United States
Environmental Protection
Agency
Atmospheric Sciences Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S3-86/004 June 1986
Project Summary
Guidelines for Using
OZIPM-3 With CBM-X or
Optional Mechanisms
H. Hogo, G. Z. Whitten, and Marcia C. Dodge
The U.S. Environmental Protection
Agency is continuing to recommend the
use of the Empirical Kinetic Modeling
Approach (EKMA) as a procedure for
relating levels of photochemical ozone
to levels of organic compounds and
oxides of nitrogen. In an earlier study.
Systems Applications developed a new
chemical mechanism that is suitable for
use in EKMA. The mechanism, called
the extended Carbon Bond Mechanism
(CBM-X), provides the most up-to-date
and verified description of urban smog
chemistry Currently available. In the
study reported here, a new computer
program, called Ozone Isopleth Plotting
with Optional Mechanisms—Version 3
(OZIPM-3), was developed to enable
the use of the CBM-X mechanism for
EKMA control strategy calculations.
The OZIPM-3 program also has the
capability to accept a chemical mecha-
nism other than the default CBM-X that
is internally stored in the program.
Volume 1 serves as the User's Manual
for OZIPM-3. It contains a detailed
description of how OZIPM-3 operates.
It also contains a thorough discussion
of the different input and output options
available to the user when exercising
either the default CBM-X mechanism or
an optional mechanism. Five examples
of OZIPM-3 simulations are presented.
Input and output files for each example
are included. Volume 2 contains the
FORTRAN listing of the computer code.
A magnetic tape of this code is also
available.
This Project Summary was developed
by EPA's Atmospheric Sciences Re-
search Laboratory, Research Triangle
Park. NC, to announce key findings of
the research project that is fully docu-
mented in two separate volumes and a
magnetic tape of the same title (see
Project Report ordering information at
back).
Introduction
For several years, the EPA has used the
Empirical Kinetic Modeling Approach
(EKMA) to estimate reductions in emis-
sions of volatile organic compounds (VOC)
needed to achieve the National Ambient
Air Quality Standard (NAAQS) for ozone.
The objective of the study reported here
was to develop a computer program to
enable the use of the latest photochem ical
kinetics mechanism in EKMA for control
strategy calculations. This mechanism is
called the extended Carbon-Bond Mech-
anism (CBM-X). It is described in the
report "Modeling of Auto Exhaust Smog
Chamber Data for EKMA Development"
(EPA/600/3-85/025). The computer
code developed is called Ozone Isopleth
Plotting with Optional Mechanisms—
Version 3 (OZIPMJ-3). It expands on
earlier codes by providing a wider com-
patibility between computers, a feature to
calculate VOC reduction without drawing
an isopleth diagram, and easier input of
photolysis rates when operational chem-
ical mechanisms are selected.
Features of the CBM-X
The expanded mechanism was com-
prehensively developed and tested to
provide the most up-to-date and verified
description of urban smog chemistry
currently available. In addition to testing
of the whole mechanism, independent
testing of various parts of the CBM-X was
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conducted. In particular, the inorganic
reactions, common to all smog chemistry,
were tested against a wide range of smog
chamber experiments involving various
combinations of NO, N02, CO, formalde-
hyde, temperature, humidity, and light
conditions. The same inorganic reactions
were then combined with each of the
subsets (such as acetaldehyde, ethene,
toluene, and xylene) to verify each chem-
istry subset using smog chamber data
specific to each. Finally, the whole CBM-
X was tested by simulating auto exhaust
and synthetic urban mixtures in single-
and multiple-day experiments. Since the
reaction set includes, directly or indirectly,
all the key reactions that have been
recommended and independently evalu-
ated for smog photochemistry, the CBM-X
is currently the most evaluated and tested
mechanism available. Other mechanisms
are being developed, however, and the
CBM-X is still being tested and refined. In
particular, the CBM-X is being evaluated
under dynamic conditions intended to
simulate entrainment of pollutants into
the mixed layer from either aloft or fresh
emissions. The fresh emissions also vary
widely in reactivity in the new tests.
Features of the New
Computer Code
Some of the features in the new
computer code OZIPM-3 expand the
EKMA model itself. These features in-
clude the ability to specify the following:
the zenith angle dependence of photolysis
reactions; hourly temperature variations;
optional start and stop times; different
mixtures of precursors and ozone plus
other species for initial, aloft, and back-
ground conditions and for emissions; and
surface deposition (which can vary in
time for up to 10 species). The model still
has the features of optional kinetic mech-
anisms, automatic zenith angle genera-
tion, and diurnally variable emission
rates. The outputs are similar to previous
OZIPM versions in that single trajectory
calculations can be performed, VOC
reduction estimates can be computed
independently of an Oa isopleth diagram'
if needed, and isopleth diagrams can be
prepared for any species, including 03.
The computer code is limited by the
timewise fixed reactivities or concentra-
tions from the precursors in emissions or
aloft. Limitations on model formulation
include those on trajectory models in
general, such as horizontal mixing, wind-
shear effects, eddy diffusion, heterogen-
eous chemistry, and aerosol light scatter-
ing. Also, EKMA modeling is not designed
to treat plumes, rural ozone problems, or
situations dominated by transport of
ozone or its precursors. OZIPM-3 has
been prepared using FORTRAN-66 to
make it adaptable to a wide range of
computers. However, the 7000 lines of
code may require computers of moderate
size.
Summary
The new CBM-X mechanism and its
use in the new computer code, OZIPM-3,
are described in detail in the project
report. The report provides guidance for
using the new chemistry and code in the
EKMA procedure developed by the EPA
for estimating VOC reductions needed to
meet the ozone standard. It should be
noted, however, that the CBM-X is still
undergoing additional testing and refine-
ment, which will not be completed until
late 1987. Until that time, it is recom-
mended that OZIPM-3 with the CBM-X
mechanism be used only as a research
tool.
The new CBM-X was developed and
tested to provide the most up-to-date and
detailed chemistry suitable for use in
EKMA. Although the new code contains
the CBM-X embedded as a default mech-
anism, other mechanisms can be utilized.
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H. Hogo and G. Z. Whitten are with Systems Applications, Incorporated, San
Rafael, CA 94903; the EPA author Marcia C. Dodge (also the EPA Project
Officer, see below) is with the Atmospheric Sciences Research Laboratory,
Research Triangle Park, NC 27711.
The complete report consists of two volumes and software for Volume 2, entitled
"Guidelines for Using OZIPM-3 with CBM-X or Optional Mechanisms:"
"Volume 1. Description of the Ozone Isopleth Plotting Package/Version 3,"
(Order No. PB 86-187 770; Cost: $22.95)
"Volume 2. Computer Code." (Order No. PB 86-194 248; Cost: $16.95)
"OZIPM-3 Source Code (software for Volume 2)," (Order No. PB 86-187 788;
Cost: $685.00, includes paper copy)
The above items will be available only from: (cost subject to change)
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Atmospheric Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S3-86/004
0000329 PS
U & ENVIR PROTECTION AGENCY
REGION 5 LIBRARY
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