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
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