United States
Environmental Protection
Agency
Environmental Sciences Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S3-84-023 Mar. 1984
6ER& Project Summary
Source Receptor Methodology for
Some Chlorinated Hydrocarbons
F.L Ludwig, E.M. Listen, and L.J. Salas
This study investigates the feasibility
of a source-receptor methodology that
is used to estimate halogenated hydro-
carbon emission rates from a manufac-
turing plant when access to the plant is
not possible. The method'estimates
fugitive emissions from sources within
10 or 15 m of ground level. If an area is
tested at night or under overcast con-
ditions, the method is generally insen-
sitive to meteorological conditions,
although it must be applied with
discretion if interfering sources are
present.
An inert tracer is released at a known
rate near the plant area. Samples are
collected downwind of the plant and
analyzed for the tracer and halogenated
hydrocarbons. The relationship between
measured concentrations and the emis-
sion rates of the tracer and the halogen-
ated hydrocarbons has been derived.
Therefore, emission rates can be deter-
mined, and conventional Gaussian
methods may be used to estimate
maximum ground-level concentrations
of halogenated hydrocarbons downwind
of the plant.
A suitable manufacturing plant was
selected, and the method was applied
to estimate emission rates for four
different halogenated hydrocarbons.
The feasibility of the methodology was
demonstrated and suggestions for
improvements were made.
This Project Summary was developed
by EPA's Environmental Sciences Re-
search 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 infor-
mation at back).
Introduction
The U.S. Environmental Protection
Agency (EPA) is concerned that some
hydrocarbon compounds, especially
halogenated hydrocarbons that may be
hazardous at low concentrations, might
have an immediate local impact downwind
of some manufacturing plants. Once a
source strength is known, maximum
ground-level concentrations can be
estimated as a function of downwind
distance and meteorological conditions.
However, lack of source-strength data
has prevented the prediction of the
amounts of these materials that are
released to the atmosphere and the
concentrations that might exist downwind
of the plants under various meteorological
conditions.
Several factors have contributed to this
lack of data. Hydrocarbon compounds are
likely to be emitted from widely distributed
sources such as valve leaks, plumbing,
incompletely sealed containers, and
filling and emptying operations or during
transport. The magnitude of such fugitive
emission sources is difficult to measure
or estimate. Furthermore, at many plants
the processes and equipment used to
produce the materials are proprietary and
for competitive reasons, manufacturers
are unwilling to reveal their production
and sales rates. In such an environment,
manufacturers are reluctant to allow
outsiders into their manufacturing plants
to make measurements that would be
necessary to characterize source strengths
directly. EPA recognized a need for a
source-receptor methodology that could
be used to estimate the source strength of
such fugitive emissions and predict
maximum ground-level concentrations
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and would not rely upon measurements
made within the manufacturing complex.
Procedure
Theoretical research and field testing
were combined to create and test a
method for measuring halogenated
hydrocarbon concentrations. The method-
ology relies upon the release of an inert,
non-toxic tracer gas at a known rate out-
side the manufacturing site. Tracer and
chlorinated hydrocarbon concentrations
are measured downwind of the site, and
the magnitude of hydrocarbon sources
within the plant is estimated. Once these
source strengths are established, conven-
tional dispersion modeling techniques
are used to estimate downwind concen-
trations for various meteorological situa-
tions.
The actual tests were conducted at the
Vulcan Materials Company plant near
Wichita, Kansas, on the nights of August
8-9, 10-11, 11-12, and 12-13, 1981. An
inert, non-toxic tracer gas was released
at a known rate from a vehicle traveling
outside and upwind of the manufacturing
site. Samples were collected at 1 to 5 km
downwind of the plant. These samples
were analyzed for tracer and chlorinated
hydrocarbon concentrations. Tracer
concentrations were measured to establish
the magnitude of the atmospheric trans-
port and dilution processes. This value
was used with simultaneous downwind
measurements of the chlorinated hydro-
carbon concentrations to estimate the
magnitude of their sources within the
plant.
Results and Conclusions
Hourly samples were collected through-
out the nighttime test periods. This
measurement approach presents an
inherent difficulty because of the potential
for wind shifts which could affect the
significance of the tracer release as well
as the downwind collection of the
pollutants by the ground-level receptors.
Difficulties with analytical procedures,
proper receptor location, high background
and low receptor concentrations were
also encountered. As a result, the data
analyses involved the five best data sets
from the entire sampling schedule.
Two equations were used to estimate
the emission rates of the measured
compounds:
QA= 0.35 CA Qi
r /v 0.3S v 0 35, 0.85
Cl (Xu - Xd ) X
where CU=area source emission rate
(g/m2-s)
CA=concentration of area source
component (g/m3)
Ci=concentration of line source
component (g/m3)
Qi=line-source tracer emission
rate (g/m-s)
Xu=distance from receptor site to
upwind edge of area source (m)
Xd=distance from receptor site to
downwind edge of area source
(m)
x=distance from integrated line
sources to receptor site (m)
(which relates the dilution of a tracer
released from a ground-level line source
to the dilution of compounds from a
nearby ground-level area source), and
Qp=KCpQ, Xp09
Ci Sin 0
where Qp=source strength of a point
source (g/s)
CP=point source ground-level
concentration at plume center
(g/m3)
Qi=line source emission rate (g/m-s)
Ci=line source ground level con-
centration (g/m3)
XP=downwind distance from point
source (m)
0=angle between wind and line
source
K=constant reflecting meteoro-
logical conditions
(which assumes the source is a point or
very small area source and that the point
source and line source are close together
compared to the downwind receptor
distance).
By using the ratios of chlorinated
hydrocarbons to the tracer concentrations
all measured at the receptor sites,
estimates were made for the hydrocarbon
emission rates. Using the area source
formulation, estimates of from 1.5 x 1CT7
to 3.1 x 10'4 g/mz-s were obtained.
Using the point source formulation,
estimates of from 0.01 to 6 g/s of
hydrocarbon emissions were estimated.
It was concluded that receptor place-
ment strategy was critical for such a
measurement approach as well as the
consistency of the wind direction. The
highly variable results of hydrocarbon
concentrations from one receptor to
another suggested that release of the
compounds was a result of localized
incidents, such as drum filling, leaking
flanges, and materials handling.
Suggested improvements include
greater spatial and temporal resolution of
receptor sites. A further improvement
would be establishing a screening
procedure of the tracer analyses results
to maximize quantitative results with a
minimum number of analyses. A final
suggested improvement in the method
was adapting its use to daytime operations
but this would be limited to neutral
conditions sampling.
F. L Ludwig, E. M. Listen, and L J. Sales are with the SRI International, Menlo
Park. CA 94025.
James L. Cheney is the EPA Project Officer (see below).
The complete report, entitled "Source Receptor Methodology for Some Chlori-
nated Hydrocarbons," (Order No. PB 84-149 16O; Cost: $1O.OO, 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 Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
U.S. GOVERNMENT PRINTING OFFICE; 1984 — 759-015/7627
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