Sciences Research
Laboratory
Activities Report
Fiscal Years 1976-1978
.
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Environmental
Sciences Research
Laboratory
Activities Report For
Fiscal Years 1976-1978
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
February 1979
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Director's Message
The enormous complexity of the
national pollution problem
reflects the many ways that man
abuses his environment. These
abuses include air pollution,
contamination of water supplies,
disposal of so/id waste, noise,
and the release of radioactive
substances, insecticides, and
herbicides. Man and his
environment must be protected
from these abuses.
To this end, the President
established the U.S.
Environmental Protection
Agency (EPA) in December,
1970. '
The Office of Research and
Development (ORD) is the
principal scientific component
of EPA, and the Environmental
Sciences Research Laboratory
at Research Triangle Park, North
Carolina, (ESRL-RTP) is one of
ORD's fifteen associate
laboratories located throughout
the country.
This report presents an overall
view of ESRL's mission and
organization, and describes a
number of important research
activities carried out during
fiscal years 1976 through 1978.
Hopefully, in reading the report
you will understand better the
role ofESRL in the national battle
against air pollution.
Dr. A. Paul Altshuller
Director
Environmental Sciences
Research Laboratory
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Table of Contents
ESRL - Introduction
The Clean Air Act
Mission .
Revision of the Oxidant
Criteria Document . . 23
Mobile Source
Emissions .
ESRL - Organization
Emissions Measurement
and Characterization
Division (EMCD) 13
Atmospheric Chemistry
and Physical
Division (ACPD) 15
Meteorology and
Assessment
Division (MAD) 17
Regional Field Studies
Office (RFSO) 19
ESRL - Research Activities
and Accomplishments
Regional Air
Pollution Study 21
Halocarbons and
Ozone Depletion
Atmospheric Sulfates
Project MISTT
Oxidant Transport
Studies .
Visibility in the
Southwestern and
Northeastern United
States .
Power Plumes in
Complex Terrain
Remote Sensing
of Gaseous
Pollutants .
Sulfur Transport and
Transformation in
the Environment
(STATE)
25
29
31
33
35
37
39
Stationary Source
Emissions .
Ambient Air Sampling
and Analytical
Techniques
Atmospheric
Modeling ...
Effects of Natural
Hydrocarbons .. ,
Houston Air
Pollution Research
Study '..
. 41
. 43
. 45
. 47
. 51
. 53
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ESRL - Introduction
During the past several
decades, the public has
become more and more aware
of environmental pollution. The
Government has recognized the
dangers to our environment by
appropriating larger and larger
budgets for research and
enforcement. In late 1970, the
U.S. Environmental Protection
Agency (EPA) was established
and charged with one overall
mission the protection and
enhancement of the
environment. A single
organizational entity was
thereby set up to regulate air
and water pollution, drinking
water quality, solid waste,
radiation and noise, pesticides,
and other toxic substances.
The Environmental Sciences
Research Laboratory (ESRL) \s
one of several laboratories
within EPA conducting research
in air pollution. This report briefly
states the legislative mandates
of the Clean Air Act supported
by ESRL research activities,
describes ESRL's mission and
organization, and highlights the
significant ESRL research
activities and accomplishments
for fiscal years 1976 - 1978.
The Clean Air Act
The Clean Air Act, as amended,
is the specific authority that EPA
responds to in its effort to protect
and enhance the quality of the
Nation's air resources. In
research and development
activities, ESRL implements,
totally or partially, certain
mandates (sections) of the
Clean Air Act by:
Conducting and supporting
the research and
development of improved
analytical techniques for
determining air pollutant
Environmental
Research Laboratory
emissions resulting from the
combustion of fuels.
(Sect. 104)
Providing scientific
knowledge for, and
contributing to. the
preparation of air quality
criteria documents.
{Sect. 108)
Developing scientific
evidence and measurement
methodology useful in
supporting national ambient
air quality standards.
(Sect. 109)
Providing air quality
simulation models and
monitoring techniques to
states tor use in developing
and carrying out
implementation plans to
achieve National Ambient
Air Quality Standards.
(Sect. 110)
Developing and improving
reference measurement
methods for inclusion in
regulations establishing new
stationary source
performance standards.
(Sect. 111)
Developing and improving
sampling and analytical
methods for inclusion in
regulations establishing
national emission standards
for hazardous air pollutants.
(Sect. 112)
Developing measurement
technology for inclusion in
regulations establishing
motor vehicle emission and
fuel standards. (Sect. 202)
Characterizing the
emissions from motor
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vehicles equipped with new
emission control devices, or
operating on new fuels or
fuels containing new
additives. (Sect. 211)
Preparing technical input in
specific research areas for
documentation in reports to
Congress. (Sect. 313)
Mission
ESRL conducts research that
produces knowledge useful in
developing the technical basis
for air pollution control
strategies, and in setting
standards for air quality and
stationary and mobile source
emissions. To accomplish its
overall mission, ESRL's
research program covers all
physical science aspects of air
pollution from source to
receptor. Specific research
objectives for different areas of
investigation are to:
Develop techniques,
methods, and instruments
for sampling, monitoring,
and analyzing pollutants
and toxic substances in
stationary and mobile
source emissions, and in the
ambient air.
* Measure and characterize
stationary and mobile
source emissions from
existing and new sources.
Characterize gaseous and
aerosol pollutants and toxic
substances in ambient air by
identifying their origins and
specific sources, and
determining their form,
transformations and ultimate
fate.
Assess the effects of
airborne pollutants on
materials, visibility, weather,
and climate.
Develop and apply air
quality simulation models for
predicting relationships
between source emissions
and air quality, and for
evaluating control
strategies.
ESRL is one of four laboratories
headquartered at EPA's
Environmental Research Center
at Research Triangle Park, North
Carolina. ESRL scientists
conduct and oversee air
pollution research through
contracts and grants in many
areas of the United States. Some
of this research is conducted in
the field; some consists of
laboratory and scientific
analysis. In addition, ESRL
provides technical consultation
and support to other federal
agencies.
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ESRL - Organization
To carry out its role as legislator
and enforcer of environmental
regulations, EPA maintains a
research function, the Office of
Research and Development
(ORD), to substantiate all
standards and regulations. ORD
is organized into four research
offices; ESRL reports to one of
these offices, the Office of Air.
Land, and Water Use.
FY-78 Budget
In-house $ 5.2 million
Extramural $15.5 million
(contracts/grants)
Educational Background of Professional Staff
Discipline
Chemistry
Engineering
Mathematics
Meteorology
Physics
Other
Total
Bachelor
12
4
1
3
13
22
Master
11
5
1
15
3
4
39
Doctorate
22
3
1
5
4
1
36
Total
45
12
3
20
10
8
98
ESRL with the EPA Organization
U.S. Environmental
Protection Agency
Douglas Costle, Administrator
Barbara Blum
Deputy Administrator
Office of Research
and Development
Stephen Gage
Office of Air, Land,
and Water Use
Thomas Murphy
Office of Monitoring
and Technical Support
Albert Trakowski
Office of Health and
Ecological Effects
Delbert Barth
Office of Energy, Minerals
and Industry
Steven Reznek
Environmental Sciences
Research Laboratory
A. Paul Altshuller, ERG
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The basic organization of ESRL
consists of the Director and his
immediate supporting staff,
three major divisions and an
office: Emissions Measurement
and Characterization Division;
Atmospheric Chemistry and
Physics Division; Meteorology
and Assessment Division; and
Regional Field Studies Office.
The divisions are further divided
into branches. This structure
enables the Laboratory to
conduct multi-faceted studies
while still being able to
concentrate on specific
disciplines.
ESRL has a team of 134
professionals with the
specialized knowledge and
experience in meteorology,
chemistry, physics, and
engineering needed to conduct
a complex air pollution research
program. The majority of the
professional staff hold degrees
in one of the physical sciences,
with over 76 percent holding
advanced degrees. This staff
conducts research directly or
supervises research awarded to
contractors and grantees.
Many ESRL projects cut across
the divisions, with a diversity of
staff members contributing to an
effort. Work within the divisions,
however, tends to be
specialized. Understanding the
specialties of the divisions helps
to understand the working of
ESRL. The following section
details their functions.
Composition of ESRL Workforce (Sept. 1978)
Position Category
Professional Positions
Chemist
Engineer
Meteorologist
Physical Scientist
Physicist
Other
Support Positions
Administrative
Officer
Aids and Technicians
Secretary
Total
OD
1
2
5
1
1
3
4
17
EMCD
14
6
1
3
8
2
34
ACPD
23
1
3
5
1
3
5
41
MAD
2
15
6
1
4
5
4
37
RFSO
1
1
2
1
5
Total
39
12
17
15
9
6
1
19
16
134
All numbers represent permanent filled positions.
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Director
Dr. A. Paul Altshuller
Technical Planning
and Review Office
Mr, Charles R. Hosier
Deputy Director
Dr. Alfred H. Ellison
Laboratory
Support Office
Miss Gloria J. Koch
Emissions Measurement
and Characterization Division
Dr. Jack Wagman
Atmospheric Chemistry
and Physics Division
Dr. Basil Dimitriades
Meteorology & Assessment
Division
Mr. L.E, Niemeyer
Regional Field
Studies Office
Dr. William E. Wilson
Stationary Source Emissions
Research Branch
Mr. John S. Nader
Mobile Source Emissions
Research Branch
Dr. Ronald L. Bradow
Special Techniques
Group
Dr. William F. Herget
Gas Kinetics and
Photochemistry Branch
Dr. Joseph J. Bufalini
Aerosol Research
Branch
Dr. Jack Durham
Inorganic Pollutant
Analysis Branch
Mr. Robert K. Stevens
Atmospheric Modeling
and Assessment Branch
Dr. Kenneth L. Demerjian
Geophysical Research
Branch
Mr. George C. Holzworth
Environmental Applications
Branch
Mr. D. Bruce Turner
Organic Pollutant
Analysis Branch
Dr. Eugene Sawicki
Air Characterization and
Special Projects Group
Dr. Philip L. Hanst
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-r"
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ESRL - Organization
Emissions Measurement and Characterization Division (EMCD)
EMCD is responsible for
research and development to:
Develop methods and
instruments for sampling
and measuring pollutant
emissions.
Identify and characterize
pollutants from stationary
and mobile sources.
Determine the impact of new
industrial and control
technology on the chemical
and physical aspects of
pollutant emissions.
To carry out these activities, the
Division divides its efforts into
two major areas: stationary
emission sources and mobile
emission sources. Stationary
sources are permanent
installations such as power
plants, industrial complexes,
and manufacturing facilities,
Mobile sources are normally
transportation media, such as
automobiles, trucks and aircraft.
Station-source research
basically involves developing
emission measurement
procedures and determining the
physical/chemical
characteristics of pollutants
from discharge points, such as
smokestacks, or extended area
sources, such as broad
industrial complexes. As part of
this work, scientists in EMCD
develop instrumentation and
methods for sampling and
identifying a wide variety of
pollutants from stacks and other
sources. Physical and chemicaf
characterizations are important
in understanding the
relationship of various fuels and
manufacturing processes to
pollutant emissions.
Determination of particulate
size, mass, opacity, and
chemical composition, as well
as the chemical constituents of
gaseous effluents, is an integral
part of this research.
Mobile-source research
concentrates on automobile
emissions, although some work
involves trucks and aircraft. The
development of methods and
instruments for identifying and
measuring pollutants is critical
to these studies as well as EPA's
regulatory programs. Simulation
of actual-use vehicle operating
conditions and the accurate
measurement of gaseous and
particulate fractions are
necessary to produce valid
results. The chemical and
physical analysis of
components in exhaust
emissions is an essential part of
the research.
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14
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ESRL - Organization
Atmospheric Chemistry and Physics Division (ACPD)
Research in ACPD involves the
basic physical and chemical
interactions between pollutants
and the atmosphere, as well as
the search for and identification
of new, unrecognized pollutants.
The Division conducts
research to:
Develop techniques,
methods, and instruments
for characterizing pollutants
in the ambient air.
Characterize the chemical
and physical properties of
ambient air pollutants.
Understand the
relationships between the
chemical composition and
physical properties of
airborne pollutants and
atmospheric processes.
Determine physical rate
constants, chemical
reaction mechanisms, and
pollutant transformations
occurring in the
atmosphere.
In conducting this research, the
Division's efforts concentrate on
characterizing both man-made
and natural pollutants in the
ambient air, and describing their
reactions, transformations and
concentrations in the
atmosphere. Laboratory, field,
and modeling studies are used
to estimate local, regional, and
global impacts of pollutant
emissions and concentrations
and their chemical and physical
processes.
ACPD scientists develop the
necessary methodology and
instrumentation to characterize
all types of pollutants including
toxic and hazardous
substances such as
carcinogens, mutagens,
pollens, and biologically active
constituents. Aerosol research
investigations include the
characterization of airborne
particles, the transformation of
gaseous pollutants to aerosols,
mechanisms of formation, and
the physical and chemical
reactivity of these substances.
Laboratory and outdoor smog
chamber studies enable
scientists to determine the
mechanisms and rates of
chemical reactions of
atmospheric pollutants. These
studies furnish vital data for
developing photochemical
models that eventually become
part of air quality simulation
models.
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in
15
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m
'A I
16
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ESRL - Organization
Meteorology and Assessment Division (MAD)
The Meteorology and
Assessment Division's research
concentrates on describing the
atmospheric processes
affecting the diffusion and
transport of air pollutants.
Specifically, MAD's research
involves:
Developing air quality
simulation models that
describe the atmospheric
link between emissions and
ambient air quality.
Assessing the effects of
pollution on weather and
climate, with consideration
- given to long-term trends in
air quality.
Providing consultation and
meteorological services to
various EPA programs.
Activities within the Division
focus on the development,
evaluation, validation and
application of air quality
simulation models; these
activities make use of
knowledge of photochemical
and meteorological processes
that affect airborne pollutants.
Field studies are conducted to
evaluate and verify the models.
A Fluid Modeling Facility
consisting of both a wind tunnel
and water channel/towing tank,
is used to study atmospheric
transport and diffusion
processes.
Meteorological research covers
a wide range of areas. In
addition to the development of
local, regional, and global
models, which describe
relationships between
emissions and air quality,
scientists in MAD provide an
updated air pollution
climatology of the U.S. and carry
out studies that describe the
interrelationships of visibility,
radiation, and precipitation to air
quality.
The Fluid Modeling Facility is
used to simulate atmospheric
dispersion under unique
circumstances, e.g., in a stable
atmosphere, over complex
terrain, in and around buildings.
From these studies, plume
dispersion in the vicinity of
specific plant situations or under
various terrain features can be
assessed to describe its effect
on pollutant distribution.
The Division also provides
specialized modeling support
for other EPA offices and for
state and local governments in
developing their implementation
plans; this includes low-cost
modeling programs on a
computer network to industrial
and commercial users.
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ESRL - Organization
Regional Field Studies Office (RFSO)
RFSO is a relatively new
research group that was
established in January 1978. Its
responsibilities are to:
Plan and manage, often in
coordination with other
government agencies and
private groups, regional-
scale air pollution field studies
designed to assess the
transformation, transport, and
deposition of pollutants over
distances of 1,000 kilometers
or more, and areas containing
many individual and complex
emission sources,
Analyze and interpret the
data collected during the
regional-scale field studies.
Provide a comprehensive
data management system
for the storage, retrieval,
processing, analysis, and
display of data from
regional-scale field studies.
Presently, RFSO is conducting
studies to determine the
impact of air pollution on
visibility, and to assess the
effects of sulfates, nitrates, and
other aerosol pollutants and
their precursors on air quality.
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ESRL - Research Activities and Accomplishments
Regional Air Pollution Study
The most comprehensive study
of air pollution ever made in a
single metropolitan area was
completed in 1977. Conducted
in Greater St. Louis, the Regional
Air Pollution Study (RAPS) was
designed to develop and
validate air quality simulation
models that describe the
pollutants, where they come
from, how they mix and move,
and what eventually happens to
them in an urban atmosphere.
These models are needed for
evaluating least-cost pollution
control strategies clean air at
the lowest possible cost.
RAPS also had international
connections since it was an
integral part of the interchange
of environmental information
between the United States and
the Soviet Union. Leningrad was
the matching Russian city for
regional air pollution studies.
St. Louis was chosen as the site
of RAPS because it is a large
metropolitan area with typical air
pollution problems. The area
has a mixture of pollution
sources, both industrial and
automotive, and is reasonably
isolated from other major
pollution sources. Also, St. Louis
is remote from major
geographical features that
might lead to unique
complications in pollutant
distribution and composition.
Although ESRL planned and
managed RAPS, most of the
field work was carried out by a
prime contractor and several
subcontractors and grantees.
Numerous special field studies
were also performed.
The RAPS study plan was to
continuously monitor key
pollutants and meteorological
parameters over a 2-year
period, make an extensive
emission inventory of the area to
determine what and how much
is going into the air, and assess
the atmospheric transformation.
dispersion, and removal
processes for urban pollutants.
To measure the pollution and
meteorological parameters and
collect the data, the prime
contractor designed,
fabricated, set up, and operated
the Regional Air Monitoring
System (RAMS), an elaborate
25-station telemetering network
that covered a region extending
about 40 kilometers from
downtown St. Louis. Each
station continuously measured
ground-level carbon monoxide,
nitrogen oxides, total
hydrocarbons, methane, ozone,
wind speed and direction,
temperature and dew point.
Data from all the stations flowed
to a central computer system
where it was collected and
stored.
The comprehensive emission
inventory of stationary and
mobile sources included both
spatial and temporal details.
Some power plant and factory
stacks were monitored, and
records were kept of fuel
consumption and plant process
schedules. To handle the many
components of the emission
inventory, an emission data
base management system was
developed.
A number of intensive studies of
particular atmospheric
processes were conducted
during predetermined
experimental periods. .
Altogether, nine experimental
periods lasting four or five weeks
were selected. The number of
additional personnel involved in
these intensive studies ranged
from about 20 during
limited-purpose periods to
about 150 during summer
periods. These studies
included: aerial sampling from
helicopters circling over each
RAMS site to provide
researchers with a
three-dimensional distribution of
pollutants; quantifying changes
in composition, as a function of
time, of individual plumes
emitted by large isolated
sources and giant plumes from
the entire urban complex;
characterizing the air structure
over the urban and surrounding
rural areas to deduce the
physical parameters
responsible for rural-urban
differences of temperature and
wind dispersion properties;
evaluating various instruments
to determine the feasibility of
new methodologies; and
assessing the dry deposition of
pollutants onto natural surfaces.
Because of the tremendous
volume of data from the entire
study, efforts to ensure the
quality of data and its
accessibility were maintained
throughout the study. Numerous
cross-checks of the
performance of RAMS were
made including independent
quality assurance audits.
Although the collection and
much of the analysis of data
have been completed and a
number of technical articles on
the special studies have been
published, the difficult task of
developing and evaluating air
quality simulation models based
on the RAPS data base is not
expected to be completed for
another year or two.
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ESRL - Research Activities and Accomplishments
Revision of the Oxidant Criteria Document
In accordance with the 1977
amendments to the Clean Air
Act, EPA was ordered to review,
and if necessary, revise the
criteria document for ozone and
oxidant pollutants. A criteria
document is a compendium of
all the latest scientific evidence
for a pollutant that justifies an air
quality standard. Each
document contains information
on public health and welfare
effects, analytical measurement
techniques, ambient air
concentrations, natural sources,
chemical and physical
properties, and atmospheric
processes.
In addition to the health-related
information necessary for
developing air quality
standards, scientific evidence is
also needed for formulating
optimum strategies for
controlling oxidant pollution.
ESRL is responsible for
generating this evidence.
As a first step and in recognition
of the importance and
somewhat controversial nature
of the oxidant control problem,
ESRL organized and conducted
a five-day international
conference in September 1976.
A. two-volume proceedings was
published in January 1977.
A thorough ESRL review of the
more than one hundred
presentations and discussions
at the conference revealed
several key issues related to the
formulation of optimum control
strategies. This observation
prompted ESRL to sponsor a
follow-up effort by selected
national experts to examine the
available evidence and attempt
to resolve the issues.
The responses to this effort were
published as a series of issue
reports. ESRL scientists used
the information in these reports
to revise parts of the'criteria
document for ozone and other
photochemical oxidants, and to
prepare a companion document
consolidating all the scientific
evidence relevant to the control
strategy aspects of the oxidant
problem.
Vo/unw /
23
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ESRL - Research Activities and Accomplishments
Halocarbons and Ozone Depletion
The stratosphere, the upper part
of our atmosphere, contains a
layer of ozone that absorbs
much of the ultraviolet radiation
from the sun. If something were
to cause a depletion in the ozone
layer, excess ultraviolet
radiation could significantly
affect living things and possibly
alter climate and weather
patterns. Many scientists
believe that the discharge of
man-made halocarbons into the
atmosphere could cause
stratospheric ozone depletion.
Halocarbons are gaseous
compounds containing fluorine,
chlorine, bromine or iodine.
Some of these compounds are
widely used as refrigerants and
propellants for dispensing
aerosols. Because they are
essentially inert, the
halocarbons continue to
accumulate when released into
the atmosphere. However, very
short wavelength untraviolet
radiation, which is available only
in the stratosphere, can
photodissociate (break down)
the halocarbons when they
eventually reach the
stratosphere.
According to some scientists,
the products of
photodissociation can react with
the ozone in the stratosphere,
thus causing a gradual
depletion of the ozone layer.
Because of this possibility, the
Clean Air Act Amendement of
1977 mandated that EPA carry
out a broad research program to
determine the effects, causes,
and methods of avoiding ozone
depletion.
ESRL scientists became
concerned over halocarbon
pollutants as far back as 1971
CCIF2CFCI2
CHFCI2
CH3Br
CH3I
SF6
Quantities Unknown
CH2CI CH2CI CH2CI2
CHF2CI CH2CICOCI
Others
j_
50
100
150
200
25
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when they started a modest
program to study the
atmospheric chemistry of these
compounds. Later that year they
publicly voiced their concern at
a workshop on pollution
measurements sponsored by
NASA. The ESRL program was
expanded in 1975. During these
years, ESRL scientists
pioneered a technique for
studying photochemical
reactions in a large cylindrical
glass chamber that also serves
as an infrared absorption cell.
26
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In recent years, ESRL research
has focused on determining:
ambient air concentrations,
lifetimes, and removal paths of
halocarbons; the identity of
secondary pollutants created
during photodissociation; and
the lifetimes and removal paths
of secondary pollutants.
Although much of this research
is still underway, some results
are now known and indicate that
halocarbons are a potential
cause of ozone depletion.
Long Path Infrared Chamber
tor Studying Photochemical
Reactions
Ultraviolet
Lamps
Infrared
Source
Vacuum
Pump
Path qf In*rare_d_Radiation_
=»H
Manifold
Interfermeter
J
Detector
Gas-Handling System
27
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ESRL - Research Activities and Accomplishments
Atmospheric Sulfates Project MISTT
Atmospheric sulfate aerosols
have been implicated in a
variety of adverse ecological
and human health effects.
Although urban sulfur dioxide
concentrations have decreased
significantly as a result of
recently successful efforts to
meet air quality standards,
urban sulfate concentrations
have not followed pace. To
explain the prevailing sulfate
concentrations, researchers
cited the theory of
transformation-transport. In
recent years, power companies
have built new generating
facilities in rural coal mining
areas to be near fuel supplies
and also to help maintain low
SO2 levels in urban areas; thus,
SO2 levels have increased in
rural areas. According to the
theory, SOz from these new
power plants may be
transformed in the atmosphere
to sulfate and transported over
long distances to urban areas.
Interest in the
transformation-transport theory
has resulted in several major
ESRL research projects; the
most important was Project
MISTT (Midwest Interstate Sulfur
Transformation and Transport),
which was essentially
completed in the fall of 1977.
The overall objective of Project
MISTT was to study the
transformation of SOz to sulfate
during the transport of polluted
air masses both urban
plumes and power plant
plumes.
Project MISTT was conducted in
the Midwest where polluted air
masses, originating mainly in the
greater St. Louis area, were
studied. In addition to EPA
personnel, researchers from a
number of outside organizations
played important roles. Each
comprehensive plume study
was a coordinated effort
consisting of aerial and ground
level measurements of pertinent
chemical and meteorological
parameters. Plumes were
tracked and sampled as far as
300 kilometers from their source.
The final product was a
three-dimensional profile of
each large plume.
The results of Project MISTT
have confirmed the
transformation-transport theory
by demonstrating,
quantitatively, the
transformation of S02 to sulfate
in power plant and urban
plumes, and the concurrent
transport of sulfate aerosol for
distances of 200-300 kilometers.
In power plant plumes, the
conversion rate of S02 to sulfate
aerosol is slow near the point of
emission, but increases to
several percent per hour as
ambient air mixes with the
plume. Furthermore, tall stacks
reduce ground-level
concentrations of S02 and,
therefore, the amount of SCh
removed by dry deposition.
Thus, tall stacks increase the
atmospheric residence time of
SO2, which results in an increase
in the formation of sulfate
aerosols. In urban plumes that
are well-mixed to the ground
near the source, dry deposition
accounts for a more rapid
removal of SOz.
In addition to Project MISTT,
laboratory and outdoor chamber
experiments were carried out to
determine the relationships
between S02 oxidation and
gaseous precursors nitrogen
oxides and reactive
hydrocarbons common in
polluted air. The experiments
showed that reactive
hydrocarbons promote and
nitrogren oxides delay the
photo-oxidation of 862.
Furthermore, the experimental
data suggest that, in real
atmospheres, the daytime
conversion of SQz to sulfate by
these precursors may be limited
to 10-20 percent. This
conversion rate, in turn,
suggests a residence time (life)
for S02, with respect to reactions
involving these precursors, of
about 100 hours.
Research on atmospheric
sulfates continues. Meanwhile,
these studies have provided
new and important knowledge
on the transport and fate of
energy-related pollutants in
ecosystems.
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ESRL - Research Activities and Accomplishments
Oxidant Transport Studies
Airborne oxidants, which consist
largely of ozone, are
photochemical products of
atmospheric reactions involving
sunlight, oxygen, and emissions
of precursor pollutants -
nitrogen oxides and volatile
organic compounds. Because
oxidant formation is a complex
function of precursor
concentrations and
meteorological conditions,
oxidant control strategies are
the most difficult to develop of all
pollutant control strategies. One
difficulty concerns oxidant
transport.
During the past few years, field
studies carried out by ESRL
have shown that wind systems
can transport oxidants and
precursors over long distances.
During transport,
photochemical reactions occur
and continue to produce
oxidants. Complications arise
from the fact that (1) ozone
during transport is being both
produced and destroyed, and
(2) ozone transported into an
area cannot be quantitatively
distinguished from locally
generated ozone. Thus, such
transport phenomena obscure
the role and impact of local
emissions and the control of
such emissions.
To gain further knowledge on the
oxidant transport problem,
ESRL conducted a major field
study in the Midwest during the
summer of 1977. The study was
designed (1) to determine if
ozone levels in plumes
downwind from small urban
areas (population 200,000 or
less) are above background
levels; (2) to explore
stratospheric ozone intrusion by
observing vertical profiles of
Radiant
Energy
ozone and its precursors for
altitudes up to 20,000 feet; (3) to
measure background levels of
ozone and its precursors in rural
areas; and (4) to relate the
passage of high pressure
systems to pollutant transport.
Although analysis of the
collected data has not been
completed, preliminary results
show that plumes from small
urban areas (Terre Haute,
Urbana and Springfield) do not
significantly affect background
ozone levels (unlike plumes from
large urban areas like Detroit
and Cleveland). Also, there was
no evidence of significant
intrusion of stratospheric
ozone into the lower atmosphere.
Data analysis continues and,
when completed, the results will
better quantify the role of long
range oxidant transport on air
quality.
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ESRL - Research Activities and Accomplishments
Visibility in the Southwestern and Northeastern United States
Visibility reduction is probably
the most obvious effect of air
pollution to the layman. Visibility
is simply defined as the farthest
distance at which an unaided
human eye can see a high
contrast object against the
horizon sky. In completely clear
air, visibility would be limited to
about 200 kilometers by
molecules that make up the
atmosphere. Actually, however,
aerosols exist throughout the
atmosphere and reduce
visibility to appreciably shorter
distances.
There has been growing
suspicion that human activity is
causing a gradual decline in
visibility throughout the United
States. EPA has supported an
analysts of visibility
measurements made at
selected airports to learn what
visibility levels are now
measured, what their trends
have been over the past 25
years, and what relationships
exist between visibility and
certain key pollutants (using
National Air Sampling Network
measurements). Studies have
been made for the Southwestern
United States and for the
Northeastern United States.
Although visibility in the
Southwest is generally good
(median values of 105-130
kilometers for nonurban
locations) compared to other
sections of the United States, it
degraded 10-30 percent from
the mid-1950's to the early
1970's. Investigations of
visibility in the Phoenix, Arizona
area indicate that, of the
pollutant components
measured, only sulfate and
nitrate concentrations
significantly correlate with
visibility. The results imply that
sulfates account for 32-53
percent of the visibility loss due
to particles and that nitrates
account for 23-37 percent. The
regional copper strike of
1967-1968 resulted in an 80
percent reduction in sulfur
oxides emissions in the
Southwest. During the strike,
sulfate levels fell 38-76 percent,
while visibility improved 5-25
percent. The regression
equations developed for
Phoenix and Salt Lake City
satisfactorily predict the
improvements in visibility during
the strike.
Visibility in the Northeast is
rather poor with a median value
of about 16 kilometers.
Furthermore, visibility is no
longer substantially better in
nonurban areas than in
metropolitan areas. From the
middle 1950's to the early
1970's, visibility exhibited only
slight downward trends in large
metropolitan areas, but
decreased on the order of 10 to
40 percent in suburban and
nonurban locations. Over the
same period, visibility declined
remarkably during the third
calendar quarter relative to other
seasons, making the summer
now the worst season for
visibility. Regression models
based on daily variation in
visibility and pollutant
concentrations indicate that
sulfate aerosol is the single
major contributor to haze in the
Northeast. Sulfates apparently
account for approximately 50
percent of the visibility loss. The
seasonal/spatial patterns in
historical visibility trends also
agree with season/spatial
patterns in sulfate trends and
sulfur oxide emission trends.
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ESRL - Research Activities and Accomplishments
Power Plant Plumes in Complex Terrain
Fossil-fuel-fired electric power
plants are major sources of air
pollutants: mainly sulfur dioxide
(SOz), nitrogen oxides (NO,),
particulate matter, and trace
metals. In designing and
specifying pollution control
systems for new and existing
power plants, engineers make
use of modeling techniques to
calculate the physical behavior
of stack plumes. Knowledge of
pollutant emissions, stack
configuration, and meteorology
serves as input to the models.
However, the models have
pronounced limitations; they
generally assume a uniform
terrain roughness and are
typically weak in their ability to
handle plume depletion of
reactive pollutants (i.e., SO2 and
NOx) due to chemcial
transformation and deposition.
A need, therefore, exists to
develop improved techniques
for calculating the behavior of
pollutants in plumes from large
power plants and especially
from plants located in complex
(hilly or mountainous) terrain.
The latter is important because a
number of large coal-fired
power plants have been and are
being built in coal mining areas.
Often, the terrain in these areas
is complex, i.e., ground
elevations as high or higherthan
the tops of plant stacks occur
within the area traversed by the
plumes emitted from the stacks.
To better understand plume
behavior in mountainous terrain,
ESRL awarded a contract
several years ago for a
multi-year project to study the
behavior of stack plumes from a
coal-fired power plant located in
the Appalachain Mountains The
research plan consisted of three
phases: literature survey,
aerometric field study, and data
analysis and model
development. The literature
survey was completed in the
spring of 1976. It provided an
up-to-date description of
existing knowledge on plume
dispersion in mountainous
terrain.
The research team next
conducted a comprehensive
aerometric study in the vicinity of
the 700 megawatt Clinch River
coal-fired power plant located in
Southwest Virginia, a rural,
mountainous area. The study
was designed to fill the
information gaps by collecting
data on stack emissions,
ambient air pollutant
concentrations, and
meteorological conditions over
a relatively long period of time.
To collect data on ambient
pollutant (sulfur dioxide and
nitrogen oxide) concentrations
and meteorological conditions,
a monitoring network was set up
consisting of eight fixed stations
that operated continuously and
automatically and transmitted
the results to a data acquisition
station located at the power
plant. Stations were strategically
located to assess the effects of
terrain and meteorological
conditions on the characteristics
of the power plant plumes. The
automatic network also included
monitors to measure
ground-level SO2 and nitric
oxide concentration's in the
stack emissions. Furthermore,
the network was supplemented
by a mobile sampling unit that
was driven four or five days a
week to locations where the
plume could be observed to
affect ground-level air quality.
Upper air measurements from
balloons provided additional
meteorological data.
During two intensive 10-day
periods, airborne monitoring
from a helicopter was
conducted to produce vertical
and horizontal profiles of the
pollutants and meteorological
conditions in the plumes. These
three-dimensional
measurements provided a
detailed picture of plume
behavior.
The aerometric field study,
which collected data over a
16-month period, was
completed in the fall of 1977,
and an edited magnetic tape
listing of all the useful data has
been prepared. Researchers
are now working on the final
phase of this project the
analysis of data and
development of improved
dispersion models for
mountainous areas.
35
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ESRL - Research Activities and Accomplishments
Remote Sensing of Gaseous Pollutants
Determining the identity and
concentration of gaseous
pollutants by using
electro-optical techniques that
do not require any sample
collection or handling is
generally called remote
sensing. The remote sensing
techniques that are most useful
for characterizing gaseous
pollutants fall into three general
categories: longpath
absorption, where a light beam
(ultraviolet, visible, or infrared
energy) is transmitted through
the atmosphere over paths of a
kilometer or so to a receiver unit
that records the spectral
signature of whatever gases are
in the optical path; infrared
emission, where the infrared
signature of hot gases exiting
industrial stacks is recorded by
instruments located at some
distance (100-1,000 meters)
from the stack; and laser
backscatter, where natural
aerosols in the atmosphere
serve as reflectors for a
multiwavelength laser beam to
allow a Lidar-type pollutant
measurement.
The ESRL remote sensing
program has two primary goals:
to develop and use these
techniques to characterize
pollutants emitted by mobile or
stationary sources, particularly
when such characterization is
difficult using conventional point
sampling methods; and to
develop remote sensing
instrumentation that can be
used in typical enforcement and
surveillance operations (similar
to the use of radar by law
enforcement officers).
ESRL investigators successfully
demonstrated the use of an
infrared instrumentation system
for characterizing gaseous
pollutants. The system is
suitable for use in either the
longpath absorption or infrared
emission modes of operation.
The heart of this sytem, called
the ROSE (Remote Optical
Sensing of Emissions) system, is
an infrared Fourier transform
spectrometer that is located in a
van. The spectrometer can be
driven to any desired location
and is used with a remotely
located infrared light source to
obtain spectral absorption
signatures of pollutants or, with
the aid of an auxiliary mirror
aimed at the top of a stack, to
obtain an infrared emission
signature of stack effluent.
Although not all pollutant gases
possess an infrared signature,
and the strength of the various
signatures can vary over several
orders of magnitude, the ROSE
system has sufficient sensitivity
in the absorption mode to
measure the concentration of
many pollutants in the 10 ppb
range over a kilometer path. The
system is less sensitive in the
emission mode because the
optical path containing the
pollutants is determined by the
stack diameter (several meters
or so); a typical lower sensitivity
is on the order of 10 to 50 ppm.
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ESRL - Research Activities and Accomplishments
Sulfur Transport and Transformation in the Environment (STATE)
Sulfates, nitrates, and other
aerosols are major constituents
of atmospheric pollution. To
develop control strategies for
reducing these pollutants,
scientists must understand their
transport and distribution in the
atmosphere. The STATE
program is designed to provide
the data base to enable
scientists to describe the
atmospheric processes on
these airborne pollutants. One of
the main objectives of STATE is
to determine the impact of
sulfates and nitrates on air
quality at locations distant
(100-1,000 kilometers) from the
sources of the pollutants.
The STATE program is designed
to encompass two distance
scales: plume scale and
regional scale. Plume-scale
studies are made over distances
up to 400 kilometers from the
source. This distance
represents the limit that an
isolated pollutant plume may be
readily identified as an entity.
Regional-scale studies
encompass large areas and
distances of 1,000 kilometers or
more. Within these areas,
emissions from many individual
sources and source complexes
mix and interact. At the plume
scale, the major concern is the
measurement of all important
variables within the plume and
their variations with time, space,
and meteorological conditions.
Regional-scale studies
investigate natural emission
sources, deposition of primary
pollutants, transformation
products, and information
essential for regional-scale
models.
The first STATE field study,
performed in August 1978,
Instrumented Aircraft
Makes Several Horizon-
tal Traverses at Differ-
ent Altitudes in a Verti-
cal Plane Perpendicular
to the Plume
Pilot Balloon to \
Measure Wind
Speed and Direc-
tion as a Func-
tion of Altitude
consisted of an intensive
investigation of the plume from
the Tennessee Valley Authority's
Cumberland power plant, a
2,600 megawatt coal-burning
plant located in north-central
Tennessee. Twenty
organizations took part in this
study. Experiments lasting up to
24 hours were carried out over
distances ranging up to 400
kilometers from the plant.
Extensive use of tracers was
included, both to Ipcate the
plume and quantify plume
dispersion, and as a constituent
to aid in interpreting chemical
changes of plume components
asthe plume dispersed and was
transported downwind. Mobile
ground-based and airborn
Lidars were used to
characterize the plume
structure; gaseous and aerosol
pollutants were measured from
four aircraft and three mobile
ground units. Two fixed and
three mobile crews obtained
meterologicai soundings during
the course of each experiment.
In addition, turbulence
parameters were extensively
measured from two fixed tower
installations and an aircraft.
Data collected during the study
are being analyzed to
characterize and quantify
dispersion and transformation
processes affecting the plume.
The eventual end product of the
STATE program will be air
quality simulation models that
describe the distribution of
sulfates and nitrates over the
eastern United States.
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ESRL - Research Activities and Accomplishments
Mobile Source Emissions
ESRL's research on mobile
sources has historically been
concentrated in two areas: the
search for new toxic emissions
that may be introduced as a
result of efforts to control other
pollutants or to decrease fuel
consumption, and the solution of
problems associated with
measuring automotive pollutant
emissions in a variety of
regulatory situations.
Recently, changes in
automotive catalysts to control
emissions of nitrogen oxides
and the introduction of diesel
passenger cars have both
created new pollutant
uncertainties and have caused
new problems with
measurement procedures for
old pollutants. Using
dynamometer test facilities,
ESRL researchers have
developed improved
procedures to measure both
unburned hydrocarbon fuel
components and soot particles
in the exhaust of diesel
passenger cars. The new
procedures have improved
EPA's capability to regulate
these pollutants and have
facilitated ESRL's studies to
characterize these emissions.
ESRL researchers have
identified a variety of previously
unrecognized pollutants in the
exhaust of gasoline powered
cars equipped with new
three-way catalyst systems for
controlling nitrogen oxides,
hydrocarbons and carbon
monoxide. To insure that these
new control systems produce no
significant amounts of harmful
secondary pollutants, ESRL
researchers have developed a
number of new techniques to
measure such emissions in both
normally operating and
malfunctioning cars. The new
techniques have been
distributed to the automobile
industry to provide guidance in
complying with new rules for
unregulated pollutants.
A major research effort has been
underway to determine the
presence of mutagenic
compounds in diesel emission
soot. ESRL chemists are
assessing the nature and
structure of potentially
cancer-causing chemicals in
soot emissions and finding ways
to sample and measure these
compounds. Large amounts of
soot have been collected and
samples sent to various parties
for biological testing.
Evaporative loss emissions from
passenger cars are also being
analysed for trace amounts of
hazardous chemicals.
These activities indicate the
special role of ESRL in EPA's
overall mobile source pollution
control program, i.e., to
anticipate problems in pollution
control and to provide the
measurement procedures and
scientific background needed
for understanding and solving
such problems before they
arise.
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ESRL - Research Activities and Accomplishments
Stationary Source Emissions
Stationary, fossil-fuel-fired
combustion sources, such as oil
and coal-fired furnaces and
power plants, are heavy emitters
of sulfur dioxide, sulfates
(particles containing sulfate
compounds), and sulfuric acid
mist, Emission control strategies
for these sources require the
accurate characterization of
particulate and gaseous
pollutants. ESRL scientists
conducted research to
thoroughly and accurately
characterize the emissions from
a variety of stationary sources
and to assess their subsequent
impact on the ambient air.
Initial ESRL studies of oil-fired
power plants showed that the
emission factors for sulfur
pollutants attributed to this
source by a previous technical
publication were somewhat low.
This finding prompted an
examination of sampling and
analytical techniques for sulfur
pollutants and specifically for
sulfuric acid mist. As a result of
laboratory and field studies,
ESRL scientists developed
significantly-improved
techniques. Subsequently, the
particle size distribution of
emissions was measured and
the sulfur pollutants in various
particle size fractions identified.
The characterization studies
showed that the sulfur and
vanadium content of the fuel oil
and the plant operating
conditions are the main factors
governing the distribution of
sulfur compound emissions.
Characterization studies were
also conducted on coal-fired
power plants using high sulfur
fuel. The studies included plants
with and without emission
control devices. The devices
included electrostatic
precipitators and wet limestone
scrubbers (flue-gas
desulfurization). Although the
scrubbers effectively removed
sulfur dioxide emissions, the
ESRL researchers found that the
scrubbers did not effectively
remove sulfuric acid mist.
of both primary sulfates
(combustion products) and
secondary sulfates (ambient air
reaction products) transported
from distant sources. Dispersion
models have shown that primary
sulfate emissions can have a
marked impact on ambient air
sulfate concentrations
downwind of a source. These
field studies are expected to
A new research effort to study
the impact of primary sulfate
emission sources (SIPSES) on
the ambient air began in the late
summer of 1978. The initial field
study involves an oil-fired power
plant located in the Northeast.
Researchers are investigating
(1) the relationships between
sulfur, sulfate, and sulfuric acid
emissions from this source and
concurrent ground-level
concentrations of sulfate in a
circular area with a 10-kilometer
radius from the plant, and (2) the
impact of stationary-source
primary sulfate emissions on
background levels of
atmospheric sulfates.
Background levels may consist
provide a more accurate
assessment of the impact of
primary sulfate emissions on the
ambient air
ESRL sponsored an important
three-day workshop on primary
sulfate emissions from
combustion sources. The
workshop brought together
scientists from government,
industry, and the academic
community to share information
on recent advances in methods
for measuring sulfate emissions
from such sources as
fossil-fuel-fired power plants
and industrial boilers, and for
evaluating the impact of the
emissions on the ambient air.
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ESRL - Research Activities and Accomplishments
Ambient Air Sampling and Analytical Techniques
Understanding and controlling
air pollution are directly related
to the ability to identify and
accurately measure airborne
contaminants. The more
complex the numbers and types
of pollutants, the more difficult
this task becomes. ESRL has
many scientists whose research
involves developing methods
and techniques for sampling
and analyzing pollutants.
Ion chromatography is a new
analytical technique that is now
in widespread use as a direct
result of ESRL's successful
application of this concept in
measuring sulfates and nitrates
in the atmosphere. Ion
chromatography is a
combination of two old
techniques: ion exchange
chromatography, and
conductivity detection. Eluent
suppression, the removal of
unwanted ions from the
sampling solvent without
affecting the ions of interest, is
the innovation that makes the
combination possible.
Ion chromatography is a highly
selective and sensitive tool. Its
advent is particularly significant
since a number of different
pollutants can be analyzed by a
single technique that formerly
required many different,
cumbersome techniques. ESRL
has demonstrated that ion
chromatography is a very
powerful analytical tool for the
precise measurement of a large
number of ions found in the
atmosphere. In addition, it is
particularly effective for
measuring atmospheric sulfur
dioxide.
ESRL researchers have
uncovered several potential
sources of error when analyzing
for nitrates in particulate
samples collected by
high-volume samplers. The
most serious error is caused by
the reaction of gaseous nitric
acid with alkaline constituents in
glass fiber filters. Acid-base
reactions result in the deposition
of extraneous nitrate material
(nitrate artifact) on the filters; the
extraneous deposit is unrelated
to particulate concentrations.
Replacing glass fiber filters with
Teflon filters has resulted in a
significant improvement.
A dichotomous sampler is a
device that simultaneously and
separately collects those
particles that are 2.5
micrometers and larger and
those that are smaller. The
smaller particles are typically
composed of sulfate
compounds and vehicle
exhaust species; the larger
particles are usually composed
of wind-blown dust and primary
emissions from industrial
activities. Major improvements
have been made that now
enhance the sampler's ability to
collect airborne particles under
a variety of hostile environmental
conditions.
A newly designed version of the
dichotomous sampler provides
for the automatic changing of
samples, thus minimizing
frequent visits to the sampling
site. The new design has fewer
parts, is economical, minimizes
sample losses, and is highly
reliable in field use. A pneumatic
flow rate controller was also
developed to maintain a
constant flow rate as aerosol
deposits accumulate on the
filters. Inert Teflon filters have
replaced glass fiber filters, thus
minimizing the problem of
artifact formation on filters. The
improved dichotomous sampler
allows scientists to measure a
wider range of inorganic and
organic species present in
ambient air particles than was
possible with previous
samplers.
A fluorescence technique for
determining ambient air
concentrations of nitrogen
dioxide was developed. Using
flashlamp-induced
fluorescence, nitrogen dioxide
is detected by its unique
electronic energy level
structures; this eliminates
interferences that exist when
using other analytical
techniques.
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ESRL - Research Activities and Accomplishments
Atmospheric Modeling
Because of the vastness and the
number of variables involved,
calculating pollutant movement
in the atmosphere is extremely
difficult. To predict the
distribution and concentration of
pollutants under specific
conditions, scientists develop
air quality simulation models
(AQSM). AQSMs use
meteorological, chemical, and
physical measurements,
together with mathematics and
sophisticated computers, to
simulate the process and
disposition of pollutants in the
atmosphere. The models can be
used to evaluate pollution
control strategies by predicting
pollutant concentration
distributions for known or
hypothetical emission sources
and weather conditions.
Most currently available AQSMs
are not adequate for use in
problems where obstructions
such as buildings or difficult
terrain block the flow of wind. For
such complex situations,
special fluid modeling
techniques are being
developed and used to simulate
atmospheric dispersion. Fluid
modeling involves the use of
scaled representations of
buildings or terrain features in a
wind tunnel or water
channel/towing tank.
Air Quality Simulation Models
(AQSM)
ESRL provides AQSMs to local,
state, and federal agencies
through a User's Network for
Applied Modeling of Air Pollution
(UNAMAP); this network
currently has 11 different
AQSMs. Available AQSMs are
47
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frequently far from perfect; thus,
ESRL scientists continue to
conduct research designed to
improve existing models and to
develop new ones.
The dispersion and dynamics of
the urban boundary layer (lower
layer of atmosphere) were
studied in St. Louis.
Concentrating on the decay of
the nocturnal inversion (stable)
layer and growth of the mixed
(unstable) layer during the early
morning, scientists observed
large differences in air quality
and meteorology between
urban and rural sites. They
concluded that wind transport
(advection) and land-use
energy budget variations must
be considered in urban
boundary layer models.
Field studies of emission plume
rise (e.g., from a smokestack)
were conducted using
measured profiles of wind and
temperature. Results show that
plumes from taller stacks tend to
remain airborne longer and are
transported farther before
breaking up than plumes from
shorter stacks.
Using meteorological data
obtained from highway field
studies, ESRL scientists have
improved the prediction
capability of a line-source model
that depicts the concentration
distribution of pollutants emitted
by mobile sources.
Researchers have used
photochemical modeling
techniques to develop more
valid, mechanistic models for
relating emissions to ozone air
quality. Unlike previous
empirical models, mechanistic
models are based on
48
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cause-effect relationships
between precursors and ozone.
The relationships are derived
from chemical reaction
mechanisms based on
laboratory studies. Mechanistic
models also have greater
usefulness because they
consider the role of nitrogen
oxides in the ozone-forming
process. Thus, the models can
be used to estimate the degree
of control of both non-methane
hydrocarbons and nitrogen
oxides that would be needed to
achieve a specific level of
ozone.
demonstrated that this is a good
rule for conventional shaped
buildings, but not for tall, thin
buildings. Fluid modeling
studies have shown that a tall,
thin building has no effect on a
plume when the stack is 11/2
times the height of the building.
These results indicate that, in the
case of tall, thin buildings,
money could be saved and
emission requirements met by
using less expensive, smaller
stacks.
Fluid Modeling
By placing a replica of the
topography surrounding a
power plant in a meteorological
wind tunnel, ESRL scientists
were able to duplicate in the
tunnel the meteorological
conditions around the Clinch
River coal-fired power plant.
These studies showed the
movement of smoke plumes
from the stack of the power plant
replica in mountainous terrain.
The wind tunnel results were
used to evaluate a dispersion
model against the data obtained
from the field studies carried out
at the power plant site.
An old "rule of thumb" in
chimney engineering says that a
stack placed next to a building
must be 21/a times the height of
the building to avoid downwash
of the plume. Such downwash
would result in high-pollutant
concentrations at ground levels.
By conducting wind tunnel
studies, ESRL scientists have
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ESRL - Research Activities and Accomplishments
Effects of Natural Hydrocarbons
Non-methane hydrocarbons
from gasoline vapors and auto
exhaust contribute to the
formation of ozone pollution in
the atmosphere over urban
areas. In recent years,
unexpectedly high levels of
ozone have been measured
over rural areas. Scientists have
observed that natural
hydrocarbons are released from
many types of vegetation. An
estimated one billion tons per
year are released worldwide.
Although the transport of ozone
and ozone-producing pollutants
to rural areas has been
established, the possibility
exists that the ozone observed in
rural areas may also be the
result of reactions involving
naturally released
hydrocarbons.
To investigate the role of natural
hydrocarbons in the production
of ozone, ESRL conducted two
complementary studies, one
that measured hydrocarbon
emission levels from loblolly
pines, and another that
determined the photochemical
reactivity of natural
hydrocarbons.
To establish the significance of
natural hydrocarbons in
producing ozone, scientists
need to know the amount
released by vegetation.
Methods normally used to
measure emission levels
(extrapolating emission levels
from an enclosed branch of a
tree to an entire forest) present
accuracy problems. To
circumvent problems
associated with earlier
techniques used to estimate the
emission levels of various types
of vegetation, ESRL scientists
measured the emissions from a
loblolly pine forest in North
Carolina. This study made use of
measurements of net radiation,
water vapor, temperature,
carbon dioxide, wind speed,
and the vertical concentration
gradient of alpha-pinene, a
hydrocarbon emitted by
coniferous trees.
Emissions of alpha-pinene
ranged from 34 to 67
/ng/m2/minute with the highest
emissions at highest
temperatures. Field studies in
many United States cities failed
to show concentrations of
natural hydrocarbons at these
levels. ESRL investgators,
therefore, have concluded that
natural hydrocarbons have little
effect on the air quality of a city,
even if heavily forested areas
were nearby.
Since even low concentrations
of hydrocarbons may still
produce high levels of ozone if
the hydrocarbons are very
efficient in producing ozone, it
was also necessary to assess
the photochemical reactivity of
natural hydrocarbons. Eight
natural hydrocarbons including
alpha-pinene were evaluated
Propylene, a hydrocarbon in
auto exhaust, was used as a
reference compound. Results
indicate that natural
hydrocarbons are not efficient
ozone producers.
These natural hydrocarbon
studies suggest that natural
hydrocarbons do not markedly
affect air quality over urban
areas, tend to serve as a sink for
ozone in rural areas, and do not
significantly contribute to the
formation of ozone in rural areas.
S[>eea & Direction
NX). CO? & Temperature, a Pmene
Heal Flux S&nsor //
- t Soil Temperature Sensors //
/ J/////////////
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ESRL - Research Activities and Accomplishments
Houston Air Pollution Research Study
ESRL is responsible for air
quality research which includes
studies to determine aerosol
composition, the accuracy of an
ozone model, natural sources of
organic compounds, and
intrusion of stratospheric ozone
into the lower atmosphere.
During the early fall of 1978, an
intensive field study was
conducted and considerable
data collected. The data has
been archived and is presently
being evaluated. Current plans
are to report the results at a
two-day conference tentatively
scheduled for late August 1979
in Houston.
The Houston study is being
carried out through in-house,
contract, and grant efforts with
substantial assistance from
local governments and EPA
Region VI. Considerable input
has also been received from
Houston industrial citizen, and
environmental groups.
Through the Clean Air Act and a
special Congressional
mandate, funds were provided
to study pollution problems
along the southern Texas Gulf
Coast. As a result, EPA initiated
the Houston Air Pollution
Research Study. The Houston
area was selected because of
certain unique features:
numerous industrial activities
and automobiles as the main
sources of pollution; high
humidity coupled with high
temperatures and abundant
sunshine that provide conditions
suitable for photochemical
pollution formation; frequent sea
breezes; and occurrences of
reduced visibility associated
with poor air quality.
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