United States
                  Environmental Protection
                  Agency
Atmospheric Research and
Exposure Laboratory
Research Triangle Park NC 27711
                                                                              o'Y-
                                                                               -
                  Research and Development
EPA/600/S3-89/020 Aug. 1989
4MEPA        Project  Summary
                  A Review of Current
                  Methods for Measuring
                  Particulate Matter  Including
                  Condensablesfrom Stationary
                  Sources

                  Joseph D. McCain and Ashley D. Williamson
                   The PM-io ambient air  participate
                  concentration standard has created a
                  need for  updating measurement
                  methods  for PM-io emissions
                  (nominally 10  nm aerodynamic dia-
                  meter and smaller) from stationary
                  sources.  Condensable  emissions
                  can be a significant portion of stack
                  emissions. Further, since these sub-
                  stances primarily condense to par-
                  ticles less than 10 pm in diameter,
                  they form a greater percentage of the
                  PM-to fraction than of  the total par-
                  ticulate matter emissions. Therefore,
                  the need  arises  for  developing a
                  source test method which includes
                  the condensable  component  of  e-
                  missions.  A review of possible tech-
                  niques was conducted to determine
                  current methodology  and to  make
                  recommendations for research. Re-
                  search is recommended on two ap-
                  proaches.  One is a dilution method
                  which simulates plume formation by
                  mixing stack gases with conditioned
                  ambient air; the other  is  an adapta-
                  tion of utilizing the Method 5  back-
                  half catch.
                   This  Project  Summary   was
                  developed by EPA's   Atmospheric
                  Research and Exposure Assessment
                  Laboratory,  Research Triangle  Park,
                  NC, to announce key findings of the
                  research  project that  is  fully
                  documented in a separate report  of
                  the same title (see Project Report
                  ordering information at back).
Introduction
  Stationary sources contribute to the
ambient particulate burden through three
distinct mechanisms. Two are normally
considered together as the formation of
"primary" particulate emissions  from
sources, and the third is the formation of
"secondary" aerosols, such as  sulfates
formed from  SC>2 and  organic smogs
formed from  photochemical processes.
Primary emissions are composed of (1)
materials that are  in particulate  form
(solid or liquid) in the gas stream before
and after discharge to the atmosphere
and (2) materials that are in the vapor
phase before discharge but that rapidly
condense to the  particulate form when
they are discharged into and  cooled by
mixing with ambient air.
  Because condensation takes place
preferentially  on  small  particles,
condensable matter  is concentrated pri-
marily in the PM-io fraction (particulate
matter less than 10 pm in diameter) of
source emissions. Since the basis of the
standard for ambient air particulate con-
centrations has been changed from total
particulate concentration to PM-|0  con-
centration, quantitative data on conden-
sable emissions rates will be  needed to
set up State  Implementation  Plans for
compliance with ambient air PM10  stan-
dards.  However, current methods for
particulate emissions measurement usu-
ally exclude the condensables fraction.
  Efforts are now being made to develop
a reference method to quantify  the
condensables fraction separately  from
measurements of  the particulate portion

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 of  primary  emissions  from stationary
 sources.  In  addition, a working definition
 for stationary sources  condensable e-
 missions must be established to develop
 a  reference  method.   A review of pos-
 sible  techniques was conducted  from
 which  recommendations are made  for
 the optimum approach  for development
 of routine field sampling procedures for
 measuring condensable emissions.

 Approaches for Measuring
 Condensable Matter
  To  explore the possible  options  for
 measuring  condensable  matter,  a
 working definition of condensable matter
 is  needed.   In particular, the quantity of
 condensable matter that is  present can
 vary because equilibrium  vapor  pres-
 sures and condensation and evaporation
 rates  vary significantly  with changes in
 temperature  and  other conditions  inc-
 luding concentrations.  Consequently, the
 partitioning  between the  vapor  and
 particulate phases of condensable matter
 will exhibit seasonal variations.  From a
 regulatory point of view,  however, the
 reference method(s) used  for measuring
 condensable matter should  provide  re-
 sults that are not  dependent on  local
 temperatures. Thus some standard tem-
 perature for sample collection is needed,
 such as  0,  5, 20,  or 25°C.  Whatever
 temperature is  designated  to  be
 standard, the operational definition of
 condensable emissions should  be  that
 material collected by the selected refer-
 ence method(s).  This type  of definition
 is now used for particulate matter collect-
 ed by Method 5.

 Adaptations of Method 5
  In considering  the back-half catch as
 described  in  Method 5  for  further
 development as a vehicle for collecting
 condensable matter,  certain  problem
 areas  must  be addressed.  A  protocol
 must  be  devised  for carrying  out the
 evaporative process to remove the  large
 volumes  of  water  from the impmger
 solutions  while reducing to acceptable
 levels any  losses of  the condensable
 materials  that are to  be  measured.
 Because  impingers used in conjunction
 with Method 5 result in vigorous contact
 between  sample gases and  impmger
solutions, the potential for reactions with
gases that  could  cause positive
measurement biases must be eliminated
or  minimized.   Also, impingers  may
enhance uptake of gases when sampling
for condensable materials with Method 5.
 Research should  be  performed  to
determine if these  effects  occur  at  a
significant  level and to eliminate or
minimize them  if necessary   Use  of a
coil-type condenser may reduce these
effects.  A filter  downstream  of the
impmger/condenser could be  used,  if
necessary, to ensure  that no aerosolized
portion of the condensate escapes  with
the spent sample gas.

Dilution Method
  In principle,  no practical method can
be  envisioned that  would precisely
duplicate the mixing process of flue gas
with ambient air for  all  conditions  that
actually occur   However, methods de-
signed  to  reproduce  the  important
features of the mixing process for some
typical conditions have been devised. All
involve  the  dilution  of  a sample  gas
stream that has been maintained at or
near stack  conditions with ambient air
that  has been  conditioned  to varying
extents. In some cases, the dilution air is
simply  filtered  to  remove  existing
particles. In others, its temperature and
humidity  are  controlled,  and  in  some
cases,  scrubbing  of  vapor  phase
components from the dilution air is done.
  Some particulate matter losses occur
during  transport  of stack  samples
through  sampling probes   Because the
sample  must be extracted  and  trans-
ported through  a  sampling  probe to  a
location outside the stack for a  dilution
sampling system,  the initial  size
distribution of the particles in the flue gas
cannot be duplicated  precisely.   How-
ever, in systems designed to reproduce
the important  features  of  mixing  the
plume with ambient air, these losses are
low enough  for sufficient quantities of
particles in the critical size range  (a few
hundredths  of  a micrometer to  a  few
micrometers) to be transported  to allow
the use of a  method involving dilution of
an extracted stack gas sample

Research Needs
  To  help  ensure  that  the  most
appropriate  and acceptable method  was
recommended, a number of people in
regulatory agencies  at  the  state  and
federal  level,  experts in  source
measurement  and  characterization,
experts in the field  of pollutant transport
and  fate, and  experts in the  field of
ambient  sampling  and  analysis were
contacted for advice  and ideas.    The
approach preferred by a majority  was
that  of air dilution  cooling rather than
condensation  in impingers or conden-
sers.  However, from  the standpoint of
ease of sampling it was generally agreed
that  the Method 5 back-half approach
would be preferable. Research would be
necessary  to  resolve  the  potential
difficulties posed by the large volumes of
condensed water and  possible reactions
of dissolved gases in aqueous solution to
form artifacts that could erroneously  be
counted  as  condensable  matter.
Research  also would  be necessary  to
develop  hardware  and  establish
operational parameters for  the  dilution
tram approach.   Hence,  it is  recom-
mended that both the air dilution and the
impmger catch  approaches be  further
developed as EPA  methods for measur-
ing  condensable  source emissions.  This
would not set any precedents in emission
sampling methodology because  the use
of air  dilution  techniques  is already
standard in  quantifying emissions from
mobile sources and from  wood-burning
stoves,  and  Method  5  back-half ap-
proaches are used in some states.

Working Definition of
Condensables
  Because  the split of any  condensable
component of emissions  from a  source
between  the  vapor  and  condensed
phases depends on temperature (and for
some compounds, the  amount of dilution
that  has taken  place  and  background
concentrations of the material), it  is rec-
ommended that  condensable emissions
be defined  as the material measured  by
the  sampling tram  selected by EPA for
collecting condensable matter.   Primary
emissions that include  condensable mat-
ter would be defined by the catch  of the
sampling train,  inclusive  of  the  nozzle
through the filter.

Suggested Dilution Sampling
Method
  The  use  of   low  mixing rates  to
preserve, insofar as possible, the detailed
size distribution characteristics that would
develop in the actual plume was not con-
sidered to be an important factor by most
of the experts who  provided advice.  By
foregoing  any  attempt  to  preserve  the
detailed particle  size distribution  of  the
final aerosol, rapid mixing of  the in-
coming  sample stream and  the dilution
air can be used.  This permits the design
of a  compact  diluter  and  keeps  the
weight  and size of the  device at  a
minimum.
  Conditioning  recommended for  the
dilution  air includes filtration to remove
background particulate matter and drying
to a dewpoint of 35°F (1 5°C), with  a final
temperature of  68°F (20°C).   The  low
dewpoint and moderately high  dilution
ratio should prevent problems of moisture'
condensation   for   most   flue

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 3ases that might be encountered.
  Because the sample flow is only a
small part of the total flow, measurement
of the sample flow at the exhaust end of
the  system,  as  in  Method 5, is  not
possible in  the  recommended setup.
Instead, a flow-metering  element may
be installed upstream of the  sample inlet
to the diluter. A venturi-type flow meter
is  recommended, but other  types might
be used

Sampling Protocol
The  suggested sampling  protocol  for a
measurement of total emissions including
condensable  matter parallels   that  of
Method  5 in most respects.  A nozzle of
appropriate size for the design sampling
rate of the system and the gas velocities
in  the   stack would be utilized.   A
standard Method 5-type  traverse pat-
tern would be used  in sampling,  and  the
sampling rate would  be set according to
the venturi  meter  readings and adjusted
as  needed  to maintain  isokmetic sam-
pling conditions.  This protocol does not
maintain  a  fixed dilution ratio, but  the
variability  induced  will  not pose a
problem.  A minimum acceptable dilution
factor should be specified (which would
in  turn set  a maximum  sampling rate);
the nozzle size to  be used for a traverse
would then  be selected to ensure that the
minimum dilution  specification  is  not
violated.
  The dilution train will  not  provide a
direct measure  of the  split  between
condensable matter  and  preexisting
particulate material  in the flue gas unless
use of a filter in the tram can be devel-
oped.  However,  by running a parallel
Method  17  sample, the  split could be
found by difference
Conclusions and Recom-
mendations
  The dilution method appears to be one
of two suitable  approaches for research
and  development for  measuring  total
primary emissions including condensable
matter from stationary sources.   This
approach forms condensed particulate
matter by the same physical mechanism
that occurs in actual  plumes.  Construc-
tion of a system with traversing capability
that  is suitable  for  field  use appears
feasible, consequently,  this approach is
recommended  for development.   The
other  suitable  method   is  the   im-
pmger/condenser  approach.  This  ap-
proach requires the  least  investment in
terms of methods development, operator
training, and capital equipment  costs
(because existing equipment may  be
adequate).   Research and coincidental
testing should be  designed to reveal the
relative  merits of the dilution  and  im-
pmger/condenser approaches

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Joseph D. McCain and Ashley  D.  Williamson are with the Southern Research
  Institute, Birmingham, AL 35255-5305.
Thomas E. Ward  is the EPA Project Officer (see below).
The  complete report,  entitled "A  Review of  Current Methods for Measuring
  Particulate Matter Including Condensables from Stationary Sources," (Order No.
  PB 89-169 9731 AS; Cost: $13.95, subject to change) will be available only from:
        National Technical Information Service
        5285 Port Royal Road
        Springfield, VA 22161
        Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
        Atmospheric Research and Exposure Assessment Laboratory
        U.S. Environmental Protection Agency
        Research Triangle Park, NC 27711
United States                   Center for Environmental Research
Environmental Protection         Information
Agency                         Cincinnati OH 45268
Official Business
Penalty for Private Use $300

EPA/600/S3-89/020

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