United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S2-86/072 Jan. 1987
&EPA Project Summary
Critical Review of
Open Source Paniculate
Emission Measurements:
Field Comparison
Bobby E. Pyle and Joseph D. McCain
This project consisted of a review of
sampling and analytical procedures used
by various testing firms to quantify panic-
ulate emissions from open sources; e.g.,
roads and storage piles. Seven firms, who
account for nearly 100 percent of all open
source data in the literature, prepared doc-
uments describing their current sampling
and analytical procedures. Five of these
firms then participated in a simultaneous
side-by-side field test on a simulated un-
paved road at a major steel plant. Each par-
ticipant independently measured the par-
ticulate emission concentrations produced
by roadway traffic. These measurements
produced not only the particle-size-
dependence of the emissions but also the
concentrations as functions of the dis-
tance above the road surface. The results
for each testing organization were ex-
pressed as emission factors for total par-
ticulate and the mass fractions of the par-
ticulate with sizes <30, <15, <10, and
<2.5 ^m diameter. Based on an analysis
of the results, it was found that all five pro-
filing systems were capable of producing
equivalent results in terms of total emis-
sions. This was not the case for emissions
by particle size. The only technique of
those tested that produced reliable emis-
sion factors by particle size was the iner-
tia! sizing method.
This Project Summary was developed
by EPA's Air and Energy Engineering Re-
search Laboratory, Research Triangle Park,
NC, to announce key findings of the re-
search project that is fully documented in
a separate report of the same title (see
Project Report ordering information at
back).
Introduction
During the past decade, research has
shown that particulate emissions from
open sources such as roads and material
storage piles contribute significantly to
ambient particulate matter concentrations
in many areas. The current EPA emission
trading policy allows excessive emissions
from one source to be offset by improved
control of another source within the same
plant. In implementing this bubble policy,
many steel plants have agreed to reduce
fugitive dust emissions in lieu of tighter
controls on process emissions. However,
the efforts of several groups to develop
equipment and methods for quantifying
emissions from nontraditional sources
such as roadways have resulted in esti-
mates of emission factors and emission
rates with substantial variability. Whereas
it is generally agreed that emission factor
estimates of process emssions from duct-
ed sources are good to ±50 percent of a
specified measured value, predictions of
open source fugitive dust emission factors
may vary from measured values by as
much as an order of magnitude. These
large uncertainties are due to differences
in both the measuring techniques used
and the site examined. Even for sites with
very similar physical characteristics,
measured emissions have been found to
differ by as much as an order of magni-
tude. In an effort to resolve these dif-
ferences, the U.S. Environmental Protec-
tion Agency contracted with Southern
Research Institute (SoRI) to conduct a
critical review of the various measurement
and predictive methods and to conduct a
side-by-side field test in which testing
-------
organizations, whose methods represent
the principal techniques which have com-
monly been applied, would simultaneously
sample emissions from an unpaved road.
Part I of this review was the compilation
of documents that describe in detail each
testing method and data reduction tech-
nique used in developing the existing data
base. As a result of Part I of this study,
documents were received from seven
organizations.
Each of these current procedures docu-
ments (CPDs) specifically addressed the
following points:
1. A description of the testing methods
and data reduction schemes em-
ployed in a specific field test con-
ducted by that organization for the
measurement of both the total partic-
ulate and the size distribution of that
particulate resulting from open
source fugitive emissions and other
ancillary measurements such as sur-
face loading of silt on the roadway.
2. A discussion of the historical devel-
opment of the current technique with
emphasis on changes that have been
made and the reasons for those
changes. If either the sampling or
data analysis technique has under-
gone change, the respective organi-
zation described how data obtained
before the modifications were insti-
tuted could be correlated with those
obtained afterward or detail why
such correlations cannot be made.
3. One or more detailed reports from re-
cent field tests which utilized the
sampling and data reduction tech-
niques described in (1), above.
Included in these reports were suffi-
cient raw data to enable the reader
to reproduce the final results quoted.
4. A discussion of how the testing and
data reduction procedures described
above would be modified for use at
various site locations and under vary-
ing site conditions.
As a result of the review of the CPDs,
four organizations were selected to partic-
ipate in the simultaneous field comparison
during Part II of this study. (A fifth firm par-
ticipated at its own expense.) The four
firms were selected because either:
1. They have made a significant con-
tribution to the existing fugitive emis-
sion data base using different meth-
odologies; or
2. They represent alternative method-
ologies not included in those selected
by (1), above.
Because much of the use of the emis-
sions trading policy with respect to road-
ways had been in the iron and steel indus-
try, the desired test site was an unpaved
road within an integrated iron and steel
facility. Negotiations were undertaken
with several companies for plant availabi-
lity for the tests; the United States Steel
Corporation responded favorably, offering
the use of their Gary Works. The nature
of the tests required a moderately long,
straight stretch of roadway that was
oriented more or less perpendicular to the
prevailing wind and clear of local perturb-
ing influences for a length of a few hun-
dred meters. It was also desirable that the
road have a moderately high traffic densi-
ty for emissions generation. Unfortunately,
all otherwise suitable roads on the Gary
Works property were either paved or had
been treated with chemical dust suppres-
sant. The most suitable road section in
terms of physical layout and traffic density
was a paved slag haul road parallel and ad-
jacent to Lake Michigan. Consequently,
this road was made to simulate an uncon-
trolled unpaved road by applying a 5-10 cm
thick layer of dirt to one 300 m section.
This portion of the road was well away
from other potentially confounding sour-
ces and wind flow obstructions. Five side-
by-side test positions, each about 15 m
wide, were laid out on both sides of the
road near the center of the simulated un-
paved road section. A total of 11 tests
were conducted over a 5-day period in
June 1984.
Conclusions and
Recommendations
Each profiling system used in these
tests exhibited both pros and cons in
terms of its versatility and ease of deploy-
ment. Consequently, no conclusions are
drawn as to the optimum mechanical de-
sign of the profiling towers or associated
hardware. However, several conclusions
may be drawn regarding the methods of
sampling.
The data from this test series clearly in-
dicate that there is significant exposure at
heights up to at least the 9 m level. Conse-
quently, the placement of a sampler at the
9 or 10 m (preferably 10 m) level is highly
recommended. Also, because the max-
imum exposure values usually occur at a
height of 1.5 to 2.0 m, any future profil-
ing system should include a sampler at this
level. The ideal profiling system would
have mass samplers at 1.5, 2.5, 4.0, 6.0,
7.5, and 10.0 m, with concurrent particle
sizing devices at 1.5, 4.5, and 7.0 m. This
configuration would better characterize
both the exposure and size distribution of
the particulates in the plume. It was also
demonstrated that sampling isokinetics
can be maintained for each sampling head
on the profiler tower. Therefore, it is rec
ommended that each sampler be equippec
with a servo system and individual velocit\
sensors to provide continuous adjustmem
of the flow rate based on wind speed a'
that elevation.
The five profiling systems tested were
found to be capable of producing equiva
lent results in terms of total emissions
This was not the case for particle size
distributions and emissions by particle
size. Long recognized problems in recon
stituting size distributions of airborne par
tides from resuspensions of collected buU
material lead to the conclusion that, foi
fugitive emission sampling of the type un
dertaken here, the sizing should take place
prior to collection (or concurrent with col-
lection as in cyclones and impactors). The
recommended procedure for measuring
the particle size distribution is the
cyclone/impactor technique (used by
Midwest Research Institute) with some
modifications. With regard to field opera
tions, first, a further reduction in the
sampling flow rate from 20 to 15 cfrr
would help minimize errors from particle
bounce. Alternatively, adhesive coatee
substrates could be used at the current 2C
cfm flow rate. Second, potential errors
resulting from the possible transfer o
material from the outlet tube of the
cyclone to the first stage of the impacto
can be avoided by counting only th<
material collected in the body of the
cyclone as its catch. The outlet tube catch
would then be combined with that of the
first impactor stage. At the current 20 cfrr
flow rate, this would result in a cyclone
D50 of 22 ^m being used rather than the
current 14 /jm. Lastly, while particle size
was measured at the lower elevations (1.E
and 4.5 m), an additional cyclone/impacto
unit at a height of about 7 m would provide
additional information regarding the
changes in size distribution as a functior
of height within the dust plume.
A better data analysis technique thar
the current cyclone/impactor procedure
would be that commonly used in reducinc
in-stack impactor data from industria
sources, where a spline fit is made to th<
cyclone/impactor data in the cumulative
percentage form of the distribution. Th<
fit is made in a manner that requires con
tinuity in the slope of the curve, and th(
solution is forced to be asymptotic to 10(
percent at a diameter equal to the max!
mum diameter present in the sample. Th<
fitted curve is then used to interpolate o
extrapolate as needed to obtain the mas:
fractions in the selected size intervals. Thii
technique avoids the requirement of as
suming a functional form for the distribu
-------
on and makes use of the complete data
et rather than just two of the data points.
With regard to the exposure integration
rocedure, the resultant emission factor
ppears to be relatively insensitive to the
schnique used so long as the exposure is
dequately characterized with regard to
eight. The most critical area is that where
le peak exposures occur (usually at 1.5
) 2.5 m). With samplers at 1.5, 2.5, and
.0 m, this should not be a major source
: error. However, under greatly different
te conditions (road type, silt content,
c), samplers at the lower elevations may
ied to be positioned at different heights.
The utility of an emission factor predic-
je equation is that of predicting the emis-
ons from a particular site in lieu of actual
leasurements. In Order that the equation
3 applicable over a wide range of site
cations and conditions, it should include
> many of the relevant parameters de-
gibing the site as possible. This reqires
lat the predictive equation be developed
om as large a data base as possible. The
luation currently described in "AP-42,
ompilation of Air Pollutant Emission Fac-
irs," was developed from a fairly broad
ita base using multiple linear regression
chniques. The data base has some un-
jrtainties particularly with particle size
stributions. These uncertainties cast
>me doubt on the accuracy of the values
:ed for the particle size multiplier, k, in
lis equation. However, without an exten-
ve evaluation of the existing unpaved
>ad emissions data base, there is no justi-
:ation for invalidating the relation. This
juation is probably the most reliable pre-
ctor of unpaved road emissions currently
/ailable. Because of past problems with
article sizing techniques, the values used
ir k are less reliable than the overall
Huation.
-------
B. Pyle and J. McCain are with Southern Research Institute, Birmingham, AL
35255-5305.
Robert C. McCrillis is the EPA Project Officer (see below).
The complete report, entitled "Critical Review of Open Source Paniculate Emissions
Measurements: Field Comparison," (Order No. PB 86-239 787/AS; Cost: $16.95,
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:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S2-86/072
00003Z9 PS
U S ENVI8 PROTECTION AGENCY
REGION 5 LIBRARY _
230 S DEARBORN STREET
CHICAGO IL 60604
------- |