REPORTS OF WORKING GROUPS
WORKSHOP ON REGIONAL AIR
POLLUTION STUDIES
REPORTS OF WORKING GROUPS
WORKSHOP ON REGIONAL AIR POLLUTION STUDIES
JUNE 7-10, 1976
Appalachian State University
Center for Continuing Education
Boone, North Carolina
Conducted by
The Triangle Universities Consortium on Air Pollution
under contract with
The Environmental Protection Agency
Environmental Sciences Research Laboratory
Research Triangle Park, North Carolina
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REPORTS OF WORKING GROUPS
WORKSHOP ON REGIONAL AIR POLLUTION STUDIES
JUNE 7-10, 1976
Appalachian State University
Center for Continuing Education
Boone, North Carolina
Conducted by
The Triangle Universities Consortium on Air Pollution
under contract with
The Environmental Protection Agency
Environmental Sciences Research Laboratory
Research Triangle Park, North Carolina
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FOREWORD
The Workshop on Regional Air Pollution Studies was sponsored by the
Environmental Protection Agency, Office of Research and Development,
Environmental Sciences Research Laboratory and conducted by the Triangle
Universities Consortium on Air Pollution (TUCAP).
Participants in the Workshop were a selected group of scientists from
throughout the contiguous United States. These individuals were invited
because of their current activity and past experience in research directed
toward contributing to the understanding of the chemical and physical pro-
cesses that affect pollutants as they are transported in the atmosphere from
their points of emission to receptors.
This select group was charged with contributing to the initial planning
for a program of field measurements and analyses during Fiscal Years 1978
through 198flf. This program would have as its objective the determination of
the fate—through transport, transformation, and removal—of sulfur and
nitrogen compounds emitted to the atmosphere as primary pollutants.
The Workshop was organized in four groups: Working Group on
Atmospheric Transformations, Working Group on Measurements, Working Group on
Transport and Dispersion, and Working Group on Data Management and Modeling.
The membership and chairman of each of these working groups were chosen from
the invited scientists by the sponsor prior to convening the Workshop.
At intervals during the week, plenary sessions of the Workshop were
held to report status and assess progress of each working group. More fre-
quent meetings of EPA personnel, the Working Group chairmen, and interlocutors
from each group provided the opportunity for disclosing, discussing, and
resolving potential areas of conflict among the plans being developed by the
several groups.
The products of the Working Groups were reports developed by each
group. These reports are presented in this document with only minor
editorial changes; each has been reviewed by the appropriate Working Group
chairman.
Provided by TUCAP from the University of North Carolina, North Carolina
State University, and the Research Triangle Institute.
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INTRODUCTORY STATEMENT
A. Paul Altshuller, Director
Environmental Sciences Research Laboratory
Office of Research and Development
Environmental Protection Agency
A significant body of experimental data is available suggesting
that adverse health effects, visibility reduction and hazes, materials
deterioration and ecological effects may be associated with sulfur
oxide, nitrogen oxides and particularly with their transformation
products in the atmosphere. These transformation products are referred
to as sulfates and nitrates. However, the chemical and physical forms
of these products are numerous and poorly characterized in the ambient
atmosphere.
Increased usage of fossil fuels, particularly coal, can be antici-
pated to result in increased atmospheric concentration levels of sulfur
oxides, nitrogen oxides and their transformation products. At the same
time it is appreciated that the mechanisms of transformation are complex
and may involve other precursor or catalytic species. Natural sources
of sulfur compounds must also be evaluated.
The lack of sufficient research on measurement techniques for these
transformation products and the need for more work on the chemistry,
physics, and meteorology of transformation, transport and removal has
been identified by EPA in its Position Paper on Regulation of Atmospheric
Sulfates of September, 1975, in the National Academy of Sciences Document
on Air Quality and Stationary Source Emission Control of March 1975, and
in the Subcommittee on the Environment and the Atmosphere's Report on
Review of Research Related to Sulfates in the Atmosphere to the
Committee on Science and Technology, U.S. House of Representatives, 94th
Congress, April 1976.
The latter Congressional document states as a primary finding that
there is not a coordinated, targeted research program on sulfates, even
within EPA. The Committee suggests that this situation probably results
from EPA regulatory officials belief that a regulation of sulfur dioxide
implies a de facto regulation of sulfates. The policy position taken by
EPA on this issue in its September 1975 paper was as follows:
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"In view of the available data, it is the judgement of EPA that an
air quality standard or other major regulatory program for sulfates is
not supportable at this time. In order to fill the information gaps
described earlier, EPA is expanding its sulfate research effort. The
research will focus on improved monitoring capability to permit identi-
fication of particle size and chemical form of toxic sulfates, develop
more comprehensive health effects data, and characterizing the long-
range transport and transformation mechanisms. The research program
will require several years to complete; consequently, it is doubtful
that a comprehensive regulatory program specifically for sulfates could
be initiated before the end of the decade. The recent reports by the
National Academy of Sciences and EPA's Science Advisory Board support
EPA's position that considerable research and data development must
preceed such a regulatory program for sulfates."
The Subcommittee of the Environment and the Atmosphere concluded
that "the sulfates issue is broad enough and of such consequence that the
EPA, coordinating with ERDA, HEW, and NSF should develop and implement
such a program without further delay." The Subcommittee also found "that
advance in knowledge in the critical areas of formation and transport of
sulfates and of health effects of sulfate depends in a key way upon
development and implementation of adequate measurement technology."
Therefore, we are faced with what appears to be a conflict between
the maintenance of air quality and the fulfillment of national energy
requirements. We also are faced with the dilemma of the need for defin-
ing an appropriate regulatory position but the inability to do so without
first implementing a coordinated research plan. The Subcommittee on
Environment and the Atmosphere emphasizes the high stakes and the keen
interest that industry, government, and the public have in research on
sulfates.
This Workshop is being held to take the appropriate first steps
towards development of a coordinated program on the measurement tech-
nology and formation and transport of sulfates. Since nitrogen oxides
and nitrates are a closely associated problem to sulfur oxides and
sulfates in formation and transport from stationary sources, the two
classes of pollutants should be considered concurrently in developing
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effective experimental programs of research, particularly large field
studies.
The atmospheric studies conducted to date primarily focus on local
or urban scale air pollution. A very modest data base has been accumu-
lated usually on a scale of 30 to 100 miles from the RAPS experiments
and the MISTT experiments following plumes in the St. Louis area.
However, RAPS will end its experimental period in 1977. The funding
level in MISTT is such as to permit only a modest continuing effort on
plumes under various meteorological and terrain conditions. Also MISTT
is dependent on the duration of the interagency environmental energy
program rather than on the regulatory time scale of EPA. The RAPS and
MISTT programs are a part of the research activities of the Environmental
Sciences Research Laboratory of EPA at the Research Triangle Park, North
Carolina. A program of atmospheric studies has been proposed by EPRI.
ERDU also has an appreciable group of individual laboratory and field
projects with participants at many locations designed as MAP3S. The
EPA and EPRI efforts along with the ERDU projects should prove to be
complementary in time, but also terms of the types of discrete experi-
ments and measurements used by these programs.
Atmospheric studies conducted through FY 77 are not expected to
provide sufficient quantitative results under the wide range of pollu-
tant concentrations and compositions, meteorological parameters and
terrains needed to permit development of quantitative relationships
between emission rates and air quality. Measurements on specific
particulate sulfur species such as sulfuric acid, acid sulfates, sulfites,
ammonium sulfate, zinc ammonium sulfate, iron sulfate are sparse or non-
existent in almost all areas of the U.S. Data is lacking to discriminate
the sulfates of greater concern such as sulfuric acid and acid sulfates
from relatively innocuous species such as calcium sulfate, magnesium
sulfate or sodium sulfate. The measurement situation with regard to
nitrates is at least equally poor. Based on limited atmospheric mea-
surements, nitrates are known to occur as inorganic vapors, organic
vapors and in particulate matter. There is uncertainty as to whether
the routine sampling done in the past for particulate matter collected
some of the nitrates in vapor form as well as the nitrates in particulate
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matter. These compositional capabilities are critical to EPA's health
effects research activities as they are to our formation and transport
research.
The Environmental Sciences Research Laboratory has been expanding
its research efforts on measurement technology for these substances.
The level of efforts in FY 77 and FY 78 become critical in bringing
these efforts to the stage where they are operational for use in health
and atmospheric transport studies.
Only a small body of experimental results will be available through
FY 77 on rates of conversion of sulfur dioxide to sulfates in plumes
compared to the rates of removal by soil, vegetation or water through
dry deposition or by precipitation processes. Even less is known about
the behavior of nitrogen oxides in plumes. The relative impact of
sulfur oxides and nitrogen oxides in various compositional forms is
extremely poorly understood in terms of soils, water, and vegetation.
Of particular importance is the impact of increased usage of coal
in various utility complexes especially in the interior of the U.S.
These sources are of great concern because of their large rates of emis-
sions of pollutants into plumes when using coal as a fuel. Because of
the use of tall stacks, the rates of removal of sulfur oxides and nitrogen
oxides would be predicted to be substantially less than from mobile
sources or stationary sources emitting near or at ground level. Some
admittedly limited experimental data indicates that these lower level
sources will not impact greatly much more than 100 miles away. However,
plumes from elevated sources travelling well aloft during some daytime
conditions and particularly during the night can carry the sulfur oxides
and nitrogen oxides very far downwind before conditions leading to good
mixing to the surface occur. Therefore, the potential regional scale
impacts over hundreds of miles of sulfur oxides and nitrogen oxides
associated with large elevated sources require a substantial program to
provide the inputs to assess impact on future regulatory policy.
The general approach suggested for the proposed EPA-ORD Sulfate
Transport and Transformations in the Environment (STATE) would be a
group of discrete, large scale intensive experimental field study periods
during FY 78 through FY 80. These intensive studies would involve the
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use of the capabilities of research groups from governmental laboratories
(EPA, ERDA, NOAA), universities, research institutes, and industry-
sponsored efforts. To the fullest expent possible, the combined resources
of the several agencies and industry would be focused on optimizing
measurements in investigating formation, transport, transformation, and
removal of sulfur oxides and nitrogen oxides on a regional scale (100 to
1000 km). While it might not be possible for each group or organization
to participate in each of these intensive field periods, every effort
would be made to coordinate utilization of all available research
resources. Because of the magnitude of the problem, the estimated com-
bined resources of governmental agencies and industry will be needed to
successfully acquire the complex sets of research results required. A
group of five to seven major intensive periods might be appropriate
depending on the sets of research capabilities and resources available.
It also would be an objective to prepare the results of each intensive
as a separate report. Therefore, sufficient time and personnel must be
made available to reduce, archive, and analyze the results of each
intensive period.
The emphasis in the EPA program would be on multiday experiments
with measurements downwind from the emission source in real time
(Lagrangian system) following the movement of plumes from large stationary
source emission complexes along with the chemical and physical transfor-
mations and removal processes. Fixed monitoring network operations in
the EPRI SURE program or other fixed networks would provide results in
an Eulerian system. Emission inventories, stack monitoring, tracers,
and flux measurements would all be used to define initial conditions at
the boundary of the emission complex. Various tracers would be used
along with extensive characterization of the concentration and composi-
tion of the pollutants within the plumes. Continuing chemical and
physical flux measurements would be involved to permit estimations of
rates of transformation and removal from plumes. Aircraft, mobile ground-
based units and remote or long-path instrumentation would be extensively
utilized.
Scientists experienced in the types of studies envisioned as neces-
sary to satisfy the purposes of this program have an opportunity during
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this workshop to participate in the design of these proposed studies.
The approach suggested should be viewed as a proposal subject to critical
review and modification. The participants should keep in mind that the
program is not an open-ended research program of indefinite duration but
instead must provide a series of well-defined research results after each
intensive period to assist in development of the appropriate regulatory
program for sulfates/nitrates. Finally, this workshop certainly should
not be considered as the only effort directed towards planning experi-
mental design. One or more subsequent workshops are likely to be
needed to cover all planning aspects fully.
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TABLE OF CONTENTS
FOREWORD ii
INTRODUCTORY STATEMENT ill
REPORT OF WORKING GROUP ON ATMOSPHERIC TRANSFORMATIONS
AND REMOVAL PROCESSES 1
I. INTRODUCTION 2
II. DATA REQUIRED 3
III. RECOMMENDATIONS 4
IV. MATRIX OF FLIGHT EXPERIMENTS 5
Appendix 1. Coordinated Independent Studies 8
Appendix 2. Wet and Dry Removal Processes 10
Appendix 3. Perspectives on Transformations in
the S Cycle 14
REPORT OF WORKING GROUP ON MEASUREMENTS 17
I. INTRODUCTION 18
II. GENERAL POLICY 18
III. DATA HANDLING 19
IV. DATA QUALITY ASSURANCE 20
V. INSTRUMENTATION—GENERAL 20
IV. INSTRUMENTATION—SPECIAL . 21
VII. AVAILABLE AIRBORNE PLATFORMS FOR AIR POLLUTION RESEARCH . . 24
VIII. STATUS OF INSTRUMENTATION FOR AIRBORNE GAS INSTRUMENTS . . 25
IX. STATUS OF INSTRUMENTATION FOR AIRBORNE, PHYSICAL
MEASUREMENT AND SAMPLING OF AEROSOLS 26
X. STATUS OF INSTRUMENTATION FOR AIRBORNE AEROSOL CHEMICAL
SAMPLING AND MEASUREMENT 27
XI. STATUS OF INSTRUMENTATION FOR INDIRECT OR REMOTE
MEASUREMENT TECHNIQUES 28
XII. AIRBORNE WISH LIST TAKING INTO ACCOUNT PROBABLE AVAIL-
ABILITY AND HIGH PRIORITY 29
REPORT OF WORKING GROUP ON TRANSPORT AND DISPERSION 30
I. INTRODUCTION ' 31
II. EXPERIMENTAL SITUATIONS 32
III. REGIONAL TRANSPORT 34
IV. SOURCE DISPERSION AND TRANSFORMATIONS .... 36
V. SUPPORTING DATA 39
VI. SUMMARY RECOMMENDATIONS FOR ADDITIONAL MEASUREMENTS .... 40
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TABLE OF CONTENTS (Continued)
REPORT OF WORKING GROUP ON DATA MANAGEMENT AND MODELING 42
I. SUMMARY AND RECOMMENDATIONS 43
II. INTRODUCTION 48
III. TECHNICAL BACKGROUND 50
IV. CRITICAL ASSESSMENT OF MODEL TYPES 53
V. DATA REQUIREMENTS FOR EMPIRICAL MODELS 59
VI. DATA NEEDED TO DEVELOP AND EVALUATE MODELS FOR SULFATE
CONCENTRATIONS IN THE ATMOSPHERE 62
VII. DATA AND MODEL MANAGEMENT 67
APPENDIX A. LIST OF PARTICIPANTS 69
APPENDIX B. SCHEDULE OF SESSIONS 71
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REPORT OF WORKING GROUP ON
ATMOSPHERIC TRANSFORMATIONS AND REMOVAL PROCESSES
Participants:
Joseph Bufalini
Robert Charlson
Basil Dimitriades
George Hidy*
James Meagher
Arthur C. Stern"1"
Bernard Weinstock
John Winchester
*Chai rman
^Interlocutor
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REPORT OF WORKING GROUP ON ATMOSPHERIC TRANSFORMATIONS
AND REMOVAL PROCESSES
I. INTRODUCTION
The panel directed its discussions to the question, "What is needed
to determine the rates of conversion of SO (and NO ) to end products,
X X
along with rates for removal of precursor and end-product species." In
addition, consideration was given to broader aspects of atmospheric
chemistry that bear on the control of sulfate and nitrate.
In the transformation and removal area, there are a number of
unresolved questions that will influence the design of experiments to
support legislation dealing with control of atmospheric sulfate and
nitrate. These include:
1. What are the key conversion mechanisms; can they be identified
by field studies?
2. How variable are conversion rates and what are the major factors
influencing these?
3. What is (are) the rate limiting parameter(s)? (Control Strategies)
(a) S0? concentration or meteorological conditions dictate rate
of production of sulfate. This case yields proportional reduc-
tion in SOT for SO- reduction.
(b) Reaction is trace constituent (NH~, 0,, metal catalyst)
limited and large reductions in SO. will be required if signifi-
cant SO. reduction is to be achieved.
4
4. What are the key end products of reactions characterized by
water soluble sulfate (and nitrate) and/or acid precipitation?
5. What are the spatial and temporal distributions of sulfate (and
nitrate) relative to the major sources of precursors?
6. How important are chemical conversion processes compared with
removal processes in determining general level S0«, sulfate
(and nitrate) concentrations?
7. What are the natural or uncontrollable factors that influence
ambient sulfate and nitrate on a regional scale?
8. What are the total burdens of the various substances of interest
over the entire test region, and how do these burdens vary with
time and meteorological processes?
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Each of these questions represents a crucial area of information
required to support the development of a rational vehicle for regional
control of sulfate and nitrate. In most situations answers will require a
feedback between field and laboratory studies, combined with air quality
modeling.
The basis for answering these questions in part will come from detailed
information from programs currently being implemented by EPRI, EPA, ERDA,
and TVA. In particular, the large network study identified with the SURE,
will serve to provide data for question 5. EPRI, EPA, and ERDA programs
also will provide information on the other questions through a variety
of plume studies, laboratory and special field programs. However, the
information projected from such studies can be enhanced significantly
by amplifying the MISTT or mass balance budget concept in the next three
years with several new field studies of a specialized nature.
It is believed that information about transformations and deposition
can be best obtained when the SO is at relatively high concentration, such
X
as in power plant and urban plumes. Therefore, the experiments relating to
these questions would best be confined to a radial distance of about 200 Ion
from major sources. Experiments of a regional nature—i.e., on a scale
of 1000 km—while an important part of the overall problem, would not be
of great value for deducing transformation and removal rates.
II. DATA REQUIRED
To provide the above information a body of data is needed that has
been collected for a sufficiently diverse set of conditions. One set of
possible variables is as follows:
A. Atmospheric Reactors—with and without clouds
1. Urban Plume—High conversion rates, large amounts of dry
deposition, photochemical activity?
2. Oil-Fired Power Plant Plume—Fairly high conversion rates,
possibly second order, vanadium catalyzed?
3. Coal Fired Power Plant Plume—Low conversion rates, possible
photochemical?
4. Natural—H-S and mercaptan emissions, oxidized through S0?
to sulfate (bogs)?
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B. Atmospheric and Plume Constitutents
1. Plume—SO., NO, N07, particulates (size and composition),
water, HC, 03, OH/H02> NH3
2. Atmosphere—NH_, 0_, hydrocarbons, OH/IKL, trace elements, water
C. Meteorological Parameters
Solar radiance, temperature, R.H., D.P., liquid water; data to
evaluate transport and mixing (Tracer experiments are essential).
III. RECOMMENDATIONS
A. General
As many sources (reactors) as feasible should be studied. Day-
night studies should be made to separate out photochemical contributions.
Measurements in the inversion layer should be made to separate out deposition.
Winter-summer studies should be made to observe effects of temperature,
dewpoint, etc. Evaluate present programs to ensure that funding will be
available for "basic" research directly related to the problem as defined.
Provide additional funding, if necessary.
Under stable atmospheric conditions a quasi-steady state would exist
and concentration gradients produced as a result of transformation and
deposition should remain constant spatially if the SO,., source strengths
remain constant. Diurnal changes in transformation rates should be then
observable—i.e., changes in photochemical conversion rates. The time
to research the steady state in passing from day/night or night/day would
also be important to obtain.
B. Specific
1. OH + S02
There seems to be general agreement that this reaction could
be important in daytime plume chemistry. If the technology is available
to measure this species then it should be done. A rate of removal by OH
can then be readily calculated and compared to the total removal rate.
Some mechanistic work may need-to be done on the product(s) of this
reaction. The main purpose of HC measurements would be to deduce OH
concentrations—which may be quite unusual in a power plant plume because
of high NO , possibly HONO.
X
2. Ammonia
Because of the importance of this compound in postulated
conversion mechanisms its concentration should be measured at plume altitude.
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If possible, continuous cross-wind profiles should also be obtained at
various distances downwind of the source.
3. Effluent Concentrations
Use can be made of power plants that have variable fuel sources
(e.g., high and low sulfur coal). By doing careful, detailed fuel analysis
in conjunction with plume studies the effect of variations in effluent
concentrations can be studied. Consideration should be given to the S
content of fuel and to fuel additives such as alkalis in the power plant
combusters.
4. Power Plant Location
Plants should be selected that are as far away from other
sources as possible, particularly urban (photochemical) plumes.
5. Chemical Transformation
The following transformations are believed to be of most
significance:
a. Photochemical
OH + SO or RO + S0_, HNO + SO.
t* £m - Z, X £
b. Clean Water
NH3 + H20 (1) + S02 = S0| + 02 = H2S04
' S03 + °3 = H2S°4
= HSO= + 03 = H2S04
c. Dirty H.O
Metal ion catalyzed S0= + 0
d. Dry catalyzed
Carbon particles/metal oxides?
e. Deposition of S0_ and sulfate
Terrain type, vegetation, and soil type
IV. MATRIX OF FLIGHT EXPERIMENTS
The purpose is to identify the various contributing components of
a first-order rate constant for transforming or removing SO-. The matrix
shown in the figure identifies the significant variables and the type of
flight experiment. Day/night experiments will give a specific measurement
of dark reaction rates without photochemical contributions. If the night
experiments are done in the inversion layer, the dark reactions would be
the sole transformation process. Similarly, the other experiments will
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EXPERIMENTS TO GET PARTS OF K [SO ]
Variable
Day/Night In Cloud/Fair Weather Hi Low NH Oil/Coal Plume Summer/Winter
Doping
°3
OH-R02
TSP
Trace Metals
Clouds (UNC)
Deposition
x
X
X
X
X
(ice?)
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give an opportunity to assess the relative magnitude of the three main
rate constants for S09 transformation and removal—i.e., dark reactions,
photochemical reactions, and deposition.
It may be desirable to do an NH, doping experiment on atmospheric
samples in the laboratory rather than in ambient air. Two additional
experiments worth consideration are 1) measurement of droplet acidity
and 2) power plant control options—e.g., scrubber and/or precipitator
on and off.
Appended are some considerations that individual panel members
would like to have considered in more detail.
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Appendix 1: COORDINATED INDEPENDENT STUDIES (J. Winchester and G. Slinn)
The panel is aware that the sulfate problem is one of extreme
complexity that requires detailed investigation of processes. Therefore,
the program should include substantial in-depth investigations of these
processes as well as coordinated field studies.
Research on the processes of sulfur sources, transformations, and
sinks must be thorough and carefully designed by individual investigators.
The panel recommends that the EPA solicit proposals from the scientific
community to undertake specialized studies that are directed to the program
objectives. These objectives should be stated clearly—e.g., to develop
information concerning sulfate and its effect on public health and welfare.
More specific program objectives may also be outlined and may include
characterization of natural as well as anthropogenic sources, conversion
of gases to particulate matter, effects of particles on biological and
meteorological phenomena, and the ultimate fates of the sulfur containing
aerosol. However, it should be the responsibility of the individual
investigator to design his strategy for investigating each problem area.
In order for the results of independent investigations to be utilized
readily by EPA, a significant responsibility will be placed upon the EPA
program manager to evaluate the results of each research project and to
facilitate communication between investigators and the agency. This commu-
nication should occur on many levels and include timely preparations
of reports, the holding of conferences and workshops, scheduling interlaboratory
visits, preparation of summary reports of significant findings to regulatory
groups and the public. In the panel's opinion, a proper balance between
coordinated field studies and independent studies of processes should be
of approximately equal weight and funding level. Coordinated field studies
may serve to document the quantitative aspects of processes whose general
character is reasonably well-understood. For example, such field studies
may lead to estimates of rates of conversion of S0« to sulfate not to the
inquiry of whether the conversion takes place since that has already been
demonstrated. In contrast, independent studies will lead to exploring the
possible significance of processes that have not previously been investigated.
For example, it has been suggested that natural sources of atmospheric sulfur
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compounds, such as emanation of sulfides from swamps or fine particle
sulfate generation from sea surface films, may be more significant than
previously recognized. Atmospheric sulfites need preliminary documenta-
tion and detailed local surveys may be undertaken.
Deposition of particles as a function of size onto biological material
cannot be quantitatively estimated until the mechanisms for deposition
can be elucidated. Independent investigations of such phenomena are likely
to lead to break-throughs in our understanding of the atmospheric chemistry
of sulfur which may have considerable public health and environmental
significance if the record of pollution research over the last few years
can serve as a guide.
The panel believes the role of EPA in the sulfate program should be
to maximize our understanding in depth concerning sulfates and their
effects. This is not readily achieved by monitoring or area wide surveys.
There are already several major national surveys underway to determine the
geographic variations in sulfate concentrations and relationships to
climatic regions of the U. S.
The results of the surveys should be made available to EPA, and if
relationships are found in the survey data that suggest transformation
processes of possible use to control strategy, EPA should seek to study
in greater depth the nature of these processes through the independent
studies program. Therefore, the independent studies and the coordinated
field studies should be linked by careful program management.
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Appendix 2: WET AND DRY REMOVAL PROCESSES (G. Slinn)
The purpose of this section is to list some recommended research in
the areas of wet and dry removal. It is envisioned that the results of
this research will be parameterizations for application in mathematical
models of varying degrees of sophistication. Further, it is envisioned
that two classes of models will be developed: one for application during
air pollution episodes; the other class for estimation of long-term
(e.g., seasonally) averaged doses. Consequently, the recommended
research is similarly classified—i.e., according to the envisioned
application of the results.
A. Application to Long Term Average Dose Calculations
Best available information for the long-term-average atmospheric
residence times for reactive gases and all aerosol particles is based on
measurements and interpretations of radionuclide concentrations. The
results, however, are not definitive to within a factor of 2 or 3. The
results suggest that for reactive gases and aerosol particles, the e-fold
tropospheric residence time in the 30°-60° N latitude zone is between 3
and 10 days.
1. Wet-Dry Network. To improve our knowledge of long-term-
average wet and dry removal in the case of SO and NO compounds, the
A X
most realistic procedure is to use a wet and dry removal network. Such
a network should be established in full coordination with existing and
planned networks with benefit from the knowledge derived from WMO and
European networks. Some features that should be included are:
Routine analysis of weekly samples
Routine analysis of back trajectories (in part to ascertain the
degree of local contamination
Routine simultaneous measurements of air concentrations, wind
speeds and direction, humidity, insolation, precipitation rate
and amount
• Analysis for more than the minimum number of compounds
Network stations completely encircling the Northeastern U. S.
study area (as well, of course, as internal to the SURE network
region)
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• Resolution of the problem: how does dry deposition to a sampler
compare with dry deposition to vegetation?
Rapid dissemination of chemical and trajectory analysis to all
air pollution research organizations in the U.S. Data for each
species at least reported as (1) dry deposition velocity,
v,, = dry flux * 2-m air concentration; (2) wet deposition
velocity, v , = wet flux * 2-m air concentration; (3) washout
ratio, r, = concentration in precipitation * 2-m air concentration.
2. Meteorological Parameterization. In order to use the wet/
dry removal fluxes in long-term-average dose calculations or to estimate
long-term-average residence times, it is essential also to have parameteri-
zations for the heights from which the pollutant is removed. For example,
in the simplest analysis, the dry removal time constant x, = h,/v and the
wet removal time constant T = h /v . In general, h, * h . The dry
www & d w J
removal characteristic height, h,, is typically the height of the mixed
layer; h depends on the pollutant's vertical distribution during precipi-
tation. It would be scientifically desirable to determine h, and h for
each of the network stations, but this probably would be prohibitively
expensive. Instead, it is recommended that a research project be initiated to:
(a) Relate measured vertical profiles of pollutants (using LIDAR,
acoustic radar, aircraft sampling, etc.) to NWS routine radio-
sonde data;
(b) Parameterize the results so that within one year the routine
back trajectory analysis for the network would also routinely
estimate h, and h .
d w
B. Application to Short-Term Episode Dose Calculations
To estimate concentrations of specific pollutants during air pol-
lution episodes, it is envisioned that detailed models of the atmosphere
and of transformation and removal processes will be necessary. Assuming
that there will be at least a two-layer atmospheric model (above and within
a time-dependent mixed layer), then the following research into removal
processes is needed.
1. Dry Deposition
Submicron aerosol particles to realistic surfaces. This
research is urgently needed. There are preliminary suggestions that
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v, for SO, particles to typical vegetation of the northeastern U.S. is
not the 0.1 cm sec that is frequently used, but may be closer to 1 cm
sec . If it is this high, then the concentration profile technique
should reveal it. Other experimental methods are the eddy correlation
technique (measure w'x'') and the measurement of the amount of tracer
(not necessarily SO.) actually deposited. Ideally, all techniques would
be used simultaneously. These studies should be carried out for the
variety of vegetation and surface types that air masses of interest would
contact. This research can proceed immediately without reliance on other
aspects of the program.
Dry Deposition of Gases. Although recent work has vastly
increased our knowledge of dry deposition of gases, most of this work
has been conducted in chambers. Deposition of gases to realistic sur-
faces, including vegetation, and under a variety of conditions [insolation
(including nighttime), soil moisture, pollution levels, plant physiology,
etc.] are needed. Dry deposition of gases to lakes and the ocean are
reasonably well in hand.
2. Wet Deposition
For episodic modelling, more detail is needed about wet
removal of both particles and gases as a function of storm and precipi-
tation type and pollutant physico-chemical properties and vertical
distribution. A series of research programs to evaluate budgets in pro-
gressively more complicated storm systems is recommended for substantial
funding (~$500 K per year) during the next three years. For scientific
and logistic reasons these studies should start with simple orographic
or lake storms, progress to stable frontal storms, finally leading to
connective storms. Budgets (inflow, outflow, and wet removal) of all
measurable pollutants and water should be made. Samples of cloud water
should be obtained and analyzed; changes in chemical speciation, particle
size distributions, and cloud particle nucleation capabilities should be
determined. Tracers and radar should be integral parts of the experi-
mental method.
C. Other Comments
Concern has been expressed about the following points. Although
the comments here are simplistic, their spirit should not go unnoticed.
12
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1. Data Interpretation
As a crude guideline for funding large field projects the
following is suggested:
(a) 20% - experimental design
(b) 20% - field work
(c) 20% - data analysis
(d) 20% - data reporting and archiving
(e) 20% - data interpretation and parameterization.
As an excellent test of the accomplishments of (a) through (d), the
contract for item (e) should be let to an organization separate from the
organization who performed tasks (a) through (d).
2. Program Execution
In A and B above, there is no clear-cut need for huge,
monolithic (Lagrangian) experiments. It is recommended that EPA announce
RFPs to accomplish specific goals within the overall objective and not
overemphasize "Lagrangian" experiments.
3. Resuspension
The implicit assumption is evident that, once deposited,
SOT and N0~ particles (and S0_ and NO gases) are not resuspended back
Q j £• X
into the atmosphere. There is no evidence to substantiate this assumption
and some evidence would conflict. Perhaps the sustained elevation of
S0~ after SO control measures, reflects the resuspension of deposited
sulfate. From this comment it is hoped that two responses are evoked:
(1) Resuspension should be investigated.
(2) The ideas of an individual researcher may be invaluable and should
be encouraged, promoted, and financially assisted.
13
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Appendix 3: PERSPECTIVES ON TRANSFORMATIONS IN THE S CYCLE
(R. Charlson and G. Slinn)
In studying the transformations and removal of compounds of interest,
it seems important to maintain perspectives as to what EPA needs to learn
and why some aspects may rate high priority. Health effects dictate a
focus on the concentration and physical properties of toxic or irritating
substances. Also, health effects imply a need for understanding the degree
of exposure at or near the earth's surface. Control implies a need for
understanding the response of both of these to increases or decreases of a
wide variety of emissions and a need for understanding the transformations
of one molecular form to another (possibly more noxious) form. In turn,
understanding the response of the atmosphere to increase/decrease of emis-
sions requires understanding not only transformations but also sink
processes. Finally, there is growing suspicion that effects such as
corrosion, soil chemistry changes, and climate change may also occur.
These demand still another degree of understanding of the processing of
material through the atmosphere.
Figure 1 is a flow diagram depicting the passage of sulfur compounds
through the atmosphere. The boxes represent identifiable classes of
sulfur species. The triangles represent unidirectional flux into or out
of the boxes. The diamonds represent equilibrium and/or reversible pro-
cesses that can go either way. Effects in the areas of health and those
related to ecological effects and climate are listed.
The overall goal of the program is to develop an understanding of
this, the NO , and other related cycles, well enough to be able to model
A
the effects in terms of inputs to the system. This goal in turn indi-
cates that we need to understand:
(1) the fluxes into and out of each box as a function of space
and time
(2) the rates of conversion from one species to another
(3) the resulting molecular forms of SO and NO
X X
(4) the concentrations as functions of time and space
(5) the burdens of material in the atmosphere reservoir as a func-
tion of time.
14
-------
Given this complexity in just the atmospheric sulfur cycle, and given
the existence of other cycles (e.g., NO ) with which this cycle interacts,
X
it is becoming increasing obvious that it is necessary to integrate the
study of transformation and removal processes into a single, internally
consistent picture. This requirement of integration poses constraints on
the approach to measurement, data analysis, and modeling. It also suggests
that the data from the other major studies (RAPS, MAP3S, SURE, etc.) will
eventually be integrated into a single picture. There is clearly a need
for careful planning of the administration and coordination of the EPA
project in order to assure communication between the various studies of
transformation and removal processes. There is also a need for coordina-
tion between the various agencies (EPA, ERDA, EPRI, etc.) in order to
optimize the transfer of information. This might be enhanced with the aid
of an external advisory committee that interacts with all of the projects.
15
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EFFECTS
-<
so2,
RSH,
H2S,
R2S, etc.
Gaseous
Aerosol
Precursors
H2SO,, (NH,)2SO,
NH4HS04, etc.
-------
REPORT OF WORKING GROUP ON MEASUREMENTS
Participants:
Don Blumenthal
Shepard Burton
Roy Evans
Thomas Hartlage
Walter J. Saucier*
Fred Shair
Robert Stevens
Dennis Thomson
Kenneth Whitby*
*Chairman
^Interlocutor
17
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REPORT OF WORKING GROUP ON MEASUREMENTS
I. INTRODUCTION
These recommendations are made considering the stated limitations on
time, money, space, number of investigators, number of institutions and
number of kinds of measurements to be made.
II. GENERAL POLICY
To obtain rapid feedback throughout all aspects of the program, the
planning, execution, data collection, preliminary analysis of results and
modeling should be done on a yearly cycle or basis. This means having
mini-computer facilities on or in each field vehicle or platform and doing
the data reduction and analysis on site immediately following data collection.
Complete crews of chemists, physicists, meteorologists, modelers, and
instrument specialists would be attached to each vehicle or platform for
4- to 6-week periods to work up older data while waiting for the first
field episode call. These crews would be available for immediate response
to that field episode call and would be used to work up the data collected
on that call while waiting for the next one, etc.
To the maximum extent possible there should be continuity of management
within each of the above crews or teams, and of overall management and
coordination of all crews or teams.
Both within the crews and overall in the program there should be
equal input and balance from all instrumentation, operational, and data analysis
disciplines and functions rather than dominance, by any one such discipline
or function.
There should be a strong overall operational headquarters for the
program as well as a strong advisory group. The latter should comprise, at
least, ERDA, NOAA, and EPRI representatives and individual chemists,
physicists, and meteorologists.
Since the scale of the program will be greater in terms of distances
and times than RAPS I, the principal emphasis of RAPS I on fixed measuring
stations must be replaced by a principal emphasis on mobile measuring plat-
forms, ground and aerial. Although some fixed ground-based stations will
still be needed, it is not recommended that new ones be added. Rather,
existing ones should be used and these should be used mainly for quality
18
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assurance of the measurements made from mobile stations. Some stations in
the existing networks may need to be equipped with supplementary instrumen-
tation for this purpose.
The bulk of the work should be performed from mobile platforms by
organizations and groups already operational at the time the study is funded.
There are now sufficient experienced and well equipped groups with ground
or aerial based mobile platforms so that few new ones will be needed to
conduct the program. Most measurements from mobile platforms would have
to be done from aircraft. Two or three air quality aircraft will be needed
for chemistry measurements and a LIDAR aircraft will be necessary for both
regional mapping of mixing depths and plume geometry, and for nighttime
plume mechanistic studies. There needs to be further development of the
airborne instruments to permit measurements to be made at altitudes up to
10,000 ft. For the most part existing aircraft dedicated to airborne
measurement can be used; however, it is conceivable that circumstances may
make it feasible to develop a specialized aircraft dedicated to this project.
In general the program should be considered as consisting of two
separate sets of experiments—one set at the "plume" scale of 5 to 200 km
and the other at the "regional" scale of 200 to 2000 km. Resources and
techniques are.not yet available to conduct "plume" studies much beyond
200 km. Although "plume" and "regional" perhaps can be considered separately
from the point of view of their chemistry, physics, and modeling requirements,
they have common problems of data handling and quality assurance.
III. DATA HANDLING
Individual investigators and contractors should be responsible for
data compression and delivery of data in industry standard 9-track tape
formats within 3 months of the end of each intensive field program. To
accomplish this they should whenever possible continuously record data and
other system electrical signals, process them on site within 24 hours,
reduce them within days or weeks to be sure they are valid before compression
onto tape for final delivery. Data should be in engineering units; tapes
should contain the equations and constants needed for conversion. Validation
or evaluation criteria should accompany the tapes or be on them and
the investigator should provide a statement of the uncertainties associated
with his data and the effect of such uncertainties on the data validity.
19
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As far as possible computer programing and debugging should be done prior
to the field studies.
IV. DATA QUALITY ASSURANCE
There needs to be a screening and selection policy before the initia-
tion of the experimental program to select the best appropriate analytical
methods, instruments, calibration procedures, and instrument operations
procedures. The individual experimenters and contractors should be
required to report the uncertainties in their data and their analysis and
evaluation of these uncertainties. Checkout calibration of all mobile and
fixed facilities should be done at either a well-instrumented fixed station
or ground-based mobile laboratory especially equipped for this purpose.
V. INSTRUMENTATION—GENERAL
Whenever possible, batch sampling should be replaced by continuous
measuring techniques for the program. The goal should be to have the
capability of analyzing a sample at least once every five minutes through-
out the field study. The main core of instruments and technology should
be those that have demonstrated applicability for field studies on the
type of platform on which they are intended to operate. They should be
available for purchase at least 18 months prior to the time of their
operational use. There is, however, a category of special purpose instru-
ments vital to the success of the project that are still in the developmental
stage. A crash developmental program must be started now to accelerate the
development of these few critical instruments. The most important ones in
this category are a continuous, real-time instrument (1-sec. to 10-min.
response time) for determining total sulfur in particles and continuous
real-time instruments for measuring sulfuric acid, nitric acid, and ammonia.
All aerosol sampling methods should be size selective. The fine
aerosol (less than 2 ym) should be separated from the coarse aerosol.
Airborne instruments need measure only the fines for most studies, but
ground-based stations should measure both fine and coarse particles.
Several components that we believe should be measured, at least on a
limited basis, during airborne traverses will necessarily depend upon gas
chromatography. There needs to be development and checkout of appropriate
gas chromatographs that can operate successfully and with ease under
20
-------
conditions of variable (reduced) pressure and temperature; these systems
must be able to be placed in medium to small aircraft.
Airborne gas chromatography technology needs development for the
following atmospheric components:
1) NH_ (needs the sensitivity improved to at least 0.5 ppb)
2) Hydrocarbons (the nonmethane hydrocarbons including aldehydes
should be emphasized)
3) H S and CH_ (SH) (needs development)
£ «J X
4) PAN (needs some development)
5) Tracers (need check-out with multiple tracers).
Tracer experiments need to be performed in order to separate the
dilution associated with the transport of the pollutants in determining
aerosol formation rates, reaction rates, and deposition rates.
An alternative to airborne gas chromatography is an improved version
of a sequential sampler and a container that will not alter the character-
istics of the sample.
IV. INSTRUMENTATION—SPECIAL
A. Tetroons
Tetroons will be useful for plume-scale experiments up to 100 to
200 km; applications for trajectories up to regional scale may be feasible,
but this should be verified.
While the Working Group does not recommend the establishment of a
large tetroon-tracking or other major hardware facility as a fixed part
of this program, one or more experiments utilizing these techniques may
be necessary.
B. LIDARs and Acoustical Sounders
The Working Group believes that all main line instruments that
require significant funding or effort for deployment should be quantitative.
The LIDAR currently is not a quantitative instrument for .particulate mass,
but possibly could be made so with 'additional investigative work. Addi-
tional work is recommended to make LIDAR quantitative so that its signals
can be compared with aircraft particulate measurements. An aircraft plat-
form equipped with LIDAR and possibly other long-path air quality devices
should be included in the program for regional mapping of mixing depths.
This facility should be supplemented by as large as possible a network of
21
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continuously recording acoustic sounders for continuous records of diurnal
variations in mixing depth. The aircraft LIDAR and ground-based acoustic
sounders are complementary when equipped with complete operational data
recording systems to obtain position, time, and beam power normalization
data.
C. Satellite Data
Satellite imagery is and will be available from the SMS and LANSAT
satellites at low cost and would add significantly to the total data base.
Such imagery will give continuous knowledge of large regional weather systems.
The satellite data for cloud coverage, back scatter, and haze should be
correlated with the SO, measurements from ground level data (obtained from
networks such as the SURE network). The synthesis of existing data (which
will be and is already available) should be the prime consideration of our
long range studies.
D. Meteorological Measurements
1. Regional Scale
a. Employ as primary data base existing and ongoing
1) Synoptic data
2) SMS and Landsat-Satellite data
3) Air pollution-related parameters derived from network
data (e.g., visibility)
b. Obtain supplemental data from
1) Existing (or planned) special purpose networks such
as SURE and TVA
2) A few selected aircraft missions designed to assess
the characteristics of urban to mesoscale anomolies
observed within the multistate "blob" regions.
2. Plume Scale
a. Restrict observations to 5-200-km scale during "steady
state" conditions in either fully developed daytime planetary
boundary layers or at night at flight levels (effective and
safe) above the maximum depth of the nocturnal surface
inversion. Neither the morning nor early evening transition
periods in the planetary boundary layer are sufficiently
well understood (nor can be monitored temporally or
22
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spatially in sufficient detail) to enable optimally
designed chemical transition studies.
b. Limit aircraft meteorological observations to high
quality static parameters and wind measurements, and
total downward component of UV and solar radiation
(daytime).
c. Supplement airborne measurements with baseline surface
observations of the aircraft-measured parameters and
employ on a continuous basis a system (such as SONAR
or LIDAR) for mixing height determination.
d. Employ a combination of double theodolite and tetroon
measurements for precise determination of the vertical
profile of hotizontal wind at one or more locations in
the plume region.
e. Design plume sampling flight patterns to insure adequate
definition of fine scale plume structure (as opposed to
mean properties normally associated with Gaussian plume
models).
E. Organic Aerosol
Some concern exists about the possible influence of aerosol
particles on radiation climate. In turn, such effects are suspected as a
»
cause of decreasing agricultural production. Measurements of radiation
(direct, global, and/or diffuse) are useful, both in aircraft and at ground
stations. Simultaneous samples on membrane filters can be taken to assess
the light absorption in particle scattering (Reference—Lin, Appl. Optics
ca. 1973 Nephelormetric Light). Backscatter determined simultaneously
will allow determination of the actual role of particles in modifying
radiation and radiative climate (Reference—Bolin and Charlson, Ambio,
Royal Swedish Academy of Science, April 1976).
23
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VII.
1.
2.
AVAILABLE AIRBORNE PLATFORMS FOR AIR POLLUTION RESEARCH*
Plane Custodian Purpose Instrumentation Cost
Electra
B26
3. B26
4. C45
5. B26
6. C45
7. Queen Air
8. Queen Air
9. 2 Queen Air
10. Saberliner
NCAR
U. of Wash.
Desert Research
Institute
Desert Research
EPA EMSL-
Las Vegas
EPA EMSL-L.V.
U. of Wyoming
CSU
NCAR
NCAR
Long Range* General Computer, anything
Med. Aerosol &
Cloud Physics
Med Size-Long
Range* Sensible
Heat Flux Measure-
ments
Small Size-Med. Range
Air Pollution
Med Size-Long
Range* Air Pol.
Med Size-Long
Range* LIDAR
Med-Long Range*
LIDAR
Med-Range
Aerosol-Cloud Phys.
Med Range,Med Size
Cloud Physics
Med Size-Med Range
High altitude
Tape Data
Acquisition System
Nearly anything
Computer, Inertial
Navigation
DAS-Distance
Measurement Equip.
Dual DME
Computer
Computer
Computer
Computer
Computer
$3000
$ 500
1000
500
200
90
400
400
400
800
This listing is not complete. Additional aircraft are probably available
from NCAR, and several commercial research organizations have planes that
would be suitable.
24
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VIII. STATUS OF INSTRUMENTATION FOR AIRBORNE GAS INSTRUMENTS
Gases
Priority Gas
..Hardware Status
Sensitivity
1
1
1
1
3
3
1
2
1
3
SO. Yes
N0» Yes
HC No continuous instr.
• Problem area — needs
airborne GC
03 OK
OH No
CH_(SH) No
CO Yes
Tracers Yes batch
No continuous
Aldehydes No
PAN Yes
NH_ Yes
H0S No
Needs dev. (to 0.1 ppb sensi
Needs dev. (need full scale
0 to 10 ppb)
Needs dev. into continuous
instr.
OK
Needs GC dev.
OK
OK
?
Some dev.
Needs more dev.
Needs GC dev.
25
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IX. STATUS OF INSTRUMENTATION FOR AIRBORNE, PHYSICAL MEASUREMENT AND
SAMPLING OF AEROSOLS
Priority
Instrument or Parameter
Hardware
Sensitivity
Characterization — in situ
1
2
2
1
3
Aitken Nuclei
Cloud Condensation Nuclei
Ice Nuclei
Nephelometer
Aerosol Charge
OK
OK
OK
OK
OK
OK
OK
OK
OK
OK
Size Distribution — in situ
1
1
3
3
Isokinetic
1
2
Collection
1
2
EAA 0.005-1
OPC 0.4-10
OPC 6-30
Water Drops
Sampling
D < 6 urn
P
D > 6 vm
P
Size Differential
Impactors
OK
OK
OK
OK
*
OK
Needs dev.
OK
OK
OK
OK
Needs dev.
OK
Could be im
OK
Many arrangements of filters or impactors might be used. However, most
devices are too large and require too much power and thus are difficult
to adapt to small aircraft. The TWOMASS (^wo-stage £n-line niass monitor
with Aerosol ^ize ^eparator) shows promise for size separation.
26
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X. STATUS OF INSTRUMENTATION FOR AIRBORNE AEROSOL CHEMICAL SAMPLING AND
MEASUREMENT
Priority
Technique
Hardware
Sensitivity
1 H SO
^ "T
1 NH SO )
4 41
3 HN03 )
1 NH , SO, \
CL U
^ *T
1 (M)S04
1 (M) SO,
X
1 (M) S J
A /
ft
1 H+
0
Samples yes 0.1-10 pg/m
Possible
Analysis
for 10-min.
sampling
dev.
of species at
present can be performed
on time-integrated samples.
30-min. integration times
required
nology at
above 1 y
with present tech-
concentrations
g/m3.
1 Cont. total Under dev. OK, 1 yg/m
sulfur
Probably
1 Intermit. Prototype
sulfate
by 1/77
available
3
available 1 yg/m /10 min
1-2
FPD total sulfur Yes
OK
2-3
NO,
Not available
2-3 NO (solid)
Not available
Elements
Will get from XFL
OK
Organic
Special experiments
The development of a package for speciation is of very high priority
and needs to be started as soon as possible.
27
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XI. STATUS OF INSTRUMENTATION FOR INDIRECT OR REMOTE
Priority Parameter Technique Ranging Airborne
MEASUREMENT TECHNIQUES
Remarks
1
3
Particles LIDAR
SO,
S0r
NO,
CO
Mixing
Depth
Wind
Speed
Differential
absorption
Laser Method
Differential
absorption
Laser method
COSPEC
COSPEC
Gas-cell
Correlation
Spectrometer
Acoustic
Sounder
Doppler
Acoustic
Sounder
Wind
Direction
Turbulence
Yes
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No .
Useful for regional mapping
of mixing depth; possibly
useful in mechanistic or
close-in plume chemistry
studies; not presently
quantitative for parti-
culate mass measurements;
more work is needed to
make the instrument a
quantitative tool
Prototype under test;
operational status
expected in 1977.
Prototype testing to begin
in 1978; may be operational
in 1979.
Instrument useful only in
up-looking mode; can be
flown at low altitudes
for special applications
Same as above
NASA instrument operational
Operational instruments are
obtainable at $50k
28
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XII. AIRBORNE WISH LIST TAKING INTO ACCOUNT PROBABLE AVAILABILITY AND HIGH PRIORITY
Parameter
so2
NO
X
°3
CO
Continuous aerosol
S or sulfate
Nephelometer
EAA
OPC D < 6
P
OPC D > 6 '
P
HC
CNC
Continuous H SO
S speciation
Tracer gases
Aerosol samples
METEOROLOGICAL
Temperature
Dew point
Altitude
Turbulence
Position
Wind speed
Wind direction
UV — up looking
BBR — up looking
IR — up looking
Priority
1
1
1
3
1
1
2
2
3
2
2
1
1
2
1
1
1
1
2
1
1
1
2
2
3
Development Needed
need 1 ppb sensitivity.
solve altitude vs. sensitivity problems.
OK
OK
prototype development
OK
OK~altitude validation
OK
need development.
dev. GC if possible; dev. bag if necessary
altitude validation
Prototype exists — needs development
under development — some species available
development needed
some OK — some needed.
OK
OK
OK
OK
OK
+5 knots
OK
OK
OK
29
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REPORT OF WORKING GROUP ON TRANSPORT AND DISPERSION
Participants:
Ray Dickson
Harry L. Hamilton, Jr."1"
William Kellogg
Michael MacCracken
Elliot Montroll
Larry Niemeyer
Donal Pack*
Fran Pooler
*Chairman
^Interlocutor
30
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TRANSPORT AND DISPERSION WORKING GROUP REPORT
I. INTRODUCTION
Integral to the study of the relations between emissions of material to
the air and the resulting concentrations of pollutants downwind is the
transport history of .the air "parcels." This history should include
documentation of the often tortuous paths typical of a three-dimensional
turbulent fluid, the concomitant changes in moisture content, temperature,
and the rates and mechanisms by which the atmosphere dilutes the pollutants
en route. The purpose of the following sections is to recommend methods of
acquiring the required atmospheric information at time and space scales
relevant to the workshop objectives of "studies to relate the form and
level of ambient sulfate and nitrate to their natural and anthropogenic
precursors."
We define "transport" in the present context as the horizontal movement
of the air containing pollutants together with an approximation of the
change in vertical position of major polluted layers, or slabs of air.
As a practical matter, however, an individual "parcel" of air containing
pollutants cannot be identified after traveling several hundreds of kilo-
meters, because it is mixed with the surrounding air by a combination of
wind shear and turbulent eddies, the process that we will refer to as
"dispersion."
Dispersion has a distinct character during the daytime when the lower
levels of the atmosphere are usually heated and convective mixing takes
place from the surface up to a stable inversion layer, sometimes referred
to as "the lid" of the mixed layer. At night, on the other hand, the
convective mixing tends to die out, the atmosphere becomes stratified, and
pollutants tend to remain in the strata into which they were introduced.
The following day these strata are once again vertically mixed.
These considerations have led us to believe that field studies of
the transport and dispersion of pollutants should be made under several
well defined conditions: a steady wind, well-mixed daytime situation;
a nighttime situation; a stagnation episode; a precipitating air mass—
all of these over limited areas (probably under 200 M) before dispersion
has made it impossible to identify the plume from a given source, whether
a city or a power plant.
31
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At the other end of the scale is the regional pollution problem, in
which individual plumes cannot be identified and the resultant level of
contamination has to be considered as a statistical aggregate of all the
sources, transformations, and removal processes operating on the air
masses. We will therefore emphasize the distinction between plume studies
and regional pollution studies in the following sections.
II. EXPERIMENTAL SITUATIONS
We are recommending that there be two types of information collection.
One is a continuous measurement-analysis program using existing meteorological
data and existing augmented surface concentration data. The second program
is an augmented measurement program in direct support of the "intensive"
field program and is designed to test transport and diffusion models that
can then operate on the routinely available meteorology-concentration data
systems.
A. Sulfate-Weather Interactions
We believe that the studies to date have already shown sufficient
relationships between sulfate concentrations and weather parameters that
the field data collection program should be designed to operate during
periods representative of a wide range of meteorological variables.
Data collection would be in two modes. Data on emissions, transport,
and concentrations collected in a routine, continuous mode could be
analyzed to describe the effects of air mass type, temperature, moisture,
etc. The second mode would operate during the intensive field program
periods. For these periods we recommend the programs be conducted during
the following types of weather patterns:
1. Stagnation (or "episode") conditions. These situations apparently
lead to the highest observed sulfate levels and are therefore of primary
concern. They are also usually periods of maximum (for the season) solar
radiation, high temperature and relatively high humidity. From an operational
standpoint the light winds and clear skies facilitate aircraft use. However,
these conditions are just those where classical transport-diffusion models
are not really applicable, hence the need for increased observations
to assist in model development and data interpretation.
2. "Steady wind" conditions. This type of situation is conducive to
coherence of the "plumes" from cities and major sources and thus extends the
32
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capability for tracking and measuring plumes and controlled tracer releases
to maximum distances. It is also the situation when the existing short
range diffusion models are most applicable and capable of (empirical)
extension to 100-200 kilometers. Experiments conducted during such
situations would be especially amenable to developing and testing chemical
transformation mechanisms and models.
3. Large area rain conditions. This type of situation could be
obtained during a pre-warm frontal rain period. The rain area should
cover 200-300 kilometers in the direction of motion of the system and
300-1000 kilometers in lateral extent. It can be expected that there will
be multiple cloud layers, high humidities and, quite often, marked wind
direction and speed shear in the vertical. The purpose of conducting
intensive studies during this period is to examine the opposite of the
stagnation episode, specifically the role of a high liquid water content
atmosphere on pollutant transformations. However, such a situation makes
aircraft operations difficult and completely rules out tetroon support.
We therefore give a lower priority to this type experiment.
In addition to the synoptic pattern "scheduling" we belive it to be
important to schedule the intensive study periods in different seasons of
the year to obtain the detailed chemical transformation data during periods
of warm/cold temperatures, vegetated/bare ground cover, high/low radiation
levels, etc. It would be desirable to examine all four seasons to incor-
porate the full range of biotic activity and meteorological parameters.
However, the time frame and resources schedule may dictate making measure-
ments in two seasons only. If this is the case, we recommend choosing the
two seasonal extremes—winter and late summer.
Notice that the specified synoptic patterns could occur in any season
of the year. Thus, by recommending seasonal rescheduling we are not necessarily
adding to the total number of intensive study periods. Also, all studies
should be made at the same geographic location to provide a common base for
comparison.
B. Geographical Locations
The proposed program area has been specified by EPA staff to be
about the same as that chosen for the SURE. There are obvious reasons why,
within this general area, the intensive period programs might be concentrated
33
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in areas where past monitoring data have shown the highest sulfate levels
(Virginia-West Virginia, thence north-northeast to New York).
However, these highest concentrations occur over the most irregular
terrain of the eastern U. S. We believe that the theoretical and practical
difficulties introduced by this terrain variability off-set any advantage
gained from observing in this area. In addition, each mountainous terrain
location will have its own wind patterns and diffusion regimes and thus
prevent any useful generalization from experimental diffusion work. It
would appear that these uncertainties could inhibit development of generalized
transformation and removal submodels.
We therefore recommend the first intensive studies be conducted over
selected uncomplicated terrain with a history of moderate to high SCL/SO,
concentrations. Based on limited information, the area from about St. Louis,
Missouri, to near Wheeling, West Virginia, has many of the above requirements.
We suggest that a climatological study of the area from the Mississippi
River to near the Atlantic seaboard be made quickly (i.e., before January 1977)
The study should determine the frequency of stagnations in various areas, the
frequency of polar and tropical air masses, wind steadiness, trajectory
distributions versus seasons, etc., for use in the regional studies to be
discussed in Section III, Regional Transport.
IIP. REGIONAL TRANSPORT
At distances of up to 2000 km, the horizontal spread of a plume from a
point or area source will be more dependent on the effects of wind shear and
large scale horizontal divergence and convergence than on turbulent diffusion.
The vertical distribution ordinarily will be determined by daytime mixing
due to convection. Furthermore, the composition of the plume probably will
be altered drastically as it passes over emission sources downwind from
its origin. Accordingly, on this scale, no attempt will be made to deter-
mine the pollutant concentration reduction resulting from turbulent dispersion.
Rather, the intent will be to determine the horizontal extent of the pollutant
downwind in a statistical way.
The proposed analysis techniques—namely, post analysis using available
meteorological data—may make difficult the extension of the study of
regional transport over the Appalachian Mountain range. Available data are
inadequate to permit an estimation of detailed meteorological transport over
this complex terrain. This limits the scale of the transport experiment.
34
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The effects of meteorological processes on the plume will be estimated
from analyses of routinely collected NWS weather data. We recommend that
the routine NWS rawindsonde data be supplemented by intermediate (06 andlSZ)
upper air (to 400 mb) observations from the approximately 20 existing
rawindsonde sites.
To estimate the effects of the wind shear indicated by the meteorological
analyses, knowledge of the mixing depth and its variations during the travel
of the pollutant must be available. For this a downward-looking LIDAR
equipped airplane is proposed. This airplane would make traverses across
the selected region (approximately 2000 km) recording the depth of the
mixed layer as indicated by LIDAR return. Initially flight paths of the
airplane would be selected to pass over rawinsonde observation stations to
provide correlations between the mixing height determined by LIDAR and by
atmospheric temperature stratification. Subsequently the flight paths
would be directed between rawinsonde stations to increase the density of
observation points.
The use of transponder-equipped, super-pressure ballons (Tetroons) that
will fly at preselected atmospheric density levels may be useful for identifying
the trajectories on a regional scale. Consideration of available techniques
for tracking these tetroons suggests that use of the Random Access Measurement
System (RAMS) is the most practical. This system is available with Nimbus 6,
a polar orbiting meteorological satellite. A follow-on RAMS will be on
Tiros-N, to be launched in 1978. The satellite identifies the location of
a regularly transmitted pulse from the platform, stores it, and then transmits
the data to an existing receiving station. Because of the polar orbit, the
position is determined only twice per 24-hour period. Up to six hours may
be required to receive the reduced data from the Goddard Space Flight Center.
Nothing precludes the following of a tetroon by the RAMS system for the life-
time of the tetroon. We recommend that the RAMS-located tetroons be flown
on a limited number of occasions selected on the basis of the meteorological
conditions.*
*Alternative systems for tracking tetroons for regional trajectory determination
include ground-based, modified tracking radars that can be used for distances
up about 50 km. With mobile units (available) using leap-frog procedures; two
units can follow a tetroon for, say, 18 hours.
Airborne radar (also modified) can also be used. Because of mobility this
mode of tracking appears to provide considerable benefit over the mobile ground-
based mode, and accuracy of derived balloon location data appears adequate for
the long range transport problem. However, neither of these latter two methods
appears to be as effective as the RAMS technique.
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IV. SOURCE DISPERSION AND TRANSFORMATIONS
A. Purpose
Meteorological data and analyses are required to identify and
define the "chamber" within which the pollutants constituting the plumes
from both urban areas and large isolated sources mix and react. Studies
of these processes must be performed in a Lagrangian framework—i.e., the
mass of air into which pollutants are emitted should be followed as it
moves from the source.
B. Scales
Since it is desired to study dispersion and transformation pro-
cesses within a system having known inputs and limits, the temporal and
spatial scales are limited by the ability to identify the source(s) of
pollutants to be studied, together with the ability to identify the plume
from a given source as it mixes with plumes from other sources to become
a nondistinguishable component of a regional pollutant mass. These
limits thus put an upper bound of. about 200 km on the spatial scale of
such studies. The corresponding temporal scale is about half a day,
although there will of course be experimental opportunities to occa-
sionally sample a parcel through a full diurnal cycle.
C. Tracers
1. Tracer selection. Extensive use of atmospheric gaseous
tracers is expected to aid in identifying the plume segments under study
as well as aid in quantifying dispersion rates. Tracers that might be
used fall into two categories: controlled tracers and tracers of opportunity.
Controlled tracers considered are listed as follows:
C6F12 CFCL3 (F-ll)
CF2Br2 (12B2)* CF2CL
C2F4Br2 (114B2) CF3Br
SF, Heavy methanes
Of these, only 12B2, 114B2, and SF, are presently considered to be suit-
/ b
able for use over the scales contemplated. The others are not tracers of
choice for various reasons: cost, availability, analytic problems, etc.
*not manufactured in U.S.
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Tracers of opportunity are those generally, although not uniquely,
associated with the concentration of human activities within an urban area
and are possible candidates for identification of the "urban" plume.
These are:
CO C2C14
CFC13 C2H2
CC1, Aitken nuclei
C2H3C13
Whatever tracer may be selected, background surveys including sampling
as required should be performed to identify sources of the tracer that
might exist in the area to be sampled as well as in a limited upwind sector
to ensure that the results of tracer experiments are not distorted by an
unsuspected source.
While relative concentrations of tracers of opportunity may provide good
indicator data, use of controlled tracers requires knowledge of true concen-
trations. Thus, it is important that all aspects of a tracer system be
thoroughly checked, and sources of bias, error, interference, or whatever,
be identified and if possible eliminated, by comparisons and cross-calibrations
with other sampling and analytic devices and systems.
2. Experimental configurations. The information to be gained through
use of atmospheric tracers determines the tracer source configuration as well
as the sampling mode and locations. To maximize the information to be gained
by use of tracers, in view of the cost of a tracer experiment, dual or
triple tracer releases should be carried out. The information gained by a
dual release for instance is greater by perhaps a factor of four over that
obtained by a single tracer release.
The uses to be made of tracer releases fall into four categories: 1). to
aid in mass flux determinations; 2) to determine the patterns and rates
of vertical dispersion, at least out to the distance at which effluents
become approximately uniform in concentration through the depth of the
boundary layer—multiple tracer releases can define the vertical dispersion
for as many injection altitudes as there are tracers employed; 3) to aid
in locating and identifying the plume from a single source by means of
addition of tracer to the effluent from that source (such releases not
only define the geometry of the effluent plume downwind, but also provide
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a standard by which the chemically active material depletion or accumulation
may be quantified); 4) to describe the transport and dispersion of pollutants
within and through different stability layers that occur near the ground
during the nocturnal period. The use of tracer releases at appropriate times,
relative to daytime-nighttime transition periods, will help quantify the
variation in mixing depth, and pollutant dispersion with the onset of night-
time stability or daytime instability.
D. Support Measurements and Sampling Vehicles
A variety of other measurements will be required in carrying out
plume studies. Tetroons provide a single parcel identifier of the location
of a diffusing mass, and with fixed, ground-based radar tracking could be
followed usually out to distances of 80 Ism. Small development of an air-
borne tracking capability would extend this range to the expected limit of
about 200 km for a given experiment.
The METRAC system could be used to provide very accurate wind profiles,
as well as provide tracking of tetroons. While the range of this system
is limited by the line of sight requirement between balloon and receivers,
a capability to obtain data over about a 40 km radius-, appears probable with
the present system.
To provide wind profile data at the location of the plume segment being
sampled, crews should be assigned to obtain PIBAL observations, with one
crew leap-frogging ahead of another, thus obtaining a suitable space/time
density of observations to characterize the wind profiles and wind shear
along the sampling path.
LIDAR observations should be an integral part of plume studies. A
ground-based system, operating either in a fixed or mobile mode, can
define both the depth of the (aerosol) mixing layer, and under suitable
circumstances, provide a measure of plume geometry in the vicinity of the
source. Airborne LIDAR systems extend this capability to the limits of
plume detectability, which at the present time is perhaps 100 km or more
for a major source.
The sampling platforms required to provide support for plume tracer
studies should be the same as used for plume sampling when feasible.
However, because the sampling times and height intervals at which sampling
is to be performed in tracer measurements are by no means identical with
those that optimize chemical constituent sampling, it will often be more
38
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practical to utilize several small aircraft for such specialized sampling
operations. In addition, release of tracers at specified locations within
the range of heights encompassed by the boundary layer will generally
require aircraft dedicated to tracer sampling. Thus, use of a number of
of small aircraft instrumented for very limited purposes should be included
in developing operational plans for plume studies. The dedicated aircraft
that will be sampling chemical constituents and small aircraft that are
ancilliary to the dedicated aircraft should have wind finding equip-
ment.
V. SUPPORTING DATA
Certain observations of a meteorological nature may be required for
chemical interpretation of collected data, for modeling, or for estimation
of effects other than ambient air concentrations of sulfates or other
pollutants—e.g., acid rain. Some analyses that might prove useful are
made on a routine basis at the present time and some data are routinely
collected and archived without analyses. Among these are:
Nephanalysis. This is a plan position analysis of each layer of
clouds derived from synoptic weather observations and satellite observa-
tions that is prepared daily by the USAF Global Weather Central.
Precipitation. Hourly precipitation amounts are recorded at all first
order National Weather Service Stations; 24 hour amounts from numerous (at
least one per county) cooperative stations are recorded. These data are
archived and available, post facto, from the National Climatic Center,
Asheville, N. C.
Weather radars at first order National Weather Service Stations offer
a source of precipitation area coverage data for a major portion of the
region of concern. Arrangements to obtain periodic scope photographs should
be possible or telecommunicated video presentations (in less detail than
photographs) are available. Plans are under way to prepare a digitized
map of range-adjusted radar return for the United States for periodic daily
transmission. This, if available for this program, will be useful in deter-
mining precipitation patterns.
Derived data. The National Meteorological Center currently derives
many variables from routinely observed data. Among these are charts of
vertical motion at several heights derived from horizontal divergence,
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local winds for numerous stations, and three-dimensional trajectories
from various locations.
The usefulness of these data must be investigated and, in addition,
an inventory of all intermediate and final outputs of the NMC analyses
must be obtained in order that their usefulness and application to this
study may be evaluated
Radiation. The limited solar radiation measurements currently obtained
should be augmented by a network that will furnish such data continuously
from a few selected locations in the region under study. At a minimum,
total hemispheric solar radiation should be measured at about 20 sites.
It would be preferable to measure more precisely the actinic component
responsible for the initiation of photochemical reactions, as well as
measure the depletion of both total hemispheric and direct solar beam
radiation at selected wave band intervals. To support plume studies,
particularly during the seasons when photochemical reactions must of
necessity be considered, special nonroutine measurements of global actinic
irradiance should be incorporated in the measurement program.
VI. SUMMARY RECOMMENDATIONS FOR ADDITIONAL MEASUREMENTS
Throughout the Working Group's report we have incorporated suggestions
for the design and conduct of the regional experiments. However, because
of their importance we list those recommendations requiring additional
measurements.
1. Augmentation of rawinsonde observations to 4 per day at the
(approximately) 20 existing National Weather Service stations within
the region.
2. Deploy and track, via the RAMS satellite locator system, tetroons
to determine regional trajectories.
3. Deploy and track, using ground-based and airborne radar systems,
tetroons to support plume studies.
4. Utilize airborne LIDAR to obtain regional mapping of the height
of the mixed layer. Also, separately use this system to observe the spread
of plumes.
5. Utilize multiple gaseous tracers to determine atmospheric dilution
on a scale of up to 200 km.
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6. Utilize special dedicated aircraft for tracer sampling.
7. Equip all aircraft with wind finding systems.
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REPORT OF WORKING GROUP ON DATA MANAGEMENT AND MODELING
Participants:
Ken Demerjian
Allen Eschenroeder
James Fay
Charles Hakkarinen
Rudolf Husar
Warren Johnson
George SI inn
John Trijonis
Fred M. Vukovicht
William Wilson
*Chairman
tlnterlocutor
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DATA MANAGEMENT AND MODELING
I. SUMMARY AND RECOMMENDATIONS
The overall objective that was adopted by the Working Group on Data
Management and Modeling as a focus for its deliberation is as follows:
To identify and recommend studies required in order to develop, by 1980,
objective, quantitative methods of relating changes in ambient sulfate
concentrations to changes in precursor emissions. In accordance with the
judgement of the Working Group, this statement presupposes that the only
effective and defensible way of developing control strategies that may
eventually be needed for sulfates is through the use of quantitative
methods, or in other words, air quality simulation (AQS) models.
In the broadest sense, AQS models can be characterized as quanti-
tative methods for calculating (or "predicting") air pollutant concentrations
given information about emissions, meteorology, and other geophysical
conditions. The Working Group's consideration of models covered all
available types—from those that are purely empirical to those that are
almost completely based upon principles of physics and chemistry. The
latter type, which is sometimes called "deterministic," is termed as
"metrochemical" in this report.
Given that suitable models are considered to be one of the necessary
endproducts of the STATE Program, it follows that the planning of STATE
must assume:
1) that appropriate model adaptation efforts are initiated and
carried forward to the point where suitable models are avail-
able for testing at the time that data and scientific results
from the field program become available, and
. 2) that suitable data and scientific results from properly
designed field programs are available in time to test and
evaluate the models adapted for application to the sulfate
management problem.
The models thus are intended to serve as a convenient framework into
which the scientific results from the field programs can be integrated
*For brevity, "AQS Models" in this report will henceforth be termed simply
as "models."
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for the purposes of interpreting and applying the results. It is
recognized by the Working Group that the body of scientific results
from field programs in itself can be considered as a useful endproduct.
However, we feel that these results, while desirable and necessary, are
not sufficient, in the absence of suitable models, to meet the anticipated
needs of EPA in developing sulfate control strategies.
Some of the more important findings of the Working Group in terms
of recommendations, conclusions and judgements are listed below:
Two types of models are required for STATE: Diagnostic-type
models are needed for use in designing and understanding the
results from the field studies. Planning-type models are
needed for use in the development of sulfate control strategies.
Real-time (episode-type) models which require that future
meteorological conditions be predicted are not required for
the STATE Program.
The main (but not only) application of diagnostic models will
be to single-source (plume) situations, while the main appli-
cation of planning models will be to multiple-source (regional)
situations.
The following scales are recommended for the required models:
Maximum Scale Resolution
Model Type
Plume
Regional
Distance
(km)
500
2,000
Time
24 Hr
1 Yr
Distance
(km)
5
50-100
Time
15 Min
3 Hr
Although these are the desired goals, it is recognized that other models
having less resolution may be useful.
• The following design goals are recommended for model accuracy in
calculating sulfate concentrations.
Ensemble Average
Accuracy Goal
Model Type (95% Confidence Level)
Plume Within a factor of 1.3
Regional Within a factor of 2.0
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Currently available models should be adapted for use in the
proposed program.
In order to maximize the likelihood of achieving a satisfactory
and operational model by 1980, both empirical and meteorochemical
models should be included in STATE.
The empirical and meteorochemical approaches that are pursued
should emphasize modern modeling techniques. Models that
should not be considered are rollback models and Gaussian plume
models.
As a design goal for computer costs, it is recommended that the
cost of one computer run of the regional planning model, for one
emission meteorological scenario, should not exceed $500. However,
the computer costs of the plume diagnostic model may exceed this
because of its more stringent accuracy requirements.
Data needs are generated by the diagnostic model in its explicit
representation of advection, turbulent diffusion, chemical trans-
formations, removal, and emission source inputs.
Detailed physical and chemical stack parameter measurements will
be needed for inputs to model analyses depending on large point
source programs.
Gridded area source inventories will be needed for modeling
interactions of elevated plumes with surface sources that are
studied in the field.
Data required to generate vertical diffusivity profiles include
wind profiles and vertical temperature profiles.
Background and plume chemical and physical parameters (concen-
trations, bscat, aerosol properties) will be needed as horizontal
and vertical profile information to serve as a validation data
base for the diagnostic model exercises.
For the synoptic scale models measurements of meteorological
parameters must be made well beyond the diagnostic model scales
because of the importance of complex transport processes.
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Table 1. DATA NEEDS FOR MODELS
DIAGNOSTIC MODELS
EMPIRICAL
METEROCHEMICAL
Multivariable Model
Emissions
so2
Dynamic
Emissions
so2
so3
NO
N00
z
NMHC*
Stack
diameter
Stack
height
Gas temp.
Primary
particulates
Particulate
sulfate
Catalytic
particles
Observations
so2
SO,
°3
HC*
TSP*
WS*
WD*
Empirical Model
Observations
WS Profile (GS*)
WD profile (GS)
Temp, profile (GS)
Solar radiation
Dewpoint (GS&A/C*)
Tracer (GS&A/C)
S02 (GS&A/C)
NO (GS&A/C)
N02 (GS&A/C)
CO (GS&A/C)
S04 (GS&A/C)
NH3 (GS&A/C)
Emissions
so2
SO,
NO
NO 2
H20
NMHC
Stack
diameter
Stack
height
Gas temp.
Gas velocity
Primary
particulates
Catalytic
particles
Observations
WS profile (GS)
WD profile (GS)
Temperature profile (GS)
Solar radiation (GS&A/C)
Dewpoint (GS&A/C)
Tracer (GS&A/C)
S02 (GS&A/C)
NO (GS&A/C)
N00 (GS&A/C)
z
0. (GS&A/C)
j
CO (GS&A/C)
NH3 (GS&A/C)
HC (GS&A/C)
A/C altitude
A/C position
Mixing depth (Lidar)
WS (A/C)
WD (A/C)
SP (GS&A/C)
CP (GS&A/C)
HC (GS&A/C)
A/C altitude
A/C position
Mixing depth (Lidar)
WS (A/C)
WD (A/C)
SP* (GS&A/C)
CP (GS&A/C)
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Table 1. DATA NEEDS FOR MODELS (Concluded)
PLANNING MODELS
EMPIRICAL
***
Emissions
so2
so3
NO
NMHC
Particulate sulfate
CP
METEROCHEMICAL
***
Observations
WS (radiosonde)
WD (radiosonde)
Temperature (radiosonde)
Solar radiation
SO 2
NO
°3
CO
so
HC
SP
CP
*HC = Hydrocarbon
TSP - Total Suspended Particulate
WS = Wind speed
WD = Wind direction
NMHC = Nonmethane hydrocarbon
GS = Ground station
SP = Suspended particulate
CP = Catalytic particles
A/C = aircraft
***
*No specific field program is necessary to implement this model.
Requirements for empirical or meteorochemical models are identical.
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II. INTRODUCTION
A. Objective
The objective of the Data Management and Analysis Working Panel
is to identify what studies are required to develop by 1980 methods of
relating changes in ambient sulfate concentrations to changes in
precursor emissions. In the working group's judgement, models represent
the best method to meet the objective within the imposed time and
resource constraints. Furthermore, the group believes that models must
assume a central, integrating role in the STATE program, with the
motivation for field studies being to provide a carefully selected data
base for the adaptation, testing, refinement and evaluation of the models.
Thus, models must serve a diagnostic function in concert with the
STATE field program, in addition to their ultimate role as planning tools
for standards development and control strategy implementation within
EPA's regulatory branch. Implicit in the diagnostic application of the
models is the requirement that they be developed and exercised concurrently
with the field programs so as to provide essential feedback on the field
design and operation.
B. Assumptions and Guidelines
In order to have a useful framework for the panel's efforts,
some guidelines were given by the workshop sponsors and certain assump-
tions were made by the panel. The guidelines consisted mainly of fiscal
and time constraints. For the fiscal, roughly $3-5 million a year should
be available for the field studies. For the time restrictions, EPA
intends to make a decision in the 1980 time frame on whether sulfates
in the atmosphere are an environmental problem. If EPA should decide
sulfates are a problem, then the methods for relating emissions to
ambient concentrations must be available in the same time frame in order
to develop control strategies.
Based on the time frame, constraints, and discussions of model work
underway, the panel decided that no new models would be started, Rather,
models under development or available would be adapted, revised and
evaluated.
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The second set of assumptions made by the panel were those of
scale and resolution. Since these depend on the types and applications
of models chosen, the scales and resolution for each model will be discussed
later in the report. It should be pointed out, however, that time resolution
of ambient sulfate concentrations depends both on capability of instru-
mentation and on the time scale of health effects.
C. Organization of the Report
This report is organized into five sections which present the
following information on the status of air quality simulation modeling,
and its recommended role within STATE:
1) The spatial and temporal scales of sulfur transport/trans-
formation phenomena as currently known are described.
2) The various types of available air quality models are
described and critically assessed for their potential
applicability in simulating the observed atmospheric
phenomena and in providing a tool for regulatory plan-
ning and control functions.
3) Data requirements are defined for the testing and
evaluation of two types of models—empirical and
deterministic. The data needs are presented for each
component commonly including in a composite model;
namely, emissions, transport, diffusion, transformation,
removal and air quality.
4) The role and logistics of applying models to the necessary
data sets are discussed in a separate chapter on data and
model management.
5) Finally, a milestone plan and time schedule for the con-
current implementation of the data collection and modeling
elements of STATE are proposed.
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III. TECHNICAL BACKGROUND
Models serve many useful purposes, from the planning and analysis
of experiments to the implementation of a pollution control program.
Given what is now known about the sulfate pollution problem, it is
likely that several different models will be needed if, by 1980, we
are to understand how sulfur (and possibly other) emissions need to be
controlled so as to meet an ambient sulfate standard. This section
discusses in a general way common aspects of.likely models that will
affect their applicability to the STATE Program.
The models to be discussed consider some or all of the following
processes: (a) emissions, (b) transport, (c) diffusion, (d) trans-
formations, and (e) removal. The simplest models will attempt to relate
emissions to air quality in terms of a few observable parameters, while
the more complex models will treat all the significant processes to
provide a description of temporal and spatial variations of relevant
species. Since sufficient evaluation of sulfate models has not been
accomplished, it is not clear how complex the models need to be and what
parameterizations are viable to provide the information for a sulfate
control program.
A dominant problem of modeling sulfate pollution is the long time
and the travel distance associated with the formation of sulfates from
sulfur emissions. Travel times of 10 to 100 hours and distances of 50
to 500 km from the source are required to produce and disperse the
sulfate associated with a given source. This implies that ambient
sulfate levels will be affected by many distant sources, and that
space and time changes in meteorological and other variables are
likely to be important in determining local sulfate concentrations.
Regional studies with areas of the order of 2000 km x 2000 km,
should use models for sulfate concentrations with grid spacing of 50 to
100 km and which employ many point and area sources. A finer subdivision
of a region of this size (such as the U.S. east of the Mississippi) does
not seem very practical at this time. This minimum grid size for such a
region is as long or longer than the length (and travel time) scale for
which there exist reliable, single source measurement of transformation,
50
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removal and other processes that are the building blocks of the
regional models. There may, therefore, be a time and length scale gap
between the regional models and the smaller scale plume (urban or
power plant) models. Measurements and analysis may be needed to close
this gap.
Because sulfates are formed slowly in the atmosphere and are seldom
directly emitted by point sources in significant quantities, the smallest
time and horizontal length scales on which variations in sulfate concen-
trations have been observed appear to be several hours and tens of
kilometers. (These should be better defined by suitable field measurements)
Measurement and modeling on such scales for single plumes (e.g., power
plants or urban areas) is possible, but the kinds of measurements and the
modeling done for this scale are certainly not practicable for large
regions. It is also noted that, in plume experiments, a typical aircraft
traverse measurement requires about an hour, which is shorter than the
time scale of changes in sulfate background.
There are three physically different length scales .that seem to be
of comparable size (about 1000 km): the travel distance for sulfate
production and dispersion from a given source, the scale for major varia-
tions in the coarse-grained emission density, and the typical size of
synoptic weather patterns. In interpreting high sulfate pollution episodes,
different models may be equally satisfactory (or unsatisfactory). A long
record of region-wide sulfate levels may be needed to determine which
models are the more reliable and useful.
It is not now known whether the most important adverse human health
effects associated with sulfate exposure or exposure from a surrogate of
sulfate (if any) will depend upon short duration, high level or long
duration,;, low level exposure. Models should be capable of addressing
both extremes, and should be devised to aid in the understanding of both
episodic and long-term observations.
Models need to be evaluated in terms of their ability to explain
measurements and predict the consequences of changes in emissions. The
models most useful to implementation programs will be those that most
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directly and validly relate emissions changes to changes in sulfate air
quality. Emphasis in the STATE program on single or multiple plume
experiments may lead more quickly to such a desirable result.
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IV. CRITICAL ASSESSMENT OF MODEL TYPES
There are two general approaches for determining the relationship
between ambient air quality and pollutant emissions: empirical modeling
and meteorochemical modeling. Empirical models are based on analyzing
air quality, emission, and/or meteorological data. Meteorochemical models
are founded on basic principles in physics and chemistry relating to
transport, diffusion, removal, and transformation processes. Actually,
.the distinction between empirical and meteorochemical models is rather
arbitrary. Empirical models can incorporate varying degrees of physical
insight. For instance, they can account for transport and can include
the spatial distribution of emissions in the source-receptor relationship.
Conversely, meteorochemical models often rely on empirically determined
constants, such as transformation or removal rate constants. Thus, a
continuum actually exists in the types of models, ranging from simple
linear rollback models to fundamental models based on first principles.
Here, the arbitrary dividing line between empirical and meteorochemical
models will be based on whether or not the model tends to emphasize data
analysis or physicochemical principles.
A. Empirical Models
The empirical modeling approach derives relationships between
air quality and emissions based on analyses of air quality, emissions
and/or meteorological data. There is a wide range of models that can be
classified as empirical, and varying degrees of physical insight can be
used in formulating these models. Meteorological variables (e.g., solar
radiation) can be explicitly included or averaged 'out. Transport phenomena
can be accounted for or neglected. Multiple precursors can be considered
simultaneously, or the focus can be placed on a single precursor.
Spatially resolved source-receptor relations can be derived, or spatial
variations in emissions can be neglected. Empirical models can be
dynamic (involving time changes) or static (involving time averaged
variables). The models can be based on simple linear regression between
two variables, or on multivariable, non-linear, non-parametric, estimation
techniques.
The most rudimentary types of empirical approaches are proportional
rollback models and regression models based on correlations between
53
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ambient pollutant levels and precursor emissions (or ambient precursor
concentrations) at a fixed location. These simplistic approaches do not
provide relationships that are appropriate for strategy analysis.
Transport is obviously important in the case of a long lived secondary
pollutant such as sulfate and must be accounted for. Precursors other
than SO emissions such as hydrocarbons, ammonia, ozone, and catalytic
a
aerosols may be potential control parameters for sulfates and should not
be neglected. The spatial distribution of emissions, both on horizontal
and vertical scales, is important and should be included.
One type of empirical model.that could include the necessary
complexities is based on relationships found between receptor sulfate
concentrations and both local and upwind S02 emissions. The emissions
distribution could be resolved according to geographic areas and to
discrete stack height levels. Trajectory analyses would be performed
to define the emission influence areas for each receptor site. Precursor
concentrations other than SOj would be determined upwind and near to the
receptor. The variation in precursors and ambient sulfate, provided by
either examining changes with time at given receptor locators or comparing
alternate receptor locations, would allow determination of a relationship
between the two variables. In the case of comparing alternative receptor
locations, confounding of the relationships by meteorological differences
between points could occur and meteorological parameters should be included
to avoid spurious correlations. An estimation technique pertinent to
this and subsequent empirical models would be multiple, nonlinear regression.
An alternative dynamic-empirical model could be formulated to act as
the chemical submodel of an otherwise deterministic approach. Ambient data
from either plume studies or a fixed monitoring system could be analyzed
to formulate multivariate functions for differential equations relating
sulfate formation to $©2 concentration, other precursor concentrations, and
meteorological variables. This approach would have the advantage of allow-
ing reaction equations that are not necessarily first order in S02 concen-
trations. The chemical.model so derived could be combined with conven-
tional models of transport and diffusion.
54
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A third type of empirical model would be based on a superposition of
pollutant plumes. Empirical parameters model could be derived through
studies of individual urban and stack plumes. These relationships would
be determined for a variety of precursor concentrations and meteorological
conditions. A regional model would be formulated by superimposing
plumes. The character of individual plumes would be derived using the
empirical parameters. The regional superposition model could be validated
using existing monitoring data.
The discussion has pertained to empirical models for use in planning,
i.e. general empirical models of the source-receptor relationship. The
last two model's described can also be diagnostic empirical models, useful
for interpreting plume studies. These diagnotic models would be used to
determine empirical parameters. For instance, a rate constant, K, for
sulfate formation might be determined of the form.
K = K (HC, TSP, 0 , meteorology...)
where dSO,
dt- = K ' S°2
In a more general form, a nonlinear differential equation could be deter-
mined with the general form,
a so.
—— = F(HC, TSP, 0,, meteorology, ..., SO )
at j i
ADVANTAGES AND DISADVANTAGES
The advantages of empirical models are their close ties to the geometric
data base. Empirical analytical approaches allow a full exploration
of the information available in the aerometric and emission data bases.
The reliance on aerometric observations allows all the complexities of
the atmospheric system to be represented even if some of the complexities
are not yet understood in fundamental terms. Also, data analytic approaches
conveniently allow a simultaneous check on data quality. Finally, empirical
models can usually be formulated and operated at low cost.
55
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The strong dependence on aerometric and emission data bases also
leads to significant disadvantages in empirical modeling. For some
empirical models, the necessary data base does not exist. Other types
of empirical models, such as the one based on Lagrangian plume analysis,
require data of very high quality. Another disadvantage is that empirical
models and parameters may be too closely tied to the specific conditions
under which they have been formulated or the model used. Part of this
disadvantage can be counteracted by careful selection of variables and
thoughtful interpretation of observed relationships.
B. Meteorochemical Models
The general term "meteorochemical model" is used to define a
large class of models of varying types and complexities, with the commonality
of mathematically representing the physical and chemical processes of
atmospheric transport, diffusion, transformation and disposition as
distinguishable identities in simulating the relationship between emissions
and ambient air quality. The general goal of the meteorochemical model
in the STATE program is to predict the concentration of S0= and its associated
precursors over space and time given the initial and boundary conditions
of the atmosphere and associated meteorological fields. The present
discussion has been limited to the deterministic class of models.that
use meteorological data as input rather than attempt to simulate these
data via prognostic meteorological models. It is proposed that the
objective of the STATE program can be achieved via the use of two modeling
scale approaches.
The first modeling scale involves ranges up to 200 km and will serve
as a diagnostic tool to aid in the interpretation of field data as well as for
elucidation of the complex chemical and physical processes associated with
SO? formation. The second modeling scale involves ranges of the order
of 2000 km x 2000 km and is earmarked for the planning proposes.
Diagnostic Models
Diagnostic models should be an integral part of the field programs
considered and should "participate either in a day to day interactive mode
with the field study or at a minimum participate in a feedback loop to
provide insight in the planning of future intensive field studies.
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Diagnostic models are currently available both in the Lagrangian and
Eulerian frameworks. Within these frameworks, consideration should be
given to the treatment of the isolated single source and multiple source
modeling problem.
The single source (reactive plume) model should consider for applica-
tion to Lagrangian puff, Eulerian grid point, and variable volume box model
approaches. The multiple source modeling to be considered for application
should include moving cell, trajectory, and Eulerian grid point approaches.
The level of complexity to be considered for any one modeling
approach chosen will be commensurate with the field study data and its
overall objective. It is quite conceivable that field studies may
warrent that simplification be considered for certain currently available
modeling approaches. These may include reductions in dimensionality,
chemical or meteorological detail, or perhaps the development of hybrid
classes of models.
Planning Models
The model scale, of order 2000 km x 2000 km, will serve as a planning
tool for regulatory needs. It will provide an understanding of the existing
S0= problem and will predict the impact emission growth will have on
ambient SO? concentration on a regional scale. Models of this scale are
most amenable to a grid type format and again may include both Lagrangian
and Eulerian approaches. Planning models are not as readily available
as those in diagnostic class, but the consensus is that several will be
available for potential application within a year period. These iwill
include the Hefter type synoptic trajectory approaches,— deterministic
Eulerian approaches, coupled planetary boundary layer-air quality modeling
approaches, and hybrid approaches.
Advantages and Disdadvantages
Meteorochemical models provide the advantage that they are formulated
from basic scientific concepts associated with physical and chemical
processes occurring in the atmosphere. This affords some confidence in
their application over ranges of conditions and areas as well as their
ability as predictive tools.
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Main disadvantages associated with the models include extensive data
input requirements, the need for specification of many model parameters,
and computational complexities (both human and material).
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V. DATA REQUIREMENTS FOR EMPIRICAL MODELS
There exists a range of empirical models that may be used for the
STATE Program. The data requirements will depend on the model type as
well as the purpose for the model. The following sections are broken
down into purposes for empirical models. In each section, the model
type is briefly described and the data requirements are described in
detail.
A. Diagnostic Model Requirements
One type of empirical model that can be used in the STATE
Program is the multivariable empirical model. These models can employ
existing data from present networks or those to be established in the
future (the network to be used in the SURE Program). No special field
experiments are required for application of the model. However, it
would be an advantage to supplement the monitoring program of SURE for
more precise application of the model.
Emission data horizontally distributed is required for the model.
Emission data would include that for SO-, SO™, sulfate particles, cata-
lytic particles, and possibly stack height. Observational data should
include SO., SO,, 0-, HC, TSP, catalytic metals, wind speed, and wind
direction. Other meteorological data may be included, but this is
optional. A dynamic-empirical model could be used as an integral part
of the plume studies and act as a chemical submodel of an otherwise
deterministic approach. Ambient data from the plume studies could be
analyzed to formulate multivariable functions for differential equa-
tions relating sulfate formation to SO- concentrations, other precursor
concentrations, and meteorological variables.
It is very important for such a model that precise emissions data
be acquired. If the plume were to originate from a stack, then data
such as stack diameter, stack height, gas temperature, and gas velocity
would be required. Average exit concentrations of SO-, SO-, NO, N0_,
H-O, and NMHC would be required diurnally. In addition to the gases
mentioned above, exit concentrations of primary particulates, particu-
late sulfate, and catalytic particles should also be obtained.
Information on the thermal stability and the velocity profile of
the flow that carries the plume would be required for turbulent diffusion
59
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calculations. Some information on solar radiation will be of value in
computations of primary photochemical rates.
Data required for evaluation of the model can be obtained mostly
through airborne sampling. Lateral traverses and vertical spirals of
the aircraft would provide a vertical cross-section of the species and
of the meteorology. Measurements should include S0_, NO, NO-, NO-, CO,
nephelometer, tracer, SO,, NH,, HC, temperature dewpoint, incoming UV
radiation, altitude, position, wind speed, and wind direction. Tetroons
would be tracked by radar, thus allowing the operations director to
vector the aircraft downwind to intercept the plume. Auxiliary measure-
ments of plume location and mixing depth can be obtained by airborne
downward-looking LIDAR.
B. Planning Model Requirements
The empirical planning model would be based on superposition
of pollutant plumes. The parameters of the model could be derived
through the studies of individual urban and stack plumes. The data
requirements for this model are similar to those for the dynamic-
empirical model discussed above. The difference is that the data
requirements in this case are not on as fine a scale as those for the
diagnostic model.
Horizontal distributions of emission data are required. Aircraft
data could supplement the network data (the network data in this case
refers to the network used by the SURE Program). (For the supplemented-
by-aircraft data, in the case where specific synoptic systems are studied,
see applications of empirical models.) One application of an empirical
model is an assessment of the transformation and removal rates for
sulfate in the atmosphere. This can be done by characterization and/or
control of source, dispersion, and ambient concentrations. The stack
heights, the kinds of fuel, operating conditions, and associate pollutant
emissions have a significant bearing on sulfur oxide transformations and
removal downwind. These source characteristics can be controlled, and
their effects on transformation and removal can be directly observed.
Dispersion affects the transformation rate by governing the method
by which the plume interacts with the environment and determines the
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rate at which matter is delivered to the surface for removal. Dispersion
can be accounted for by use of conservative tracers or by establishing a
mass balance of primary and secondary pollutants. The use of a conserva-
tive tracer allows estimation of local transformation removal rates
through consecutive downwind measurements of concentration ratios of
primary and secondary pollutants. This computation also requires that
wind speed and direction be obtained. The determination of mass flow
rate by detailed measurements of concentration of primary and secondary
pollutants and the wind field permits an estimation of above transforma-
tion and removal rate by performing a mass balance at each downwind
cross-section. Besides the primary and secondary pollutants, additional
environmental parameters that may influence the transformation or removal
rate should be observed. These parameters should include 0~, EC, NO,
particulates, ammonia, temperature, humidity, solar radiation, surface
characteristics, and in-cloud residence time. These data may be used
to perform a multivariable analysis of the transformation and removal
rates to acquire the empirical relationships under a wide range of
environmental conditions.
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VI. DATA NEEDED TO DEVELOP AND EVALUATE MODELS FOR SULFATE CONCENTRATIONS
IN THE ATMOSPHERE
A. Diagnostic Model Requirements
A Lagrangian photochemical/diffusion model based on a multistep
transformation mechanism is recommended as a guide for defining some of
the fundamental field measurements on large point sources. Conversely,
this diagnostic model will be applied to the testing of hypotheses once
the experimental data are available. First, the model structure will be
defined, and second, its data requirements will be outlined.
The model structure is aimed at the objective of highlighting funda-
mental processes of transport, diffusion, transformation, and removal as
they determine the ground concentrations of sulfates in the air. This is
done by adopting a set of species budget equations each of which expresses
the following contributions to the time rate of change of concentration:
Advective flux
Turbulent diffusion
Chemical transformations as governed by a multistep mechanism
Removal
Emission source inputs.
The last named process is expressed either as a lower boundary condition
for surface-based emission sources or as a time-dependent embedded source
term for stack emitters. The horizontal advective flux is handled by
moving the coordinate system with the mean wind while the vertical component
is neglected. Turbulent exchange in the transverse and vertical may be
represented by a gradient diffusion term based on K-theory. Chemical
transformation and removal (other than at the surface) are expressed as
summations of net production rates for each species participating in
a series of elementary steps. Surface removal is characterized as a flux
condition imposed on the lower boundary.
The model is operated by specifying initial vertical and transverse
profiles and numerically integrating the equations from this point in
time. As the Lagrangian frame sweeps over emission sources, computations of
the spread of primary pollutants proceed using time and space dependent
values of eddy diffusivity and chemical rate coefficients. The output at
each time step is a set of concentrations for each species averaged over
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each grid cell. Conditions at successive times in the plume are obtained
by repeating this procedure using updated values of initial conditions,
emission input rates, eddy diffusivities, chemical rate coefficients,
and windfields.
The data requirements of this type of model begin with a specification
of stack sampling information needed for the primary point source. In
addition to stack diameter, stack height, gas temperature, and gas velocity,
details of chemical composition are needed. Average exit concentrations
over each operational hour of SCL, SO., NO, NO., H.O, and NMHC will be
measured in addition to primary particulates, particulate sulfate and
catalytic particle loading. It will also be desirable to disperse a
measurable inert tracer material into the stack exit stream. Along every
plume path of interest, area source and other point source emissions of
these same materials will provide boundary conditions. These too will be
needed on an hourly basis on a 10- to 20-km square-cell grid.
Turbulent diffusion calculations require a knowledge of the stability
and velocity profile of the flow that carries the plume. This indicates
a need for sounding and pilot balloon information (which will also provide
wind speed and direction for the adve.ctive trajectory calculation). Solar
radiation in the ultraviolet must be measured to provide primary photochemical
rate data. Secondary chemical rate data must be obtained from laboratory
experimental results available in the literature. This suggests that both
fundamental kinetic measurements and smog chamber programs must be purpose-
fully designed and executed to feed timely information into the field
program through the model. Similarly, dry deposition (and rainout, if
appropriate) data must be developed to check out the model.
Evaluation of the model is done by subjecting its output concentrations
to comparison with experimentally observed values. This determines the
primary requirements of an airborne sampling program. Lateral traverses
and vertical spirals of the aircraft (ideally executed in a moving coordinate
frame) would provide a geometrical emulation of the model's control volume
used for calculation. Measurements to be taken should include S0«, NO, N0?,
0-, CO, nephelometer, tracer, SOf ,,. NH,, HC (bag samples), temperature, dew
point, incoming uv radiation, altitude, position, wind speed,* and wind direction.*
*These may be best taken by a separate aircraft.
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Gas concentration and temperature measurements should be recorded on a 5- to
10-sec. interval on some suitable machine-readable medium. The use of
tetroons tracked by radar would permit the operations director to vector
the aircraft downwind to intercept the plume at the same center-of-mass
point as originally tracked in the first flight pattern. Auxiliary
measurements of plume location and mixing depth should be taken with
airborne down-looking UDAR.
B. Planning Modeling Requirements
A grid-type regional model will be needed to assess the attainment
and maintenance of any proposed ambient air quality standard for sulfate.
The objective of the model is to incorporate field-tested principles in
a method for relating air quality to emissions under specified meteorological
conditions. The reason for recommending a grid model is the need to express
spatial patterns of sulfate concentrations under different control scenarios.
Ideally, the use of the diagnostic model development for building the
grid model consists of adaptation of the chemical mechanism and the diffusion
formulation learned in the development phase to a large scale network
simulation. The air movement relative to the grid can be treated either
as Lagrangian (short trajectories back calculated from each cell centroid)
or as Eulerian (air flowing across a fixed grid with advective flux terms
establishing the flow rates). The transport and diffusion, however, may
well need to undergo major upgrading. This is likely to be the case because
the expansion to regional scale (-2000 km) encompasses considerably more
flow field complexity than the diagnostic model scale (~200 km). Typically,
significant synoptic scale phenomena include the stagnating flow under
a subsidence inversion created by a large anticyclone. Recirculation may
trap a considerable amount of pollutant within a central zone of the
region. Another synoptic scale phenomena is a frontal passage with a
displacement of polluted air differentially with height. Rain associated
with some fronts can cause significant changes in the transformation and
removal mechanisms.
For these reasons, additional field measurements to cover large scale
phenomena are of interest to the development and evaluation of the planning
model. One key question is the degree of horizontal transport of material
below a high pressure cell as it moves across the land mass. One view is
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that trapped air moves along with it, and another is that the high pressure
area moves as a propagation of a pressure disturbance leaving all of the
original air behind. The actual case lies somewhere between these extremes,
and experimental designs must be implemented to determine the modes of
horizontal transport in anticyclones. The use of aircraft traverses,
spirals, and tracer tracking in the high pressure regions will give infor-
mation needed to devise approximations in the models.
Similarly, the investigation of frontal structure with the same
techniques will determine the degree of transport and dispersion in the
region of the front. The modification of the transformation and removal
mechanisms in rainy areas will also be clarified by aerial measurements of
concentration changes. Specific model modifications and approximations to
describe these synoptic phenomena cannot be recommended until the data
are gathered on the scales required. This is a good example of the
iterative approach that involves model.needs influencing experiments and
then experimental results feeding in improvements in the model.
C. Some Major Issues Involving Field Data Needs for Model Evaluation
A maximum degree of confidence in model performance may be gained
by testing it over the widest possible range of parameter values expressive
of the influential factors. Although the atmosphere is not subject to
the controls of a.laboratory experiment, we may maximize generality by
choosing extremes of pollutant conditions, geographical settings, and
meteorological conditions to test individual influences. Some examples
of such test designs are as follows:
Influence of hydrocarbon control on sulfate formation; Consider
interactions of large hydrocarbon sources with sulfur bearing plumes
by studying a power plant plume as it reaches ground level near a petro-
leum refinery or marine oil terminal. Also, consider interactions
where such a plume grounds in an area where natural hydrocarbons
are emitted. In photooxidation, hydrocarbons provide alkoxy and
alkylperoxy radicals which react quickly with SCL to oxidize it
to SO,. This is a chain-initiation step in the formation of
sulfate. Other reactions of these radicals generate hydroxyl
radicals which also initiate sulfate formation from SO™.
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Influence of oxides of nitrogen on sulfate formation; Compare
rates of sulfate formation in a plume with oxides of nitrogen at
moderate concentration (e.g., power plant) with a plume dominated
by S0_ (e.g., smelter). Oxides of nitrogen react rapidly with
oxidizing free radicals to remove them from chemical chains.
These radicals play important roles in the photochemical formation
of sulfate from SO-.
Catalysis by emitted particulate of the conversion of SO,, to sulfate;
Using variable application of particulate emission controls, the
experimenter can study the effect of dry surfaces in catalyzing
the reactions of S0? to form sulfates.
Influence of natural factors on sulfate production; Where pre-
existing SO- is available to oxidize in liquid water droplets, the
effect of ambient ammonia can be investigated. Sulfur bearing
plumes over various types of soil conditions are exposed to
various ammonia concentrations. The conversion rate as a function
of ammonia concentration is a significant factor in testing models.
Also, the emission of natural sulfur bearing compounds such as
1LS may generate atmospheric sulfates. Monitoring of air masses
passing over such source areas will test such hypotheses.
Competition of surface removal rates with sulfate formation; Sulfur
and SO mass balances in plumes will lend insights into the relative
roles of stack height and surface type in the determination of the
relative dominance of surface vs. above-surface processes in
removing S0_ and forming sulfate. Experiments could be conducted
with various stack heights and plumes passing over desert, foliage,
and water surfaces to consider the relative roles.
Urban plumes interactions with other polluted air masses; The growth
of an urban plume into a background influenced by upwind urban areas
provides a measurement environment to study the S0--sulfate conversion
from one source as influenced by another. Similar measurements
should be made on the interaction of an elevated source plume with
anaurban plume to shed light on this area. Comparisons of urban
plume sulfate mechanisms with those in elevated source plumes will
assist in the use of these results to develop and evaluate the
models.
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VII. DATA AND MODEL MANAGEMENT
To meet its objective, EPA's STATE Program must be concerned with two
key conceptual, planning and operational constraints: (1) timeliness and
(2) cost-effectiveness. The panel on modeling and data management strongly
believes these two key constraints necessitate that STATE programs be
designed to serve a strong separate, but clearly complementary field
measurements and modeling role with both ERDA (MAP3S Program) and EPRI
(SURE Program): The design necessarily raises issues of paramount impor-
tance for data and model management.
A. Inter-Organizational Cooperation and Coordination
Problem
The prospect of three major organizations participating in separate
but complementary measurements and modeling studies creates crucial inter-
dependencies in four major areas:
1. Timeliness of data reduction, data review and reporting
2. Quality assurance
3. Model management
4. Comparability of data.
Recommendations
1. Elements of each organization's data management, model management
and qualtiy assurance management teams must be active participants
in all steering and review processes.
2. Inter-organizational schedules for data reduction, data review,
data and modeling reporting must be established.
3. Inter-organizational quality assurance activities must be independent
yet responsible for corrective feedback.
4. Data reporting standards must be developed and followed.
B. STATE Program
Problem
The prospect of several intensive field study programs and large
numbers of different platforms, investigators, measurement techniques, and
data reduction requirements creates significant problems for both data and
model management within STATE.
Recommendations
Experience gained from several previous large scale programs (LARPP, RAPS,
BOMEX, GATE, IFYGL) suggest the following key recommendations:
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1. There is a critical need for rapid data reduction and feedback
to the field investigator as soon as possible (e.g., within
24 hours).
2. Each investigator must submit format descriptions and a sample
dat.a tape, if possible, prior to his actual field experiment.
3. Data reduction (i.e., the process of converting from voltage to
physical units) should be accomplished at a single central
ADP/DM facility. The proximity of this facility to the field
programs and telecommunications capabilities to the larger data
management computer facility are key to the timely reduction.
reporting and review of data.
4. The central ADP/DM facility should be operated by a single
contractor responsible for providing:
Reduced and/or graphical data feedback to the investigator
• An original copy of all data tapes received for data management
and for subsequent corrective editing/validating (nondestructive
flagging)
Working with investigator to resolve and document problems/
corrections.
5. A formal review and reporting of each study's data and investigator
conclusions should be released within three months.
6. Common physical units and methods of position reporting (e.g.,.;
UTM or Lat-Long) must be used.
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APPENDIX A
List of Participants
Colloquium-Workshop on Regional Air Programs
A. Paul Altshuller"
Environmental Protection Agency
Research Triangle Park, N.C. 27711
John Bachman
Environmental Protection Agency
Research Triangle Park, N.C. 27711
Don Blumenthal
Meteorology Research, Inc.
Altadena, California 91001
Joseph Bufalini
Environmental Protection Agency
Research Triangle Park, N.C. 27711
Robert Browning
Environmental Protection Agency
Research Triangle Park, N.C. 27711
Shepard Burton
Systems Applications, Inc.
950 Northgate Drive
San Rafael, California
Robert Charlson
University of Washington
FX-10
Seattle, Washington 98105
Steven Cordle
Environmental Protection Agency
Washington, D.C.
Ken Demerjian
Environmental Protection Agency
Research Triangle Park, N.C. 27711
Ray Dickson
ARL Field Research Office
Energy Research and Development
Administration
Post Office Box 2108
Idaho Falls, Idaho 83401
Basil Dimitriades
Environmental Protection Agency
Research Triangle Park, N.C. 27711
Jack Durham
Environmental Protection Agency
Research Triangle Park, N.C. 27711
Allen Eschenroeder
Environmental Research and Technology, Inc.
203 Chapala
Santa Barbara, California 93101
Roy Evans
Environmental Monitoring and Sensing
Laboratory
Environmental Protection Agency
Post Office Box 15027
Las Vegas, Nevada 89114
James A. Fay
Massachusetts Institute of Technology
Cambridge, Massachusetts 02138
Charles Hakkarinen
Electric Power Research Institute
Post Office Box 10412
Palo Alto, California 94303
Harry Hamilton
Research Triangle Institute
Research Triangle Park, N.C. 27709
Thomas Hartlage
Environmental Protection Agency
Research Triangle Park, N.C. 27711
George M. Hidy
Environmental Research and Technology
741 Lakefield Road, Suite B
West Lake Village, California 91361
Charles Hosier
Environmental Protection Agency
Research Triangle Park, N.C. 27711
Rudolf Husar
Department of Mechanical Engineering
Box 1185
Washington University
St. Louis, Missouri 63130
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Warren B. Johnson, Jr.
Atmospheric Sciences Laboratory
Stanford Research Institute
333 Ravenswood Avenue
Menlo Park, California 94025
William Kellogg
National Center for Atmospheric
Research
Post Office Box 3000
Boulder, Colorado 80302
Michael MacCracken
Lawrence Livermore Laboratory
Post Office Box 808
Livermore, California 94550
James E. Meagher
Air Quality Branch
River Oak Building
Tennessee Valley Authority
Muscle Shoals, Alabama 35660
Elliot W. Montroll
Department of Physics and Astronomy
University of Rochester
Rochester, New York 14627
Lawrence Niemeyer
Environmental Protection Agency
Research Triangle Park, N.C. 27711
Fred Shair
Chemical Engineering
California Institute of Technology
1202 East California Boulevard
Pasadena, California 91125
George Slinn
Battelle North West Laboratories
Richland, Washington
Arthur Stern
Department of Environmental Science
and Engineering
University of North Carolina
Chapel Hill, North Carolina 27514
Robert Stevens
Environmental Protection Agency
Research Triangle Park, N.C. 27711
Dennis Thomson
Department of Meteorology
Pennsylvania State University
University Park, Pennsylvania
16802
Donald Pack
1826 Opaloca Drive
McLean, Virginia
John Trijonis
TRW Environmental Services
120 Wavecrest Avenue
Venice, California 90291
Fred Vukovich
Research Triangle Institute
Research Triangle Park, N.C.
27709
22101
Robert Papetti
Environmental Protection Agency
Washington, D.C.
Frances Pooler
Environmental Protection Agency
Research Triangle Park, N.C. 27711
Jerry Romanovsky
Environmental Protection Agency
Research Triangle Park, N.C. 27711
Walter Saucier
Department of Geoscience
North Carolina State University
Raleigh, North Carolina 27607
Bernard Weinstock
Ford Scientific Research Center
Post Office Box 2053, Room 3-3084
Dearborn, Michigan 48121
Kenneth Whitby
Mechanical Engineering
University of Minnesota
Minneapolis, Minnesota 55455
William Wilson
Environmental Protection Agency
Research Triangle Park, N.C. 27711
John Winchester
Department of Oceanography
Florida State University
Tallahassee, Florida 32306
Herbert Wiser
Environmental Protection Agency
Washington, D.C.
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APPENDIX B
Schedule of Sessions
Colloquium-Workshop on Regional Air Programs
Appalachian State University Conference Center - June 7-11, 1976
Monday
June 7
5:30 pm
9:00-12:00 pm
Dinner
Sponsors (EPA, TUCAP, RTI)
Tuesday
June 8
8:00-10:00 am
10:00-11:30 am
11:30 am
12:00-12:55 pm
1:00- 4:00 pm
5:00 pm
6:00- 6:30 pm
6:30-9:30 pm
Introduction
EPA statement of objectives
Summaries of other programs
Operation of Workshop
Expectation of sponsors
Procedures
Designation of working groups
Lunch
Meeting of Working Group Chairmen
(sponsors and chairmen)
Working Group meetings
Dinner
Evaluation (sponsors and chairmen)
Working Group meetings
Wednesdayj
June 9
7:00 am
7:30- 8:00 am
8:00-11:00 am
11:30 am
1:00- 2:00 pm
2:00- 5:00 pm
5:00 pm
6:30- 9:00 pm
Breakfast
Evaluation (sponsors and chairmen)
Working Group meetings
Lunch
Meeting of Working Group Chairmen
Working Group meetings
Dinner
Plenary meeting—summary of progress
Thursday
June 10
7:00 am
8:00-11:00 am
11:30 am
1:00- 2:00 pm
2:00- 4:30 pm
5:30 pm
8:00- 9:00 pm
Breakfast
Working Group meetings
Lunch
Meeting of Working Group Chairmen
Working Group meetings
Dinner
Plenary meeting—summary and consensus
Friday
June 11
7:00 am Breakfast
7:30 am Depart for airport
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