c/EPA
United States
Environmental Protection
Agency
Environmental Sciences Research
Laboratory
Research Triangle Park NC 27711
EPA 600 3-79-090
September 1 979
Research and Development
Houston Urban
Plume Study—1-974
Microscopical
Identification of
Collected Aerosols
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RESEARCH REPORTING SERIES
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EPA-600/3-79-090
September 1979
HOUSTON URBAN PLUME STUDY - 1974
Microscopical Identification of Collected Aerosols
by
Ronald G. Draftz and Jean Graf
IIT Research Institute
Fine Particles Research Section
Chicago, Illinois 60616
Grant No. R803078
Project Officer
Jack L. Durham
Atmospheric Chemistry and Physics Division
Environmental Sciences Research Laboratory
Research Triangle Park, North Carolina 27711
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
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DISCLAIMER
This report has been reviewed by the Environmental Sciences Research
Laboratory, U.S. Environmental Protection Agency, an approved for publication.
Approval does not signify that the contents necessarily reflect the views
and policies of the U.S. Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or recommendation
for use.
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ABSTRACT
An urban plume study was conducted in Houston during July 1974 to gain
preliminary data on the concentration and composition of primary and second-
ary aerosols contributing to Houston's air pollution problem. Selected
membrane filter samples containing urban aerosols were analyzed by polarized
light and scanning electron microscopy to identify the aerosols and their
possible sources.
The aerosol samples, collected by aircraft at elevations from 1,000 to
4,000 feet above sea level, consisted principally (more than 95 percent by
number) of mineral silicate fragments. The silicates measured from less than
1 ym to approximately 10 pm in diameter. The particles size modes were 1-2
ym upwind of the city and 4-5 ym for sampling traverses downwind of the
commercial and industrial areas. A trace to minor quantity of carbonaceous
particles (resembling diesel exhaust), lead bromide compounds (from vehicle
exhausts), and sea salt were also found in most samples. No discrete parti-
cles of ammonium sulfate were present.
This report was submitted in partial fulfillment of Grant R803078 by
IIT Research Institute under the sponsorship of the U.S. Environmental
Protection Agency. This report covers a period from July 1, 1974 to October
31, 1977, and work was completed as of June 15, 1979.
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CONTENTS
Abstract iii
1. Introduction 1
2. Sample Collection 2
3. Sample Preparation 4
4. Sample Descriptions and Microscopical Results 5
Friday, 19 July 1974 5
Saturday, 20 July 1974 6
Sunday, 21 July 1974 7
5. Discussion of Results 8
References 9
Appendix
A. Figures 1-75 10
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SECTION 1
INTRODUCTION
An atmospheric pollutant study sponsored by the U.S. Environmental Pro-
tection Agency was conducted in Houston, Texas during July 1974 under the
direction of Dr. James R. Brock of the University of Texas.1 The purpose of
that study was to gain preliminary information principally on the spatial and
temporal distribution of primary aerosols and secondary aerosols and their
precursors.
Aerosols were sampled and gaseous pollutants were monitored using an in-
strumented CESSNA 206 airplane operated by Meteorology Research, Inc. Wind
speed and direction data were collected at a number of ground-based stations
using pibals.2 Additional meteorological data, including daily rawindsondes,
were also used for predicting weather and for calculating pollutant flux.1
Sampling flights were usually made at right angles to the wind direction
between two ground-level locations. Pollutant concentrations were measured
by performing repeated traverses at various elevations (usually 1,000, 2,000,
3,000, and 4,000 feet) between the ground-level locations. This provided a
cross-sectional concentration of pollutants which, when coupled with wind
data, gave the pollutant flux.
The collected aerosol mass from each flight traverse was too small to
measure gravimetrically; however, aerosol concentrations were measured with
a condensation nuclei counter and an integrating nephelometer. In addition
to aerosol measurements, the concentrations of CO, NOx, S02» 03, and gaseous
hydrocarbons were measured during each flight.
A number of aerosol samples were selected for microscopical examination
by IITRI to determine the identity and sources of aerosols upwind and down-
wind of Houston and also downwind of the industrial area east of Houston.
These aerosol analyses could then be compared to the spatial and temporal
concentrations of gaseous pollutants so that trends for the formation of
secondary aerosols could be examined.
This report presents the results of microscopical analyses as a contri-
bution to an understanding of Houston's urban pollutants.
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SECTION 2
SAMPLE COLLECTION
Aerosol samples were collected on 0.8 ym pore size MILLIPORE membrane
filters (type AA) at a sampling rate of 10-15 liters per minute through
a 0.125 inch inlet tube. The aircraft flight speed ranged from 60 - 120 miles
per hour during sampling.
Table 1 is a summary of samples that were analyzed microscopically. This
is only a partial list of samples collected and flights made during the study.
An explanation of the column title flight paths is presented in Section 4.
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TABLE 1. SUMMARY OF AEROSOL SAMPLES ANALYZED MICROSCOPICALLY
Sample
Date No .
19 July 1974
20 July 1974
21 July 1974
•••^•^•••^••i^ ^•••^^i^^^**^ •••
Notes: (1) wind
(2) data
(3) wind
(4) wind
1
2
3
4
5
6
7
8
9
Flight
Path
L to A
A to L
L to A
A to L
L to A
M to Q
V to W
H to D
H to D
^^•^^•^•^•Ml M 1 • • . •^^^^•^•^•^•^^•^^
speed and direction
not available
speed and direction
speed and direction
Start
Time 5
CDT
9:27
9:47
10:01
10:14
10:31
9:04
10:26
13:44
6:33
«^« ^««M^^— _^*«^^^^^—
measured
measured
measured
Sampling
Duration,
min.
11
11
10
10
10
11
49
35
38
^^^^^^^_^^^H^V^««*M--IIMVBVIMV-IIB.^MIB
at Westbury H.
at EMSU pibal
at San Jacinto
Elevation,
ft.
1000
2500
3500
4500
1000
1700
1000
2000
3000
1000
2000
3000
4000
1000
2000
3000
4000
ta^^»M»V*«B^»»4>*^MW^H^^^^^^M
S. and Hobby
site
pibal site
Approx. Wind Approx. Wind
Direction at Speed at
Elevation Alt., knots
WSW(l)
WSW
S
(2)
W
W(3)
WNW(4)
WNW(4)
NW(4)
SW(5)
WSW(5)
NW(5)
NW(5)
SW(5)
SW(5)
SSW(6)
SE(5)
Airport pibal sites.
5-10
5-10
5-10
(2)
5-10
15-20
5-10
5-10
0-5
0-5
0-5
5-10
5-10
15-20
10-15
0-5
0-5
- -
(5) wind speed and direction measured at Hobby Airport pibal site
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SECTION 3
SAMPLE PREPARATION
Each of the cellulose acetate membrane filters was examined with a stere-
omicroscope using reflected light to determine whether the collected aerosols
were uniformly distributed over the filter surface. Particles were generally
more heavily loaded in the center third of the filter, which typically occurs
when the sampling tube inlet diameter is significantly smaller than the filter
diameter.
Those filters sampled for approximately 10 minutes were so lightly loaded
that it was difficult to judge whether particles were uniformly distributed.
Therefore, pie-shaped radial segments were cut from the filters to ensure
that a representative sample would be analyzed.
The filter segment for polarized light microscopy was mounted between a
glass slide and glass covers!ip. The mounting procedure consisted of adding
several drops of immersion liquid (refractive index = 1.515) to a glass slide,
placing the filter segment onto the puddle of immersion liquid, and, once the
liquid had penetrated the filter, adding the coverslip. The immersion liquid
serves the dual function of making the filter transparent and providing a
reference refractive index for particle identification.
A second pie-shaped radial filter segment was cut for scanning electron
microscopy (SEM). These segments were taped to glass slides and coated with
a thin film (^15 nm) of carbon in a vacuum evaporator (pressure = 10"5 mm Hg).
The carbon film provides a conductive layer that minimizes sample charging
which interferes with image formation. The coated segment is then placed on
an aluminum specimen stub and electrically grounded by placing a thin stripe
of conductive paint, from the edge of the filter onto the stub.
4
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SECTION 4
SAMPLE DESCRIPTIONS AND MICROSCOPICAL RESULTS
This section presents microscopical results and brief descriptions of the
sampling locations (Brock's report1) and weather conditions (Hoffnagle's
report2).
The results are presentefefor each sampling day and flight traverse. The
integrated results for the fnilre experiment are presented in Section 5, Dis-
cussion of Results.
FRIDAY, 19 JULY 1974
Sampling Plan and Wearier Conditions
Sampling was conducted west (upwind) of Houston's commercial and indus-
trial areas to obtain background aerosol samples. The sampling flight paths
were approximately at right angles to the wind directions. Five membrane
filter samples were collected at various elevations along a flight path from
points L to A (Figure 1). The aerosol samples collected during this flight
are shown in Table 1.
At 1000 CDT, there was a general pattern of winds from the west and
southwest at 5-10 knots. The inversion layer was at about 2,000 ft when
measured at 0700 CDT by rawindsonde. At the time of sampling, however, all
the samples were believed to^have been collected in the mixing layer.
f S
Microscopical Results--
All of the samples collected ori^Friday, 19 July 1974L had very low con-
centrations of aerosols (Figures 2-5]§ Almost all the particles were mineral
fragments; very few were carbonaceous aerosols and even fewer, if any, ammon-
ium sulfate particles. Most particles.&ere smaller than 5 ym in diameter,
with a modal size of 1-2 ym.
Scanning .electron microscopy -(SEM) confirmed the low concentration of
aerosols on -$fe filter. Energy dispersive x-ray microanalysis also showed
that many of the aerosols were mineral silicates. Representative scanning
electron micrographs are shown in Figures 6-27.
Unusual spheroids, measuring between 0.5 ym and 3 ym in diameter;, were
found in samples 1 through 5 (Figures 6, 7, 14, 15, 16, and especially 10 and
11). Based on their microscopical morphology, the spherical particles were
part of the membrane filter and were not atmospheric aerosols. X-ray
-------
microanalysis of the spheres gave a spectrum without any detectable elements.
Some of the spheres began to degrade (thermally) during the x-ray microanaly-
sis, suggesting that they were carbonaceous. Polarized light microscopy
showed no discrete, black, opaque particles in the 0.5 ym to 3 ym range that
could be carbonaceous combustion products. In fact, these particles could not
be detected by optical microscopy on an oil-immersed filter segment, indi-
cating that the particles are isotropic and match the refractive index of the
oil and the filter. There are very few atmospheric aerosols that fit this
morphology.
Also found in samples 1 through 5 were micro whiffle balls—atmospheric
aerosols shown in Figures 23 and 24--which generally cluster by hundreds to
form a spherical cage. They are black and opaque and presumed to be carbon-
aceous because they contain no elements detectable by x-ray microanalysis.
They are most unusual in that they are monodisperse, 0.4 pm in diameter, and
have a complex, symmetrical skeleton that is also a spherical cage.
These particles have been detected in aerosol samples from St. Louis,
Miami, and the iron range in northern Minnesota. They are believed by one
of the authors (RGD) to be ancient spores that are present in and emitted
from diesel fuel. Micro whiffle balls always seem to occur as agglomerates
and therefore do not act independently as light-scattering aerosols. Despite
their large numbers they probably contributed very little to the b scat
measured with the integrating nephelometer.
SATURDAY, 20 JULY 1974
Sampling Plan and Weather Contributions
Pollutant concentrations upwind of Houston (L to A), downwind of the
commercial area (H to D), and downwind of the commercial and industrial
areas (V to W), Figure 28, were made during morning and afternoon flights.
(The upwind cross-section flight, L to A, is not shown since the sample was
not analyzed microscopically.) A traverse was also made in the wind
direction (M to Q). Samples 7 and 8 were used for multiple flights at varying
elevations along the same path, as shown in Table 1.
The morning winds were principally from the west, whereas the afternoon
winds shifted to the north and became calmer.
Microscopical Results--
Sample 6 showed about the same particle concentrations (Figure 29) as
seen for samples 1 through 5. Samples 7,8 and 9, which were used for sampling
periods approximately four to six times longer than sample 6, show corres-
pondingly greater particle concentrations. Again, the dominant particle
types collected on samples 7,8 and 9 were minerals (Figures 30-33). The
mineral particles of the commercial and industrial areas collected downwind
(samples 7 and 8) had a larger particle size than those collected upwind of
Houston. These downwind minerals had a modal size of 4-5 ym, suggesting that
these minerals were injected from Houston rather than merely transported from
rural areas upwind of Houston.
6
-------
The principal aerosol addition to sample 8, collected downwind of the
Houston commercial area, was minerals, with a slight though trivial addition
of lead compounds and carbonaceous agglomerates from vehicle exhausts.
SUNDAY, 21 JULY 1974
Sampling Plan and Weather Conditions
The sampling plan was similar to that of 20 July 1974. Two flight paths
were flowrf: one downwind of the commercial area, the other downwind of the
industrial area. The only sample analyzed microscopically was from the urban,
downwind, commercial area (Figure 68). Sampling data for this flight are
shown in Table 1,
The winds were principally from the southwest during sampling. An in-
version layer was found at approximately 1200 feet at 0700 CDT, but no inde-
pendent sample was collected above and_below the inversion layer.
Microscopical Results—
The particles found on this filter were mainly mineral fragments with an
estimated modal particle size of 4-5 urn, similar to those collected on 20 July
1974. Besides the minerals, there were traces of carbonaceous particles and
lead-containing particles from vehicle exhausts.
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SECTION 5
DISCUSSION OF RESULTS
The aerosol collected upwind and downwind of Houston and downwind of the
industrial area (ship channel) were remarkably similar in composition. In
every sample, minerals comprised more than an estimated 95% of the particle
types by number. The remaining particles ranges from sea salt to carbonaceous
deposits (mainly diesel emissions) and lead bromides (from vehicle exhausts).
Whereas a few minerals contained minor x-ray fluorescence peaks for sulfur,
there were no discrete particles of ammonium sulfate, commonly found in urban
aerosols.
Two points are worthy of further discussion. First, high ozone concen-
trations (0.2 ppm) were noted in the presence of (relatively high b scat
values (^5 x 10~'*m~1) above the mixing layer.1 While the high b scat values
appear due to the mineral particles, secondary aerosols may have been present
also. These secondary aerosols were not detected microscopically, suggesting
that they may have been present as liquids.
Secondly, a greasy deposit was reported to have formed on the airplane
wings. The deposit was heavy enough to require washing the airplane after
every two days of sampling. Some of this grease or thick oil would be
expected on the membrane filters, but none was found on any of the filters,
even those downwind of the industrial area.
The absence of grease on the filters may be linked to sampling bias.
The grease particles that accumulated on the wings may have been larger
than 10 ym in diameter. Since the inlet tubing had a diameter of only 1/8
inch, the grease particles would never reach the filter. Alternately, the
grease particles may have been not only large but also few in number.
Spread on the wing, they may have looked more abundant than was actually the
case.
8
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REFERENCES
1. Brock, J.R. Houston Urban Plume Study—1974, Description and Summary
of Results. EPA-600/3-78-048a, U.S. Environmental Protection Agency,
Research Triangle Park, NC, 1978. 32 pp.
2. Hoffnagle, G.F. Air Pollution Meteorology During the Houston Urban
Plume Study, July 1974. EPA-600/3-77-073, U.S. Environmental
Protection Agency, Research Triangle Park, NC, 1977. 63 pp.
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APPENDIX
FIGURES 1 - 75
Number Page
1 Flight path for 19 July 1974 sampling mission 16
2 Photomicrograph of sample no. 1, showing very light loading
of mineral fragments (bright); polars uncrossed 10°, 406X. ... 17
3 Photomicrograph of sample no. 2, showing very light loading
of minerals and some iron oxides; polars uncrossed 10°, 406X. . 17
4 Photomicrograph of sample no. 3, showing a light loading
(though heavier than samples 1 or 2) of minerals; polars
uncrossed 10°, 406X 18
5 Photomicrograph of sample no. 4, showing mineral particles;
crossed polars, 406X 18
6 Scanning electron micrograph (SEMG) of 2-ym diameter mineral
fragment on sample no. 1 containing silicon, aluminum,
potassium,and iron; 10,OOOX .- 19
7 SEMG of typical field of view for sample no. 1, showing an
absence of particles away from the filter center; 10,OOOX ... 19
t
8 SEMG of sample no. 2, showing the area of greatest aerosol
concentration (the bright spots); 500X 20
9 Scanning electron x-ray microanalysis (SEXM) of area in
Figure 8, showing a very weak spectrum for aluminum and
silicon, which corroborates the low aerosol concentration ... 20
10 SEMG of sample no. 2, showing apparent spherical particles
that are actually part of the membrane filter structure; 3.000X.21
11 Same as Figure 10, except that the electron beam was rastered
over the central portion of the area that caused some thermal
degradation of the membrane polymer; 3.000X 21
12 SEMG of sample no. 3, showing low concentration of aerosols, 500X.22
10
-------
Number
13 SEXM of area in Figure 12, showing peaks for aluminum,
silicon and copper ....................... 22
14 SEMG of sample no. 3, showing -membrane filter structure
and triangular mineral fragments near the center; 10.000X. ... 23
15 SEMG of sample no. 4, showing a low aerosol concentration
and the artifact spherical aerosols that are part of the
membrane structure; 3.000X ................... 23
16 Same as Figure 15, but at higher -magnification: 10.000X ...... 24
17 Large (8 -urn) cluster of calcium sulfate crystals on sample no. 4,
probably formed from sulfuric acid attack of calcium
carbonate; 10,OOOX ....................... 24
18 SEXM of large cluster in Figure 17, showing peaks for Mg
(01.3 Kev}, aluminum [01.5 Kev) , silicon (01.7 Kev) ,
sulfur (02.3 Kev), and calcium ("03.7 and 04.0 Kev) ....... 25
19 SEMG of 10 ym mineral flake containing silicon, aluminum
and calcium; 8,OOQX ....................... 25
20 SEMG of calcium sulfate, elongated prism (5.5 -pm x 0.7
with an attached mineral flake containing silicon, magnesium,
sodium and potassium; 8,OOOX .................. 26
21 SEMG of sample no. 5, showing the greatest aerosol concentrations
among samples 1-5. Itost of the particles are mineral fragments;
500X .............................. 26
22 SEXM of area in Figure 21 showing peaks for sodium (01.1 Kev),
aluminum (01.5 Kev), silicon (main peak, 01.7 Kev), sulfur
(02.3 Kev) ........................... 27
23 SEMG of small, dark deposit appearing as a hole in Figure 21
3.000X ............................. 27
24 SEMG of particles in Figure 22 showing numerous 0.4 -pro
Micro Whiffle Balls and calcium alumino silicate needles;
10.000X. . . .......................... 28
t
25 SEXM of Micro Whiffle Balls in Figure 23. Weak peaks for
aluminum and silicon are from the silicate needles shown
in Figure 23 .......................... 28
26 SEMG of carbonaceous agglomerate (probably auto exhaust)
in sample no. 5; 3.000X ..................... 29
11
-------
Number
27 SEMG of sample no. 5, showing unusual agglomerate (perhaps
aggregate) in the center of the photo. The upper, right
portion of the duo contains lead and bromine (probably
PbBrz) while the lower left portion contains magnesium,
aluminum and silicon 29
28 Flight paths for 20 July 1974 sampling mission 30
•29 Photomicrograph of sample no. 6, showing a low concentration
of particles that are principally minerals; crossed polars, 406X. 31
30 Photomicrograph of sample no. 7, showing predominantly mineral
fragments (bright) plus a few clusters of carbonaceous agglom-
erates (black); polars uncrossed 20°, 163X 31
31 Photomicrograph of large, carbonaceous cluster shown in Figure 30;
polars uncrossed 20°, 652X 32
32 Photomicrograph of sample no. 8, showing a moderate concentration
of minerals plus a few carbonaceous clusters; polars uncrossed
10°, 406X 32
33 Micrograph of sample no. 9, showi'ng moderate concentration of
minerals plus a trace of opaque, carbonaceous agglomerates
on the filter as received; reflected light, 65X 33
34 Micrograph of sample no. 6, taken with back scattered electrons
that show increasing brightness with increases in atomic
weight; 300X 33
35 SEMG of the two bright particles seen just to left of center in
Figure 34. Both particles are sodium chloride, probably
sea spray; 6,OOOX 34
36 SEMG of sample no. 6, showing artifact spheres from the filter;
3,OOOX 34
37 SEMG of sample no. 7, showing area of moderate mineral concentra-
tion along with a few carbonaceous clusters; 100X 35
38 SEXM of area in Figure 37 showing major peaks^ for aluminum,
silicon and calcium ' 35
39 SEMG of sample no. 7, showing mineral fragments and artifact
spheres; 3,OOOX 36
40 SEMG of alumino silicate mineral sliver seen in upper right
quadrant of Figure 39; 20.000X 36
12
-------
Number
41 SEXM of mineral sliver in Figure 40, showing major peaks for
aluminum and silicon 37
42 SEMG of artifact sphere seen in upper right corner of Figure 39;
10,OOOX . . . . . 37
> • *j i
43 SEMG of sample no. 7, showing black, carbonaceous cluster; 1,OOOX. . 38
44 SEMG of black, carbonaceous cluster in Figure 43; 10.000X 38
45 SEMG of thin mineral fragments sample no. 7. Particle A is an
alumino silicate, particle B contains only silicon (probably
quartz) and particle C contains sodium, magnesium, aluminum,
silicon, sulfur, potassium, calcium, and iron; 10.000X 39
*
46 SEXM of particle C in Figure 45 39
47 SEMG of lead chloro bormide particle in center of photo, from
sample no. 7; 10,OOOX 40
48 SEXM of PbClBr particle in Figure 47 showing peaks for sodium
(01.0 Kev), bromine (01.5 Kev), lead (02.4 Kev), chlorine
(02.6 Kev), calcium (03.7 Kev), and lead (10.5 Kev) 40
49 SEMG of large (3 ym) lead bromide particle on sample no. 7, 10,OOOX. 41
50 SEXM of lead bromide particle in Figure 49; compare with Figure 48 . 41
51 SEMG of sample no. 7, showing artifact spheres. The filter area
photographed is outside the central aerosol deposit; 3,OOOX. ... 42
52 SEMG of sample no. 7, near the outer filtration periphery showing
artifact spheres; 3,OOOX 42
53 SEMG of highest aerosol concentration on sample no. 8, 100X 43
54 SEXM of filter area shown in Figure 53. The peaks correspond with
sodium (01.0 Kev), magnesium (01.3 Kev), aluminum (01.5 Kev),
silicon (01.7 Kev), sulphur (02.3 Kev), chlorine (02.6 Kev),
potassium (03.3 Kev), calcium (03.7 and 04.0 Kev), and iron
(06.4 Kev) 43
55 SEMG showing portion of area in Figure 53, at higher magnification;
l.OOOX 44
56 SEMG of mineral needle (or flake on edge) from sample no. 8; 10.000X.44
57 SEXM of mineral needle in Figure 56 showing principal peaks for
Al, Si, and Ca. The adjacent particles maybe also contributing
to this spectrum 45
13
-------
Number Page
58 SEMG of rounded mineral grain in sample no. 8, containing
calcium as the major constituent (probably calcite); 10.000X . . 45
59 SEXM of rounded mineral grain showing peaks for Na, Mg, Al, Si,
P, S, Cl, K, Ca, and Fe. The nearby mineral grains are also
contributing to the spectrum 46
60 SEMG of cubic crystal, probably Na2C03 from sea spray, on
sample no. 8; lO.OOOX 46
61 SEXM of cubic crystal showing a major peak for sodium with minor
peaks for aluminum, silicon, sulfur, potassium, and calcium.
The peaks other than sodium are due to the adjacent particle . . 47
62 SEXM of particle attached to cubic crystal in Figure 61 47
63 SEMG of calcium alumino silicate mineral grain from sample no. 8,
lO.OOOX 48
64 SEXM of silicate mineral in Figure 63 with major peaks for Al
(01.5 Kev), Si, (01.7 Kev), and Ca (03.7 and 04.0 Kev) 48
65 Back scattered electron image to detect heavy metals, especially
lead in sample no. 8. The five small, very bright dots that
are circled are lead compounds from auto exhaust; 500X 49
66 SEMG of lead chloro bromide particle marked A adjacent to a
mineral fragment of sample no. 8; lO.OOOX 49
67 SEXM of lead chloro bromide particle in Figure 66 showing peaks
for Al (01.5 Kev), Si (01.7 Kev), Pb (02.3 Kev), Cl (02.6 Kev),
K (03.3 Kev), Ca (03.7 and 04.0 Kev), Fe (06.4,Kev), Pb (10.5
and 12.6 Kev), and Br (11.9 Kev). All the peaks but Pb, Cl
and Br are from the mineral cluster adjacent to particle A ... 50
68 Flight path for 21 July 1974 sampling mission 51
69 SEMG of sample no. 9, showing area with greatest aerosol concen-
tration (of minerals); 100X 52
70 SEXM of area shown in Figure 69 with prominent peaks for Al, Si,
S, and Ca 52
71 Back scattered electron image of central area in Figure 69
showing the presence of lead compounds from vehicle exhaust
as small bright dots. The diaphanous, rectangular particle
at the center is a moth scale; 300X 53
72 SEMG of sample no. 9, showing a PbClBr particle at the center,
10,OOOX w
14
-------
Number Page
73 SEMG of sample no. 9, showing angular mineral grains covered
by a fine, carbonaceous agglomerate; 10,OOOX 54
74 SEMG of artifact spheres in sample no. 9; 3.000X 54
75 SEMG showing artifact from a sample collected in Texas City,
Texas on 24 July 1974; 10,OOOX 55
15
-------
LEGEND
—«^—tM^^^^^W
• End point of troverse
O locofion of o spiral
O Other points
Figure 1. Flight path for 19 July 1974 sampling mission.
16
-------
Figure 2. Photomicrograph of sample no. 1, showing very
light loading of mineral fragments (bright);
polars uncrossed 10°, 406X.
Figure 3. Photomicrograph of sample no.
light loading of minerals and
polars uncrossed 10°, 406X.
2, showing very
some iron oxides;
17
-------
Figure 4. Photomicrograph of sample no. 3, showing a
light loading (though heavier than samples
1 or 2) of minerals; polars uncrossed 10°, 406X.
Photomicrograph of sample no. 4, showing
mineral particles; crossed polars, 406X.
18
-------
Figure 6. Scanning electron micrograph (SEMG) of 2 ym diameter
mineral fragment on sample no. 1 containing silicon,
aluminum, potassium and iron; 10,OOOX.
Figure 7. SEMG of typical field of view for sample 1 showing
an abscence of particles away from the filter center;
10,OOOX.
19
-------
Figure 8. SEMG of sample no. 2 showing the area of greatest
aerosol concentration; (the bright spots); 500X.
see
BEU 87868 INT
KEUEX-RAY HS= 29EU/CH
Figure 9. Scanning electron x-ray microanalysis (SEXM) of area
in Figure 8, showing a very weak spectrum for aluminum
and silicon, which corroborates the low aerosol concen-
tration.
20
-------
Figure 10. SEMG of sample no. 2, showing apparent spherical
particles that are actually part of the membrane
filter structure; 3.000X.
Figure 11. Same as Figure 10, except that the electron beam was
rastered over the central portion of the area that
caused some thermal degradation of the membrane
polymer; 3,OOOX.
21
-------
Figure 12. SEMG of sample no. 3, showing low concentration of
aerosols; 500*.
Figure 13. SEXM of area in Figure 12, showing peaks for aluminum,
silicon and copper.
-------
Figure 14. SEMG of sample no. 3, showing membrane filter structure
and triangular mineral fragments near the center; 10.000X.
Figure 15. SEMG of sample no. 4, showing a low aerosol concentra-
tion and the artifact spherical aerosols that are plirt
of the membrane structure; 3.000X.
23
-------
Figure 16. Same as Figure 15, but at higher magnification; 10,OOOX.
Figure 17. Large (8 ym) cluster of calcium sulfate crystals on
sample no. 4, probably formed from sulfuric acid
attack of calcium carbonate; 10.000X.
24
-------
Figure 18. SEXM of large cluster in Figure 17, showing peaks for
Mg (01.3 Kev), aluminum (01.5 Kev), silicon (01.7 Kev),
A sulfur (02.3 Kev), and calcium (03.7 and 04.0 Kev).
Figure 19. SEMG of lOym mineral flake containing silicon,
aluminum and calcium; 8.000X.
25
-------
Figure 20. SEMG of calcium sulfate, elongated prism (5.5 ym x
0.7 ym) with an attached mineral flake containing
silicon, magnesium, sodium and potassium; 8,OOOX.
Figure 21. SEMG of sample no. 5, showing the greatest aerosol
concentrations among samples 1-5. Most of the
particles are mineral fragments; 500X.
26
-------
see
8EU 36633 IHT
KEUEX-RAY HS- 18EU/CH
Figure 22. SEXM of area in Figure 21 showing peaks for sodium
(01.1 Kev), aluminum (01.5 Kev), silicon (main peak,
01.7 Kev), sulfur (02.3 Kev).
Figure 23. SEMG of small, dark deposit appearing as a hole in
Figure 21; 3.000X.
27
-------
Figure 24. SEMG of particles in Figure 22 showing numerous 0.4 ym
Micro Whiffle Balls and calcium alumino silicate
needles; lO.OOOX.
Figure 25. SEXM of Micro Whiffle Balls in Figure 23. Weak peaks
for aluminum and silicon are from the silicate needles
shown in Figure 23.
28
-------
Figure 26. SEMG of carbonaceous agglomerate (probably auto exhaust)
in sample no. 5; 3.000X.
Figure 27. SEMG of sample no. 5 showing unusual agglomerate
(perhaps aggregate) in the center of the photo. The
upper, right portion of the duo contains lead and
bromine (probably PbBra) while the lower left portion
contains magnesium, aluminum and silicon.
29
-------
LEGEND
• End point of traverse
O Location of a spiral
o Other points
Figure 28. Flight paths for 20 July 1974 sampling mission.
30
-------
Figure 29. Photomicrograph of sample no. 6, showing a low concen-
tration of particles that are principally minerals;
crossed polars, 406X.
Figure 30. Photomicrograph of sample no. 7.^ showing predominantly
mineral fragments (bright) plus a few clusters of
carbonaceous agglomerates (black); polars uncrossed 20C
163X.
31
-------
Figure 31. Photomicrograph of large, carbonaceous cluster shown
in Figure 30, polars uncrossed 20°, 652X.
Figure 32. Photomicrograph of sample no. 8, showing a moderate
concentration of minerals plus a few carbonaceous
clusters; polars uncrossed 10°, 406X.
32
-------
Figure 33. Photomicrograph of sample no. 9, showing moderate
concentration of minerals plus a trace of opaque,
carbonaceous agglomerates on the filter as received;
reflected light, 65X.
Figure 34. Micrograph of sample no. 6 taken with back scattered
electrons that show increasing brightness with increases
in atomic weight; 300X.
33
-------
Figure 35. SEMG of the two bright particles seen just to left of
center in Figure 34. Both particles are sodium chloride,
probably sea spray; 6000X.
*>: £%
Ml '%
4
«^ff ,* —iff
^?€^r^^^
r^V*-;^'' >
» *-z ^ t
Figure 36. SEfIG of sample no. 6 showing artifact spheres from the
filter; 3.000X.
34
-------
Figure 37. SEMG of sample no. 7 showing area of moderate mineral
»' concentration along with a few carbonaceous clusters; 100X,
f s .
Figure 38. SEXM of area in Figure 37 showing major peaks for aluminum,
silicon and calcium.
35
-------
Figure 39. SEMG of sample no. 7 showing mineral fragments and artifact
spheres; 3.000X.
Figure 40. SEMG of alumino silicate mineral sliver seen in upper
right quadrant of Figure 39; 20.000X.
36
-------
Figure 41. SEXM of Mineral sliver in Figure 40 showing major peaks
for aluminum and silicon.
Figure 42. SEMG of artifact sphere seen in upper right corner of
Figure 39; 10.000X.
37
-------
Figure 43. SEMG of sample no. 7, showing black, carbonaceous cluster;
1,OOOX.
Figure 44. SEMG of black, carbonaceous cluster in Figure 43; 10,OOOX.
38
-------
Figure 45. SEMG of thin mineral fragments of sample no. 7.
Particle A is an alumino silicate, particle B contains
only silicon (probably quartz) and particle C contains
sodium, magnesium, aluminum, silicon, sulfur, potassium,
calcium, and iron; lO.OOOX.
Figure 46. SEXM of particle C in Figure 45.
39
-------
Figure 47. SEMG of lead chloro bromide particle in center of photo,
from sample no. 7; lO.OOOX.
Figure 48. SEXM of PbClBr particle in Figure 47 showing peaks for
sodium (01.0 Kev), bromine (01.5 Kev), lead (02.4 Kev),
chlorine (02.6 Kev), calcium (03.7 Kev), and lead
(10.5 Kev).
40
-------
Figure 49. SEMG of large (3 ym) lead bromide particle on sample
no. 7; 10,OOOX.
Figure 5V. SEXM of lead bromide particle in Figure 49; compare
with Figure 48.
41
-------
Figure 51. SEMG of sample no. 7, showing artifact spheres. The filter
. area photographed is outside the central aerosol deposit;
3,OOOX.
Figure 52". SEMG of sample no. 7, near the outer filtration periphery
showing artifact spheres; 3,OOOX.
42
-------
Figure 53. SEMG of highest aerosol concentration/on sample no. 8, 100X.
Figure 54. SEXM of filter area shown in Figure 53. The peaks
correspond with sodium (01.0 Kev), magnesium (01.3 Kev),
aluminum (01.5 Kev), silicon (01.7 Kev), sulphur (02.3
Kev), chlorine (02.6 Kev), potassium (03.3 Kev), calcium
(03.7 and 04.0 Kev) and iron (06.4 Kev).
43
-------
Figure 55. SEMG showing portion of area in Figure 53, at higher
magnification; 1,OOOX.
Figure 56. SEMG of mineral needle (or flake on edge) from sample
no. 8; 10.000X.
44
-------
Figure 57. SEXM of mineral needle in Figure 56 showing principal
peaks for Al, Si and Ca. The adjacent particles maybe
. also contributing to this spectrum.
Figure 58. SEMG of rounded mineral grain in sample no. 8 containing
calcium as the major constituent (probably calcite);
10.000X.
45
-------
Figure 59. SEXM of rounded mineral grain showing peaks for Na,
Al, Si, P, S, Cl, K, Ca and Fe. The nearby mineral
grains are also contributing to the spectrum.
Mg,
Figure 60. SEMG of cubic crystal, probably Na2C03 from sea spray,
on sample no. $, 10.000X.
46
-------
Figure 61. SEXM of cubic crystal showing a major peak for sodium
with minor peaks for aluminum, silicon, sulfur, potas-
sium and calcium. The peaks other than sodium are due
to the adjacent particle.
Figure 62. SEXM of particle attached to cubic crystal in Figure 61,
47
-------
Figure 63. SEMG of calcium alumino silicate mineral grain from
sample no. 8; 10.000X.
Figure 64. SEXM of silicate mineral in Figure 63 with major peaks
for Al (01.5 Kev), Si (01.7 Kev), and Ca (03.7 and
04.0 Kev.)
48
-------
Figure 65. Back scattered electron image to detect heavy metals,
especially lead in sample no. 8. The five small, very
bright dots that are circled are lead compounds from
auto exhaust; 500X.
Figure 66. SEMG of lead chloro bromide particle marked A adjacent to
a mineral fragment of sample no. 8; 10.000X.
49
-------
Figure 67. SEXM of lead chloro bromide particle in
Figure 66 showing peaks for Al (01.5 Kev),
Si (01.7 Kev), Pb (02.3 Kev), Cl (02.6 Kev),
K (03.3 Kev), Ca (03.7 and 04.0 Kev), Fe
(06.4 Kev), Pb (10.5 and 12.6 Kev) and
Br (11.9 Kev). All the peaks but Pb, Cl
and Br are from the mineral cluster adjacent
to particle A.
50
-------
LEGEND
End point of traverse
Locution of o spiral
o Other points
Figure 68. Flight path for 21 July 1974 sampling mission.
51
-------
Figure 69. SEMG of sample no. 9 showing area with greatest aerosol
concentration (of minerals); 100X.
Figure 70. SEXM of area shown in Figure 69 with prominent peaks
for Al, Si, S, and Ca.
52
-------
Figure 71. Back scattered electron image of central area in Figure 69
showing the prescence of lead compounds from vehicle exhaust
as small bright dots. The diaphanous, rectangular particle
at the center is a moth scale; 300X^,
Figure 72. SEMG of sample no. 9 showing a PbClBr particle at the
center; 10.000X.
53
-------
Figure 73. SEMG of sample no. 9 showing angular mineral grains
covered by a fine, carbonaceous agglomerate; lO.OOOX.
«SMf
,: * r
,.1%^P-I
m*i3&*v«
Figure 74. SEMG of artifact spheres in sample no. 9; 3,OOOX.
54
-------
Figure 75. SEMG showing artifact spheres from a sample collected in
Texas City, Texas on 24 July 1974; 10.000X.
55
-------
TECHNICAL REPC'HTDATA
(Please read Instructions on the re\ crse before completing)
REPA-T600/3-79-090
-;. TITLE ANOSUBTITLE
HOUSTON URBAN PLUME STUDY - 1974
Microscopical Identification of Collected Aerosols
3. RECIPIENT'S ACCESSION-NO,
5. REPORT DATE
September 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Ronald G. Draftz and Jean Graf
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
IIT Research Institute
Fine Particles Research Section
Chicago, Illinois 60616
10. PROGRAM ELEMENT NO.
1AA603 AH-005, AH-011 (FY-77
11. CONTRACT/GRANT NO.
R803078
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Sciences Research Laboratory - RTP, NC
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
Interim 7/74 - 10/77
14. SPONSORING AGENCY CODE
EPA/600/09
15. SUPPLEMENTARY NOTES
16. ABSTRACT
An urban plume study was conducted in Houston during July 1974 to gain preliminary
data on the concentration and composition of primary and secondary aerosols contribu-
ting to Houston's air pollution problem. Selected membrane filter samples containing
urban aerosols were analyzed by polarized light and scanning electron microscopy to
identify the aerosols and their possible sources.
The aerosol samples, collected by aircraft at elevations from 1,000 to 4,000
feet above sea level, consisted principally (more than 95 percent by number) of
mineral silicate fragments. The silicates measured from less than 1 ym to approxi-
mately 10 urn in diameter. The particles size modes were 1-2 ym upwind of the city
and 4-5 pm for sampling traverses downwind of the commercial and industrial areas. A
trace to minor quantity of carbonaceous particles (resembling diesel exhaust), lead
bromide compounds (from vehicle exhausts), and sea salt were also found in most
samples. No discrete particles of ammonium sulfate were present.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
~*Air pollution
*Aerosols
*Plumes
*Electron microscopy
*Polarized electromagnetic radiation
*Particle size distribution
*Silicate minerals
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Houston, TX
13B
07D
21B
20C
20N
086
B. DISTRIBUTION STATEMEN1
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
•21. NO. OF PAGES
62
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
56
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