United States
Environmental Protection
Agency
Atmospheric Sciences Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S3-85/066 Dec. 1985
<&EPA Project Summary
Impact of Primary Sulfate and
Nitrate Emissions from Selected
Major Sources: Phase I.
Coal-Fired Power Plant
J. D. McCain, W. G. Kistler, and D. H. Carnes
The impact of local point sources
emissions on the near source atmos-
phere has been investigated. This study
was in two phases. The phase 1 study
was to investigate the impact of a coal-
fired power plant on the near source
atmosphere. Phase 2 was to study the
impact of a sulf uric acid plant and a pulp
and paper mill. The results of phase 2
are presented in a separate report.
Sampling for phase 1 took place
during late January and early February,
1981 at the Scholz Steam Plant of the
Gulf Power Company, located in North-
west Florida. Source measurements
were made for emission rates of HzSO4,
particulate sulfate and nitrate, SO2,
NOĢ, total particulate matter, and ele-
mental compositions by particle size.
Ambient sampling was made for all the
preceding pollutants plus HNO3 and
pertinent meteorological parameter re-
quired for dispersion modeling.
The Scholz Plant was found to be the
dominant source of gaseous sulfur and
nitrogen oxides in the area. However, it
was found to contribute only about
1.5% of the ambient particulate sulfate
and nitrate. The H2SO4 was about 95%
of the sulfate emissions and account for
most of the ambient H2SO4.
Four factors in the Principal Compo-
nent Fraction Analyses accounted for
about 80% of the variance in the input
data matrix. They were: the first factors
showed the plant was connected heavily
with SO2, NO, NO2, As, Se, and sulfate;
the second factor showed a connection
among mineral elements, TSP, and
sulfates; the third factor tied alkali
metals, Cl, Mn, and P together but no
satisfactory source was found; and the
fourth factor coupled Br, S, mineral
elements and total nitrate. This factor
was probably related to vehicular traffic.
This Project Summary was developed
by EPA's Atmospheric Sciences He-
search Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
Most current studies on the mecha-
nisms of sulfate and nitrate formation
and transport in the atmosphere have
dealt with long-range transport. However,
a significant portion of the problems
associated with these compounds may
arise in the vicinity of the source. The
program described here was intended to
provide information on the partitioning of
sulfates and nitrates in ambient air
between local primary sources and long-
range transport/secondary sources. The
report presents the results of the first
phase of a two-phase source-ambient
study. This first phase concerned the
impact of a coal-fired power plant. Phase
2 concerned the impacts of a sulf uric acid
plant and a pulp and paper mill. The
results of Phase 2 are presented in i.
separate report.
Sulfur and nitrogen compounds are of
particular concern because of their pre-
ponderance in flue gas and in decomposi-
tion products of other process streams.
High levels of S02, NO, N02, and various
-------
sulfates and nitrate's are found in ambient
air associated with industrial activity and
in areas with high automotive traffic
densities. Serious deterioration of the
environment has been linked to these
compounds. In 1964, SO2 emissions
began to be regulated in this country. The
use of high-sulfur fuels was inhibited,
and taller stacks were employed to im-
prove local air quality. This improved the
measured levels of SO2; however, am-
bient air sulfate levels have not been
substantially improved. Thus, it is impor-
tant that the specific contributions of
sulfate aerosols to the atmosphere be
delineated, the controlling mechanisms
be determined, and the local and long-
range concentrations and transports be
determined.
Sampling for Phase 1 took place during
late January and early February 1981, at
the Scholz Steam Plant of the Gulf Power
Company, located in Northwestern Flor-
ida. Three approaches were taken to
quantify the impact of the plant on the
study area. First, dispersion modeling
was used to predict average downwind
concentrations. Second, principal com-
ponent factor analysis (PFA) was applied
to an ambient air data base comprised of
the concentrations of SOz, NO,, total
suspended particulates (TSP), sulfates,
nitrates, wind direction relative to the
source and sampler locations, and the
concentrations of a number of elements
found in the particulate matter collected
by hi-vol samplers. Finally, target trans-
formation factor analysis (TTF A) was used
in data analysis to isolate and quantify the
impacts of specific sources at each sam-
pling location.
Measurement Methods
The primary variables of interest in this
study were particulate and gaseous sul-
fates and nitrates in the ambient air that
were directly or indirectly the result of
emissions from the Scholz plant. Further,
it was desirable to differentiate between
sulfate and nitrate salts and sulfuric and
nitric acids. Thus, data were needed on
the ambient air and source concentrations
of these species and their precursors.
Source measurements were made of
the emission rates of sulfuric acid, sulfate
salts, sulfur dioxide particulate nitrates,
nitrogen oxide, nitrogen dioxide, total
particulates matter; and of elemental
composition by particle size. Measure-
ments in the ambient air included all of
the preceding plus nitric acid and all
pertinent meteorological parameters re-
quired for dispersion model predictions of
downwind concentrations. The sources
total particulate measurements were
made by using a modification of EPA
Method 17, which minimized the inclu-
sion of sulfuric acid in the sample. Sulfuric
acid determinations were made by using
the method described by Cheney and
Homolya. The plant's S02, NOX, 02, and
H20 monitors were used to provide the
data needed for source variables.
A grid of acceptable monitoring loca-
tions was developed in the vicinity of the
plant and, based on anticipated wind
flow, sites were selected for monitoring
at the beginning of each test day. Data
were taken at four fixed stations and two
mobile stations. TSP samples were col-
lected by hi-volume samplers equipped
with Sierra Model 234 cascade impactors.
Similar samplers without the impactors
were used to obtain samples for sulfate,
nitric acid, and nitrate analysis. Conven-
tional glass fiber filter media were used in
the impactor-equipped samplers; these
were analyzed gravimetrically to deter-
mine TSP concentrations. Teflon mem-
brane filters were used in sampling for
sulfate, nitric acid, and nitrates to mini-
mize artifact formation. A sodium chloride-
impregnated filter was installed down-
stream of the Teflon filter for the nitric
acid determination. Segments of the
Teflon hi-vol filters were also submitted
for X-ray fluorescence (XRF) and neutron
activation analyses (NAA) to determine
elemental compositions of the deposited
particulate matter for use in apportioning
the material found on the filters among
the various possible sources.
Sulfuric acid and sulfate salts were
measured separately by techniques pre-
viously developed by Southern Research
Institute. The concentrations of SO2 were
measured with Meloy Model SAE-185-2A
S02 monitors. Meloy 8440E monitors
were used for NO and NO2 measure-
ments.
Data to identify dispersion characteris-
tics were taken from a 60-m (200-ft)
meteorological tower maintained by Gulf
Power Company. Upper air measure-
ments were made by using pilot balloons
and temperature sonde equipment.
Measurement Results
An overview of the source emission
parameters is given in Table 1. This table
summarizes all emission rate measure-
ments for the principal components of
interest; particulate matter, S02, H2SOĢ,
and NO,.
When sulfuric acid was excluded, be-
tween 2 and 5% of the total particulate
matter emissions were found to be soluble
sulfates. The data indicated that the
H2S04 present in the flue gas was essen-
tially all in the vapor phase; the sulfate
was associated with H2S04 at concen-
trations 10-15 fold greater than that
associated with the fly ash. The particle
size distribution of the emissions could be
reasonably well represented by a log-
normal distribution with a mass median
diameter of about 10 fjm.
A summary of the ambient air data is
given in Table 2. All values in this table
represent averages over the time periods
during which the hi-vol samplers for
sulfate and nitrate determinations were
in operation.
Only a few days of data were obtained
with the ambient air H2SO4 samplers. The
sampler operations concentrated on the
collection of data in the plume; therefore,
the ambient air H2SO4 data are highly
biased toward in-plume samples and are
not representative of average conditions.
The data indicated that the plant's con-
tribution to the local, ambient air sulfate
was about 90 to 95% H2SO4.
Particle size distribution measurements
were attempted in two ways. First, high
volume impactor heads were used on the
TSP samplers; second, Lundgren impac-
tors were used to provide samplers for the t
determination of the distribution of "
selected elements by particle size-XRF
and NAA analyses of the material col-
lected by the impactor were used for the
latter purpose. Neither technique was
notably successful because the ambient
air particulate concentrations actually
encountered were much lower than
anticipated. The data show that the
ambient aerosol is probably comprised of
two modes, a sub-micron mode typified
by sulfur and perhaps containing other
"condensible" species and a second
super-micron mode typified by more
refractory mineral elements.
Source Impact on Study Area
The Factor Analysis was performed on
the correlation matrix of the complete set
of elemental analysis data from the hi-vol
filters augmented by the concentrations
observed for nitrates, nitric acid, sulfates,
SO2, NO, N02, TSP, and a variable related
to the wind direction relative to the source
and sampler locations. Elements that
showed low values of communality in this
analysis were excluded from the data set
used in further analyses. This analysis
showed that four factors were sufficient
to explain 79% of the variance in the input
data matrix. The first factor showed heavy
-------
factor loadings for S02, NO, N02, As, Se,
and sulfate and clearly represented the
plant. The second factor showed no
significant connection with the gaseous
pollutants, but had high factor loadings
for the mineral elements, TSP, and sul-
fates. This was taken to represent a soil
component. A third component was found
to be tied to the alkali metals, chlorine,
manganese, and phosphorus No satis-
factory source for this factor was identi-
fied; it may have been related to the
scrubber, as it showed some connection
to the wind direction variable, or it may
have resulted from contaminants from
the impregnated filters used in conjunc-
tion with the Teflon filters. The fourth
factor showed strong ties with bromine,
sulfur, the mineral elements associated
with soil, and a significant loading for
total nitrates. This factor was probably
related to vehicular traffic.
Conclusions
The Scholz Steam Plant, around which
this study was performed, was found to
be the dominant source of gaseous sulfur
and nitrogen oxides in the area. However,
it was found to contribute only about 15%
of the ambient paniculate sulfate and
nitrate burdens. The major contributor to
the ambient particulate nitrates appeared
to be automotive in origin, while the
sulfates appeared to be primarily associ-
ated with windblown soil, possible auto-
motive sources, and indeterminate
sources lying at large distances from the
test area.
The plant's oxides of nitrogen emissions
were almost entirely in the form of NO in
the stack; approximately 40% had oxidized
to NO2 within 2 to 5 km of the plant. The
ratio of sulfate to S02 associated with the
plant's emissions was found to be about
twice as large in the ambient air as in the
stack. The could have resulted from
continuous oxidation of SO2 at a rate of
about 0.25%/h, but the data also supports
a much more rapid oxidation rate im-
mediately upon discharge from the stack
that was followed by a much slower rate.
Approximately 95% of the sulfate emis-
sions from the plant were in the form of
sulfuric acid. The available data do not
indicatethat any significant neutralization
took place before the plume reached the
sampling sites.
As expected, the dispersion models did
not predict plume concentrations of re-
active components well. However, the
poor performance of the ISC model in
prediction of concentrations near the
source probably resulted from over-pre-
dictions of plume height by the Brigg's
Table 1. Plant Emission Summary
Unit 1
Unit 2
Scrubber
Gas flow, m3/s
Gas temperature, °C
Unit load, MW
Particulate matter, mg/DNM3
HaSOt, ppm
SOz. ppm
/VO* ppm
104
148
48.9
26.5
2.94
2030
472
108
147
499
44.4
6.21
1900
44O
20.2
2.7
NA
-200
-450
'Values not determined?
NA = Not applicable.
Table 2. Ambient Air Data Summary
Upwind
Crosswind
Downwind
Sampling parameters
Average distance from plant, km
Average distance from major road, km
A verage sampling duration, min
Measured concentrations
Particulate matter, fjg/m3
Sulfates, fjg/m3
Nitrate salts, fjg/m3
Nitric acid, fjg/m3
Bromine, ng/m3
SO* ppb
NO,, ppb
NO, ppb
Concentrations attributed to plant by
target transformation factor analysis
Particulate matter, ug/m3
Sulfates, fig/m3
Nitrates, ug/m3
Bromine, ng/m3
SOz ppb
1.72
2.09
480
29.8
1.71
0.48
1.13
1.54
0.63
2.38
0.22
0
0
2.63
4.04
473
30.8
2.35
0.20
0.88
5.80
1.04
2.86
1.15
2.16
0.19
0.030
0.56
11.2
2.53
6.24
348
43.2
3.82
0.27
0.75
6.63
50.9
20.6
11.9
7.60
1.03
0.154
2.88
54.9
*Not determined?
equation, as much better results were
obtained by using the Holland plume rise
algorithm. The Holland algorithm results
in substantially lower values for plume
rise.
Target transformation factor analysis
provided an excellent means of quantify-
ing the impact of the source, but good,
measure source signatures are needed
for optimal application of the technique.
Source vectors found in the literature
were not particularly useful in this study.
-------
J. D. McCain and W. G. Kistlerare with Southern Research Institute. Birmingham,
AL 35255-5305; and D. H. Carnes is with TRC, East Hartford. CT06108.
Kenneth T. Knapp is the EPA Project Officer (see below).
The complete report, entitled "Impact of Primary Sulfate and Nitrate Emissions
from Selected Major Sources: Phase 1. Coal-Fired Power Plant," (Order No. PB
86-103 678/AS; Cost: $16.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Atmospheric Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
10
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use S300
EPA/600/S3-85/066
0000329 PS
U S ENVIR PROTECTION AGENCY
REGION 5 LIBRARY
230 S DEARBORN STREET
CHICAGO IL 60604
------- |