United States
Environmental Protection
Agency
Atmospheric Research and Exposure
Assessment Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S3-91/065 Dec 1991
EPA Project Summary
A Regional Fine Particle Field
Study: Data Base and Initial
Results
Roy L. Bennett and Leonard Stockburger
The Fine Particle Network (FPN), a
group of rural sites located In the north-
ern two-thirds of the eastern United
States, has been used to determine fine
particle concentrations during selected
periods between August 1988 and Feb-
ruary 1989 and then continuously from
July 1989 through May 1990. Samples
from the network, collected 24 h each
day, were analyzed for the most abun-
dant elements by wave length disper-
sive x-ray fluorescence (WDXRF). About
30 sites were In operation during each
sampling period. These included 17
sites that were operating during the en-
tire program schedule and others that
were available only during parts of the
schedule.
The FPN data base can be used to
enhance the understanding of the sea-
sonal variation of fine particle concen-
trations in the eastern United States.
The data base, combined with meteoro-
logical data, will be useful for evalua-
tion of regional aerosol models and the
development of methodologies to esti-
mate regional contribution to urban par-
tlculate concentrations. The 14 sam-
pling sessions produced 12,859
samples for the 44 stations that were
analyzed by WDXRF. Seasonal aver-
ages of fine partlculate mass and el-
emental sulfur concentrations were de-
termined for each of the seven seasons
in which samples were collected. Con-
centrations of both were highest in the
summer. The average concentrations
for all sites and all collection dates were
15.5 and 1.9 u.g/m3 for the fine particu-
late mass and elemental sulfur, respec-
tively.
This Project Summary was developed
by EPA's Atmospheric Research and
Exposure Assessment Laboratory, Re-
search Triangle Park, NC, to announce
key findings of the research project
that Is fully documented In a separate
report of the same title. (See Project
Report ordering Information at back).
Introduction
A sampling program has been spon-
sored by the Environmental Protection
Agency to sample ambient air fine par-
ticles daily at 44 rural sites in the northern
two-thirds of the eastern United States
during periods of 1988, 1989, and 1990.
This Fine Particle Network (FPN) consisted,
of a subset of sampling locations selected
from the Acid Model Operational and Di-
agnostic Evaluation Study (Acid MODES)
surface sampling program. The Acid
MODES monitoring program was designed
to evaluate regional acid deposition mod-
els. Since the FPN operation was subor-
dinate to the larger Acid MODES pro-
gram, changes in the latter during Decem-
ber 1989 necessitated shifts in the FPN
sites. Samples were delivered to EPA by
the contractor responsible for collection
and mass measurements, ENS5R, Inc.
Analyses for elemental composition by x-
ray fluorescence were made by ManTech
Environmental Sciences.
The objective of the fine particle field
study was to obtain a data base for fine
particle (less than 2.5 u.m aerodynamic
diameter) concentrations that would rep-
resent extensive synoptic measurements
of fine particle mass. This fine particle
Printed on Recycled Paper
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data base, along with other chemical spe-
cies and meteorological measurements
made in the Acid MODES program, is
useful to
(1) develop methods for estimating and
understanding regional contributions
to urban fine particulate concentra-
tions,
(2) evaluate regional particulate mod-
els, and
(3) enhance the understanding of the
spatial, and temporal variations of
fine participate concentrations within
each season in the eastern United
States.
Estimates from previous experimental
field studies indicate that regional back-
ground particulate concentrations are ma-
jor contributors to urban particulate con-
centrations. Because this contribution is
large, it is desirable in urban particulate
field studies to have upwind sampling sites
to estimate the regional background input.
This often is difficult because the back-
ground sites may not be free of local
source contributions. One alternative ap-
proach is to use concentrations from mea-
surements made at other times during
comparable meteorological conditions.
However, backgrounds may vary, even
for the same wind directions if the par-
ticles that arrive at the urban boundary
have traveled along different trajectories.
This report describes the FPN sampling
network, the sampling procedures, and
the x-ray fluorescence analytical method
for elemental content determination.
Network Description
The EPA-sponsored program, collec-
tively named the Acid Model Operational/
Diagnostic Evaluation Study (Acid
MODES), was a part of a large coordi-
nated field program to evaluate acid depo-
sition models. The fine particle measure- •
ment study sites were a selected subset
of the Acid MODES stations. Selection of
sites for the Acid MODES stations was
based on location in a high acid deposi-
tion area, the northeastern United States,
and attempts to place the sites at existing
National Dry Deposition Network (NDDN)
locations when those sites met certain
siting criteria. These criteria included loca-
tions away from population areas, away
from large sources emitting sulfur and ni-
trogen oxides, and away from the Great
Lakes and the Atlantic Ocean. Attempts
were made to select sites that were ac-
cessible in all weather conditions, secure
from vandalism, and free from potential
local contamination sources such as
nearby plowed fields, roadways, and stor-
age facilities.
The Acid MODES network included
three groups of stations: the model evalu-
ation (ME-35) network, a gradient resolu-
tion (GRAD) group, and sub-grid variabil-
ity (VAR) set of stations. The original 35
sites of the ME-35 network were supple-
mented with additional stations to provide
uniformly distributed site spacing for re-
gional scale model evaluation. The 12
GRAD sites were located in Pennsylvania
and New York in a relatively small area
where steep concentration gradients were
expected. The VAR network was five sta-
tions in western Kentucky that were spaced
in a small cluster to measure variation
within a model grid.
The broad range of measurements
made at all Acid MODES stations included
precipitation chemistry (pH, conductivity,
and the pollutant species sulfate, nitrate,
chloride, ammonium, sodium, potassium,
calcium and magnesium) aerosol particle
chemistry (sulfate, nitrate, and ammonium),
and gases (sulfur dioxide, nitric acid, ni-
trogen dioxide, and ammonia).
The Fine Particle Network did not in-
clude all Acid MODES stations. Sites that
were included at one time or another dur-
ing the FPN program are listed in Table 1.
Duplicate samplers to determine collec-
tion repeatability were placed at close prox-
imity at three stations: State College, PA
(306), Oxford, OH (322) and Plainville, IL
(359). The duplicate sites were designated
by 100 units higher than their companion
site (i.e., sites 408, 422, and 459).
At the start of the FPN sampling pro-
gram the original 32 sites were selected
from the 68 Acid MODES stations. Be-
cause of budget and program changes,
29 Acid MODES stations were shut down
in December 1989. Of these, 16 were
FPN sites including one of the co-located
stations (Plainville, IL). However, fine par-
ticulate samplers were transferred and in-
stalled at other Acid MODES stations that
were not previously included in the FPN
study. Therefore, during the last four
months of operation, the total complement
of FPN sites was brought back to 28. One
of the new sites (Oxford, OH, site no.
322) had co-located samplers. Besides
affecting the sampling continuity, the
change of sites altered the geographic
distribution of the network.
Sampling Procedures and
Schedule
The fine particle measurement samplers
were assembled for the FPN sites by
ENSR Consulting and Engineering, Inc.
The sampling system consisted of a train
of the following sequence of components
positioned in a protective cabinet: a small
cyclone for removing coarse particles, a
47-mm filter holder for a fluorocarbon-type
membrane filter, a critical flow orifice to
maintain an 8.8-l/min flow, and the pump-
ing system with flow-metering devices.
During the course of the sampling pro-
gram the type of fluorocarbon filters being
used was changed. The high incidence of
filter breakage with the fragile Teflo filters
and its higher cost led to its replacement
with Zefluor in the last 11 sampling ses-
sions.
The Fine Particle Network sampling was
started at the original 32 sites on August
15, 1988 and concluded at a different
combination of sites on May 31,1990, but
sampling was not continuous during the
entire period. The first three sessions were
six week periods starting in mid-August
1988, mid-October 1988 and mid-January
1989. After examination of the data pro-
duced in the total Acid MODES program
the network managers proposed some
changes so that sampling was not re-
sumed until July 1989. After that time op-
eration was continuous until May 31,1990
with the exception of one week before
January 1, 1990. The interruption unfortu-
nately eliminated the collection of samples
in the spring of 1989 and limited sampling
in the spring of 1990 to two months.
The sampling schedule was further com-
plicated by the closing of some of the
original sites and starting new sites, as
described in the network description sec-
tion. Only 17 sites operated from the start
to the end of the program. Specific dates
that each site operated are indicated in
Table 1.
Analytical Procedures
After the samples were delivered to
EPA, those with invalid quality control
codes were removed and the remainder
were analyzed by wavelength dispersive
x-ray fluorescence (WDXRF) spectrometry.
The WDXRF spectrometer, a Siemens
MRS-3 system with one scanning mono-
chromator and 13 fixed monochromators,
gives analytical capability for elements from
sodium through bismuth. The fixed mono-
chromators were tuned to one element
and dedicated to that element; all other
elements were analyzed sequentially by
the scanning monochromator. A chromium
target x-ray tube operated at 54 kv and 44
ma was used to excite the samples. The
characteristic radiation from each element
was defracted by a crystal and its inten-
sity measured by a detector for each
monochromator. The type of crystal and
detector employed was optimally selected
for the characteristic wavelength of each
element. Spectrometer operation and data
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Table 1. Locations and Operation Dates for Fine Paniculate Network Stations
Site
Number
301
302
303
305
306
307
308
310
312
314
315
316
318
319
320
321
322
323
324
326
327
328
329
333
334
335
337
340
344
346
357
359
362
367
368
369
370
373
374
381
383
406
422
459
Location
PKtsboro, NC
Wartburg, TN
West Point, NY
Whiteface Mountain, NY
•State College, PA
Parsons.WV
Prince Edward SF, VA
Danby. NY
Kane Forest, PA
Deer Creek Park, OH
Pickney, Ml
Beltsville, MD
Tanner's Ridge, VA
Cedar Creek SP, WV
Mountain Lake, VA
Lilley Cornett Woods, KY
'Oxford, OH
Brokensword, OH
Unionville, Ml
Roaring Creek, NC
Edgar Evins SP, TN
Arendtsville, PA
Perryville, KY
Salamonie Lake, IN
Perkinstown, Wl
Ashland, ME
Coweeta (Otto), NC
Vincennes, IN
Washington Crossing, NJ
University Park, IL
Piseco, NY
*Plainview, IL
Hawthorne, PA
Renovo, PA
Williamsport, PA
Wirt, NY
Little Marsh, PA
Brackney, PA
North Orwell, PA
Eddyvjlle, KY
New Concord, KY
*State College, PA
•Oxford, OH
*Plainvjew, IL
Latitude
35.67
36.08
41.35
44.38
40.78
39.10
37.17
42.35
41.60
39.42
42.42
39.03
38.52
38.88
37.37
37.09
39.53
40.92
43.63
36.11
36.04
39.92
37.68
40.80
^45.20
46.62
35.05
38.78
40.32
41.45
43.45
39.08
41.03
41.37
41.17
42.15
41.90
41.94
41.90
37.07
36.53
40.78
39.53
39.08
Longitude
79.23
84.54
74.05
73.85
77.93
79.66
78.31
76.49
78.77
83.22
83.90
76.82
78.48
80.85
80.52
82.99
84.72
83.00
83.38
82.05
85.73
77.31
84.97
85.60
90.60
68.41
83.43
87.49
74.87
87.72
74.52
89.95
79.27
77.53
76.92
78.11
77.44
75.92
76.28
88.03
88.09
77.93
84.72
89.95
Operating
Start
09/12/88
02/12/90
08/15/88
10/13/88
08/15/88
01/22/90
10/13/88
08/15/88
08/15/88'
08/23/88
01/21/90
1 1/07/88
08/26/88
09/01/88
09/12/88
09/07/88
01/22/90
08/15/88
08/22/88
01/22/90
09/01/88
09/02/88
09/02/88
08/15/88
08/16/88
11/06/89
08/31/88
08/15/88
11/14/88
08/22/88
01/25/90
08/15/88
08/15/88
08/30/88
09/12/88
01/15/90
08/15/88
01/15/90
03/02/90
01/08/90
01/11/90
08/15/88
02/14/90
08/15/88
Dates"
Stop
12/08/89
05/31/90
12/08/89
05/31/90
05/31/90
05/31/90
05/31/90
12/08/89
05/31/90
05/31/90
05/31/90
12/03/89
09/18/88
05/31/90
05/27/90
05/31/90
05/31/90
05/31/90
05/31/90
05/31/90
12/08/89
12/08/89
05/31/90
12/08/89
12/08/89
12/08/89
05/31/90
05/31/90
12/08/89
12/08/89
05/31/90
12/08/89
05/31/90
05/31/90
12/10/89
05/31/90
05/31/90
05/31/90
05/31/90
05/31/90
05/31/90
05/31/90
05/31/90
12/08/89
Co-located sites
All sites were shut down during these periods:
2 weeks 09/26/88 - 10/09/88
8 weeks 11/21/88-01/15/89
processing were done by dedicated labo-
ratory computers.
For the first three sampling sessions,
33 elements were determined for all
samples. A survey of these results led to
a decision to reduce the analyses to these
11 elements for the last sampling ses-
sions: Mg, Al, Si, P, S, Cl, K, Ca, Fe, Zn
and Cd,
18 weeks
1 week
02/27/89 - 07/02/89
12/25/89 - 12/31/89
Results and Discussion
During the period from mid-August 1988
through May 1990, fine particle sampling
was conducted at 45 sites. The network
was not operating continuously during the
entire period, but samples were collected
for a total of 65 weeks. Only 17 of the
sites were operating at all times during
the network operation. After the removal
of invalid samples, 12,589 filters (includ-
ing blanks) from 14 sampling sessions
were analyzed for elemental content by
WDXRF spectrometry. Duplicate analyses
were made by reanalyzing at a later date
13% of the filters from the first three ses-
sions and 5% of the samples in the re-
maining sessions. Repeatability was ex-
cellent, greater than 90% for the six most
abundant elements. Chlorine analyses
were consistently lower in the second de-
termination, apparently because of loss
by volatilization, either direct or as the
result of chemical reaction.
The average fine particulate mass value
for all sites and all collection dates was
15.5 ng/m3. The XRF analysis gave an
average sulfur concentration of 1.9 u.g/m3,
or a mean sulfur content of 12.1% for all
10,927 samples. If the gravimetric factors
for SO,2' (3;00), NH.HSO, (3.59), or
(NH4)2SO4 (4.13) are applied, the follow-
ing equivalent.percentages would be ob-
tained: 36% SO.2', 43% NH.HSO., or 47%
(NH4)2S04.
The seasonal averages for all sites of
the fine paniculate mass and sulfur con-
centrations are summarized in Tables 2
and 3 for each of the seven quarters in
which sampling was made. The concen-
trations of fine particulate mass and par-
ticulate sulfur were highest during the two
summers and lowest during tiie winter and
fall seasons.
The increase of fine particulate sulfur
concentrations in the summer is consis-
tent with results of previous studies and
has been attributed to increased use of
electrical power for air conditioning de-
mands and to more intense solar radia-
tion, which converts SO2 to sulfate aero-
sols. The increase in the percentage of
sulfur is demonstrated in Table 4, where
the percent of sulfur in the total fine par-
ticulate is summarized for the seasons at
the co-located sites 306 and 406 and for
the average concentrations from all 44
sites.
Conclusions and
Recommendations
A data base of fine particulate mass
and 11 chemical element concentrations
has been produced by daily sampling of
ambient air aerosol at 44 sites selected
from the Acid MODES network at intermit-
tent periods from July 1988 to May 1990.
The data base was generated from 10,952
samples that were collected during 65
weeks and seven different quarters (sea-
sons). Analysis for elemental composition
was accomplished by wavelength disper-
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Table 2. Fine Particulate Mass Seasonal A verages for All Sites
SEASON NO. OF SAMPLES MEAN STD. DEV.
(ng/m3) (ng/m3)
Summer 1988 401
Fall 1988 661
Winter 1989 985
Summer 1989 2127
FaM 1989 1803
Winter 1990 1920
Spring 1990 1478
Table 3. Sulfur Seasonal Averages for All Sites
SEASON NO. OF SAMPLES
Summer 1988 461
Foil 1988 929
Winter 1989 1149
Summer 1989 2311
Fall 1989 2180
Winter 1990 2175
Spring 1990 1646
20.04 11.47
12.46 5.51
14.89 7.05
24.87 15.52
16.57 9.59
13.79 6.69
14.95 7.14
MEAN STD. DEV.
(Hg/m3) (ng/m3)
2.16 1.60
1.15 0.70
1.30 0.74
3.12 2.75
1.52 1.32
1.37 0.77
2.03 1.25
Table 4. Seasonal Variation of Sulfur ConcentoaSon Averages at the Pennsylvania Co-heated Sites fag/trf)
SEASON SITE 306 SITE 406
Mean Std. Dev.
Summer 1988 2.29 1.05
Fall 1988 1.20 0.64
Winter 1989 1.50 0.54
Summer 1989 3.21 2.55
Fall 1989 1.79 1.31
Winter 1990 1.53 0.75
Spring 1990 2.08 1.42
sive x-ray fluorescence spectrometry
(WDXRF) on the total of 12,589 filters
(including field blanks) for the following 1 1
elements, which were the most consis-
tently present: Mg, Al, Si, P, S, Cl, K, Ca,
Fe, Zn, and Cd. The continuity and com-
pleteness of the FPN study was affected
Mean Std. Dev.
2.20 1.32
1.31 0.67
1.48 0.62
3.15 2.44
1.82 1.40
1.61 0.81
2.12 1.49
by budget and operational problems in
the parent Acid MODES network, which
caused interruptions in the sampling
schedule, the closing of some of the origi-
nal sites, and the moving of sites later in
the program.
The original form of the data base that
was generated by the collection, gravi-
metric, and analytical procedures consisted
of 384 files with about 17.5 MB of com-
puter data. This large data base includes
for each of the 12,589 samples the weight,
volume sampled, filter collection area, qual-
ity control codes, and other collection data.
Each sample also contains the analytical
data for each of the 1 1 elements, includ-
ing concentrations, detection limits, and
random error estimates.
A special software package was devel-
oped by ManTech Environmental to com-
press the large original data base to a
more transportable size and to develop
an interface for the user to conveniently
retrieve selected information. Programs
were written in Pascal language to pro-
duce a file that could be read directly into
a personal computer for further data analy-
sis.
The FPN data base produced by this
field study is a valuable contribution to the
understanding of the climatology of
nonurban fine particulate aerosols and their
contribution to urban particulate loadings.
Cursory examination of the data indicate
high variability of the daily concentration.
Future efforts should assess the relation-
ship between meteorological conditions
and site concentrations to better under-
stand the variations. A recommended ap-
proach is to classify samples by meteoro-
logical data. This might be done by at-
tempting to correlate concentration levels
with meteorological parameters such as
surface wind direction, synoptic weather
classifications (warm, cold, occluded, or
stationary fronts) and by back-trajectory
calculations. Initially, the concentration
observations that are within distinct com-
mon wind directions may be compared.
However, incoming air from the same di-
rection can arrive through different trajec-
tories. Attempts should be made to corre-
late observations with trajectory-defined
sources to promote an understanding of
how the observed variations are related to
fluctuation in meteorology.
•&U.S. GOVERNMENT PRINTING OFFICE: 1992 - 648-080/40131
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Ft. Bennett (also the EPA Project Officer) andL. Stockburger are with the
Atmospheric Research and Exposure Assessment Laboratory, Research
Triangle Park, NC 27711.
The complete report, entitled "A Regional Fine Particle Field Study: Data Base
and Initial Results," (Order No. PB92-106939/AS; Cost: $19.00, 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 Off her can be contacted at:
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
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