EPA-45O/3-77-027
QUANTIFICATION
OF DUST ENTRAINMENT
FROM PAVED ROADWAYS
by
Chatten Cowherd, Jr., Christine M. Maxwell, and Daniel W. Nelson
Midwest Research Institute
425 Volker Blvd.
Kansas City, Missouri 64110
Contract No. 68-02-1403
Task Order No. 25
EPA Project Officer: Charles Mann
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
July 1977
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This report is issued by the Environmental Protection Agency to report
technical data of interest to a limited number of readers. Copies are
available free of charge to Federal employees, current contractors and
grantees, and nonprofit organizations - in limited quantities - from the
Library Services Office (MD-35), Research Triangle Park, North Carolina
27711; or, for a fee, from the National Technical Information Service,
5285 Port Royal Road, Springfield, Virginia 22161.
This report was furnished to the Environmental Protection Agency by
the Midwest Research Institute, 425 Volker Blvd., Kansas City, Missouri
64110, in fulfillment of Contract No. 68-02-1403, Task Order No. 25.
The contents of this report are reproduced herein as received from the
Midwest Research Institute. The opinions, findings, and conclusions
expressed are those of the author and not necessarily those of the
Environmental Protection Agency. Mention of company or product names
is not to be considered as an endorsement by the Environmental Protection
Agency.
Publication No. EPA-450/3-77-027
11
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ACKNOWLEDGEMENTS
This report was prepared for the Environmental Protection Agency's
Office of Air Quality Planning and Standards under EPA Contract No.
68-02-1403 (Task 25). Mr.. Charles 0. Mann served as EPA Project Officer.
The program was conducted in MRI's Environmental and Materials Sciences
Division under the supervision ;of Dr. Larry J. Shannon, Director. Dr. Chatten
Cowherd, Jr., was the Principal Investigator for MRI. Dr* Cowherd was assisted
by Ms. Christine Maxwell, Mr. Daniel Nelson, Mr. Nicholas Stich, Mr. Thomas
Cuscino, and several members of MRI's Environmental Measurements Section.
Approved for:
MIDWEST RESEARCH INSTITUTE
L. J. Shannon, Director
Environmental and Materials
Sciences Division
July 19, 1977
iii
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CONTENTS
Introduction. • «•«••.•••••...«............. 1
Background* • •••«••••••«...«............ 3
Field Test Sites. ......................... 7
Field Measurements. • «•••••••....».......... 9
Sampling Equipment • ••••••...••.......... 9
Tests with Artificial Loading. ................ 12
Sample Handling and Analysis ................. 12
Calculation Procedures. ...................... 19
Isokinetic Corrections • •••.......«........ 19
Particle Size Distribution ............ 20
Test Results. • •••••••«••..»............. 23
37th Street Site 23
Stillwell Avenue Site. .................... 23
Fairfax Trafficway ...................... 34
Comparative Particle Size Distributions. .. 34
Computed Emission Factors. .................. 47
Corrections to Emission Factors ........ 51
References. ••••••••......»...»......... 57
Appendix A - Particle Size Distributions of Atmospheric Dust From
Unpaved Roads .......................... 59
Appendix B - Estimation of Suspended Particulate Emissions Generated
by Wind Erosion ...... . . . . . ........ ...... 72
v
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Figure
1
2
3
8
9
10
11
12
13
FIGURES
Title
Diagram of Street/Atmospheric Exchange of Particulate
Matter. .
MRI Exposure Profiler
Location of Sampling Instruments at 37th Street Site--
South Wind. •• ..<
Location of Sampling Instruments at 37th Street Site—
North Wind.
Location of Sampling Instruments at Stillwell Site--
North or South Wind •••••••*••••••••<
Location of Sampling Instruments at Fairfax Trafficway
Side View ; • •
Location of Sampling Instruments at Fairfax Trafficway
Overhead View .............••••••<
Traffic Flow (37th Street)
Airborne Particle Size Distributions (37th Street). .
Vertical Profiles of Particulate Concentration (37th
Street)
Airborne Particle Size Distributions (Stillwell-
Pulverized Topsoil) ................
Airborne Particle Size Distributions (Stillwe11-Gravel
Fines). ................. <
Vertical Profiles of Particulate Concentration
(Stillwell-Pulverized Topsoil). ... ..
2
11
13
14
15
16
17
25
27
29
32
33
36
VI
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FIGURES (concluded)
Figure Title
14 Vertical Profiles of Particulate Concentration
(Stillwell-Gravel Fines) 37
15 Downwind Distribution of Dust Deposition (Stillwell-
Pulverized Topsoil) ....<>... .......... 38
16 Downwind Distributions of Dust Deposition (Stillwell-
Gravel Fines) ..................... 39
17 Traffic Flow (Fairfax Trafficway) 42
18 Airborne Particle Size Distribution (Fairfax Trafficway). 44
19 Emission Factor Versus Average Silt Loading (Stillwell) . 52
A-l Location of Sampling Instruments at 207th Street Site-
South Wind. ...................... 61
A-2 Location of Sampling Instruments at 207th Street Site--
North Wind. ................ 62
A-3 Location of Sampling Instruments at 167th Street—South
Wind. 63
A-4 Location of Sampling Instruments at 167th Street—North
Wind. 64
A-5 Airborne Particle Size Distributions (207th Street-
Gravel) ........................ 67
A-6 Airborne Particle Size Distribution (167th Street-Dirt) . 71
B-l Map of PE Values for State Climatic Division. ...... 75
B-2 Mitigative Effect of Vegetative Cover .......... 76
vii
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TABLES
tle
1 Contaminant Loadings on Street Surfacets. ........ 4
2 Test Site Characteristics „ . . 8
3 Field Measurements—Paved Roads. ............. 10
4 Emissions Test Parameters (37th Street). ........ 24
5 Vehicle Mix (37th Street). ...... 26
6 Suspended Particulate Concentration and Exposure Mea-
surements (37th Street). ........ 28
7 Emissions Test Parameters (Stillwell),, ......... 30
8 Vehicle Mix (Stillwell) . . 31
9 Suspended Particulate Concentration arid Exposure Mea-
surements (Stillwell) » 35
10 Surface Loading Intensities and Silt Content
(Stillwell) ,, « 40
11 Emissions Test Parameters (Fairfax Trafficway) 41
I
12 Vehicle Mix (Fairfax Trafficway) ..<»......... 43
13 Suspended Particulate Concentration arid Exposure Mea-
surements (Fairfax Trafficway) ..<>......... 45
14 Comparative Particle Size Data .............. 45
15 Emission Factors (37th Street) .............. 48
viii
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Table
16
17
18
19
20
A-l
A-2
A-3
A-4
A-5
A-6
B-l
B-2
TABLES (Concluded)
Title
Comparison of Calculated Versus Probable Surface Load-
Emission Factors for Major Land Use Categories. ....
Suspended Particulate Concentrations at 207th Street. .
Suspended Particulate Concentrations at 167th Street. .
Soil Erodibility for Various Soil Textural Classes. . .
Values of Equivalent Vegetative Cover for Common Field
Page
48
49
53
54
56
65
fifi
66
67
70
70
74
77
IX
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ABSTRACT
This report presents the results of a field testing program to de-
velop emission factors for fugitive dust entrainment from paved urban
roads. Substantial evidence has been compiled which indicates that dust
emissions from city streets are a major cause of nonattainment of national
air quality standards for total suspended particulates (TSP). Therefore,
the quantification of this source is necessary to the development of ef-
fective attainment and maintenance strategies.
Field testing was conducted at representative sites in the Kansas
City area. At one location, controlled amounts of pulverized top soil and
gravel fines were applied to the road surface. The basic measurements con-
sisted of isokinetic exposure and concentration profiles of airborne dust,
particle size distributions, dust deposition profiles, surface dust loading,
and traffic characteristics. In addition, conventional high-volume samplers
were used to determine attenuation of TSP concentration with distance from
the source.
Emissions are found to vary directly with traffic volume and surface
loading of silt (fines). The dust emission factor for normally loaded ur-
ban streets ranges from 1 to 15 g/vehicle-km, depending on land use. Approx-
imately 90% of the emissions (by weight) is less than 30 |o,m in diameter and
50% less than 5 jj,m in diameter.
xi
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INTRODUCTION '
In a number of metropolitan areas of the country failure to attain
national primary air quality standards for total suspended particulates
(TSP) has spurred a detailed reexamination of the nature of the urban TSP
problem. While TSP control strategy development has routinely included an
analysis of the contributions of conventional point and area sources super-
imposed on a constant "background" concentration, adequate consideration
has not been given to the contributions of local open dust sources and ad-
vection from both confined and fugitive sources in adjacent regions.
Microscopic analysis of filters from urban air sampling stations where
measured TSP levels are routinely higher than expected has yielded conclu-
sive evidence that dust emissions from paved streets are a major cause of
the nonattainment of the primary standard.-i*2/ Although emissions from paved
streets are generated primarily by vehicular traffic, appreciable emissions
are added when the wind velocity exceeds the erosion threshold value of about
13 miles/hr, i.e., the observed limit of the ventilation flushing effect.—/
Figure 1 presents a diagram of particulate transfer processes occurring on
urban streets.
Following a review of the published results of previous investigations
on the subject, this report presents the results of a field testing program
conducted by Midwest Research Institute to develop quantitative emission
factors for dust entrainment from paved urban roads. Specific items dis-
cussed include field test sites, field measurements, calculation procedures,
test results and the relationship of resultant emission factors to traffic
volume and street surface dust loadings. Appendix A presents the results
of a separate series of field st.udies to determine particle size distribu-
tions of atmospheric dust generated by traffic on unpaved roads.
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PARTICULATE ENTRAINMENT "FROM URBAN" STREETS.
. Background
Local
Vehicles
Sanding,
Salting,"
Spills
Ground- Level
" Suspended" ~~
Parti culates"
Urban
Sources—
Conventional
;& Fugitive
DEPOSITION'
ENTRAINMENT
Runoff.
{ Sewers)
(¥y Wind"& Vehicle Motion)
Vehicular Deposits
(Carrybut from Unpaved
I Ar6as, Ti r& Wear>, Oj I, etc;
.Mechanical Removal
(Street Cleaners)
Figure 1. Diagram of Street Surface/Atmospheric
Exchange of Particulate Matter
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BACKGROUND
In a comprehensive study of runoff from street surfaces as a source
of water pollution,^/ the major constituent of street surface contaminants
was consistently found to be mineral-like matter similar to common sand and
silt. Typically, 78% of the material was located within 6 in. from the curb
and 88% within 12 in. from the curb. The silt content of the material (par-
ticles smaller than 75 micrometers (fim)'in diameter), fell in the 5 to 15%
range reported elsewhere.?i.5.*^/ for surface dust from paved streets and park-
ing lots and from gravel roads and parking lots. However, the silt size
fraction, which is readily suspendable in the atmosphere, was found to con-
tain a substantially larger than proportional percentage of the total heavy
metals and pesticides.
Table 1 summarizes the results of field measurements of surface load-
ings at sites in 12 cities.£/ In addition to land use characteristics, dust
loadings were found to depend on:
• Time elapsed since the last cleaning by mechanical means or by
substantial rainfall (exceeding 0.5 in. accumulation).
. Street surface characteristics: Asphalt streets had loadings that
were 80% higher than concrete-surfaced streets} and streets in
fair-to-poor condition had loadings about twice as high as streets
in good-to-excellent condition.
. Public works practices: Average loadings were reduced by regular
street cleaning (as reflected by lower values for commercial areas),
and loadings were increased during winter in areas where sand and
salt were applied.
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Table 1. CONTAMINANT LOADINGS ON STREET SURFACE
Mean initial
accumulation rate
Land use (lb/mile/dav)r
Residential ' 373
Low/old/single
Low/old /multi
Med/new/single
Med/old/ single
Med/old/multi
Industrial 447
Light
Medium
Heavy
Commercxal 226
Central business
district
Loadine intensity fib/curb mile)^ ,
Minimum
120
31
180
260
140
260
280
240
60
63
Maximum
i.,900
1,300
1,200
1^900
6,900
12,000
1,300
12,000
1,200
640
Numerical
mean
850
890
430
-
1,400
2,600
890
3,500
290
290
Weighted
mean,
1,200
2,800
290
Shopping center
Overall
348
a/ There are 2 curb miles per street mile.
1,500
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Although traffic speed and density were believed to be important factors,
effects of these parameters could not be separated from more dominant fac-
tors such as land use.
On the average, vehicular carry-out from unpaved areas (unpaved roads
and parking lots, construction sites, demolition sites) may be the largest
source of dust on paved streets. Maximum carry-out occurs in wet weather
when dust emissions from open sources are at a minimum. In a study conducted
in the Seattle area£*Z/ a car driven at 10 miles/ hr on a wet gravel road
collected approximately 80 lb of mud on tires and underbody, and carry-out
on tires from a wet unpaved parking lot averaged about 3/4 Ib/vehicle.
An American Public Works Association study—/ found that 10,2 lb of
dust under 1/8 in. in size comes onto each 100 ft of curbless paved road
in Chicago each day; this amount is cut by a factor of four if curbs are
added.
As evidence of the importance of the carry-out process, a positive
correlation has been observed between TSP concentration and the occurrence
of precipitation several days before sampling, i.e., after sufficient time
for the carry-out residue to dry out•—/
Other potentially significant sources of street dust are:
. Water and wind erosion from adjacent exposed areas -(sparsely
vegetated land, unpaved parking lots, etc.).
. Motor vehicle exhaust, lubricant leaks, tire and brake wear.
. Truck spills.
. Street repair.
. Winter sanding and salting.
• Atmospheric dustfall.
• Vegetation and litter.
In a recent field study of street surface contaminants in the Washington,
B.C. area,!0/ roadway deposition of traffic related materials was found to
be directly proportional to the traffic volume, at a rate of about 10-3
vehicle-mile. The rate appeared to be independent of the loading already
present.
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However, the accumulation of materials on the roadway has been found
to level off within a period of 3 to 10 days after a rain storm or street
cleaning.£ta!2/ This leveling-off occurs when traffic-related removal rates,
which increase with loading intensity, balance traffic-related deposition
rates. The equilibrium is established more rapidly with increasing traffic
speed.
Few data on directly measured dust emissions from paved streets are
available in the literature. An isolated study of dust emissions from a
paved road in the Seattle area yielded an emission factor of 0.83 Ib/vehicle-
mile at 20 mph.^iZ/ The test road was noticeably dusty, and had no curbs or
street cleaning program; it was located adjacent to gravel roads and unpaved
parking lots from which dirt was tracked. Dust emissions generated by vehic-
ular traffic with average daily traffic exceeding 200 vehicles was estimated
to equal the amount removed by sweeping every 2 weeks JJ
In less populated areas of the country, particularly those areas with
a dry, windy climate, the advective portion of urban TSP originates largely
from wind erosion of land with sparse vegetation, including tilled cropland.
Whenever the wind velocity exceeds the critical wind erosion threshold and
the exposed soil is sufficiently dry, wind forces cause soil movement by
three distinct mechanisms--surface creep, saltation (jumping), and suspension.
Although the total erosion of soil by wind has been studied in detail
and quantitatively related to soil, field, and wind properties, compara-
tively little is known about the proportion of suspended particulate gener-
ated by wind erosion. Up to now, TSP generation by wind erosion has been
estimated by assuming that a fixed percentage of the total erosion, as
quantified by the Wind Erosion Equation,!!/ is transported as suspended
particulate. This factor has ranged from 2.5 to KYE-lZjlS/
An analysis of quantitative emissions of suspended dust generated by
wind erosion is presented in Appendix B. A mathematical expression, similar
to the Wind Erosion Equation, is derived which incorporates experimental
measurements of vertical fluxes of fine particles from wind eroding fields.
The remainder of this report describes a program of field testing of
fugitive dust emissions from paved roadways and the derivation of emission
factors from test results.
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FIELD TEST SITES
Three sites in the Kansas City area were selected for measurement of
fugitive emissions from paved roadways. Two of the sites (37th Street and
Fairfax Trafficway) were on four-lane arterial streets in areas where at-
tainment of particulate standards has been a problem. The 37th Street test
roadway passes through an old residential neighborhood interspersed with
light-to-medium industrial activity. Medium industry surrounds the Fairfax
Trafficway test site. The test pavement along 37th Street test was concrete,
but Fairfax Trafficway was surfaced with asphalt; both streets were bordered
by unpaved parking areas. The Stillwell site, a local four-lane street in
an undeveloped area of a new industrial park, was chosen for testing with
artifically loaded surface materials. Table 2 summarizes the characteristics
of each test site.
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FIELD MEASUREMENTS
Field testing of dust emissions from paved roads was conducted at the
37th Street site in September and October 1975, at the Stillwell Avenue
site in October and November 1975, and at the Fairfax Trafficway site in
March 1976. To the extent possible, emission sampling was restricted to .
periods with moderate crosswinds, 3 or more days after significant rain-
fall (accumulation exceeding 0.5 in.).
Table 3 specifies the kinds and frequencies of field measurements
that were conducted during each run. "Composite" samples denote a set
of single samples taken from several locations in the area; "integrated"
samples are those taken at one location for the duration of the/run.
Sampling Equipment ,
The primary tool for quantification of emission rate was the MRI ex-
posure profiler (see Figure 2), which was developed-under EPA Contract No.
68-02-0619.5i!6/ The profiler (modified for this study) consists of a por-
table tower (4 m height) with four sampling heads. Each sampling head was
operated as a directional exposure sampler (with automatic separation of
settleable dust), i.e., in the "exposure mode" illustrated in Figure 2.
In addition to airborne dust passage (exposure), fugitive dust param-
eters that were measured included suspended dust concentration, particle
size distribution and deposition (dustfall). Conventional high-volume fil-
tration units were operated at breathing height (2 m above ground) upwind
and downwind of the test street. Deposition rates were measured with dust-
fall buckets at ground level and elevated locations downwind of the street.
A Sierra Instruments high-volume parallel-slot cascade impactor with
a 40 cfm flow controller was used to measure particle-size distribution
at 2 m above ground along side of the exposure profiler. The impactor unit
was equipped with a Sierra cyclone preseparator to remove coarse particles
which otherwise, would tend to bounce off of the glass fiber impaction sub-
strates, causing fine particle measurement bias. By means of a pivotal
bearing and wind vane, the cyclone sampling intake was directed into the
wind, resulting in isokinetic sampling for a wind speed of 10 mph.
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Mode
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Figure 2. MRI Exposure Profiler (with illustrations of sampling modes)
11
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Other types of parameters that were measured during each test included
prevailing meteorology and vehicular traffic. Wind speed and direction were
monitored with a recording wind instrument. Traffic counters were used to
record traffic volume during each test at the 37th Street and Fairfax sites,
while manual counts were made during the tests at the Stillwell site.
Figures 3 through 1 show the locations of sampling instruments at the
37th Street, Stillwell, and Fairfax sites. Distances from curbings are speci-
fied.
Tests with Artificial Loading
As indicated previously, the Stillwell site was selected for testing
of emissions from an artificially loaded test strip. This necessitated
closing the street to normal traffic for a period of 3 weeks.
On October 21, 1975, a salt/sand spreader was used to spread pulver-
ized topsoil over an 85 m test strip; on October 30, 1975, limestone gravel
fines were spread on a 105 m test strip. Four runs were conducted with each
material, the loading being reduced for each successive run. No rainfall
occurred during either series of runs. Prior to application of the gravel
fines, the road was cleaned with wet brushing equipment.
Immediately before and after each run at the Stillwell site, compos-
ite samples of in-place road dust were removed from 1-ft wide lateral
strips of road surface. First, loose material was manually swept from the
15-in. curbing areas and then from the rest of the strip and placed in poly-
ethylene bags. This step was followed by dry vacuuming of the strip. Samples
were returned to MRI for determination of mass and texture.
Traffic at Stillwell was provided by test vehicles which traveled back
and forth over the test strip at a speed of 30 mph. Each of the four traffic
lanes was utilized to the same extent during a run. Vehicle spacing was main-
tained to minimize vehicle interaction effects.
Sample Handling and Analysis
At the end of each run, the collected samples of dust emissions were
carefully transferred to protective containers within the MRI instrument
van, to prevent dust losses. High-volume filters (from the MRI exposure
profiler and from standard high-volume units) and toipaction substrates were
folded and placed in individual envelopes. Dust that collected on the in-
terior surfaces of each exposure probe was rinsed with distilled water into
separate glass jars. The contents of the deposition samplers were also
rinsed into glass jars. Dust was transferred from the cyclone precollector
in a similar manner.
12
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Dust samples from the field tests were returned to MRI and analyzed
gravimetrically in the laboratory. Glass-fiber filters and impaction sub-
strates were conditioned at constant temperature and relative humidity for
for 24 hr prior to weighing (the same conditioning procedure used before
taring). Water washes from the exposure profiler intakes, cyclone precol-
lector and dustfall buckets were filtered, after which the tared filters
were dried, conditioned at constant humidity, and reweighed.
Samples of road dust from Stillwell were dried and screened to deter-
mine the weight fraction passing a 200-mesh screen, which corresponds to a
74 p,m particle size. A conventional shaker was used for this purpose.
18
-------
GALGUIATION PROCEDURES
Dust entrainment from a paved roadway may be quantified by measuring
the total passage of airborne dust (after subtraction of background) at
some distance downwind of the roadway. Total dust passage (per unit length
of roadway) is determined by integration of vertically distributed measure-
ments of exposure obtained with the MRI exposure profiler (described earlier).
Exposure is defined as the horizontal flux of airborne dust (mass of sam-
pling intake area per time) integrated over the time of measurement.
Isokinetic Corrections
If it is necessary to sample at a nonisokinetic flow rate (for example,
to obtain sufficient sample under light wind conditions), the following mul-
tiplicative factors should be used to correct measured exposures and concen-
trations to corresponding isokinetic values:
Fine Particles Coarse Particles
(d < 5 urn) (d > 50 urn)
Exposure Multiplier U/u 1
Concentration Multiplier 1 u/U
where u = sampling intake velocity at a given elevation
U = wind velocity at same elevation as u
d = aerodynamic (equivalent sphere) particle diameter
For a particle-size distribution containing a mixture of fine, intermediate,
and coarse particles, the isokinetic correction factor is an average of the
above factors, weighted by the relative proportion of coarse and fine par-
ticles. For example, if the mass of fine particles in the distribution
equals twice the mass of the coarse particles, the weighted isokinetic cor-
rection for exposure would be '
1/3 [2(U/u) + 1]
19
-------
Particle Size Distribution
As stated above, a cyclone preseparator was used in conjunction with
a high-volume cascade impactor to measure airborne particle size distri-
bution. The purpose of the preseparator was to remove coarse particles
which otherwise would tend to bounce through the impactor to the back-up
filter, thereby causing fine-particle-measurement bias.
Although the cyclone precollector was designed by the manufacturer
to have a 50% cutoff diameter of 7»6 fim (particle density of 2.5 g/cnr*),
laboratory calibration of the cyclone, reported in May 1976, indicated the
effective cutoff diameter to be 3,5 p,m. Because this value overlapped the
cutoff diameter of the first impaction stage (6.4 jj,m), it was decided to
add the first stage catch to the cyclone catch, in calculating the parti-
cle size distribution.
As indicated by the simultaneous measurement of airborne particle-
size distribution, one impactor being used with a precollector and a second
without a precollector, the cyclone precollector is very effective in re-
ducing fine particle measurement bias. However, the following observations
indicate that additional correction for coarse particle bounce is needed:
1. There is a monotonic decrease in collected particulate weight on
each successive impaction state, followed by a several-fold increase in
weight collected by the back-up filter.
2. Because the assumed value (0.2 fim) for the effective cutoff di-
ameter of the glass fiber back-up filter fits the progression of cutoff
diameters for the impaction stages, the weight collected on the back-up
filter should follow the particulate weight progression on the impactor
stages.
The excess particulate on the back-up filter is postulated to consist
of coarse particles that penetrated the cyclonei (with small probability)
and bounced through the impactor.
To correct the measured particle size distribution for the effects
of residual particle bounce, the following procedure was used:
1. The calibrated cutoff diameter for the cyclone preseparator was
used to fix the upper end of the particle-size distribution.
2. At the lower end of the particle-size distribution, the particu-
late weight on the back-up filter was reduced to fit the particulate weight
distribution of the impactor stages, thereby extending the monotonic de-
crease in particulate weight observed on the impactor stages).
20
-------
One effect of these corrections was to reduce substantially the mass
median diameter determined for a given field test site.
21
-------
-------
TEST RESULTS
37th Street Site
Table 4 gives information on the time of each run, prevailing mete-
orological conditions, and vehicular traffic for three of six runs at the
37th Street site. Wind conditions during Runs 1, 2 and 4 were not accept-
able for test purposes. Figure 8 shows the variation of traffic flow for
each run, and Table 5 gives a typical vehicle mix observed over a period
of 75 min.
Because of the combination of relatively low airborne dust concen-
trations and low wind speeds, it was necessary to obtain profiler samples
at highly over-isokinetic sampling rates. Based on the adjusted aerodynamic
particle size distributions (solid lines) shown in Figure 9, measured ex-
posures and concentrations were corrected to corresponding isokinetic val-
ues, as described under Calculation Procedures.
Table 6 gives the results of exposure and concentration measurements
at the 37th Street site. Vertical profiles of isokinetic concentration at
3 to 5 m downwind from the edge of the roadway are shown in Figure 10. For
a sampling height of 2 m, there is good agreement between the profiler mea-
surements and standard hi-volume measurements of particulate concentration
obtained at approximately the same distance downwind.
Still well Avenue Site
Table 7 gives information on the time of each run, prevailing mete-
orological conditions, and controlled vehicular traffic at the Stillwell
site. The vehicle mix for each test is given in Table 8.
Figures 11 and 12 show the aerodynamic particle size distributions
for Stillwell. The adjusted distributions (solid lines) were used to cal-
culate isokinetic correction factors. Results of Run 7 are suspect because
of sampler overloading.
23
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24
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SITE: 37th Street
lOOOp
Run 3 (9/17/75)
Run 5 (9/23/75)
J—Run 6 (10/9/75)
11 12 13 14 15 16
HOUR OF THE DAY
17
18
19
20
Figure 8. Traffic Flow (37th Street)
25
-------
Table 5. VEHICLE MIX (37th Street)
Observation
Vehicle type
Gar
Bus
Pick-up truck
Small cargo truck
Tractor trailers
Other
Total
period:
No. of
axles
2
2
2
2
6
2
1445 to 1600s./
No. of
vehicle passes
472
21
123;
45
11
3
675
Percentage
of total
70.0
3.1
18.2
6.7
1.6
0.4
Note: Run: 6
Sampling Period: 1400 to 1830 .
No. of Vehicle Passes: 2440 (2-axle equivalent)
26
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30
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Table 8. VEHICLE MIX (Stillwell)
Number of vehicle passes
Run Passenger car Station wa%on Van/truck Totaj.
7 108 54 52 214
8 65 0 35 100
9 112 0 38 150
10 145 0 55 200
11 75 25 0 100
12 94 54 52 200
13 102 0 148 250
14 275 .191 134 600
31
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as 90 .80> 70 80 90 40 30 ML : l» 8 8 1 . 0&. Olfi
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WEIGHT % LESS THAN STATED SIZE
* MMD = Mass Median Diameter
** Sampler Overloaded on Run 7
Figure 11. Airborne Particle Sizie Distributions
(Stillwell-Pulverized Topsoil)
32
-------
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so
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WEIGHT % GREATER THAN STATED SIZE
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RUN 12
RUN 13
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WEIGHT % LESS THAN STATED SIZE
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Figure 12 - Airborne Particle Size Distributions
(Stillwell-Gravel Fines)
33
-------
Table 9 gives the results of exposure and concentration measurements
at the Stillwell site. Vertical profiles of isokinetic concentration mea-
sured at 5 m downwind of the roadway are shown in Figures 13 and 14.
Downwind distributions of unit dust deposition as a function of mean
drift time are shown in Figures 15 and 16. Mean drift time equals drift
distance divided by mean wind speed; for example, a drift time of 1 sec
represents a distance of 4«5 m for a wind speed of 10 mph (4.5 m/sec). As
indicated, the deposition intensity decays rapidly over the first few sec-
onds of drift time.
Table 10 sunmarizes measurements of loading intensity and silt con-
tent of pulverized topsoil and gravel fines which were artificially ap-
plied to the test strip. As expected, loadings decayed with traffic (and
wind erosion during periods between tests); surface material tended to be
depleted much more rapidly in the traveled areas than along the curbs.
Fairfax Trafficwav
Table 11 gives information on the time of each run, prevailing mete-
orological conditions, and vehicular traffic for the runs at the Fairfax
site. Figure 17 shows the variation of traffic flow for each run, and Table
12 gives a typical vehicle mix observed over a period of 10 min.
Based on the adjusted aerodynamic particle size distributions (solid
lines) shown in Figure 18, measured exposures and concentrations were cor-
rected to corresponding isokinetic values, as described under Calculation
Procedures.
Table 13 gives the results of exposure and concentration measurements
at the Fairfax site. There is fairly good agreement between the profiler
measurement of particulate concentration for particles less than 30 pm in
diameter, and the standard hi-vol measurement of particulate concentration,
obtained at about the same distance downwind. The complexity of this site
is evidenced by the high background concentrations, possibly due to inter-
ference from Sunshine (see Figure 7).
Comparative Particle Size Distributions
Table 14 compares particle-size distributions of atmospheric dust gen-
erated by vehicular traffic on paved and unpaved roads. (Testing results
for paved roads are presented in Appendix A.) With the exceptions of Run
Nos. 7 and 23, for which samplers were overloaded, particle-size data are
consistent from site to site. Emissions from dirt roads or paved roads with
topsoil loading exhibit the largest mass median diameter, while dust en-
trainment from normal city streets consists of the smallest particles. For
emissions from unpaved roads and heavily loaded paved roads, there is a
consistent ratio (approximately 0.3) between fine particles (less than 5
|im in diameter) and particles less than 30 jj,m in diameter, the effective
cutoff diameter of the standard hi-vol sampler.
34
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.2, 216)
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SITE: Stillwell Avenue
SURFACE LOADING: Pulverized Topsoil
v Run 7
o Run 8
a Run 9
A Run 10
Silt
Loading
( gm/rn^)
114
82.2
62.4
52.4
Wind
Speed
(mph)
4.0
10.5
12.0
13.0
2 3 4 5 6 789
MEAN DRIFT TIME (sec)
10 11 12 13
Figure 15. Downwind Distribution of Dust Deposition
(Stillwell-Pulverized Topsoil)
38
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41
-------
Site: Fairfax Trafficway
Test 15(3/16/76)
test 16 (3/24/76)
Figure 17.> Traffic Flow (fnitfa* traf£tew»3r)
42~
-------
Table 12. VEHICLE MIX (Fairfax Trafficway)
Observation
Vehicle type
Car
Pick-up truck
Small cargo truck
Tractor trailers
Total
Period: 1447 to
No. of
axles
2
2
2
6
1457
No. of
vehicle passes
229
71
!3
11
324
Percentage
of total
70.7
21.9
4.0
3.4
Note: Run: 15
Sampling Period: 1330 to 1730
No. of Vehicle Passes: 3791 (2-axle equivalent)
43
-------
o
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WEIGHT % GREATER THAN STATf-D SIZE
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DRUN 15 6.5 87 1-T "
ORUN 16 5.3 92 42
Solid Line Indicates Adjusted -
Particle Sia:e Distribution
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Raw Data . ' ,
O.I02O9I2 9 K> 20 50 40 30 W TO «0 *099 MM Mff
WEIGHT % LESS THAN STATED SIZE
* MMD = Mass Median Diameter
too
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Figure 18. Airborne Particle Size Distribution
(Fairfax Trafficway)
44
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Computed Emission Factors
The environmental impact of dust emission from unpaved roads varies
greatly with particle size. Large particles (d > 75 M-m) drift short dis-
tances from the road during the settling process, and create mainly a
nuisance problem. On the other hand, fine particles (d < 5 |j,m), which
represent a potential health hazard and which effectively reduce atmo-
spheric visibility, may remain suspended for long periods of time and be
dispersed over distances of regional scale. Thus, it is imperative that
emission factors be developed for specific particle-size ranges.
The upper particle-size limit for total suspended particulates is
about 30 p,m for a particle density of 2 to 2.5 g/cm3. This is the effec-
tive cutoff diameter for the capture of fugitive dust by a standard high-
volume filtration sampler.5^
The total emission factor for fugitive dust from a test road is equal
to the vertically integrated exposure divided by the number of vehicle
passes. This excludes particles which settle out between the edge of the
street and the exposure profiler. Emission factors for specified size
ranges are calculated by multiplying the total factor by the measured
(isokinetic) fraction of particles in the particular size range of interest,
Computed emission factors for the 37th Street, Stillwell, and Fairfax sites
are presented in Tables 15 through 17, respectively.
47
-------
Table 15. EMISSION FACTORS (37th Street)
Run
3
5
6
sJ
Run
7
8
9
10
11
12
13
14
(g/vehicle-km)
Total < 30 pm
4.2 3.7
5.6 5.4
3.4 3.3
Isokinetic.
Table 16.
(ke/vehicle-km)
Total < 30 urn
9.8 5.5
7.5 2.7
3.4 1.0
1.9 0.59
2.8 1.4
1.9 1.0
1.5 0.62
0.31 0.13
Measured emission factor—
db/vehicle-mile)
< 5 iffii Total < 30 urn
2.0 0.015 0.013
3.7 0.020 0.019
2.3 0.012 0.012
I
EMISSION FACTORS (Stillwell)
a/
Measured emission factor—
(Ib/vehicle-mile)
< 5 urn Total < 30 urn
1.8 34.7 19.4
0.90 26.7 9.6
0.31 12.2 3.7
0.17 6.9 2.1
0.45 10.0 4.8
0.27 6.8 3.7
0.21 5,3 2.2
0.039 1.1 0.46
0.007
0.013
0.008
< 5 urn
6.2
3.2
1.1
0.62
1.6
0.95
0.74
0.14
a/ Isokinetic.
48
-------
Table 17. EMISSION FACTORS (Fairfax Trafficway)
Run
15
16
a/
Measured emission factor—
(g/vehicle-km) (Ib/vehicle-mile)
Total < 30 urn < 5 urn Total < 30 urn < 5 urn
5.4 4.8 2.3 0.019. 0.017 0.008
2.8 2.6 1.2 0.010 0.0092 0.0042
a/ Isokinetic.
49
-------
-------
CORRECTIONS TO EMISSION FACTORS
As indicated in Figure 19, a nearly linear relationship between the
computed total emission factor and the measured silt loading for silt load-
ings (excluding curbs) below about 20 g/m2 (280 kg/km or 1,000 Ib/mile)
can be assumed for the Stillwell site. Based on this representation of the
data, the following functional relationship is proposed:
KLs
where e = Emission factor (kg/vehicle-km)
K= Proportionality constant (vehicle"1)
L = Surface loading excluding curbs (kg/km)
s = Silt content of the surface material (fraction)
The curb area extended 15 in. from the curb toward the center of the street.
Computed total K-values for Stillwell are given in Table 18. These
values, which are based on total silt loading excluding curbs (Ls), apply
to the loading range normally observed on urban streets (Ls < 280 kg/km or
1,000 Ib/mile). Table 18 also shows the K-values as a function of particle-
size for 37th Street and Fairfax Trafficway, based on the uniform applica-
tion of the average total K-value for Stillwell Avenue.
To check the consistency of the emissions data between sites, the
average total K-value determined for Stillwell was used to calculate the
silt loading excluding curbs for 37th Street and Fairfax, yielding the
results shown in Table 19. As indicated in Table 19, the calculated silt
loadings for 37th Street and Fairfax compare well with the silt loadings
found by Sartor and Boydl' based on the assumption that the 10% of the
total loading between curb areas has a 10% silt content.
As a further check on the validity of these factors, a comparison may
be made with the factors of 1 to 3 x 10~5 per axle estimated in a previously
cited study of contaminant loadings on paved urban streets.i2/ Assuming two
axles per vehicle and 10% silt in the surface material, these estimated fac-
tors are transformed to 20 to 60 x 10-5 vehicle"1.
51
-------
52
-------
Table 18. EMISSION PROPORTIONALITY FACTORS
K-Factor (x 1Q5)
Site Total < 30 urn < 5 um
Stillwell Avenue
Pulverized topsoil 125 sJ ' a/
Gravel fines 71 a/ a/
Average 98
37th Street
Run 3 98 85 47
Run 5 98 95 63
Run 6 98 97 69
Average 98 96 60
Fairfax Trafficway
Run 15 98 85 40
Run 16 98 90 41
Average 98 87 40
Average K-Factor^' 98 91 50
a/ Stillwell entrained dust size distributions are not representative
of paved urban roadways (see Table 14).
b/ Average of 37th Street average and Fairfax Trafficway average.
53
-------
Table 19. COMPARISON OF CALCULATED VERSUS
PROBABLE SURFACE LOADINGS
Sit
37ST Street
Run 3
Run 5
Run 6
Fairfax Trafficway
Run 15
Run 16
Silt loading excluding curbs (kg/km).
Calculated . Sartor
usine K = 98 x 10"5 and Bovd£/
4.3
5.7
3.5
5.5
2.9
residential-low/old/single
4.8
4.8
4.8
industrial-medium
5.0
2.5S/
^7Table 1 gives loading intensities measured by Sartor and Boyd for
various land uses.
b/ Assuming half the normal loading following thorough street cleaning
on the day prior.
54
-------
The time-average silt loading on a paved street is a complicated func-
tion of traffic-related and other parameters as discussed earlier. Perhaps
these are best related to land use, as given in Table 1. To the extent that
traffic-related deposition is the major source of surface material, emissions
become independent of traffic speed after the deposition-reentrainment equi-
librium is reached.
Therefore, in calculating an emission factor for dust emissions from
paved roadways, with the equation e = KLs, the following parameter values
should be used (based on the data in Table 18):
e = Calculated emission factor (kg/vehicle-km)
K = 98 x 10~5 vehicle'l for total emissions
91 x 10-5 vehicle"1 for particles < 30 (j,m in diameter
50 x 10~5 vehicle"1 for particles < 5 p,m
L = Surface loading excluding curbs (kg/km) estimated as a function
of land use (Table 1)
s = Silt content of the surface material (10%)
Table 20 shows calculated emission factors as a function of land use,
based on 10% (the noncurb portion) of the surface loadings given in Table 1
and a 10% silt content.
55
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REFERENCES
1. Harrison, P. R., "Considerations for Siting Air Quality Monitors
in Urban Areas," Paper No. 73-161, presented at the 65th Annual
Meeting of the Air Pollution Control Association, Miami Beach,
Florida, June 18 to 22, 1972.
2. Harrison, P. R., R. Draftz, and W. H. Murphy, "Identification and
Impact of Chicago's Ambient Suspended Dust," paper submitted to
Atmospheric Environment (1974).
3. Abel, M. P., "The Impact of Refloatation on Chicagofs Total Suspended
Particulate Levels," Master's Thesis, Purdue University, August
1974.
4. Sartor, J. D., and G. B. Boyd, "Water Pollution Aspects of Street
Surface Contaminants," U.S. Environmental Protection Agency,
Publication No. EPA-R2-72-081, November 1972.
5. Cowherd, C., Jr., K. Axetell, Jr., C. M. Guenther, and G. A. Jutze,
"Development of Emission Factors for Fugitive Dust Sources," EPA
Publication No. EPA-450/3-74-037, June 1974.
6. Roberts, J. W., A. T. Rossano, P. T. Bosserman, G. C. Hofer, and
H. A. Watters, "The Measurement, Cost and Control of Traffic Dust
and Gravel Roads in Seattle's Duwamish Valley," Paper No. AP-72-
5, presented at the Annual Meeting of the Pacific Northwest Inter-
national Section of the Air Pollution Control Association, Eugene,
Oregon, November 1972.
7. Roberts, J. W., H. A. Watters, C. A. Margold, and A. T. Rossano,
"Cost and Benefits of Road Dust Control in Seattle's Industrial
Valley," Paper No. 74-83, presented at the 67th Annual Meeting
of the Air Pollution Control Association, Denver, Colorado, June
9 to 13, 1974.
57
-------
8. American Public Works Association, "Water Pollution Aspects of Urban
Runoff," APWA, Chicago, pp. 171-175 (1969).
9.
10.
11.
12.
13.
Hanna, T. R. , and T. M. Gilmore, "Applicability of the Mass Concen-
tration Standards for Particulate Matter in Alaskan Areas," Alaska
Department of Environmental Conservation, Juneau, Alaska (1973).
Shaheen, D. G. , "Contribution of Urban Roadway Usage to Water Pol-
lution," U.S. Environmental Protection Agency, Publication No.
EPA-600/2-75-004, March 1975.
14.
15.
16.
17.
18
Woodruff, N. P., and F.H. Siddoway, "A Wind Erosion Equation,"
Science Society of America Proceedings, 2£(5):602-608, September
to October
19.
"Investigation of Fugitive Dust Emissions Impact in Designated Air
Quality Control Regions," Final Report, EPA Contract No. 68-02-
044 (Task 9), prepared by PEDCo-Environmental Specialists, Inc.,
May 1973. ;
Amick, R. S., K. Axetell, Jr., and D. M. Wells, "Fugitive Dust Emis- •
sion Inventory Techniques," Paper No. 74-58, presented at the
67th Annual Meeting of the Air Pollution Control Association,
Denver, Colorado, June 9 to 13, 1974.
"Reference Method for the Determination of Suspended Particulates
in the Atmosphere (High Volume M^hodL" Federal Register, .36:28,
Appendix B, 22388-22390, November 25, 1971.
"Standard Method for Collection and Analysis of Dustfall," ASTM
Method D 1739-62.
Cowherd, C., Jr., J. H. Southerland, and C. 0. Mann, "Development
of Emission Factors for Fugitive Dust Sources," Paper No. 74-81,
Air Pollution Control Association, Denver, Colorado, June 1974.
Pasquill, F., "The Estimation of the Dispersion of Windborne Mate-
rials," M^teorolj^Magi, 90:1063 (1961).
Gillette, G. A., "Production of Fine Dust by Wind Erosion of Soil:
Effect of Wind and Soil Texture," paper presented at the 1974
Symposium of Atmosphere-Surface Exchange of Particulate and Gaseous
Pollutants, at Battelle Pacific Northwest Laboratories, Richland,
Washington, September 1974.
Thornthwaites, C. W. , "Climate of North America According to a New
Classification," Geograph. Rev., ^1:633-655 (1931).
58
-------
APPENDIX A
PARTICLE, SIZE... PISTRIBUTIONS OF ATtfiSP.HErKt.CT...DUST FROM
UNPAVED ROADS
59
-------
This Appendix presents the results of a separate series of field stud-
ies to determine particle-size distributions of atmospheric dust generated
by vehicular traffic on unpaved roads. Field tests were conducted in an
agricultural area (Southern Johnson County, Kansas) characterized by rela- *
tively flat, open terrain. Testing at the gravel road site (207th Street)
St°
took place in September 1976, and testing at the dirt road site
(167th Street) in October 1976.
Figures A-l through A-4 show the layout of sampling equipment used
for each run. As in the case of paved roads, the primary device for mea- ;
surement of particle-size distribution was a Sierra Instruments high-volume,
i
cascade impactor equipped with a cyclone preseparator«
i j
Gravel Road Results j
Table A-l gives information on the time of each run, prevailing me-
teorological conditions and vehicular traffic for the three runs at the ; !
207th Street site. Table A-2 gives the vehicle mix for each run. Measured
particulate concentrations are listed in Table A-3.
Figure A-5 shows the aerodynamic particle size distributions measured •
downwind of the test gravel road. The solid lines are the distributions :
adjusted to eliminate bias caused by residual coarse particle bounce, fol-
lowing the procedure outlined in the body of this report.
60
-------
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Table A-2. VEHICLE MIX (207th Street)
Run
20
21
22
Table A-3.
No.
Passenger car
52
50
50
SUSPENDED PARTICULATE
of vehicle passes
Van/ truck
54
50
50 .
Total
106
100
100
CONCENTRATIONS AT 207th STREET
Particulate concentration Ctig/m^ at 2 m
Run
20
21
22
Background
1,484
76
18
Downwind, excluding
Cascade
impactor
with cyclone
3,250
i
i
2,486
3,127
above ground
background
Standard
Hi-Vol
4,958
3,258
3,790
66
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RARTICLE DIAMETER (MICRONS)
£ jo U — f» a o o * °«g
WEIGHT % GREATER THAN STATED SIZE
9 89J3 99 99 S* 98 ffiQ TO «0 SO 40 3O a© K> 9 £ 1 OS.CtgO-l...
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?UN 21 19 62 20
*UN 22 24 54 20
Dlid Line Indicates Adjustec
article Size Distribution
3
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Raw Data
so
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s
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K> 20 30 40 80 CO 70 90 98 »S W M
% LESS THAN STATED SIZE
* MMD = Mass Median Diameter
Figure A-5. Airborne Particle Size Distributions
(207th Street-Gravel)
67
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Dirt Road Results
Table A-4 gives information on the time of each run, prevailing me-
teorological conditions' and vehicular traffic for the three runs at the
167th Street site. Table A-5 gives the vehicle mix for each run. Measured
particulate concentrations are listed in Table A-6.
Figure A-6 shows the aerodynamic particle size distributions measured
downwind of the test dirt road. The solid lines are the distributions ad-
justed to eliminate bias caused by residual coarse particle bounce, fol-
* ~
lowing the procedure outlined in the body of this report.
68
-------
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69
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Table A-5. VEHICLE MIX (167th Street)
Run
23
24
25
Passenger car
50
25
25
Van/Truck
50
25
25
Total
100
50
50
Table A-6. SUSPENDED PARTICULATE CONCENTRATIONS AT 167th STREET
Particulate concentration (ug/rn3) at 2 m above ground
Downwind, excluding background
Run
23
24
25
Background
218£/
2188./
191
Cascade
impactor
with cyclone
12,658
13,062
5,383
Standard
With
Cascade impactor
7,565
6,784
' _
Hi-Vol
Without
Cascade impactor
10,120
11,058
6,348
&J Average over both Runs 23 and 24.
70
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Site.- 167th Street
Surface; Dirt
M
MMD* %< %< «
{jlm) 3Q fJ,m 5pi,m^
3 RUN 23** 11 78 27 M
5RUN24 84 30 7 -
^ RUN 25 66 35 10
Solid Line Indicates Adjusted m
Particle Size Distribution
Dotted Line
Raw Data
WEIGHT % LESS THAI
5 TO 8O .$
N STATED S!Z
Indicates -
B W «
E
1 99 «tt>«
Son
so
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IO
S
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as
at
c&t
k»
* MMD = Mass Median Diameter .
** Sampler Overloaded on Run 7
Figure A-6. Airborne Particle Size Distribution
(167th Street-Dirt)
71
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APPENDIX B
ESTIMATION OF SUSPENDED PARTIGUIATE EMISSIONS
GENERATED BY WIND EROSION
72
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Recently Gillettei^' measured vertical fluxes of suspended dust
smaller than 20 ^m in diameter generated by wind eroding fields in West
Texas. As expected, emissions increased sharply with increasing friction
velocity, above the threshold value of about 25 cm/sec. In addition, the
vertical flux was significantly higher for one of eight soils which had
a substantially higher content of silt (particles between 2 and 50 Hm
in diameter). This finding confirmed Gillette's previously developed theory
that the generation of suspended dust by wind erosion is a function of the
silt content of the eroding soil, in addition to the total rate of wind
erosion*
The Wind Erosion Equation—^' relates the total rate of wind erosion
to the following field and climatic parameters:
Soil erodibility - potential annual loss rate for a wide, un-
sheltered, isolated field with a bare, smooth surface.
. Ridge roughness - a function of ridge (clod) height and spacing.
. Climate factor - contains in addition to wind speed, Thornthwaites
19/
Precipitation-Evaporation Index— as a measure of average soil
moisture content.
. Vegetative cover - expressed as equivalent small grain stubble.
. Field length - distance along which erosion builds to its maxi-
mum (equilibrium) value.
73
-------
Soil erodibility for various soil texture classes^' is given in
Table B-l. Erodibility is related to the percentage of erodible dry
aggregates (particles smaller than 0.84 mm in diameter) in the surface
soil.
Table B-l. SOIL ERODIBILITY FOR VARIOUS SOIL TEXTURAL CLASSES
Predominant soil Erodibility, I :
text.ur.al class (torts/acre/vear)
Sand-^7 220 '
Loamy sand—' 134
Sandy loam^' 86 ;
Clay 86 !
Silty clay 86 !
Loam 56 j
Sandy clay loarn^' 56 •
Sandy clay^' 56
Silt loam 47
Clay loam 47 ;
Silty clay loam 38
Silt 38 i
.§/ Very fine, fine, or medium sand.
Figure B-l shows a map of P-E values for the United States.— These
values were calculated from annual precipitation and temperature data,
19/
using the relationship developed by Thornthwaite.—
74
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75
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The reduction in wind erosion due to vegetative cover— is given
in Figure B-2. The conversion of measured residue density to equivalent
flat small-grain stubble is described elsewhere.il/ Typical values of
equivalent vegetative cover for common field crops^/ are given in Table
B-2.
IT
O
I
P
o
en
UJ
o
O.tl 2 3 4 S C • K)
WIND EROSION WITHOUT
SO 40 60 80 K» 200 300
Figure B-2. Mitigative Effect of Vegetative Cover
Based on the above information, the following equation is proposed
for the calculation of emissions of suspended dust (particles smaller
than 30 \im in diameter) from wind erosion:
E = 0.0089
,
(PE/50)Z
where E = Emissions of suspended dust in tons/acre/year
e = Soil credibility in tons/acre/year
s = Silt content "of surface soil In percent
76
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Table B-2. VALUES OF EQUIVALENT VEGETATIVE COVER
FOR COMMON FIELD CROPS
Crop V Clb/acre)
Alfalfa 3,000
Barley 1,100
Beans 250
Corn 500
Cotton 250
Grain Hays 1,250
Oats 1,250
Peanuts 250
Potatoes 400
Rice 1,000
Rye 1,250
Safflower 1,500
Sorghum 900
Soybeans 250
Sugar beets 100
Vegetables 100
Wheat 1,350
77
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f = Fraction of time wind exceeds the threshold value for
wind erosion (12 mph)
r = Mitigative fractional reduction in wind erosion due to
vegetative cover, calculated from Figure B-2.
PE = Thornthwaite's Precipitation-Evaporation Index
The proportionality constant in the above equation was derived from
18/
the previously cited field measurements.—' The soil erosion parameters
for the test field were as follows: i
Silt content = 8.5%
Potential erodibility = 100 tons/acre/year
Ridge roughness = 2.5 cm ;
Precipitation-Evaporation Index = 40
Vegetative cover = 33 Ib/acre
Field length = 1.6 km
The above value for ridge roughness is an average value for a plowed field,
and the vegetative cover is negligible. In addition, a factor of 0.85 has
been inserted into the proportionality constant to reflect a typical field
length of 2/3 km.
78
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
1. REPORT NO.
EPA-450/3-77-027
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Quantification of Dust Entrainment from Paved
Roadways
5. REPORT DATE
July 1977
6. PERFORMING ORGANIZATION CODE
. AUTHOR(S)
Chatten Cowherd, Jr., Christine M. Maxwell,
Daniel W. Nelson
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Midwest Research Institute
425 Volker Boulevard
Kansas City, Missouri 64110
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-1403, Task Order 25-
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park3 North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final-July 1975 to June 1977
14. SPONSORING AGENCY CODE
200/04
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report presents the results of a field testing program to develop emission
factors for fugitive dust entrainment from paved urban roads. Substantial evidence
has been compiled which indicates that dust emissions from city streets are.a major
cause of nonattainment of national air quality standards for total suspended partic-
ulates (TSP). Therefore, the quantification of this source is necessary to the
development of effective attainment and maintenance strategies.
Field testing was conducted at representative sites in the Kansas City area.
At one location, controlled amounts of pulverized top soil and gravel fines were
applied to the road surface. The basic measurements consisted of isokinetic exposure
and concentration profiles of airborne dust, particle size distributions, dust de-
position profiles, surface dust loading, and traffic characteristics. In addition,
conventional high-volume samplers were used to determine attenuation of TSP concen-
tration with distance from the source.
Emissions are found to vary directly with traffic volume and surface loading
of silt (fines). The dust emission factor for normally loaded urban streets ranges
from 1 to 15 g/vehicle-km, depending on land use. Approximately 90% of the emissions
(by weight) is less than 30 ym in diameter and 50% less than 5 ytn in diameter.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Emission Factors
Paved Roads
Fugitive Dust
Particulates
Sampling Techniques
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (ThisReport)'
Unclassified
21. NO. OF PAGES
90
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
79
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