United States
Environmental Protection
Agency
Atmospheric Sciences
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/6Qq^i$-86/O70 Mar. 1987
<>EPA Project Summary
Comprehensive Experimental
Design Plan to Relate Pollutant
Sources to Acidic Deposition
D. J. McNaughton, N. E, Bowne, R, J. Londergan, D. L. Shearer, D. A. Stewart,
G. E. Moore, J. E. Langstaff, M. K. Liu, S. M. Greenfield, S. E. Schwartz, and
D. H. Stedman
Because verifiable numerical models
that incorporate all processes deter-
mining the dispersion, transformations,
and deposition of emitted pollutants
associated with acidic deposition from
the atmosphere are only now under
development, it was deemed worth-
while to determine whether other
methods might be available to empiri-
cally relate acidic deposition to pre-
cursor emissions. After determining
that the most promising direct ap-
proaches, large-scale source modulation
and use of reactive tracers would not
be feasible, an indirect experimental
plan named the combined experimental
approach was developed. This approach
consists of three major components:
long-range tracer experiments; short-
range experiments, including reactive
tracers, local deposition experiments,
and local source modulation; and routine
monitoring of aerometric parameters.
Analyses of data would provide esti-
mates of source contributions to deposi-
tion at receptor sites. The collected
data would also be used for developing
and testing upgraded regional models
and model components.
This report describes the workshop
used to develop the general experi-
mental design and the follow-up
analyses of the various components.
Some of the design sections describe
experiments that will yield data for
evaluation of acid deposition models.
Finally, the costs of the various experi-
mental efforts are described.
This Project Summary was developed
by EPA's Atmospheric Sciences Re-
search Laboratory, Research Triangle
Park, NC, to announce key findings of
the research protect that Is fully docu-
mented In a separate report of the same
title (see Project Report ordering In-
formation at back).
Introduction
The comprehensive field study plan to
relate pollutant sources to acid deposition
was developed under the sponsorship of
the U.S. Environmental Protection Agency
Environmental Sciences Research Labo-
ratory by a research team headed by TRC
Environmental Consultants, Inc. and
consisting of TRC, Brookhaven National
Laboratory (BIML), and Systems Applica-
tions Inc. (SAI).
The objectives of the plan are to design
experiments which will:
1) Relate empirically the mass transfer
from acid pollutant (and precursor)
source areas to acidic deposition.
2) Provide a data base to aid in the
development and evaluation of re-
gional acidic deposition models.
In designing these experiments, TRC
convened a workshop to provide a con-
sensus opinion on potential experimental
concepts and guidance to the team on
details of the design. The workshop was
held at Brookhaven National Laboratory
in May 1984.
Workshop participants identified a
number of experimental approaches
which could serve as the core of the
program. The most technically promising
of these approaches for directly deter-
mining source attribution with confidence
were source modulation experiments and
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isotopic reactive tracer experiments.
Several indirect approaches for deter-
mining source attribution were also
identified. They included inert tracers,
emulators, process evaluation, and in-
tegration of existing data. Subsequent to
the workshop, it was determined that
economic and logistical constraints would
not permit source modulation experi-
ments on a regional scale. The reactive
tracer experiments were likewise deter-
mined to be infeasible due to the expected
adverse public reactions to releases of an
unstable (radioactive) isotope and the
limited availability and high cost of stable
isotopes.
Because of constraints on direct experi-
ment approaches, the design team de-
cided to pursue an indirect experimental
approach, which for this plan, is named
the combined experiment approach. The
name is meant to convey the concept of a
collection of interactive experimental
components which together provide data
for determination of quantifiable source/
receptor relationships and a data base for
model evaluation.
It is expected that relationships devel-
oped from the combined experiment will
provide an improvement on current source
attribution techniques, but uncertainties
associated with the combined experiment
cannot be quantified without pilot and
uncertainty studies. Because of the
complexity of the combined experiment,
the adequacy of the experiment cannot
be determined at this time. To compensate
for not having an estimate of uncer-
tainties, the experimental plan uses re-
dundancy of tasks in staged experiments.
The staged approach provides pilot studies
prior to the main experimental program
to refine techniques, estimate uncertain-
ties and establish feasibility as well as
providing the sponsor with milestones
for program control. Results of initial
studies are given in this report. Results of
preliminary uncertainty analyses are
given in a comparison report.
Combined Experiment
The combined experiment is designed
on the basis of a transmittance approach
consisting of three major components.
Transmittance refers to the method by
which source attribution is determined.
First, the vertical pollutant distribution in
the vicinity of a receptor is determined
from the fractional transmittance of mass
as it is transported between a source and
receptor. In this context, fractional trans-
mittance is that fraction of pollutant mass
which is not lost en route due to deposi-
tion. Second, the mass distribution in
combination with the local deposition rate
determines the contribution of a source
to deposition at a receptor. Fulfilling the
data needs of the transmittance approach
and the secondary objective of providing
a data base for model evaluation, leads to
a program with the following components:
Long Range Tracer Experiments
The major objectives of the long range
tracer study are to simulate transport and
dispersion of pollutants using inert tracers
and to determine the mass distribution
and mass balance of the tracers in a
receptor area. Tracer releases will be
made at major emission source areas.
These will be selected for study on the
basis of SO2 emissions and forecast
meteorological conditions (i.e. expected
transport routes). The source areas are
located 500 to 1000 km from the Adiron-
dacks Region of New York State which
was identified as the primary receptor
area for the study although alternative
areas could be selected as the focus of
the experiments. From these source
areas, inert tracers will be released and
tracked by means of a ground network of
sampling sites throughout the Northeast.
A fine resolution ground level sampling
grid will be established in the Adirondack
Region where aircraft sampling will be
conducted to support studies of deposition
and transmittance in a small area.
Short Range Experiments
A series of short range experiments is
proposed to provide information on plume
depletion. This is an important process in
the transmittance approach. Current
estimates are only available on a local
scale and are associated with a high
degree of uncertainty. To overcome these
uncertainties, a combination of three
types of experiments are proposed:
• Reactive Tracer Deposition Experi-
ments — Sulfur-34 tracer studies will
be performed to provide information
on deposition and plume depletion.
The experiments will represent a
variety of meteorological and surface
conditions. Experiments will include
releases of sulfur-34 and two additional
inert tracers. The tracer samples will
provide deposition estimates by plume
depletion and tracer ratio techniques.
• Deposition Experiments — Experi-
ments will be conducted to determine
deposition rates using fixed deposition
monitoring sites in conjunction with
aircraft eddy correlation techniques for
ozone. Fixed site data will be used to
determine the relationships of ozona
and sulfur and nitrogen oxide fluxes!
These data will then be available for
use in extrapolating aircraft ozone eddy
correlation measurements to estimate
sulfur and nitrogen oxide deposition
for large areas.
• Source Modulation Experiments — The
last type of short range experiments
proposed are local source modulation
experiments. Data from these studies
will provide a direct measure of local
source attribution and plume depletion
as a test for derived source/receptor
relationships.
Routine Monitoring and Support
Data Collection
This component of the combined ex-
periment will provide the primary data
base for model evaluation. It will provide
wind and concentration data to help
determine transport trajectories and
transmittances associated with long-
range transport. In addition, the data will
be used to study the variability of acidic
species and precursors as a function of
meteorological and emissions patterns
and to provide a historical perspective for
these patterns relative to past or ongoing
programs. An important role of the data
collected under the routine monitoring
component will be to provide a limited
data set for analysis of the chemistry of
deposition processes. Support meteoro-
logical and emissions data from other
programs will be collected as part of this
component.
Analysis
Analyses of the data collected by the
three components will characterize de-
position episodes. More importantly they
will provide fractional transmittance
functions, tracer transport statistics, and
deposition estimates. Combination of
these derived values will provide an
estimate of the mass arriving at a receptor
and thu potential for depositing that mass,
thus completing the source/receptor
relationships.
Conclusions
The combined experimental program is
designed to meet the data requirements
of a transmittance approach. Data col-
lected under the program will also be
sufficient for additional parallel analyses
including analyses using upgraded ver-
sions of current regional models, and
analyses by statistical inference.
The plan utilizes some untested
methods and unproven combinations of
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techniques. Therefore, success of the
pesign must be gauged in pilot experi-
ments and uncertainty assessments
examining these approaches.
Costs associated with the various
components are described in the report.
Implementation of the full design and
subsequent analysis would cost in excess
of $100 million.
D J. McNaughton, N. E. Bowne, R. J. Londergan. and D. L. Shearer are with
TRC Environmental Consultants, Inc.. East Hartford, CT06108,• D. A. Stewart.
G. E. Moore, J. E. Langstaff, M. K. Liu, and S. M. Greenfield are with Systems
Applications, Inc., San Rafael, CA 94903; S. E. Schwartz is with Brookhaven
National Laboratory, Upton, NY 11973; and D. H. Stedman is with the
University of Denver, Denver, CO 90209-0179.
Francis Pooler. Jr., is the EPA Project Officer (see below/.
The complete report, entitled "Comprehensive Experimental Design Plan to
Relate Pollution Sources to Acidic Deposition," (Order No. PB 87-14O 950/
AS; Cost: $24.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Atmospheric Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park. NC 27711
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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