst Case Point for Bailly
Wind Direction
Contributor
North
South
-as t
Su=er ?M
3-9; SO'?
Mix Depth -800 m
R aax '2.5 '/NO « 1/2
Win tar AM
C-3; 20°7
Mix Depth - 272 =
'R sax -3.5 '«
N02/N0x - I/A |
Power Plan:
CT's
Other Point
. Sources
Vehicles
Non-Vehicles
Total NO
X
Total N0:
Power Plant
CT's
Other Point
Sources
Vehicles
Non-Vehicles
Total N0x
Total NO:
Power Plant
CT's
Other Point
Sources
Vehicles
Ncn-Vehiclas
Total NQx
Total N02
300
10
0
3
0
313
157
1508
100
0
5
1
1614
807
1592
100
0
5
4
1701
425
300
10
0
5
1
316
158
1508
100
0
S
3
1619
810
1592
100
0
9
10
1711 "
428
300
10
0
24
5
339
170
1508
100
0
7
2
1617
809
1592
100
0
8
6
1706
427
I
300
10
7
35
8
360
180
1508
IOC
31
100
45
1784
892
1592
100
35
117
215
2059
515
43
-------
N0y Concentrations
Year: 1975
Study Conditions
(Mg/m3) at Power Plant Worst Case Point for Will County
Wind Direction
Concributor >Jorch South East Vest
Scnner ?M
3-9; 80s?
Mix Depch -800 n
R aax - 1 . 6 ka
! S02/N0x - 1/2
Susaer AJt
C-5; 70 e?
Mix Depch -282 E
R nax -3.6 '«
N02/MOY - 1/2
x
Winter AM
C-3; 20°7
Xix Depch « 282 a
R max - 3 . 6 Ira
j K0,/M0x - 1/4
Power Plant
CT's
Other Point
Sources
*
Vehicles
Non-Vehicles
Total NO'
Total NO z
Pover Plant
CT's
Other Point
Sources
Vehicles
Mon -Vehicles
Total HOX
Total NO 2
Power Plant
CT's
Other Point
Sources
Vehicles
Kon-Vehi-les
Total N0x
Total N02
67o
0
134
15
1
826
413
1419
0
135
41
6
1601
801
1498
0
148
48
43
1737
434
676
0
128
4
1
809
405
1419
0
165
5
2
1591
796
1498
0
176
6 .
14
1694
424
676
0
129
5
1
811
406
1419
0
138
12
4
1573
787
1498
0.
149
14
29
.690
423
676
0
167
2
0
845
423
1419
0
146
3
1
1569
785
1498
0
157
L
10
1669
417
44
-------
NOX Concentrations (ug/m3) at Power Plant Worst
Year: 1975
Study Conditions Contributor North
Case Point for Waukegan
Wind Direction
South Ease "esc
Suzner ?M
3-9; 80 5T
Mix Depca -800 a
may » L . U &a
MA /MA m 1/0
MUl / * 1/2
Winter AM
C-5; 20'r
Mix Depth -282 a
S aax "3.6 ka
- N0a/N0 - 1/4 !
x i
Power Plant
CT's
Other Point
Sources
Vehicles
Non-Vehicles
Total N0x
Total NOs
Power Plant
CT's
Other Point
Sources
Vehicles
Non-Vehicles
Total NOX
Total NO 2
Power Plant
CT's
Other Point
Sources
Vehicles
Non-Vehicles
Total. NOX
Total SOj
328
53
0
18
2
401
201
1043
474
0
35
10
1567
784
1106
474
0
40
74
1694
424
328
53
51
67
8
507
254
1048
474
193
188
44
1947
974
1106
474
135
219
326
2260
565 .
328
53
2
0
1
384
192
1048
474
9
23
5
1559
780
1106
474
10
27
35
1652
413
328
53
0
18
2
401
201
1048
474
28
25
7
1582
791
1106
474
28
29
5^
1691
423
45
-------
N0x Concentrations
Year: 1975
Study Conditions
(yg/n ) at Power Plant Worst Case Point for Joliet 7
Wind Direction
Contributor
North
South
East
Ves;
Su=er ?M
3-9; 30":
Mix Depth -800 m
R aax -2.6 ka
H0a/S0x - 1/2
Sucaer AM
C-5; 70s?
Mix Depch -312 a
S =ax -4 .0 '*=
so2/:iox - 1/2 j
Winter AM
C-3; 20T
Mix Depth -312 m
R sa.x -4 o ka
^02/NO « 1/4 I
x !
Power Plant
CT's
Other Point
. Sources
Vehicles
Non-Vehicles
local MO
Total NO 2
Fewer Plane
CT's
Other Point
Sources
Vehicles
Son-Vehicles
Total NOX
Total N02
Power Plant
CT's
Other Point
Sources
Vehicles
Non-Vehicles
Total MCx
Total N*0Z
247
86
4
24
2
363
182
1020
219
15
68
13
1335
668
1077
219
15
80
97
1488
372
247
86
1
4
2
340
170
1020
219
2
10
6
1257
629
1077
219
2
11
41
1350
338
247
86
1
5
1
340
170
1202
219
3
11
6
1259
630
1077
219
3
13
48
1360
3.10
247
86
8
2
1
344
172
1020
219
31
4
4
1278
639
1077
219
33
5
29
1363
3£1
46
-------
XOX Concentrations
Year: 1975
Study Conditions
) at Power Plant Worst Case Point for Fisk
Wind Direction
Co nrcri outer North South Ease \"es;
Suaser ?M
3-9; 80s:
Mix Depth -800 n
^0,/NO » i /2
Susaer AM
.C-5; 70'?
Jlix Depth - 272 =
X sax » 3.5'&a
J»oz/:iox - 1/2
Winter AM
C-3; 20°?
Mix Deuch -2 72 a
X aax - 3 .5 ks
M0j/N0x » 1/4
Power Plant
CT's
Other Poiac
Sources
Vehicles
Non-Vehicles
Total H0x
local N02
Power Plane
CT's
Other Point
Sources
Vehicles
Non-Vehicles
Total NOX
Total H02
Power Plane
CT's
Other Point
Sources
Vehicles
Non-Vehicles
Total NOX
-Tcttl'SOj
383
84
2
98
18
585
293
758
798
9
242
67
1874
937
797
798
9
283
503
2390 -
59Q
383
84
8
114
20
609
305
758
798
36
312
84
1988
994
797
798
39
366
627
2627
657 -
383
84
0
59
14
540
270
758
798
147
127
58
1888
944
797
798
133
148
433
2309
| 577
383
84
74
104
17
662
331
758
798
204
269
70
2099
1050
797
798
204
315
524
2638
660
47
-------
NOX Concentrations
Year: 1975
Study Conditions
(Ug/m3) at Power Plant Worse Case Point for Bethlehem Steel
Wind Direction
Concribuccr
North
South
Sezzaer ?M
3-9; 80'F
Mix Depth -800 a
R aax "1 .4 ka
NOs/NO^ - 1/2
Sunnier AM
C-5; 70'F
Mix Depth -200 a
R aax -2.5 lea
N02/N0x - 1/2
Winter AM
C-3; 20°F
• Mix Depth - 200=i
R max - 2.5^a
NO 2 /NO - 1/4
Power Plant
CT's
Other Point
Sources
Vehicles
Non-Vehicles
Total N'0x
Total N02
Power Plant
CT's
Other Point
Sources
Vehicles
Non-Vehicles
Total NOX
Total NOj
Power Plant
CT's
Other Point
Sources
Vehicles
Non-Vehiclas
Total N0x
Tctal NO;
813
0
0
1
1
815
408
2623
0
0
2
5
2630
1315
2494
0
0
3
16
2513
628
813
0
0
2
1
816
408
2623
0
1
5
4
2633
1317
2494
0
1
5
42
2542
636
813
0
0
3.
2
818
409
2623
0
0
7
2
2632
1316
2494
0
0
8
7
2509
627
813
0
12
31
9
865
433
2623
0
62
88
46
2819
1410
4819
0
66
103
226
2389
722
48
-------
APPENDIX D
PREDICTED NOX AND N02 CONCENTRATIONS
FOR SIX CHICAGO-AREA POWER PLANTS--
REACTIVE PLUME MODEL
49
-------
PLANT - BAILLY
LOW OZONE BACKGROUND
STABILITY
B
B
B
C
C
C
D
D
D
WIND SPEED
METERS /SEC
1
2
3
3
4.5
6
6
7
8
DISTANCE OF NOK
PEAK FROM 1ST
STACK (m)
_
6400
4400
10800
7600
6000
34400
28800
24400
NOX IN EXCESS
OF BACKGROUND
NOX (ppra)
N02 IN EXCESS OF
BACKGROUND
UgTm3
EXCESS
HIGH OZOHE BACKGROUND
EXCESS NO,
EXCESS
(ppm)
N02 IN EXCESS OF
BACKGROUND N0?
Mg/m ppm
EXCESS
(ppm)
.102
.127
.083
.105
.121
.032
.037
.041
115
126
102
116
124
48
54
60
.062
.068
.055
.063
.067
.026
.029
.032
.61
.54
.67
.60
.56
.80
.78
.78
170
207
139
175
198
56
64
71
.092
.112
.076
.095
.107
.030
.035
.038
.90
.88
.91
.90
.88
.93
.93
.93
Background Concentrations:
Low Ozone Case:
[Oj] - .1 ppm, [NOx] - .05 ppm, [NOj - .00455 ppm, [N021 - .0455 ppra
High Ozone Cnse:
[03] - .2 ppm, (NOX) - .05 ppm, (NO] - .00238 ppm, [N02] - .0476 ppn
-------
PLANT - WILL COUNTY
HIGH OZONE BACKGROUND
STABILITY
B
B
B
C
C
C
D
D
D
WIND SPEED
METERS/SEC
1
2
3
3
4.5
6
6
7
8
DISTANCE OF NOX
PEAK FROM 1ST
STACK (m)
11600
4000
2800
6400
4800
4000
16800
14400
12800
NO IN EXCESS
OF BACKGROUND
NOX (ppra)
.152
.220
.257
.184
.214
.229
.082
.088
.093
NOZ IN EXCESS OF
BACKGROUND NO,
133
144
147
140
143
145
102
106
109
ppm
.072
.078
.080
.076
.078
.078
.055
.058
.059
EXCESS NOZ
EXCESS NO^
(ppra)
.48
.35
.31
.41
.36
.34
.66
.65
.64
NOj IN EXCESS OF
BACKGROUND N02
Ug/m'
240
305
325
275
301
311
138
148
155
ppm
.130
.165
.180
.150
.160
.170
.075
.080
.080
EXCESS N02
EXCESS NOU
(ppm)
.85
.75
.69
.81
.76
.74
.91
.91
.90
Background Concentrations!
Low Ozone Case:
[0,J - .1 pp™. [NOXJ - -05 pp«, [NOJ - .00455 ppm, [N02] - .0455 ppra
High Ozone Case:
I0t] - .2 ppm, [NOX] - .05 PP«, [NOJ - .00238 ppm, [N02J - .0/.76 ppra
-------
PLANT - WAUKEGAN
LOW OZONE BACKGROUND
HIGH OZONE BACKGROUND
Ui
STABILITY
B
B
B
C
C
C
D
D
D
WIND SPEED
METERS/SEC
1
2
3
3
4.5
6
6
7
8
DISTANCE OF N0y
PEAK FROM 1ST
STACK (m)
11600
4400
3200
7200
5600
4400
19600
16800
14800
NOX IN EXCESS
OF BACKGROUND
NOX (ppm)
.093
.127
.204
.105
.126
.139
.046
.049
.053
N02 IN EXCESS OF
BACKGROUND
Vlg/m3
109
126
134
117
126
130
65
69
73
N02
ppm
.059
.068
.073
.063
.068
.071
.035
.037
.040
EXCESS N02
EXCESS N0x
(pprn)
.64
.54
.36
.60
.54
.51
.77
.76
.75
NOZ IN EXCESS OF
BACKGROUND
Vg/m'
155
206
241
174
205
222
78
85
90
N02
ppm
.084
.112
.130
.094
.111
.120
.042
.046
.049
EXCESS N02
EXCESS N0)(
(ppm)
.90
.88
.64
.90
.88
.87
.93
.93
.92
Background Concentrations:
Low Ozone Case:
[0,J - .1 ppm, [NOXJ - .05 ppm, [NO]
High Ozone Cose:
[03] - .2 ppm, [NOX1 - .05 ppra, [NO]
- .00455 ppra, [N02] - .0455 ppm
- .00238 ppm, [NOZ] - .0176 ppra
-------
PLANT - JOLIET
HIGH OZONE BACKGROUND
Ui
U>
STABILITY
B
B
B
C
C
C
D
D
D
WIND SPEED
METERS /SEC
1
2
3
3
4.5
6
6
7
8
DISTANCE OF NOX
PEAK FROM 1ST
STACK (m)
11600
4800
3200
8400
6000
4800
23600
20000
18000
NOX IN EXCESS
OF BACKGROUND
NOX (ppni)
.107
.226
.276
.180
.219
.242
.070
.077
.082
N02 IN EXCESS OF
BACKGROUND NO,
ug/V
118
144
148
139
144
146
91
97
102
ppm
.064
.078
.080
.076
.078
.079
.049
.053
.055
EXCESS NQz
EXCESS NOK
(ppm)
.56
.35
.29
.42
.36
.33
.71
.69
.67
N02 IN EXCESS OF
BACKGROUND N02
Vg/ra3
177
309
332
271
304
318
119
130
139
ppm
.096
.167
.180
.147
.165
.172
.064
.070
.075
EXCESS N02
EXCESS NO,,
(ppm)
.90
.74
.65
.82
.75
.71
.92
.91
.91
Background Concentrations:
Low Ozone Cnse:
[0,] - .1 ppm, [N0x] - .05 pp«, [NO] - .00455 ppm, [N02] - .0455
High Ozone Cnse:
[0,] - .2 ppm, (NOXJ - .05 ppm, [NOj - .00238 ppm, fN02] " .0476 ppm
-------
PLANT - FISK
LOW OZONE BACKGROUND
Ui
-P-
HIGH OZONE BACKGROUND
STABILITY WIND SPEED
METERS /SEC
B
B
B
C
C
C
D
D
D
1
2
3
3
4.5
6
6
7
8
DISTANCE OF NOX
PEAK FROM 1ST
STACK (m)
4000
2400
2000
4000
2800
2400
8800
8000
7200
NOX IN EXCESS
OF BACKGROUND
NOX (ppm)
.128
.182
.210
.157
.178
.187
.079
.082
.083
N0a IN EXCESS OF
BACKGROUND NO;
Ug/mJ
127
139
143
135
139
140
99
101
103
ppm
.069
.076
.077
.073
.075
.076
.054
.055
.056
EXCESS NO 2
EXCESS NO
(ppm)
.54
.42
.37
.46
.42
.41
.68
.67
.67
NOZ IN EXCESS OF
BACKGROUND N02
Pg/mJ
207
273
298
266
270
278
133
137
140
ppm
.112
.148
.162
.133
.146
.151
.072
.074
.076
EXCESS N02
EXCESS NO
(ppm)
.88
.81
.77
.85
.82
.81
.91
.91
.91
Background Concentrations:
Low Ozone Case:
f03] - .1 ppm, [N0x] - .05 ppm, [NO] - .00455 ppm, [N02] - .0455 ppn
High Ozone Cage:
[031 - .2 ppm, [NOXJ - .05 ppm, [NOJ - .00238 ppm, [N02] - .0476 ppn
-------
PLANT - BETHLEHEM STEEL
HIGH OZONE BACKGROUND
Ui
Ui
STABILITY
c
c
D
WIND SPEED
METERS/SEC
1
2
3
3
4.5
6
6
7
8
DISTANCE OF NOX
PEAK FROM 1ST
STACK (m)
4800
2800
2000
4000
2800
2400
8800
7600
6400
NOX IN EXCESS
OF BACKGROUND
NOX (ppro)
.225
.334
.421
.312
.381
.427
.180
.196
.207
N02 IN EX
BACKGROU
Hg/m'
144
151
153
150
152
153
139
141
143
:CESS OF
EXCESS NOZ
IND N02 EXCESS NO^
ppm
.078
.082
.083
.081
.082
.083
.075
.077
.077
(ppm)
.35
.24
.20
.26
.22
.19
.41
.39
.37
N02 IN EXCESS OF EXCESS N02
BACKGROUND N02 EXCESS NO^
JJg/tn3
308
347
356
342
352
356
272
286
296
ppm
.167
.188
.193
.185
.190
.193
.147
.155
.152
(ppra)
.74
. 55
.46
.59
.50
.45
. 82
.79
.77
Background Concentrations:
Low Ozone Case:
[0,] - .1 ppm, [NOX] " .05 ppm, [NOj - .00455 ppm, [N02J - .0455 ppra
High Ozone Case:
10,1 - .2 pp», [NOX] - .05 ppm, [NO] - .00238 ppm, [N02] - .0476 ppm
-------
APPENDIX E
PREDICTED NO2 CONCENTRATION FOR
INTERACTION OF EIGHT CHICAGO-AREA
POWER PLANTS--REACTIVE PLUME MODEL
56
-------
COLLINS
LINt Of IXTEIUCTIOI. 51UDIEQ
0C»»lffgi!r
-Pu
courtt
?
OlHMO
JOLUI 7,8
"JOLIET 2.3,6
10,000 20,000 IO.IXW 40.000 SO.000 60.000 '0.000 M.OOO 90.HOT 100.000
OlUtncf (Hptf*)
INTERACTION CASE FOR B STABILITY, LOW OZONE
57
-------
m LI us
IIHE Of IKTIRACIIOH S1UOIF.C
QCRAWrpBC'
o
Kill
r.ou»Tv
on««co
OJOtlf! 7,8
OjOLICT ?.J.S
-
I-/SM
0 10.000 20.000 30.000 «0.000 50.000 60.000 70.000 80.0OO 90.000 100.000
l Hlstince |*I»rs)
INTERACTION CASE FOR B STABILITY, HIGH OZONE
58
-------
10.000
UOUIHS
LIME Of l«TfB»CT10« STUDIED
ORIDGfUW
OCRAWrORD
10.900
O
• '.'..
O rtx*co
iJOlin 7.8
3JOUE1 J.3.6
10.000 30.000 30,000 40,000 50.000 M.OOO 70.000 M.OOO 90.000 100.000
l DKtincr IMttfrs)
INTERACTION CASE FOR C STABILITY, LOW OZONE
-------
lO.OOOi
COLLINS
LIKE Of INTERACTION STUDIED
S 0 C
10,000
KILL
COUNTr
OTE«»CO
OJOIIEI 7.8
OJOIIET ?.3.6
I ?00
|
3"/S»c
<.5«/S»
to/Sit
10.000 20,000 30.000 «0,000 50,000 60.000 70.000 '0.000 90.000 100.000
Oluince (Mrltri)
INTERACTION CASE FOR C STABILITY, HIGH OZONE
60
-------
ic.ono-
ORIOGEKMO
L cou INS
LINE Of IHTEMCTIOtl STUDIED
W1U
COUNTY
10.000-
OTtI«CO
J.8
OJOLICT P.3.6
'
4
100-
10.000 ?0.000 30.000 10.000 SO.000 60.000 70.000 RO.OOO 90.000 100.000
INTERACTION CASE FOR D STABILITY, LOW OZONE
61
-------
10,000
S o<
1
10,000
UNE OF INTERACT 10" STUIIED
QCKAItfOW
o
WILL
COUNTY
OtEXttO
OJOIIET 7.8
°JOUU 2.3.6
6-/5rc
10,000 20.000 30.000 40.000 50.000 60.000 70.000 80.000 90.0OK 100.000
Downwind Olsttncr (Meters 1
INTERACTION CASE FOR D STABILITY, HIGH OZONE
62
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/7-80-036
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Investigation of NO2/NOx Ratios in Point Source
Plumes
5. REPORT DATE
February 1980
6. PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
J. P. Blanks, E. P.Hamilton m, B.R.Eppright, and
N.A.Nielsen
8. PERFORMING ORGANIZATION REPORT NO.
PERFORMING ORGANIZATION NAME AND ADDRESS
Radian Corporation
P.O. Box 9948
Austin, Texas 78766
10. PROGRAM ELEMENT NO.
INE624
11. CONTRACT/GRANT NO.
68-02-2608, Task 63
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Task Final; 12/78 - 12/79
14. SPONSORING AGENCY CODE
EPA/600/13
15.SUPPLEMENTARY NOTES JERL-RTP project officer is J. David Mobley, Mail Drop 61,
919/541-2915. EPA-600/7-78-212 is a related report.
IB. ABSTRACT
repOrt gives results of B. study to relate ground level NO2 concentra-
tions to NOx emissions (NO2/NOx ratio) in plumes from six large power plants in the
Chicago area, using a photos tationary state reactive Gaussian plume model. The aim
of the study was to assess the level of NOx control required to meet a probable short-
term NO2 national ambient air quality standard (NAAQS). The major uncertainty of
an earlier study (EPA-600/7-78-212) was its assumption of uniform, fixed NO2/NOx
ratios of 0. 5 (summer) and 0.25 (winter). The reactive model used in this study pre-
dicted significantly higher NO2/NOx ratios at the point of maximum plume impact
(0. 93 for worst case) with high ambient ozone levels (0.2 ppm). Average NO2/NOx
ratios for all high ozone cases studied were 0. 76-0. 9. The reactive model predicts
significantly higher ground level NOx impacts from the six plants. These results
indicate that the threshold short-term NO2 NAAQS level requiring NOx flue gas treat-
ment technology could increase by 40%. The previous study indicated that most of the
six plants could meet a 500 microgram/cu m short-term NO2 standard using NOx
combustion modification techniques (50% NOx control); this study indicates NOx flue
gas treatment technology (90% control) may be required on these plants to meet a
750 microgram/cu m standard, and most certainly for 500 micrograms/cu m.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Combustion
Nitrogen Oxides
Nitrogen Dioxide
Mathematical Modeling
Normal Density Functions
Flue Gases
Electric Power Plants
Ozone
Pollution Control
Stationary Sources
Gaussian Models
13B
21B
07B
12A
10B
S. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport!
Unclassified
21. NO. OF PAGES
71
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
63
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