United States
                Environmental Protection
                Agency
               Environmental Sciences Research
               Laboratory
               Research Triangle Park 2771 1
EPA-600/3-83-041
June 1983
                Research and Development
x>EPA
Atlas of  Source
Emission  Particles

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                                           EPA-600/3-83-041
                                           June 1983
      ATLAS OF SOURCE EMISSION PARTICLES

                      by

                 John L Miller
  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 TRIANLGE PARK, NORTH CAROLINA  27711

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                      NOTICE

This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication.  Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
                       11

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                                     PREFACE
     A major effort in environmental protection is to develop measurement
technology needed for source and ambient air monitoring of pollutant emis-
sions.  These efforts depend on detection, identification, and quantification
of specific pollutants, and assessment of their effects.  The Emissions
Measurement and Characterization Division conducts studies to identify and
determine the chemical and physical nature of both stationary and mobile
source emissions.

     One important means of making such measurements is electron microscopy.
The application of this technology to the characterization of emissions from
power generation, various manufacturing operations, mining and quarrying, and
automotive commerce has led to the compilation of data that has been indis-
pensible to developing instrumentation and methodology for the safe disposal
of discarded consumer goods and industrial scrap and wastes.

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                                 ABSTRACT
     An atlas of various source emission particles characterized by electron
optical techniques has been compiled for use by air pollution investigators.
The particles studied were emitted by mobile, stationary, and natural
sources.  Sources included automobiles, manufacturing operations, power
plants, smelters, mining and quarring.  Filter media and sample preparation
methodology as well  as morphological and chemical  data are presented.
                                    IV

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                                    CONTENTS

Preface	iii
Abstract	   iv
Illustrations 	   vi
Acknowledgments 	 viii
   1.  Introduction 	    1
   2.  Sample Preparation Procedure 	    3
            Vacuum-Evaporated Coatings  	    7
            Sample Transfer to Electron Microscope  Grid   	   10
   3.  Results and Discussion	   12
References	   41

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                                ILLUSTRATIONS
Number
  1      Mixed cellulose acetate and nitrate filter 	  14
  2      Aromatic polymer filter  	  14
  3      Acrylonitrite polyvinylchloride filter 	  14
  4      Triacetate filter  	  14
  5      Polytetrafluorethylene filter  	  16
  6      Polytetrafluorethylene filter  	  16
  7      Acrylic copolymer filter 	  16
  8      Polytetrafluorethylene filter  	  16
  9      Polycarbonate filter 	  16
 10      Glass filter	16
 11      Serpentinite	19
 12      Serpentinite spectrum  	  19
 13      Chrysotile asbestos fibers from mining operation 	  19
 14      Chrysotile spectrum  	  19
 15      Asbestos insulation debris from building demolition  	  19
 16      Asbestos insulation debris spectrum  	  19
 17      Crocidolite asbestos 	  21
 18      Crocidolite asbestos spectrum  	  21
 19      Bulk crocidolite	21
 20      Bulk crocidolite	21
 21      Tremolite, nonasbestos variety 	  21
 22      Tremolite spectrum 	  21
 23      Actinolite, nonasbestos variety  	  23
 24      Actinolite spectrum  	  23
 25      Fibrous grunerite, amosite asbestos  	  23
 26      Amosite asbestos spectrum  	  23
 27      Bulk amosite asbestos  	23
 28      Amosite asbestos lathes  	  23
 29      Anthophyllite, nonasbestos variety 	  25
 30      Anthophyllite spectrum 	  25
 31      Mineral wool	25
 32      Mineral wool spectrum	25
 33      Textile dust	25
 34      Textile manufacturing dust	25
 35      Grain elevator debris  	  28
 36      Graphite fibers	28
 37      Automobile brake drum debris 	  28
 38      Automobile brake lining spectrum 	  28
 39      Automobile exhaust system catalyst 	  28
 40      Automobile exhaust system catalyst spectrum  	  28
 41      Automobile exhaust emission leaded fuel  	  30

                                     vi

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Number                                                                   Page

 42     Automobile exhaust emission leaded fuel spectrum 	  30
 43     Automobile diesel exhaust emission 	  30
 44     Gas turbine exhaust emission 	  30
 45     Automobile exhaust tube debris 	  30
 46     Automobile exhaust tube debris spectrum  	  30
 47     Coal-fired power plant fly ash showing encapsulation 	  32
 48     Coal-fired power plant fly ash spectrum  	  32
 49     Coal-fired power plant fly ash showing various morphology  ...  32
 50     Coal-fired power plant fly ash spectrum  	  32
 51     Oil-fired power plant fly ash	32
 52     Oil-fired power plant fly ash spectrum 	  32
 53     Oil-fired power plant fly ash	34
 54     Oil-fired power plant fly ash spectrum 	  34
 55     Ambient air Hi-vol catch	34
 56     Diatomaceous earth 	  34
 57     Secondary lead smelter emission  	  34
 58     Secondary lead smelter emission spectrum 	  34
 59     Zinc  smelter particulates	36
 60     Zinc  smelter particulates spectrum 	  36
 61     Copper ore concentrate	36
 62     Copper ore spectrum	36
 63     Lead  smelter concentrate	36
 64     Lead  smelter concentrate spectrum  	  36
 65     Alumina particle 	  38
 66     Alumina particle spectrum  	  38
 67     Particulates from steel mill	38
 68     Particulates from steel mill  spectrum	38
 69     Crushed coal	38
 70     Crushed coal spectrum	38
 71     Lead  smelter baghouse particulates 	  40
 72     Lead  smelter baghouse particulates spectrum  	  40
 73     Phosphate rock feed	40
 74     Phosphate rock feed spectrum	40
 75     Mount Saint Helen's ejecta particulates  	  40
 76     Mount Saint Helen's ejecta particulates spectrum 	  40

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                              ACKNOWLEDGMENTS
     I would like to thank the following Northrop Services,  Inc.,  personnel
for their assistance in the photographic work and preparation of this manu-
script:  Bernard Bell, photographer;  Laura Smith, laboratory assistant;
Julia A. Davis, laboratory technician,  Carole Moussalli,  technical  writer/
editor; and John Wai rath, photographic  services.

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                                  SECTION 1

                                INTRODUCTION
     The methodology and instrumentation for controlling various source
emissions depends on the physical and chemical nature of these emissions.
There are as many instruments designed to measure particle size as there are
to determine the chemistry of particles.  But to ascertain the morphology and
chemistry of each particle there is only one suitable instrument, the electron
microscope.

     There are two types of electron microscopes -- the transmission and the
scanning.  Both instruments can be fitted with x-ray spectrometers for analy-
tical purposes.  The transmission electron microscope (TEM) can be used for
particulate sizes down to 0.05 ym with good analytical results using energy-
dispersive x-ray fluorescence (EDX); selected area electron diffraction (SAED)
makes possible the compound identification in much the same manner as x-ray
diffraction.  However, identification by morphology alone is limited, and
instrument geometry restricts the size of the sample to be examined.

     The scanning electron microscope (SEM) while not limited to sample size,
does not have the TEM's resolution.  The SEM, fitted with EDX is capable of
obtaining the chemical composition of the particles plus rendering excellent
morphological data from secondary electrons emitted from the sample.  Both
types of scopes are indispensible in the study of particulate material
because of the particular image-forming mechanism peculiar to each instrument.

     Studies of large.numbers of samples from many varied sources result in
data that is suitable for presentation as an atlas.  One which is in general
use is called the "Particle Atlas" (1) and covers almost every conceivable
material.  Other publications of more limited scope are the "Asbestos Fiber
Atlas" (2) and "Identification of Selected Silicate Minerals and their Asbesti-
form Varieties by Electron Optical and X-Ray Techniques" (3).

     This atlas contains data from sources such as the manufacture of insu-
lating materials, textile, smelting, steel, fertilizer, light weight compo-
site material, grain storage, electric power production, and automotive
vehicular emissions.  Such a concise collection of data can be of considerable
usefulness to those working in source apportionment analysis and various as-
pects of pollution control.

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                                   SECTION 2

                          SAMPLE PREPARATION PROCEDURE


     In preparing samples for SEM examination consideration must be given to
the type, condition, and data required from the sample.  Some data requires
that the sample be dispersed well enough to determine particle size and dis-
tribution.  Depending on the type of sample, e.g., solid bulk, loose powders,
or powders on filters, the method of dispersal may require one of the following
treatments:  ball milling, grinding with mortar and pestle, ultrasonic dispersal,
or ashing and redistribution.  Obtaining a representative sample is the most
significant problem associated with bulk samples.   This problem is always
addressed in light of the mineral form of the sample.  One of the most difficult
forms is a mineral like serpentinite where the several forms of the same mineral
have different physical characteristics.  A preparation procedure addressing
this problem has been published (3) and is excerpted below.

     Rock fragments should be from 1/2 to 1 in in  diameter.  About 1/2 pt
should be submitted for the analysis.   In the laboratory, the sample of
quarry rock is placed in a 1-pt roller-type ball mill jar (size 000) and
tumbled without balls for 6 to 10 h.  Tumbling and mutual grinding of the
rocks results in comminution of a layer of material at the rock surfaces and
also produces a thoroughly mixed dust sample.

     A small sample of the powder (^5 mg) from the ball mill jar is placed
in a 50-mm diameter agate mortar.  Approximately 0.1 ml of amyl acetate is
mixed with the powder in the mortar, and grinding  is carried out with a no 3
mullite pestle until the amyl acetate evaporates to dryness (approximately
20 min).  The mulling reduces the number and size  of asbestos fiber bundles.
The mulled sample is transferred to a stainless steel Wig-L-Bug container and
mixed for 2 min.  (The Wig-L-Bug is a high-speed reciprocating ball in cylinder
type grinder, but is used here to mix the powder thoroughly.)  A 3-to 10 pg
sample is weighed on an electronic balance and placed in a 2-ml glass vial.
A total of 100 to 300 pi of 0.001% aerosol OT (as  surfactant) is placed in the
vial and the suspension is ultrasonicated for 5 min.  A Virsonic cell dis-
rupter fitted with a microtip and run at 28% of full power was used in this
step, breaking up any remaining fibers or bundles  to fibrils.

     After ultrasonification the sample is transferred to a 30-ml glass
beaker and the volume adjusted to 25 ml by adding  0.001% OT.  The sample is
covered with parafilm and sonicated for 5 min using a low-powered ultrasonic
cleaner.

     A 47-mm diameter filtering apparatus is assembled with a 47-mm, 0.1 \*m
pore size, Nuclepore filter backed up by a 0.8-ym  pore size Millipore filter

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on the glass frit.  Suction is applied and the filters are recentered if
necessary.  The filter funnel is mounted, the vacuum is turned off, and
suction is allowed to cease.  The beaker is removed from the ultrasonic
cleaner and the aerosol OT suspension of sample is poured into the funnel.
The beaker is rinsed 3 times with the solution and the rinsings are added
to the suspension in the funnel.  Suction is applied and continued until
drainage is completed.  The vacuum is turned off and the filter is allowed
to dry in still air.

     After drying, the filter should be carbon-coated immediately (see
Section 2.3 in the "Provisional Methodology Manual," EPA Report 600/2-77-178)
(4), and analysis for asbestos carried out as described in this manual be-
ginning with Section 2.4.  The weight of powdered rock sample and the total
deposit area of the filter are taken into account in calculating the fiber
mass concentration from the TEM data.

     Powders, especially fine powder, can be dispersed by ultrasonification,
but some consideration must be given to the dispersing mediums, e.g. whether
it reacts with the sample.  Generally, amyl acetate is a satisfactory dis-
persing medium.

     Coarse powders either must be ground to smaller size, dispersed in a
suitable medium and filtered, or placed directly on a substrate with a small
amount of liquid and dispersed by using a wiping action with a needle.  Those
samples obtained on filters are examined directly, or depending on the filter
type, removed by ultrasonification or low temperature ashing.  Alternatively,
the filter is dissolved and the sample recovered by centrifugation.  The
particular approach and the required information, establishes the level of
care one must take in recovering the sample.  Mounting the sample for exami-
nation in the SEM also depends on the information required.   For a cursory
examination of the morphology, the bulk sample can be cemented to an aluminum
stub; moreover, elemental data can be obtained from a sample mounted this way
provided one realizes that some x-ray scattering from the surroundings can
and will be seen in the resulting spectrum.

     Fine powders can be mounted by placing a small amount of powder on an
aluminum stub, adding a drop or two of amyl acetate, then dispersing it with
a probe needle.  Where morphology, size distribution, and elemental analysis
is needed, the sample must be placed either on a carbon planchet or a beryllium
substrate to avoid contribution to the spectra by the substrate, since
neither carbon or beryllium x-rays are detected by the spectrometer.

     For good size distribution data the sample should be placed in about
5 ml  of amyl  acetate and ultrasonicated for about 5 min.   An aliquote then is
placed quickly on a substrate with a pi pet.  Another approach to good dis-
persion is to place a small quantity of the sample in distilled water con-
taining a surfactant such as "OT", ultrasonifying for about 5 min, and
filtering onto a 0.1 ytn Nuclepore filter.

     Ambient air samples collected on filters can be examined directly by
placing a small piece of the filter onto a carbon planchet or beryllium
substrate.  However, size distribution is difficult to obtain because of

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pooer dispersion, though morphology and chemical  composition may be obtained.
The chemical composition by x-ray fluorescence will be somewhat unreliable
because of the proximity of other particles.

     Where size and distribution data are required of the filter sample, a
redispersal is necessary.  This can be accomplished, if the filter is not
glass, by low temperature ashing, redispersing in water--OT by ultrasonifi-
cation and refiltering onto a 0.1 ym Nuclepore filter, or dissolving the
filter with a suitable solvent, centrifuging, rinsing about 3 times in solvent
with centrifuging after each rinse, redispersing  in water-OT, and refiltering
onto a 0.1 ym Nuclepore.

     If the sample is on glass or quartz fiber filters, little or no chemi-
cal data is obtainable because of the contribution to the spectrum by the
various elements in the fiber.  Removal of some of the particulate material
can be accomplished by placing a piece of the filter in a small beaker in
amyl acetate and ultrasonifying.  However, for best analytical results, glass
or quartz filters should be avoided.

     All samples proposed for analysis using the  SEM must be coated with an
agent that allows the electric charge built up by the electron beam to leak
off.  Depending on the information needed, these  coatings can be single or
multiple layers.  Where determining chemical composition is important a single
layer of carbon should be used.  Carbon does not  contribute to the x-ray
fluorescence spectrum because the x-ray detector  is insensitive to x-ray
energy of elements with atomic numbers lower than 9.

     Where morphology and size distribution are required, a layer of carbon is
placed on first, followed by a layer of gold or palladium.  In this case, the
carbon is used to remove the electric charge while the heavier elements
contribute significantly to the secondary electron emission, and thereby,
produce higher image contrast and resolution.  The coatings required in sample
preparation are obtained by vacuum evaporation.

                           VACUUM-EVAPORATED COATINGS

     A vacuum evaporator is usually an apparatus  having a set of vacuum
pumps, e.g., a mechanical and oil diffusion, and  a vacuum chamber such as a
glass bell jar.  The mechanical pump is used to rough pump the bell jar
to about 10 to 50 mm Hq; the diffusion pump is then activated and pumps the
chamber to 10~5 or 10-° Torr.  At that point, a current is sent through a set
of electrodes to heat the elements used to coat the sample to the melting
point or sublimation point, thereby vapor-depositing a thin coating of the
material onto the sample surface.  The sample is  now ready for examination
in the SEM.

     Sample preparation for TEM use follows a somewhat different procedure
than for SEM use because of sample size restrictions and because of substrate
type required.

     A sample must be reduced to a powder of 1 ym or less.  It can then
be placed on a carbon film supported by a 3mm diameter copper grid by first

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dispersing the powder in a suitable liquid medium using ultrasonification and
then placing a drop of the suspension onto the substrate with a micro pipet.

     If the sample is on a polycarbonate filter it can be coated with a car-
bon film in a vacuum evaporator, and a 3-mm diameter disc cut from the filter.
The filter material can then be dissolved away, with a suitable solvent,
leaving what is known as an extraction replica containing the particulate
material.  This procedure, described in detail below, is excerpted from
EPA publication 600/2-77-178 entitled "Electron Microscope Measurement of
Airborne Asbestos, a Provisional Methodology Manual" (4).

     The polycarbonate filter containing the sample deposit and suitable
blanks and standards should be coated with carbon as soon after sampling is
completed as possible.  The carbon coating forms an almost continuous film
over the filter and bonds the collected particles to the filter surface.
Losses are thus reduced during subsequent handling of the filter, and
during the transfer process to the electron microscope grid.  A carbon film
of about 40 nm thickness is most suitable.

     It is highly recommended that the handling and processing of the fil-
ters after their receipt by the analyzing laboratory be conducted in a clean
room or clean bench to reduce the possibility of contamination. Tweezers
should be used for handling the filters; static charge eliminators will
facilitate handling of the polycarbonate filters by neutralizing the surface
electrostatic charge.

     Because a thin, uniform, carbon film is desired, the coating of the
filter deposit with carbon should be carried out in a vacuum evaporator.
Carbon sputtering devices should be avoided because they produce a film of
uneven thickness.   Too thick a film can lead to problems during the subse-
quent steps in the procedure, particularly filter dissolution, fiber sizing,
and fiber identification.  Electron diffraction patterns tend to be faint
when operating the TEM at less than 100 KV.

     Typically, vacuum evaporators accept samples as large as 10 cm in
diameter.  Thus, if the personal sampler was used for sample collection,
the entire filter may be carbon-coated at one time.  It is convenient to
use the petri dish in which the polycarbonate filter is being stored.  After
inspecting the filter to be sure it is securely tacked to the bottom of
the petri dish, the cover is removed and placed in the bottom of the dish
containing the filter in the vacuum evaporator for coating.   If the airborne
asbestos was collected on the 20 cm x 25 cm polycarbonate filter using the
high-volume (Hi-vol) sampler, the entire filter cannot be coated at once.
Portions, about 2.5 cm x 2.5 cm, should be cut from the central region of the
filter using a pair of scissors or a scalpel.  The portions  should be tacked
with cellophane-tape to a clean glass microscope slide and placed in the
vacuum evaporator for coating.

     Any high-vacuum carbon evaporator may be used to carbon-coat the fil-
ters (CAUTION:  carbon sputtering devices should not be used).  Typically,
the electrodes are adjusted to a height of 8 to 10 cm from the level of

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the turntable upon which the filters are placed.   A spectrographically pure
carbon electrode sharpened to a 0.1  cm neck is used as the evaporating
electrode.  The sharpened electrode  is placed in  its spring-loaded holder
so that the neck rests against the flat surface of a second graphite elec-
trode.  The samples, in either a petri dish bottom or on a glass slide, are
attached to the turntable with double-sided cellophane tape.

     The manufacturer's instructions should be followed to obtain a vacuum
of about 1 x 10"  Torr in the bell jar of the evaporator.  With the turn-
table in motion, the carbon neck is  evaporated by increasing the electrode
current to about 15 A in 10 s, followed by 25-30  s at 20-25 A.  If the turn-
-table is not used during carbon evaporation, the particulate matter is not
coated from all sides and there is an undesirable shadowing effect.  The
evaporation should proceed in a series of short bursts until the neck of the
electrode is consumed.  Continuous prolonged evaporation is not recommended
since overheating and consequent polymerization of the polycarbonate filter
may easily occur and impede the subsequent step of dissolving the filter.
The evaporation process may be observed by viewing the arc through welders
goggles.  (CAUTION:  never look at the arc without appropriate eye protection.)
A rough calculation shows that a graphite neck of 5-mm  volume, when evapo-
rated over a spherical surface of 10 cm radius, will yield a carbon layer 40
nm thick.

     After carbon coating, the vacuum chamber is  slowly returned to atmos-
pheric pressure, the filters are removed and placed in clean, marked petri
dishes, and stored in a clean bench.

SAMPLE TRANSFER TO ELECTRON MICROSCOPE

     The transfer of the collected airborne asbestos from the coated poly-
carbonate filter to an electron microscope grid is accomplished in a clean
room or bench using a Jaffe-washer technique with some modification.

     Transfer is made in a clean glass petri dish about 10 cm diameter and
1.5 cm high.  A stack of 40 clean, 5 1/2-cm diameter paper filter circles is
placed in the dish; alternatively, a 3- x 3- x 0.6-cm piece of polyurethane
foam (like those used as packing in  Polaroid film boxes) may be used.
Spectroscopic grade chloroform is poured into the petri dish until it is level
with the top surface of the paper filter stack or the foam.  On top of the
stack or foam a piece of about 0.6 cm x 0.6 cm 60-mesh stainless steel screen
is placed.  Several transfers may be completed at one time, and a separate
piece of mesh is used for each grid.

     Sections of the carbon-coated polycarbonate  filter on which the sample
is deposited are obtained either by  using a punch to punch out 2.3-mm discs
or sharp scissors to cut out approximately 1 mm x 2 mm rectangles.  A
section is laid carbon side down on  a 200-mesh carbon-coated TEM grid.
(Alternatively, one may use formvar-coated grids  or uncoated TEM grids.
Here, the carbon coat on the polycarbonate filter forms the grid substrate.)
Minor overlap or underlap of the grid by the filter section can be tolerated
since only the central 2-mm portion  of the grid is scanned in the microscope.

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This pair, TEM grid and filter section, is picked up with tweezers and care-
fully placed on the moist stainless steel  mesh of the Jaffe washer.  The
1 mm x 2 mm section is wetted immediately by a 5 yl drop of chloroform.

     When all the samples are in place in the washer, more chloroform is
carefully added to increase the level back to where it just touches the top
of the paper filter stack.  Raising the chloroform level any higher may float
the TEM grid off the mesh or displace the polycarbonate filter section;
neither is desirable.  The cover is placed on the washer and weighted to
improve and seal and reduce the chloroform evaporation.

     More chloroform should be added periodically to maintain the level with-
in the washer.  After a minimum of 24 h, the polycarbonate filter should be
completely dissolved.  The TEM grid is removed by picking up the stainless
steel mesh with tweezers and placing it on a clean filter.  When all  traces
of chloroform have evaporated, the grid may be lifted from the mesh and
examined in the electron microscope or stored for future examination.

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                                SECTION 3

                          RESULTS AND DISCUSSION
     Generally, there are two kinds of filters used in ambient air samp-
ling -- depth-type and screen type.  Some membrane filters are sometimes
referred to as screen filters even though their structure is neither regu-
lar nor defined.  They differ from the fiber-depth filter in that they do
not contain a random mat of fibers pressed together.  The screen type fil-
ter is one with pores that penetrate from front to back in a relatively
straight line and have openings of uniform size.  Micrographs #1 through
#10 are some typical examples of these filters.

     Micrograph #1.   Millipore filter type RAWP.  Here the labyrinthian
structure is apparent in this membrane filter.

     Micrograph #2.   Aromatic polymer filter, made by the Gelman Company.
It is one of a family of unsupported membrane filters marketed under the
name of Metricel.  "Unsupported" means that the filters do not include a
supporting substrate.

     Micrograph #3.   Gelman filter marketed under the name of Acropor.
These are nylon-supported membrane filters that are used for analytical
purposes and can be of hydrophillic, hydrophobic, or ion exchange type.

     Micrograph #4.   Gelman filter called HT Tuffryn of high-temperature
membrane type.  This filter can be used at dry heat temperatures up to 138*C,

     Micrograph #5.   Fluoropore filter produced by the Millipore Corporation,
The membrane is bonded to a polyethylene net.  These filters can be used up
to a temperature of 130°C.

     Micrograph #6.   Fluoropore filter produced by Millipore Corporation,
showing a slightly different structure which results in a larger effective
pore size.

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    Mixed cellulose acetate and
    nitrate filter
 2. Aromatic polymer filter
                                 4500X
3.   Acrylonitrile polyvinylchloride filter
4.  Triacetate filter
                                                                                   900X
                                  4500 X
                                  4500X                       h-^-l          2000X
5.   Polytetraf luorethylene filter                 6.   Polytetraf luorethylene filter

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     Micrograph #7.  Gelman product called Vesapor.    It is made of acrylic
copolymer with a nonwoven nylon substrate that allows a capacity similar to
glass fiber filters.

     Micrograph #8.  Membrana, Inc., product called  Zefluor.  It is com-
posed of polytetrafluorethylene, and has no fibrous  or net support.

     Micrograph #9.  Etched-track polycarbonate membrane filter produced
by the Nuclepore Corporation.  This filter more nearly approaches the two-
dimensional screen type than do other membrane filters.  Its structure re-
sults in a more sieve-like filtration.

     Micrograph #10.  Typical depth filter fabricated from microfilaments
of glass.  This filter has wide application in air pollution sampling, but
limited application in obtaining samples to be examined by analytical elec-
tron microscopy.
                                    10

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                  I 22 pin

 7   Acrylic copolymer filter
                   50 pm

9-   Polycarbonate filter
                                                                   50 pm
450X                        H^^           200X
             8.   Polytetrafluorethylene filter
900X
                               50 fin
200 X
           10.   Glass filter
                                            11

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     Micrograph #11.  Crushed serpentinite, taken with a TEM and showing
many fibers of chrysotile.  Serpentinite is a rock composed mostly of ser-
pentine.  Serpentine is the name of a group of minerals -- chrysotile
asbestos is the best known — whose composition is Mg(Si205)(OH)4.  There
are three polymorphs of serpentine:  antigorite — a platy variety; lizar-
dite --a fine-grained and platy variety; and chrysotile — the fibrous
variety.  All serpentine rock contains a significant amount of chrysotile.
One of the principle uses of serpentinite is the construction of road beds.

     Photograph #12.  EDX spectrum showing the chemical composition of bulk
serpentinite.  The copper is not from the serpentine but from the grid of
wires used to hold the specimen in the microscope.  The copper spectrum is
used to calibrate the x-ray spectrometer.

     Micrograph #13.  Chrysotile asbestos fibers seen using a SEM and taken
from a large solid specimen from a mining operation.  Chrysotile occurs as
cross-fiber veins varying in size from microscopic to greater than 6 in.
Chrysotile is the principle asbestiform mineral used industrially.

     Photograph #14.  EDX spectrum showing the chemical composition of bulk
chrysotile asbestos.  Note the characteristic ratio of magnesium-to-silicon
along with some iron, which is usually due to magnetite trapped in the body
of the mineral vein.

     Micrograph #15.  Asbestos insulation debris from building demolition
using a SEM to show the morphology of the debris.  One of the principle uses
of chrysotile asbestos has been as building insulation and as acoustical
material.  The asbestos was usually bound or combined with other materials
as a filler or strengthening agent.  In the demolition of old buildings,
this material is liberated and falls as debris into the surroundings.

     Photograph #16.  EDX spectrum showing the chemical composition of
asbestos insulation debris.
                                    12

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                   2 pn
                                 5000X
 11.   Serpentinite
                   SOi
                                  200X
13.   Chrysolite asbestos fibers from
      mining operation
                   11 pm
                                  900X
   .   Asbestos insulation debris from
      building demolition
     Serpentinite spectrum
                                              Mil
    f.   Cl





14.   Chrysotile spectrum





               Ca


              K  '
       i        t


       ", S
                                                                         Fe
16.  Asbestos insulation debris spectrum
                                           13

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     Micrograph #17.  Ball-milled crocidolite asbestos taken with a TEM.
It is another common asbestos-forming mineral of the arriphiboles class.
These rock-forming minerals include crocidolite, the fibrous form of
riebeckite; the fibrous forms of tremolite, actinolite, grunerite "amosite"
(the fibrous form of grunerite, amosite, derives its name from the acronym
for Asbestos Mines of South Africa); and anthophyllite.  The chemical
formula for crocidolite is NagFe^Fe^ (SigC^HOH^.  The fibers are flexible,
and bluish gray (hence the name  blue asbestos"), and they have a higher
tensile strength than chrysotile asbestos.   One of the principle uses for
this asbestos is as primary insulation in ship building.

     Photograph #18.  EDX spectrum showing  the chemical composition of
crocidolite.  The copper peak is from the TEM grid.

     Micrographs #19 and #20.  Crystal growth habit of crocidolite.  The
cleavage habit and the cross-parting planes are readily seen.

     Micrograph #21.  Nonasbestos variety of tremolite taken with a TEM,
and exhibiting a bladed-to-acicular morphology.  Tremolite (Ca2Mg5Si8022(OH)2
is usually gray to white and consists of coarse, silky fibers.  It
occurs most commonly as long, slender needles that radiate in all directions
into the adjacent rock body.  Tremolite is  one of the most common amphiboles.

     Photograph  #22.  EDX spectrum showing the chemical composition of
tremolite.  Copper is not part of the mineral's spectrum.
                                    14

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                                                                               c«
                                 4200 X
17.   Crocidolite asbestos
                                             18.  Crocidolite spectrum
19.  Bulk crocidolite
                                             20.   Bulk crocidolite
                                                  Si
                      \
                                                                              4500X
                                                                                Cu
                 i  'r"' i         5000 X
21.  Tremolite, nonasbestos variety            22.  Tremolite spectrum
                                          15

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     Micrograph #23.   Nonasbestos variety of actinolite taken  with  TEM.   It
exhibits a prismatic  morphology after having been crushed  in a ball  mill.
Actinolite (Ca^C^Fe^SigCLplOOp)  is a high iron member  of tremolite-
actinolite series.   However the pure-iron member is not found.  Usually  the
maximum iron content  is on the order of 20%.  Actinolite is commonly green
or greenish gray, and the fibers are quite brittle.  Occurrence is  similar
to tremolite, but with more iron-rich sediments  in the  vicinity.

     Photograph #24.   EDX spectrum showing the chemical  composition  of
actinolite.  The presence of aluminum indicates  that actinolite is  compo-
sitionally near hornblends.  Copper is not part  of the  mineral's  spectrum.

     Micrograph #25.   Fibrous grunerite or amosite asbestos showing  acicular
to fibrous morphology and lathe-shaped individual crystal  pattern.   Amosite
asbestos is found in  iron-rich sediments that contain little or no  sodium.
The chemical formula  for grunerite (amosite) is  (Mg.FeKSigOpoCOHK).
Amosite used in the asbestos industry is mined in South Africa, but  is
a contaminant in iron mining operations in the Lake Superior area of the
United States.   It occurs as cross-fiber veins and is usually  brown.

     Photograph #26.   EDX spectrum of amosite.

     Micrographs #27  and #28.  Growth habit of bulk amosite.
                                    16

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                    2 pm
                                 5000X
23. Actinolite, nonasbestos variety            24  Actinolite spectrum
                                                   Si
                                9500 X
25. Fibrous grunerite, amosite asbestos       26.
      Amosite spectrum
                                4200X
                    1 pm
                                                                            9000 X
27.   Bulk amosite asbestos
28 •  Amosite asbestos lathes
                                          17

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     Micrograph #29.  Nonasbestos anthophyllite showing bladed to acicular
morphology.  Anthophyllite occurs in short, fibrous cross-fiber veins in
schists.  The fibers are slightly flexible, and the color varies from
green to brown depending on weather exposure.  Anthophyllite is fairly
common in mafic igneous rocks in the Blue Ridge mountain range.  It is the
only orthorhombic fibrous amphibole.

     Photograph #30.  EDX spectrum clearly resembling that of chrysotile
except for a difference in the magnesium-to-silicon ratio.  Copper is not
part of the mineral's spectrum.

     Micrograph #31.  Mineral wool, a popular insulating material in the
building industry.   The material is fabricated from various molten
silicates by high-pressure steam or air jet.  The fibers seldom reach the
small size found in most asbestos.

     Photograph #32.  EDX spectrum showing the chemical composition of this
sample of mineral wool.  Composition, however, can vary widely depending on
the particular silicate mineral or glass being used.

     Micrograph #33.  Textile dust generated during a cotton carding
operation.  The samples are from cyclone separations used to collect the
dust from the manufacturing environment.  This micrograph shows cotton
fibers taken from the cyclone separation inlet.

     Micrograph #34.  Textile manufacturing dust.  This respirable dust is
implicated in Brown Lung disease.
                                    18

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                   2pm
                               4500X
29.  Anthophyllite, nonasbestos variety
                  22H"
                                 450X
31.   Mineral wool
                                           30-   Anthophyllite spectrum
                                                            Ca
                                                   S4
                                                                       F«
                                           32.   Mineral wool spectrum
33.  Textile dust
                                 450X                      |50>"" |          200X
                                           34 .  Textile manufacturing dust
                                         19

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     Micrograph #35.  Grain elevator debris.  The long fiber like parts are
trichomes (hairlike growth from the epidermis of a plant) from wheat.  Much
of this material is respirable and would tend to cause the same physiological
problems as cotton dust.

     Micrograph #36.  Typical group of graphite fibers used in the manufacture
of carbon composite materials.  The greatly increased use of carbon-fiber
composites in industrial applications could constitute significant hazards
because of the susceptibility of electronic and electric power equipment to
damage by these highly conducting fibers.  Because of their large size po-
tential, health problems are of less concern.

       Micrograph #37.  Automobile brake drum dust taken with TEM.  Brake drum
dust consists mostly of iron and iron oxide particles along with mineral
dust that has crept in during normal automobile use.  However, a small
amount of the dust is chrysotile asbestos fibers and fibrils that are small
enough to become airborne and respirable.  The hazards of respiring asbestos
has been well publicized in recent years, and care is now being exercised
in automobile repair shops to minimize this danger.   The dust shown in this
micrograph was treated to remove most of the iron and iron oxide particles,
leaving behind the asbestos fibers and fibrils.

     Photograph #38.  EDX spectrum of the elements found in automobile
brake lining.

     Micrograph #39.  Ground automobile exhaust system catalyst material.
Anti-pollution devices on automobiles use a catalytic reactor to reduce
nitrous oxides, carbon monoxide, and carbon dioxide to a safe level.  These
reactors contain a material called a catalyst made up of an aluminum silicate
material coated with a thin film of platinum.

     Photograph #40.  EDX spectrum from exhaust system catalyst.  The vertical
scale of the spectrum has been expanded so that the platinum peak could be
seen.  This expansion causes the aluminum and silicon peeiks to go off-scale.
                                     20

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                                                                            450X
35.  Grain elevator debris
                                            36.  Graphite fibers
                                                          Ba
                                2000X

37 .  Automobile brake drum dust            38 .   Automobile brake lining spectrum

                                1100X
39 .   Automobile exhaust system catalyst
                                           40 •  Automobile exhaust system catalyst
                                                 spectrum

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     Micrograph #41.  Leaded fuel from automobile exhaust emission.  These
are agglomerates of necklace-like carbon ribbons on a carbon planchet
substrate.

     Photograph #42.  EDX spectrum from leaded-fuel automobile exhaust
emission.

     Micrograph #43.  Rounded carbon particles from diesel automobile exhaust
emission.  These rounded particles are characteristic of incomplete fuel
burning not only in diesel automobiles but in gas turbines and oil-fired
power plants.

     Micrograph #44.  Carbon particles from a-25 mega watt electric gas tur-
bine using #2 distillate oil fuel with no additives.  The sample was taken
from a stack 60 ft from the combustion chamber using a Battelle impact
sampler.

     Micrograph #45.  Automobile exhaust tube sweepings showing sands and
mineral debris from the road or pavements.

     Photograph #46.  EDX spectrum from auto exhaust debris.
                                    22

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                              9000X
41.  Automobile exhaust emission
     leaded fuel
               r-i±i-         4500X

43. Automobile diesel exhaust emission
                 200
                                 SOX
45. Automobile exhaust tube debris
                                            Br *


                                             •**•"
                                         42 .  Automobile exhaust emission leaded
                                              fuel spectrum
                                                            2 pm
                                                                        4500X
                                          44. Gas turbine exhaust emission
                                         46.  Automobile exhaust tube debris
                                              spectrum
                                       23

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     Micrograph #47.  Coal-fired power plant fly ash showing encapsulation.
Encapsulation occurs most frequently when limestone is injected into the
combustion chamber to reduce sulfur emission.  The shell  contains calcium
aluminum silicate, which is a lower melting material than the cenospheres
that are encapsulated.

     Photograph #48.  EDX spectrum showing elemental composition of the
outer shell of the sphere in micrograph #47.

     Micrograph #49.  Various morphologies found in coal-fired power plant
fly ash.  The nodular sphere is magnetite.  This sample shows a high degree
of combustion since most of the spheres are smooth glass.

     Photograph #50.  EDX spectrum taken of the bulk sample in micrograph #49
showing the high iron peak contributed by the large magnetite particle.

     Micrograph #51.  Open sponge-like structure of an oil-fired power
plant soot particle.  The structure results from incomplete combustion.
Carbon analysis of these particles showed them to be 30 to 70% carbon.  The
sample was taken from an operating plant using low oxygen and high vanadium
Venezuelan crude oil.

     Photograph #52.  EDX spectrum from the sponge-like soot particle in
micrograph #51.  The high background reflects the high carbon content of the
particle.
                                    24

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                                                       Ca
                                900X
47. Coal fired power plant fly ash showing
    encapsulation
48. Coal fired power plant fly ash spectrum
                                                                      F«
                                                 m
                                               Al
                                                         V
                                                              Tl
                              Fe
                              *»

                               V.
                   IS pm
                                 550X
49 .  Coal fired power plant fly ash showing    50 •  Coal fired power plant fly ash spectrum
     various morphology
                                2500 X

 51   Oil fired power plant fly ash              52 .   Oil fired power plant fly ash spectrum
                                         25

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     Micrograph #53.  Oil-fired power plant fly ash.  In operating plants
using sufficient oxygen for complete combustion of the fuel oil, the fly ash
emitted has few open sponge-like soot particles.   Instead, the ash becomes
small smooth glass spheres much like that found in coal-fired power plants.

     Photograph #54.  EDX spectrum reflecting complete combustion of oil-
fired power plant fly ash as well  as reduction of the ash to a glass princi-
pally of silicon and aluminum.

     Micrograph #55.  Hi-vol catches of ambient air taken from an urban
environment.  Catches are generally made on large glass  fiber filters because
the information usually needed is  the weight of material suspended in the air.
However, microscopic examinations  can be and are  made from these catches, and
they do reflect the contributions  of the surrounding environment.  Urban,
manufacturing districts, rural, proximity to highways., power plants, etc. all
contribute a somewhat distinguishing morphology to the; overall catch.

     Micrograph #56.  Particle of  diatomaceous earth, a  material frequently
encountered in ambient air samples.  It is the skeletal  remains of tiny marine
animals and is composed of silica.

     Micrograph #57.  Secondary lead smelter emissions taken from a re-
verberatory furnace.  The conditions in the furnace were such that terminal
growth of some material could occur, forming rhombic crystals; they are most
probably lead oxide crystals.  The gray spongy material  contains aluminum and
silicon.  The copper is from the TEM specimen grid.

     Photograph #58.  EDX spectrum of secondary lead smelter emissions.
                                    26

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                                                                       ?»
                                              *
                 I 2t"" I         4500X

53 .  Oil fired power plant fly ash              54 .  Oil fired power plant fly ash spectrum
                 , 22 pen |



55.   Ambient Hi-vol catch
450X
900X
           56 •  Diatomaceous earth
                  O.S^im
                                1900X
57.  Secondary lead smelter emissions        58 .  Secondary lead smelter emissions
                                                spectrum
                                        27

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     Micrograph #59.  Zinc ore concentrate.   Zinc ore contains some iron
pyrite and calcium silicate, but is mostly g-zinc sulfide.

     Photograph #60.  EDX spectrum showing the relative abundance of the
various elements in the zinc ore concentrate.

     Micrograph #61.  Copper ore concentrate.   Principally chalcocite (Cu^S),
it often contains chalcopyrite which contains  iron (CuFeSo).

     Photograph #62.  EDX spectrum of copper ore showing the  presence of the
pyritic form.

     Micrograph #63.  Lead ore concentrate.   The principle mineral  of lead is
Galena which is usually associated with zinc ores.  Good cleavage is a
quality of Galena that makes it easily recognized.  Some of this cleavage
is seen in particles in this micrograph.

     Photograph #64.  EDX spectrum from the  lead ore concentrate showing the
presence of zinc.
                                   28

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  «r
                                                                                   I«
                   6pm
                                1700X
59.  Zinc smelter participates                60-  Zinc smelter participates spectrum
                                                                      ft,
                                                 s*
                 t-lil^H           900X
 61 •  Copper ore concentrate                 62.  Copper ore spectrum
                                                                              Cu
                                               •I          p,
                                               :*V -         * **
                                               „«* ' _\A^n*«)««w«*«
                                4500X
63-  Lead smelter concentrate
64 .  Lead smelter concentrate spectrum
                                          29

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     Micrograph #65.  Alumina, or corundum in the natural state.  Alumina is
manufactured from bauxite and has replaced corundum as an abrasive.  The
characteristic rhombohedral faces and barrel-shaped hexagonal pyramids are
shown in this fused agglomerate.

     Photograph #66.  EDX spectrum of alumina reflecting the purity of the
material analyzed.


     Micrograph #67.  Particulates from steel mill showing submicron spheres
of iron oxide obtained from the electrostatic precipitator of a basic oxygen
furnace.

     Photograph #68.  EDX spectrum from steel mill particulates.  The silicon
and potassium are from slag material that generally is present in such
emissions.

     Micrograph #69.  Crushed bituminous coal.  This is an eastern coal and
contains a higher percentage of potassium than western coals.  The fly ash
from the burning of coal results from such impurities as shale, clay, slate,
quartz, limestone, and mineral residue of plant life.

     Photograph #70.  EDX spectrum of crushed coal.  The high background is
a result of the carbon content of the coal.
                                    30

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                                              AI
                                 900X
65 .   Alumina particle
66 •  Alumina particle spectrum
                                                     Si
                  0.6 urn
                               17.500X
 F7.  Particulates from steel mill              68 .   Particulates from steel mill spectrum
                   22 pm
                                   450X
 69.  Crushed coal
 70.  Crushed coal spectrum
                                          31

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     Micrograph #71.  Lead oxide spheres taken from a lead smelter baghouse.

     Photograph #72.  EDX spectrum of lead smelter baghouse spheres.

     Micrograph #73.  Phosphate rock feed used in the fertilizer industry
to produce super phosphates.

     Photograph #74.  EDX spectrum from the phosphate rock feed showing the
rock to be calcium phosphate.

     Micrograph #75.  Mt. St. Helen's ejecta particulates.  During the first
eruptions of Mt. St. Helen's, large quantities of ash were ejected into the
atmosphere.  Here the morphology of this ejecta is shown to be a frothy glass,
with sharp fracture edges.

     Photograph #76.  EDX spectrum of Mt. St. Helen's ejecta showing princi-
pally a calcium aluminum silicate, very rich in silica.
                                   32

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                                                Pb
                                             AI
                                                             Zn   y*
                                450X

71.  Lead smelter baghouse particulates
72 .  Lead smelter baghouse particulates
     spectrum
      3         Ca
                                                            "C*
                   1 1 p
                                 900X
73.   Phosphate rock feed
74.   Phosphate rock feed spectrum

     Si
                   I 1 um
                                 900X
75 .   Mt. St. Helen's ejecta particulates
 76 .  Mt. St. Helen's ejecta particulates
      spectrum
                                         33

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                                 REFERENCES
1.   McCrone, W. C. and J. G. Delly.  The  Particle  Atlas,  second edition.
     Ann Arbor Science Publishers  Inc., Ann  Arbor,  Michigan,  1973.

2.   Mueller, P. K., A. E. Alcocer, R. L.  Stanby, and  G.  R.  Smith.   Asbestos
     Fiber Atlas.  EPA-650/2-75-036, U.S.  Environmental  Protection  Agency,
     Research Triangle Park, North Carolina  27711,  1975.   50  pp.

3.   Miller, J. L.  Identification of Selected  Silicate  Minerals and Their
     Asbestiform Varieties by Electron Optical  and  X-Ray Techniques.  The
     Norelco Reporter, Vol. 25, Number 3.  Published by  Philips  Electronic
     Instruments Inc. North American Philips  Company,  Mahwah, New Jersey
     07430, December 1978.  pp. 1-11.

4.   Samudra, A. V., C. F. Harwood, and J. D. Stockhan.   Electron Microscope
     Measurement of Airborne Asbestos Concentration, A Provisional  Methodo-
     logy Manual.  EPA-600/2-77-178 revised,  U.S. Environmental  Protection
     Agency, Research Triangle Park, North Carolina 27711, June  1978.   49 pp.
                                        34
                                                     U. S GOVERNMENT PRINTING OFFICE 1983/659-095/1952

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