United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S4-84-070  Sept. 1984
Project  Summary
Philadelphia  Roadway  Study
R. Burton and J. Suggs
  The primary objective of this study
was to  collect  participate  mass
concentration data to define vertical
and horizontal  distances  from
roadways  required  for  inhalable
particulate (IP)  monitor  siting.
Secondary objectives were to compare
the particulate mass measurements to a
simple  model which considers  both
dilution and  settling  of  particulate
matter and to determine if the siting
criteria for inhalable particulate matter
(<15  fjm}  applies  to  lead  (Pb)
measurements   made  with   an  IP
sampler.
  This Project Summary was developed
by  EPA's Environmental Monitoring
Systems Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see  Project  Report ordering
information at back).

Introduction
  Existing  guidelines  for  siting  TSP
samplers near roadways are contained in
Federal Register Methods Vol. 44, No. 92,
May 10,  1979.  For ambient  24-hour
general  population  exposure  and
surveillance monitoring a sampler set too
close to any localized source such as a
heavily  traveled  roadway  would
overestimate  the  level  of TSP for the
general surrounding area.Theguidelines
restrict  sampling closer to the roadway
than 25 m at a two m height and five m at
a 15 m height. A straight line connecting
these two points defines the restricted
boundary.
  The development and implementation
of a size-specific  ambient  particulate
standard instead  of the current  Total
Suspended  Particulate  standard will
require additional information on howthe
various size fractions of particles disperse
in the area surrounding a major roadway.
The information would be usedto replace
the criteria for TSP sampling.
  Since the rate of deposition and vertical
diffusion depends upon particle size, the
criteria for TSP cannot be assumed to
apply to both the larger coarse (2.5 up to
10 or 15 pm)  particles and the smaller
fine (<2.5 yi/m) fraction. Smaller particles
are assumed to deposit from the atmos-
phere much slower than the larger ones,
with the very small submicron size parti-
cles behaving nearly as a gas. Assuming
no  reaction,  pollutant  gases  tend  to
decrease in concentration away from the
source  because ^i dilution. Suspended
particles are i educed in concentration by
both dilution and deposition.

Experimental Procedures
Approach
  The approach was to collect the fine
and coarse particulate mass fractions at
one point upwind, one point in the center,
and nine points directly downwind of  a
major roadway when the wind direction
was within a 90 degree sector centered
about the perpendicular to the  road.
Horizontal distances are referenced from
the edges  of the 60 m  wide roadway
unless otherwise noted. Likewise, verti-
cal distances are referenced from ground
level. These data could then be used to
construct concentration  isopleths. The
upwind  sampling  site  was  used for
estimating  the background concentra-
tions. A sampling site was located in the
roadway median on the perpendicular to
verify the  maximum   concentrations
extrapolated  from the  roadside
measurements.  Sierra  Model  244E
Dichotomous  S3mplers  with  15  fjm
inlets were  used for collecting the fine
and coarse  fractions on  37 mm teflon
filters. The dichotomous samplers were
operated in accordance with procedures
of the  Inhalable   Particulate Network
(IPN).  The  particle   separation

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characteristics of the sampler are based
on  aerodynamic  particle size  which
transforms the actual diameter to the
equivalent  diameter  of  a unit  density
sphere having the same settling velocity
as the particle in  question of  whatever
shape  and  density.  All  particle  sizes
referred to in the report are aerodynamic
diameter.  Sampling  was  initially
performed (Phase I) at ground level two m
height above the doorway to determine at
what point downwind the concentration
had been reduced by upwind diffusion
and particle deposition to approximately
the background level. Sampling  in the
vertical direction  was then  conducted
using two towers -- one  located at road-
side five m downwind,  and the  other
approximately half-way downwind from
roadside to  the  point  at which the
roadway particulate mass concentrations
had dropped to within 10% of background
level. The half-way point was found to be
approximately 25 m downwind.
  Meteorological  measurements  for
wind speed, wind direction, temperature
and humidity were made from a 15 m
height at the monitoring site located 5 m
downwind of the roadway. A Climatron-
ics electronic weather station was used
to acquire  the  data on strip   chart
recordings.
  Based on historical meteorological data
for  the  area, particle  sampling was
initiated in March, 1982, to obtain the
downwind  particle concentration
gradient under wind direction conditions
that  were   expected  to be  primarily
perpendicular within ±45° of the  road-
way. In order to minimize variations in
wind speed and direction during particle
sampling,  sampling  periods of  "accept-
able"  meteorology were  limited to a  14
hour (7:00 AM - 9:00 PM) daytime sam-
pling period. With this schedule the early
morning inversions, wind instability and
the night  time low traffic count  were
eliminated.
  Based on  data from an earlier  study,
sampling was only conducted when wind
speeds were above two  mph and wind
directions within ±45° of the  freeway
perpendicular. Wind speeds below two
mph do not provide adequate transport to
define  a  profile.  Wind  directions
perpendicular within   ±45°  were
expected to provide ratios of downwind to
upwind concentrations exceeding at least
a factor of two.
  A Climatronics Wind Controller (Model
WMIII  - PN100864)  activated  by  wind
speed  and  direction sensors  limited
sampling to periods  when parameters
were  within  preset specifications. The
                                  2
statistical study design recommended at
least  10  valid sample runs  for  the
horizontal  configuration and  10 for the
vertical configuration. A sample run was
required to last for at least four hours in
order to have adequate mass collection
on each dichotomous sample filter.
  The number of vehicles operating on
the roadway during  the study was very
important.  Any  large  fluctuations  in
traffic count would affect the particle con-
centration levels (and  hence  the iso-
pleths) around the study site. Mechanical
car counters were used to obtain real
time hourly traffic  counts. Daily traffic
flows ranged  from  2119 to 3906 vehi-
cles/hour   during   sampling  periods
(average = 3177 + 460). The 7:00 AM -
9:00  PM  sampling   period  had   a
reasonably constant traffic density during
this time period.

Site Location and Description
  The study was conducted in Northeast
Philadelphia   at  Roosevelt  Boulevard
between  South  Hampton  and
Woodhaven Roads.  Roosevelt Boulevard
serves as  one  of the two major north-
south  traffic   arterials  for  the  city.
Preliminary meteorological  monitoring
and review of historical data indicated that
winds could be expected to flow across
the roadway into  the sampling cross-
section at least 80% of the days allotted
for the study.  The sampling  cross-sec-
tions were located on the grounds of the
Pennsylvania State Hospital where the
upwind  and downwind sites were on
open grass covered fields extending more
than 1200 meters from the roadway in
both the upwind and downwind direc-
tions. The sampling  site  reach  was
without interfering buildings and service
roads for approximately 3500 m along the
roadway. The  location was within two
miles of an EPA Inhalable Particulate (IP)
Network site which averaged 33 /vg/m3
for IP  mass during the period March,
1980 through  May, 1981.


Sampling Scheme
  Particulate  sampling  points on  the
roadway perpendicular were located 220
m upwind, the  roadway median, five, 25,
75, 125, and   175 m downwind during
Phase I sampling. After 12 sample runs
were  completed  for  Phase   I,   the
dichotomous samplers were relocated for
vertical, Phase II sampling. Towers were
used  for  elevating  the  dichotomous
samplers to seven and 15 m  heights.
Samplers were located at 220 m upwind
(two m elevation), the roadway median
 (two m elevation), five m downwind (two,
 seven, 15 m elevations), and 25 m (two,
 seven, 15m elevations).  Sampling was
 begun simultaneously  at each of the
 seven points  located on  the  roadway
 perpendicular  if  the wind  speed  and
 direction were within acceptable limits. A
 collocated sampler at the 25 m downwind,
 two m height sampling site was operated
 throughout the study to obtain precision
 data.  Sampler flow checks were made
 daily, and a performance audit completed
 to verify that  the calibrations had not
 changed during the study.


 Sample Analysis
  The dichotomous coarse  and  fine
 fraction  samples  were  analyzed
 gravimetrically for mass  concentration.
 Lead  and bromine concentrations were
 determined by energy dispersive X-Ray
 Fluorescence.  The analysis  procedures
 used  for  the IP  Network, Standard
 Operating Procedures for the X-Ray Flu-
 orescence Analysis of Multielements on
 Dichotomous Sample Filters,EMSL-RTP-
 SOP-EMD-010, November, 1981,  were
 followed.


 Results and Discussion
  Twenty-four sample runs were com-
 pleted between March 5, 1982 and May
 7, 1982 with an average sample time of
 10.3  hours.  Eight  horizontal  and ten
 vertical sets of samples (complete at all
 sampling points) were used for defining
 the horizontal and vertical  particulate
 mass  concentration  gradients.  In
 addition,  horizontal  profiles  were
 obtained  on  two  days  immediately
 following  "salting"  of  the  roadway to
 prevent   icing.  These  data  were  not
 included  in   the  general  statistical
 analysis but are described separately.


Horizontal Profile
  Average  downwind  concentrations
(/jQ/m3) of fine, coarse, and total (coarse
+ fine) particles for mass and lead mass
were examined as a function of distance
(m) from the  highway.  Concentrations
measured at ground level (two m height)
were  averaged  over  eight  days  of
sampling at each  of six downwind and
one upwind sites. The sampling  days
cover  a range of hourly traffic densities
from 2160 to 3906 vehicles with wind
speeds ranging from 5.8  to  18.5 mph.
Based on the  concentration measured
five m downwind  of the roadway edge,
the average maximum  increases above
background (at two m height) in particu-

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late mass and lead concentration down-
wind of the roadway were:
                      Phase I  Phase II
Coarse mass
Fine mass
Total mass
Fine lead
Coarse lead
Total lead
Wind speed (mph)
4.6
2.6
7.2
0.47
0.08
0.55
11.2
8.5
4.8
13.3
0.48
0.11
0.59
8.4
  The  coarse particulate mass concen-
tration at the two m elevation increases
from  the  roadway  centerline  to five
meters downwind and then decreases
with distance while the fine particulate
mass decreases with distance immedi-
ately from the centerline. The total mass
decreases  with   distance  from  the
centerline.  A significant contribution is
made  to  the   coarse  fraction  from
pavement wear and particle re-entrain-
ment, which contribute little to the fine
fraction. This fact and  the effect  of
atmospheric  turbulence probably
account for the difference  in concentra-
tion profiles for the different size fractions
of the mass.
  Logarithmic equations fitted by least
squares   methods  were  used   to
empirically  describe (for distances
between five  m and 175 m downwind of
the roadway  edge) the relationship be-
tween the horizontal two m  mass concen-
tration (C)  in  fjg/m3 and distance (D) in
meters downwind as follows:
                             Standard
                              error of
                     Correlation estimate
Fraction	Equation  Coefficient  (//g/m3)
Coarse  mass C =  17.56 -  0.990    0.40
            1.71  InD
Fine mass   C=  18.82-  0.964    0.53
             .99 In D
Total mass  C = 36.378 - 0.990    0.66
            2.71  In D


The coefficients show good correlation of
C and In D. Setting the equations equal to
background concentration and solving for
distance, the  downwind point at which
levels reach   background  were
determined. These distances are  74  m
(coarse), 87 m (fine), and 77 m (total).
  Correlation coefficients between traffic
density and mass concentration for each
particulate  size fraction (fine and coarse)
were  calculated  for  each of the  six
downwind  ground  level sampling
stations.  Statistically   significant
correlation  at the 90% probability level
occurred for fine mass and traffic at 5 m
downwind and at the roadway. No other
correlations between particulate mass
fractions and traffic density were found at
the 90% probability level apparently due
to the  limited range  of traffic densities
present during the study.  Correlations
between wind speed and fine particulate
mass were statistically significant at the
90% probability level for all sites. In the
case of the coarse fractions none of the
sites correlated with  wind speed except
for the  site five m downwind at a height of
seven m. Total mass correlated with wind
speed at the 90% probability level for all
sites except at 175 m downwind.
  Lead mass concentration averages also
were plotted  versus horizontal distance
downwind.  The   lead  concentrations
decrease with distance from the roadway
with   the   highest  concentrations
occurring at the center of the roadway
(0.17 fjg/.m3 coarse, 0.60pg/m3 fine, and
0.78 fjg/m3 total). The concentrations for
total and fine fractions remain  signifi-
cantly above background for at least 175
m downwind.  The lead  concentration
apparently does not dilute vertically at the
same rate as the fine mass  mode. Loga-
rithmic equations fit  by least  squares to
empirically describe the deposition and
vertical diffusion are given as follows (for
distances  between five m  and  175  m
downwind of the roadway edge):

(C = mass concentration, jug/m3; D = dis-
tance downwind,  m)
                              Standard
                              error of
                     Correlation estimate
Fraction       Equation  Coefficient (//g/m3)
Coarse Pb

Fine Pb

Total Pb

C = .187-
.029 In D
C = .715 -
.106 In D
C = .903 -
.135 In D
0.985

0.990

0.990

.095

.032

.032

  The correlation between traffic density
and lead concentrations for the fine size
fraction  were significant at the  90%
probability level for all ground level sites
except 175  m downwind.  Correlations
between fine lead and wind speed were
found for all sites at the 90% probability
level. The  correlation  between  coarse
lead and traffic density was significant at
the 90%  probability level only for sites at
five m, 25 m, and 75 m downwind. Coarse
lead and wind speed correlations were
significant at the 90% probability level at
all downwind sites except for five m and
25 m at a height of seven m. Wind speed
was a  more dominant factor than traffic
density in determining  both  mass and
                                                                                 lead concentration levels over the range
                                                                                 of conditions encountered.
                                                                                 Vertical Profile
                                                                                   Vertical profiles for mass and lead in
                                                                                 each particle  size fraction  were  first
                                                                                 examined   by  plotting  the  average
                                                                                 concentration for 10 sample runs versus
                                                                                 heights of two m,  seven m, and 15m
                                                                                 based on  measurements  from towers
                                                                                 located at five m and 25 m downwind.
                                                                                 Background measurements were made
                                                                                 at the two m height.
                                                                                   Mass concentrations  measured at the
                                                                                 two tower locations and upwind at a two
                                                                                 m height were averaged over 10 days of
                                                                                 sampling  at  each  of   the  six  tower
                                                                                 locations. The coarse particle concentra-
                                                                                 tions were statistically different from two
                                                                                 m background (95% probability level) only
                                                                                 at  the  ground  level  locations.  Fine
                                                                                 particulate  mass was significantly
                                                                                 different from two  m background for  at
                                                                                 least 15 m  vertically  at  the 25  m
                                                                                 downwind site  and at  least  seven  m
                                                                                 vertically at the five m downwind site.
                                                                                 Total  particulate  mass  measured  at
                                                                                 heights above ground level (two m) were
                                                                                 found to be significantly different from
                                                                                 two m background for only the seven  m
                                                                                 vertical at the five m downwind location.
                                                                                 The vertical gradient mass data was not
                                                                                 fit to empirical equations since  it was  at
                                                                                 background level at some of the elevated
                                                                                 measuring points.
                                                                                   In the vertical profiles, lead concentra-
                                                                                 tions for fine and total particles were
                                                                                 significantly different from background
                                                                                 up to 15 m vertically for both downwind
                                                                                 towers.  Coarse lead was significantly
                                                                                 above background for at least  seven  m
                                                                                 vertically at both downwjnd towers.
                                                                                   No significant correlations were found
                                                                                 between composite mass fractions and
                                                                                 traffic density at the elevated sites. The
                                                                                 same was  true for the lead  fractions.
                                                                                 Wind speed correlated with fine mass at
                                                                                 the 99% probability level for  all sites
                                                                                 except the five m downwind, 15m height
                                                                                 site. Coarse particle mass fractions corre-
                                                                                 lated significantly with  wind only at the
                                                                                 five and 25 m downwind sites at the
                                                                                 seven m  height. Coarse lead  fractions
                                                                                 correlated significantly only at the 15m
                                                                                 height at five m and 25 m downwind. Fine
                                                                                 lead showed a significant correlation
                                                                                 with wind speed at all sites.
                                                                                   Since  fine  and total  lead concentra-
                                                                                 tions were above background up to a 15 m
                                                                                 height, logarithmic equations as follows,
                                                                                 were fitted by least squares to empirically
                                                                                 describe the vertical dilution, (C = mass

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concentration,  /ug/m3;  H  =  distance
above ground, meters):
Fraction
Fine lead
(5m dw)
Total lead
(5m dw)
Fine lead
(25m dw)
Total lead
(25m dw)
Equation
C = 0.674 -
0.222 In H
C = 0.833 -
0.273 In H
C = 0.498 -
0.145 In H
C = 0.609 -
0.1 77 In H
Correlation
Coefficient
0.990
0.990
0.998
0.998
Standard
error of
estimate
(//g/m3)
0.030
0.057
0.013
0.008
Bromine/Lead Ratios
  The Br/Pb ratios found to exist in the
downwind  roadway particulate  matter
were consistent with ratios reported  in
the literature. As described by Harrison
and  Sturges,  the  major  particulate
species  of exhaust lead and bromine in
the United  States is PbBrCI and should
give a Br/Pb mass ratio  of 0.386 in the
exhaust. The average Br/Pb ratio for all
ten downwind monitoring locations was
0.36 ± .06 in the fine fraction and 0.55 ±
.26 in the coarse fraction. Eighty percent
of the lead mass was found in the fine
fraction.
Development of Empirical
Model for Roadway Generated
Particulate Levels
  Rodes  and  Holland  developed  an
expression in the Los Angeles Catalyst
Study which predicts  (for two m height)
the exponential horizontal decrease of an
initial  concentration  of an  inert  gas
measured at a given point downwind of
the  centerline   of  a  roadway.   This
approach  was   used to  develop  an
equation  for computing particulate and
lead mass concentration at heights up to
15 m above ground level and distances
between five m and 175 m downwind of
roadway  edge for cross-wind cases at
wind  speeds between  three and  six
mph. Rodes and Holland's equation is
        C = C
"Hr   1+c"
     Where C = mass cone, at distance
     downwind (/jg/m3)

     C26  =  mass  cone,   at   initial
     point  downwind  26  m  from
     roadway centerline (/yg/m3)

     B, = "vertical" dilution  parameter

     X = distance downwind from center-
     line (m)  where 26M 
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confidence level also were found for the
lead component of the mass fractions.
  Within wind speed and traffic density
boundaries of the study, the downwind
mass  gradients  in  the  vertical  and
horizontal  directions were predictable
from  an  empirical   relationship.
Therefore,  zoning graphs  for  use  in
developing  siting   constraints   were
obtainable  for  the mass  and   lead
fractions.  The bromine/lead ratio was
found to be consistent with other studies
indicating that the increased lead  mass
levels were generated from the roadway.
The  criteria  for  siting  TSP  samplers
(presently in the Federal Register) cannot
be used for siting IP samplers since the
constricted area  is not bounded  by a
straight line as given in the TSP criteria.
The  area  is  bound by an exponential
function with respect to height and dis-
tance.  The downwind  mass  and  lead
concentration  profiles  for  each  size
fraction measured are similar in shape
but extinction rates vary considerably for
the different fractions measured.
  The  paniculate  mass  settling  rate
(deposition) downwind to a distance  of
175  m is not  significant. The downwind
horizontal decrease  in  particulate
concentration at a height of two m is due
mostly to the upward diffusion of the
particles. Only 1.2% of the fine mass is
lost between five m and 25 m downwind
at a height up to 15 m. The coarse  mass
decreased 9.7% at the same height and
over the  same  distance.  One cannot
assume  that   correct  siting  can  be
accomplished by placing the sampler at a
greater height, sincetheplume rises with
distance   downwind.  The  downwind
dilution rate of lead associated with the
fine fraction is different from that of the
fine or coarse mass fraction. Most of the
lead remains below a height of seven  m
vertically, and is significantly above zero
at a distance of 175 m downwind.
  It was possible to empirically derive two
dimensional  exponential equations
describing dilution of mass and lead con-
tent  in both the horizontal  and vertical
directions downwind which account for
greater than 90% of the variability in the
data. The equations are of the form used
to describe dilution of an  inert gas.
However,  the exponents  in the  fitted
equations are not in agreement with the
values found previously. The dilution rate
is highly influenced by the difference  in
concentration upwind and that directly
downwind of the source.
P. Burton (also the EPA Project Officer, see below) and J. Suggs are with
  Environmental Monitoring Systems Laboratory, U.S. Environmental Protection
  Agency, Research Triangle Park, NC 27711.
The complete report, entitled "Philadelphia Roadway Study," (Order No. PB 84-
  226 927; Cost; $8.50, 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:
        Environmental Monitoring Systems Laboratory
        U.S. Environmental Protection Agency
        Research Triangle Park. NC27711
                                                                        . S. GOVERNMENT PRINTING OFFICE: 1984/759-102/10672

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