f/EPA
                                 United States
                                 Environmental Protection
                                 Agency
                                 Environmental Sciences Research     |
                                 Laboratory
                                 Research Triangle Park NC 27711
                                 Research and Development
                                 EPA-600/S2-81-070 July 1981
Project Summary
                                 Development  of Measurement
                                 Methodology  for  Evaluating
                                 Fugitive  Particulate Emissions

                                 Edward E. Uthe, John M. Livingston, Clyde L. Witham, and Norman B. Nielsen
                                   An experimental study was  con-
                                 ducted  to demonstrate a measure-
                                 ment  methodology for evaluating
                                 fugitive particulate emissions. The
                                 program focused on the application of
                                 the lidar (laser radar) technique under
                                 field conditions but in circumstances
                                 that  simplified  and controlled  the
                                 variables of the general problem.
                                   The lidar was used to make elevation
                                 scans perpendicular to an  aerosol
                                 plume generated by controlled release
                                 of particulate material into the atmos-
                                 phere. The lidar backscatter signa-
                                 tures were processed  in  terms of
                                 cross-plume integrated  backscatter,
                                 and these values were related to inde-
                                 pendently  measured  particulate
                                 emission rates. A very high correlation
                                 was obtained between time-averaged
                                 lidar observations and emission rates
                                 (correlation coefficients of  0.9 or
                                 better in most runs), with substantially
                                 less correlation for individual  lidar
                                 observations. Relatively high correla-
                                 tions were also obtained between
                                 smoke-reader   data on  downwind
                                 plume opacity and smoke emission
                                 rate as  well as lidar backscatter. For
                                 dense smoke,  attenuation of the lidar
                                 energy was shown to be of importance
                                 in interpreting data in terms of smoke
                                 concentration.
                                   Finally, the lidar was used at the site
                                 of an actual fugitive particulate source
                                 to demonstrate that appropriate data
                                 can be collected for measuring source
                                 emission rates.
                                   This Project Summary was develop-
                                 ed by EPA's Environmental Sciences
                                 Research Laboratory, Research  Tri-
                                 angle Park, NC, to announce key find-
                                 ings of the research project that is fully
                                 documented in a separate report of the
                                 same title (see Project Report ordering
                                 information at back).
                                 Introduction
                                   The total source strength of pollution
                                 emitted by industrial plants is the aggre-
                                 gate of all diffuse and minor specific
                                 emissions as well as major identifiable
                                 point sources.  Therefore, for many
                                 plants,  measurement  of  individual
                                 emissions from a multiplicity of sources
                                 is neither economical nor practical. The
                                 only feasible approach is to measure, as
                                 accurately as possible, the concentra-
                                 tion throughout a cross section of the
                                 downwind plume of the combined fugi-
                                 tive emissions, to integrate these, and,
                                 from a measurement of the integrated
                                 wind velocity through the plume of the
                                 cross-section, to calculate the pollutant
                                 mass flow.
                                   The problems of accomplishing  such
                                 measurements with existing technol-
                                 ogy are many. Specifically, with in-situ
                                 samples  it is  virtually  impossible to
                                 characterize adequately the concentra-
                                 tion of particles throughout  the  total
                                 cross section of the plume, to relate any
                                 measurements  made to  the plume's
                                 total envelope, or  to determine its
                                 extent. This is especially the case above

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the surface, because of the extended
and  variable nature of the  multiple
sources of fugitive emissions.
  Lidar observation fulfills, as no other
method  does,  the  requirement for
delineating the spatial  distribution of
elevated  particulate pollution plumes
and for readily distinguishing between
pollution background and pollution from
the  source  being  studied.  Although
there are limitations and difficulties in
using lidar backscatter  measurements
for  determining absolute  particulate
concentrations,  it  is possible  to
evaluate,  with  useful  accuracy,  the
near-instantaneous  distribution  of
particulate  material within  a  selected
cross section or envelope. It is thus
possible to obtain a series of such cross
sections in time and, from a measure-
ment of mean wind velocity and infor-
mation  on  the backscatter-to-mass-
concentration   ratio,  to  derive  an
estimate of source emission rate.
  In  the present study, three experf-
mental field programs were conducted
to demonstrate  a lidar methodology for
measuring  fugitive  particulate  emis-
sions. The first two field programs used
controlled release of various  types of
particulate  material   to  simulate
emissions from  fugitive sources.  A lidar
system  was  used  to  make elevation
scans perpendicular  to the transport
direction of the aerosol plume  about
500  m downwind from the source. The
lidar  backscatter signatures for each
elevation  scan  were  processed for
values of cross-plume integrated back-
scatter,  and these values were related
to independently measured particulate
emission rates.  In the second field test,
a trained smoke inspector made  down-
wind plume-opacity readings in addition
to the lidar observations. The third field
program was conducted to demonstrate
use of the lidar  technique at the site of
an actual fugitive emission source.
  Results of this study showed that
downwind   measurements  of  lidar
cross-plume integrated backscatter and
smoke-reader plume  opacity generally
increase  linearly   with   particulate
emission rate.  Relatively high correla-
tion  coefficients  between  these
measured quantities demonstrate that
lidar  and smoke reader provide  two
possible methods for evaluating fugitive
particulate emissions.


Procedure
  A  series  of  field experiments  was
designed to demonstrate the method-
ology by making lidar measurements of
an aerosol plume generated by continu-
ous release of particulate material of
known properties into the atmosphere
at known rates. The lidar system used
was SRI International's Mark IX, which
is van-mounted  complete with data-
processing and power-generating
capabilities. Figure 1  is an example of an
intensity-modulated  video display
depicting cross-plume aerosol structure
observed by scanning the lidar in eleva-
tion.  Computer-generated vertical
concentration profiles are plotted on the
cross section for locations indicated by
the  cursor  marks  drawn above  the
plume  return. Similarly, the  backscat-
tered data  can be spatially integrated to
determine   a   relative  cross-plume
density.
  The Mark IX lidar  was used to make
cross-plume  observations downwind
from controlled emission  sources with
known particulate properties, as shown
by the  example presented in Figure 1.
The lidar typically observed the  plume
from a distance of about 300  to 500 m,
about 200 to 500 m downwind from the
source.  On some experimental data
runs, the trained smoke inspector made
plume-opacity readings near  the emis-
sion  source; on  other  runs  he made
readings at downwind distances corre-
sponding to the lidar observations.
  Three methods of  aerosol generation
were used. An aerosol generator  was
constructed for  releasing fine silica
powder in the atmosphere at 1-m and
10-m heights.  The powder emission
rate  was controlled by a grooved-disk
feeder.
  A second method of aerosol genera-
tion  used a smoke generator operated
by the State of California Air Resources
Board for certifying smoke inspectors.
Both white smoke (produced by vapor-
ization and condensation of diesel fuel)
and black  smoke  (produced by incom-
plete combustion  of toluene) could be
emitted through a 10-m modified stack.
The white smoke  was found to evapor-
ate downwind from the source; there-
fore, only black smoke was used in the
experiments.  The emission  rate  was
controlled  by the fuel combustion rate,
and smoke quantity was evaluated with
an in-stack white-light  transmissom-
eter  calibrated   in  terms  of  mass
emission.
  The third method of smoke generation
consisted  of  igniting   zinc  chloride
smoke  pots and  candles.  The  mass
emission  rate was  determined  by
experimentally evaluating the emission
from a single pot and candle and multi-
plying by the number of pots or candles
(1, 2, 4,  or 8) ignited simultaneously.


Results and Discussion         (
  The experimental results of this study
show linear relationships of relatively
high correlation among the quantities of
downwind lidar cross-plume backscat-
ter, smoke-reader plume opacity, and
particulate emission rates. This is illus-
I
-j
2
o
-Q
I
                        Horizontal Distance From Lidar


Figure 1.     Example of computer-generated profiles of vertical plume density.
             Lidar is located at lower left corner. The height and distance scale is
             75 m/div. Vertical concentrations of the plume (relative to clear air, with ,
             a scale of JO dB/div) are plotted at the lower left and the horizontal
             position associated with each profile is plotted in the upper right.

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  rated  by the example presented  in
 Figure 2 for data collected during a
 smoke candle experiment. This example
 and other data presented  in the final
 report  demonstrate the feasibility  of
 using either lidar or smoke inspectors
 for estimating participate emission from
 fugitive sources.
   Relatively large scatter of data occur-
 red,  probably caused by  downwind
 aerosol density fluctuations introduced
 by turbulent transport. Linear correla-
 tion  coefficients squared  for all data
 points (R,2) collected during an experi-
 mental run typically ranged from 0.6 to
 0.9. By averaging data from three or four
 lidar scans at each smoke concentration
 (requiring a 5-to 10-minute period), the
 correlation coefficients  squared  (Rm2)
 typically were greater than 0.9. There-
 fore, the data clearly  show that time-
 averaged measurements of the down-
 wind plume are required.
   For high-density smoke generated by
 igniting smoke pots, significant attenu-
 ation of the laser energy was evident. A
 factor-of-two increase in the emission
 rate resulted in substantially less than a
 factor-of-two  increase in  the cross-
 plume   integrated lidar   backscatter.
_ Experiments with lower-density smoke
 provided   the  expected  one-to-one
 jorrespondence  between  lidar
 response and smoke emission rate.
   Plume opacities derived from the lidar
 data by analyzing the  clear-air returns
 on the far side  of the plume  returns
 were substantially less tha'n those esti-
 mated by the smoke reader. Correction
 applied  because of .the longer wave-
 length  lidar and submicrometer smoke
 particles  explained only a  part of the
 difference between lidar and  smoke-
 reader observations.
   A field  program was conducted  to
 demonstrate the use of the  lidar system
 at an actual fugitive emissions source.
 The lidar was used successfully to make
 downwind  vertical scans  across  the
 particulate  plume generated  by  the
 Permanente Cement  Plant located  in
 Cupertino,  California.  The  data were
 collected in the same way as the test
 smokes and therefore  could have been
 processed in the same way as the test
 data  to   estimate  plant   particulate
 emission rates.


 Conclusions
 The major conclusions of this study are:

   •  Cross-plume  integrated  back-
      scatter   evaluated   from  data
      collected  by  scanning  a  lidar
      system across a downwind smoke
      plume behaved  predictably  with
      variations in particulate emission
      rate.

  •  Correlations between downwind
      lidar  observations  and   source
      emission   rates   were  greatly
      increased by averaging data  from
      multiple lidar  observations made
      at  each  emission rate (three or
      four lidar scans requiring 5 to 10
      minutes).

  •  For low-density plumes, the  lidar
      responded  linearly in a  one-to-
      one ratio with  changes in particu-
      late emission rate. Linear correla-
      tion coefficients greater than 0.9
      were obtained in most cases.

  •  For  higher-density plumes,  the
      lidar  signal   increased   with
      increasing  particulate emission
      rate, but at less than a one-to-one
      ratio  because  of  extinction
      processes.

  •  Correlations between downwind
      lidar observations and particulate
      emission rates were only slightly
      improved when  corrections for
      wind speed variations (measured
      at the lidar site) were applied.
  •  Testing of lidar methodology was
     best  accomplished  using
     commercially   available  smoke
     candles. The quantity of smoke
     was controlled by the number of
     units ignited.

  •  Downwind plume opacities evalu-
     ated  by a  trained Method-9 ob-
     server were highly correlated with
     particulate emission rate and with
     the lidar cross-plume integrated
     backscatter.

  •  A mobile lidar system can  suc-
     cessfully make appropriate cross-
     plume  observations  at  actual
     fugitive particulate  emission
     sources.
Recommendations
  This study demonstrated a methodol-
ogy,  using  the  lidar  technique  for
measuring  fugitive particulate emis-
sions.  Several  additional  studies
suggested  to  further  develop  and
demonstrate the lidar technique for this
purpose are discussed below:

  •  In-Situ  Measurement  of Back-
     scatter-to-Mass-Concentration Ratio
     —The study  showed  that the
     cross-plume integrated backscat-
     ter evaluated by scanning a lidar
     system across an aerosol plume"
     responds predictably with particu-
     late  emission  rate.  However,
     measurement  of  the   absolute
     emission rate requires calibration
     of the lidar backscatter in terms of
     aerosol concentration. An in-situ
     measurement of the backscatter-
     to-mass-concentration ratio
     would provide the needed calibra-
     tion.  In addition, the  measure-
     ment of the variability of this ratio
     for different types  of  particles
     would provide an estimate of the
     accuracy of lidar measurement for
     the case of particle characteristics
     changing  in  the vertical.
     Therefore,  an  instrument that
     measures  absolute values   of
     backscatter-to-mass-concentration
     should be developed.

  •  Airborne Lidar Measurement  of
     Particulate Emissions from Large-
     Area  Sources—Many   fugitive
     emission sources,  including coal
     mining, oil refining, and cement
     plant  operations,    generate  a
     particulate plume  with a  large
     horizontal  and  vertical  extent.
     From these sources, the pollution
     plume is  more readily observed
     with an airborne lidar than with a
     surface-based   system.   A
     downward-pointing lidar could be
     flown along a path that encom-
     passes the plant site to observe
     upwind and downwind particulate
     flow. Observations made in com-
     plex terrains  would be greatly
     simplified as compared with those
     using  a  surface-based  lidar.  A
     two-wavelength  airborne  lidar
     system has recently been demon-
     strated.*  Backscatter data at two
     wavelengths   may  provide  the
     necessary information to estimate
     absolute  mass concentration  of
     observed  aerosols.  An airborne
     lidar system should be considered
     for measurement of particulate
     fugitive emissions.
*Uthe, E E , N B Nielsen, and W Jimison, "Air-
 borne Lidar Plume and Haze Analyzer (ALPHA-1),"
 Bull. Am Mel Soc, 61:1035-1043, 1980

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Choice of Lidar Wavelength or
Wavelengths— Successful use of
the  lidar  technique for  remote
measurement of particulate con-
centrations require knowledge of
the  relation  between  aerosol
optical and physical parameters.
Because  fugitive  emissions
frequently are comprised of emis-
sions from several  source types
and the percentage  of particulate
from  each type  may  vary,  the
particle  characteristics (size,
shape, and composition) may also
vary in both space and time. The
backscatter-to-concehtration ratio
is dependent on these  particle
characteristics and,   therefore,
a fugitive-emissions lidar system
m.ust be designed to be insensitive
to changes in particle characteris-
tics.   Experiments   should  be
conducted to  establish the proper
wavelengths  for minimizing  the
effect of particle characteristics
on the backscatter-to-concentra-
tion ratio.
Edward E. Uthe. John M. Livingston, Clyde L Witham, and Norman B. Nielsen
  are with SRI International. Menlo Park, CA 94025.
William D.  Conner is the EPA Project Officer (see below).
The complete report, entitled "Development of Measurement Methodology for
  Evaluating Fugitive Particulate Emissions." (Order No. PB 81-196 594; Cost:
  $8.00,  subject to change) will be available only from:
        National Technical Information Service
        5285 Port Royal Road
        Springfield. VA22161
        Telephone: 703-487-4650
The EPA  Project Officer can be contacted at:
        Environmental Sciences Research Laboratory
        U. S. Environmental Protection Agency
        Research Triangle Park. NC 27711
                                                                                I US GOVERNMENT PRINTING OFFICE 1861-757-012/7164

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