U.S. Environmental Protection Agency
                                       Office of Research and Development
 June 2001
  NATIONAL  EXPOSURE  RESEARCH LABORATORY
 JVTERI,      £001
»^^^^^^^^^^L^_^^L^^jB           ilta^^^^^-
                 Volume 4, Issue 2
  In This Issue
      Click On A Topic

Research
  "MIMS" the Word
  Detecting Dangerous Molds
  COPP Exposure Behind the
   Wheel
  More Research

Top Side
  A Tale of Success
  Multi-year Planning
  HPO Update

NERL Notables
  Awards
  Open House

Feedback
  "Doing Your Thing" Behind
   the Boss' Back...

Task Information
                            "MIMS" the Word
         Models form the cornerstone of virtually
       every regulatory program and policy deci-
       sion in the EPA.  Models are used for set-
       ting discharge limits for point sources to
       waterways, for registering pesticides, for
       determining whether a waste should be
       "listed" as hazardous, and for guiding State
       plans that determine allowable limits for air
       pollution sources, just to name a few ex-
       amples. No one knows exactly how many
       models EPA uses or sanctions for use, but
       the number is certainly in the hundreds, and
       most share one
       characteristic:
       they have been
       developed to
       support a single
       regulatory pur-
       pose.
         The result
       has been that
       existing models
       tend to focus on
       the sources,
       transport, and
       fate of particu-
       lar pollutants of
       concern, and
       often on a narrow range of sources and/or
       media of concern. Typically, all other things
       (sources, pathways, media, receptors) are
       treated as equal, and the models reflect time
       and space scales peculiar to the regulatory
       or policy decision, whether or not there are
       other relevant processes occurring at other
       time and space scales (e.g., local versus re-
       gional, or daily versus seasonal averages).
       Inputs to the model from other media, or
       occurring at other scales, are usually treated
       as forcing functions or parameters that are
       not themselves influenced by the processes
       being simulated by the model, and the be-
       havior of receptors is often treated simplis-
tically or ignored. Increasingly, however, a
broader environmental scope must be con-
sidered to understand all of the contribu-
tions and interactions that might have a
significant effect on policy options and deci-
sions.
  The recent attention to Total Maximum
Daily Loads (TMDLs) under section 303 of
the Clean Water Act provides a good ex-
ample. For all water bodies not attaining
their designated use, States must determine
the Total Maximum Daily Load of the
                       pollutant(s)
                       allowed to enter
                       that water body
                        (with an ad-
                       equate margin
                       of safety) and
                       still allow it to
                       attain its desig-
                       nated use. The
                       State then must
                       allocate the
                       current loads of
                       the pollutant
It's clear there is a pronounced need
for a flexible, Multimedia
Integrated Modeling System
(MIMS) that will allow scientists to
efficiently and effectively couple
the kinds of models already
developed for single media, single
scale applications into a functioning
modeling system suitable for the
environmental management
decisions of the next decade.
                                                                                          ous present and
                                                                                          anticipated fu-
                                                                   ture sources and devise an implementation
                                                                   plan for reducing pollutant inputs from the
                                                                   various sources to achieve the TMDLs. In
                                                                   the case of nitrogen, a pollutant which
                                                                   threatens roughly one third of the estuaries
                                                                   in the U.S., sources include atmospheric
                                                                   deposition from power plants, cars, trucks,
                                                                   boats, lawnmowers, fertilizer applications,
                                                                   and land application of fertilizer or animal
                                                                   manure ranging in scales from hundreds of
                                                                   miles distant to a few tens of meters from
                                                                   the receiving stream. Other sources include
                                                                   storm water runoff from streets, golf
                                                                   courses, and farms (including overflows
                                                                   from wastewater treatment plants and

-------
                                             Research
         Research
Top Side
 NERL
Notables
Feedback
lagooned animal wastes), septic tank drainage, soil mineraliza-
tion, and even atmospheric deposition that enters the water
body as groundwater. Allocating the nitrogen load among the
various sources requires a model that can accurately simulate
the movement of nitrogen from the atmosphere to the land
and water surfaces (and vice-versa), the movement of nitro-
gen from point and non-point sources to groundwater and
surface water channels (with particular attention to storms),
the movement of nitrogen through groundwater to the water
body, and eventually the behavior of nitrogen in the estuary,
in addition to quantifying the uncertainties involved.
  NERL began development of the Multimedia Integrated
Modeling System (MIMS) three years ago, building on the
success of integrating several air quality and meteorological
models into the Models-3/Community Multi-scale Air Qual-
ity (CMAQ) model now used by EPA's Office of Air Quality
Planning and Standards, and the States to evaluate and sup-
port air quality management decisions across the U.S. The
project has involved two  closely interacting activities:
  •  Developing better models for air, water, soil, and recep-
    tor interactions and
  •  Developing a MIMS  software framework.
  An important early success has  been the development of
the Frames/3MRA Model in conjunction with the  Hazardous
Waste Identification Rule (HWIR). This model simulates the
movement of any of a large number of potentially hazardous
substances away from a waste site  through air, water, and
groundwater pathways, and their ultimate exposure to hu-
mans and wildlife, along with the associated uncertainty. The
model is user-friendly and is appropriate for use at individual
sites, as opposed to regions.
  We are studying nitrogen in the Neuse River Basin in
North Carolina, because  it spans many issues that are or will
be common to solving problems in a multimedia framework
at multiple scales (e.g., site to region) and involves feedback
among the different media and pollutants.  [See Virtual Field
Reference Database  article.] The Neuse nitrogen issue chal-
lenges us because we must work in a complex watershed and
with a pollutant that originates from a myriad of sources trav-
eling though all major media. [See NEXRAD article.]
  The MIMS framework that will be evaluated during the
Neuse modeling effort is intended to provide a software in-
frastructure for constructing, composing, and applying multi-
scale, cross-media models, and evaluating and applying the
results to the watershed management needs of the States and
Tribes.  The MIMS framework will allow multimedia model-
ers to focus more on the science and less on the mechanics
                    of acquiring and applying new combinations of models and
                    data.  By designing the framework with an open architecture
                    and working with external modelers and framework develop-
                    ers, the MIMS team is working to foster a community ap-
                    proach to multi-disciplinary ecosystem modeling and analysis.
                      This community approach is critical. The Models-3/
                    CMAQ effort, Frames/3MRA, and the Neuse projects have
                    involved modelers working in several NERL divisions, the
                    EPA Programs and Regions, the States, other federal agen-
                    cies, and independent academic grantees. To promote future
                    progress, ORD has entered into an interagency Memoran-
                    dum of Understanding with the Nuclear Regulatory Commis-
                    sion, Corps of Engineers, and Departments of Energy,
                    Interior, and Agriculture to promote coordination across the
                    federal agencies with an environmental mission.
                                      Gary Foley, NERL Director, (919) 541-2106
                                                         NERL Task #6449
                   Detecting Dangerous Molds
                      Two NERL-Cincinnati scientists have developed an inno-
                   vative way to detect potentially dangerous molds much faster
                   and with greater accuracy.  The new technology can be used
                   to detect the mold Stachybotrys, commonly known as "black
                   mold," and more than 50 other possibly problematic molds.
                                                •S
                          *22

                              f
                              Richard Haugland and Stephen Vesper

                      Molds typically grow in buildings affected by water damage
                   and have been found in homes, hospitals, schools, and office
                   buildings. It is estimated that about 50 to 100 common in-
                   door mold types have the potential for creating health prob-
                   lems.  Exposure to mold has been identified as a potential
                   cause of many health problems including asthma, sinusitis,
                   and infections.  It is also believed that molds play a major role
                   in cases of sick building syndrome and related illnesses.
                                                      PageS

-------
                                             Research
         Research
Top Side
 NERL
Notables
Feedback
  Drs. Stephen J. Vesper and Richard Haugland conducted
their research at the NERL Microbiological and Chemical
Exposure Assessment Research Division where they have
developed a DNA-based system that allows rapid identifica-
tion and quantification of molds in a matter of hours versus
current methodologies, which require days or weeks to iden-
tify molds before remedial action can be taken.  With the new
technology, up to 96 analyses can be run simultaneously by
laboratory technicians, reducing the labor required to analyze
samples while significantly increasing the accuracy and validity
of the analysis.  The new technology also enables scientists to
make risk assessments by identifying which mold is present
and in what numbers.
  In recognition of their work in developing the technology,
the Drs. Vesper and Haugland received the prestigious Fed-
eral Laboratory Consortium Award for Excellence in Tech-
nology Transfer. They were in competition with researchers
from all the Federal laboratories.
  This innovative technology is being introduced by the En-
vironmental Technology Commercialization Center, head-
quartered in Cleveland, one of the Agency's technology
transfer centers established to assist U.S. industries in the li-
censing of EPA technologies. The technology is available  on
a non-exclusive basis by laboratories, indoor air quality spe-
cialists, or other environmental professionals. Aerotech
Laboratories, Inc., a small Arizona business, is the first lic-
ensee under this government patent.  The preceding text was
issued as an EPA press release on May 8, 2001.  Additional
information on molds is available at www.epa.gov/iaq/molds/
index.html.
             Stephen Vesper, NERE-Cmannati, (513) 569-7367
           Richard Haugland, NERE-Gncmnatt, (513) 569-7135
                                     NERE Task #6175

COPP Exposure Behind the Wheel
  Americans' love affair with the automobile is well known,
but how is health affected by time spent behind the wheel?
In July, the NERL Human Exposure and Atmospheric  Sci-
ences Division will conduct a study of highway patrol troop-
ers to measure their exposure to emissions inside their
vehicles during duty hours and to evaluate the immediate
health effects  of this exposure.  The Car-related Occupa-
tional PM and Air Toxics Exposure to Patrolmen (COPP)
Study is being conducted in collaboration with the NC High-
way Patrol, the University of North Carolina at Chapel Hill,
and the National Health and Environmental Effects Research
Laboratory.
  Since the average American spends 1.5 hours in a car each
                    day, understanding the effects of exposure to emissions is an
                    important step in assessing the associated health risks.  Those
                    whose jobs involve being on the road, such as Troopers, may
                    spend up to 9 hours driving during each shift, resulting in a
                    longer duration of exposure.  While in their cars, people may
                    be exposed to high concentrations of toxic air pollutants
                    from vehicle emissions.  Many of these pollutants, at certain
                    levels, have been associated with various health problems and
                    are regulated by the EPA. Ozone, fine particles (also known
                    as soot), nitric oxide, nitrogen dioxide and carbon monoxide
                    are among the air pollutants of concern from vehicle emis-
                    sions and their reaction products.
                     Thirteen troopers will participate in the COPP Study for
                    24 days. Patrol cars will be equipped with air quality monitors
                    so that scientists can  measure a variety of air pollutants from
                    automobile emissions and conduct tests to determine lung
                    function and heart rate variability, shown in other studies to
                    be affected by exposure to fine particles.  Health parameters
                    for each Trooper will be measured before and after the work
                    shift, and heart rate variability will be assessed continuously
                    both during work and the night following their shift.
                     Results from the COPP Study are expected early next year
                    and will be used to improve models that predict exposure to
                    pollutants, better determine how people are exposed to po-
                    tentially toxic gases while in cars, and provide new informa-
                    tion on acute health effects. The study also will improve
                    understanding of the potential occupational risk among State
                    Troopers from exposure to air toxics.
                                      Ron Williams, NERE-RTP, (919)541-2957
                                    Michael'Rtedtker, NERE-RTP, (919) 541-0327
                                                        NERE Task #5676

                    NERL to  Study  Children's Exposure to Persis-
                    tent Pollutants
                     This past spring NERL researchers in the Human Expo-
                    sure and Atmospheric Sciences Division launched a pilot
                    study of Ohio preschool children to examine how they are
                    exposed to persistent pollutants, including pesticides. These
                    pollutants are chemical substances that persist in the environ-
                    ment, accumulate in the food chain, and pose a risk of harm-
                    ing human health and the environment.
                     Preschool children are thought to have more frequent con-
                    tact with a variety of these pollutants than older children or
                    adults because of what they eat and drink, where  they spend
                    their time, and their activities. Children may be more sensi-
                    tive to the toxic effects of some  chemicals found in or  on
                    lawns, carpets, toys, furniture, and many other items.
                     About 260 children between 18 months and five years of
                                                      PageS

-------
                                             Research
         Research
Top Side
 NERL
Notables
Feedback
age at day care centers and individual homes will participate in
the three year study which is also being conducted in North
Carolina. "The study has been endorsed by the National
Head Start Association, the Ohio Department of Human
Services and several local child service agencies. The Agency
emphasizes that additional research, beyond the pilot study,
will be needed before reaching any conclusions." EPA has
been directed under the Food Quality Protection Act and the
Safe Drinking Water Act of 1996 to give special attention to
protecting children from environmental health risks.
                Marsha Morgan, NERL-RTP, (919)541-2598
                                    NERL Task #3941

Got Water? Protecting Drinking Water with
Landscape-Scale Research
  Current philosophy is evolving toward examination  of
critical environmental problems over larger spatial scales and
assessment  of cumulative risk resulting from multiple stresses
or stressors. In response to this need, a landscape-scale re-
search program was initiated in 1992 by the NERL Environ-
mental Sciences Division.
      Location and Land Cover of the Catskill/Delaware
              Watersheds in New York State
   Land Cover Types
  The landscape-scale assessment approach is being tested in
small community-based watersheds in the southeast New
York state Catskill/Delaware Watersheds, located 100 miles
northwest of New York City. The six watershed basins each
end in a human made reservoir. Together they supply 90%
of New York City's drinking water. Currently, the City is try-
ing to save tax-payers the cost of a billion dollar filtration
system by protecting water quality through implementing a
long-range watershed protection program. The primary goal
of this study is to make a 25-year historic assessment of land-
                   scape and water data from these watersheds. Studying the
                   relationship between land use and water quality can help in
                   the evaluation of the pollution trends and help develop land
                   use strategies that would further reduce non-point pollution
                   to streams and reservoirs.
                      The project will produce a land cover database with satel-
                   lite imagery from 1975, 1984,1991, and 1998.  In addition to
                   the imagery data, a set of supplemental geographic data on
                   elevation, watershed boundaries, surface geology, aqueducts
                   and tunnels,  stream drainage, city and State owned lands, sew-
                   age treatment plants, roads and population will be collected
                   and produced.  The project will also produce a set of land-
                   scape metrics important to identifying surface water quality
                   conditions and an expanded knowledge of the impacts of
                   land cover patterns on water quality. The information will be
                   summarized and distributed in numerous formats including
                   EPA reports, fact sheets and journal publications.  Addition-
                   ally, the project will produce a set of metrics compiled into an
                   easy to use format within a Geographic Information System
                   that can be used to measure ecosystem integrity and target
                   areas in need of maintenance or restoration in the Catskill/
                   Delaware Watersheds.
                               Megan Mehaffej, NERL-Las Vegas, (702) 798-2245
                                                        NERL Task #5447

                   Environmental  Decision Making: Crossing
                   Boundaries
                      In February, Mr. William Kepner, research ecologist at the
                   NERL Environmental Sciences Division, presented The San
                   Pedro River Case Study for Community Assessment at the Collo-
                   quium on Community Assessment in Washington, D.C.,
                   sponsored by the ORD Office of Science and Policy.
                      The case study illustrates how certain tools were developed
                   and used to answer questions posed by a diverse community
                   located within the San Pedro watershed in southeast Arizona
                   and northeast Sonora, Mexico. Remote satellite imagery was
                   used to examine change throughout the watershed, and a
                   geospatial database browser was created.  The data browser is
                   available  online and is currently being used by the interagency
                   San Pedro Partnership Committee as the data source for
                   community planning and development decisions.
                      The study demonstrates how the creation of an interdisci-
                   plinary, multinational, and multi-agency science consortium,
                   which includes NERL as a founding member, has served as a
                   platform for research coordination to facilitate environmental
                   decision-making within the San Pedro community.  The pro-
                   gram has been a means of exchanging ideas and building con-
                   sensus on significant environmental issues.
                                                     Page 4

-------
                                           Research
         Research
Top Side
 NERL
Notables
Feedback
  More information is available online at www.epa.gov/
nerlesdl/land-sci/san-pedro.htm
            William Kepner, NEKL-Las Vegas, (702) 798-2193
                                   NERL Task # 5447

Remote Sensing—Above and Beyond
  Las Vegas was home to Above
and Beyond 2001—An EPA Re-
mote Sensing Conference co-spon-
sored by the NERL
Environmental Sciences Divi-
sion (ESD), Environmental
Photographic Interpretation
Center, and the EPA Region 4
GIS Information Management
Branch in Spring 2001. The conference was designed to up-
date attendees on the latest developments in the field of re-
mote sensing as they apply to  environmental issues at EPA.
More than 29 speakers gave presentations on a broad range
of remote sensing topics and applications to an audience of
approximately 100 people from the Office of Research and
Development (ORD), all ten EPA regional offices, Superfund
and RCRA program offices, Regional Remote Sensing,  GIS
and GPS Coordinators, the National Enforcement Investiga-
tions Center, the Office of Environmental Information, the
Office of Enforcement and Compliance Assurance, and the
All Indian Pueblo Council.  Sixteen of the presenters, who
were remote sensing or GIS scientists from ORD, showcased
both the technical support and research and development
work being performed at various ORD locations around the
country. Dr. John Lyon, ESD Director, gave the keynote
address. The conference underscored the continuing value of
traditional remote sensing technologies  for meeting EPA
needs, and also demonstrated  the value of the newer tech-
nologies, such as high spatial resolution spaceborne systems
and hyperspectral remote sensors, in performing more de-
tailed site-specific to region-wide environmental assessments.
Conference participants expressed interest in holding follow-
on conferences every two to three years. A compilation of
the conference abstracts is available  upon request.
  Donald Garofalo, NERE-Eas Vegas [Reston, VA], (703) 6484285
                                   NERE Task #1839

Raising Awareness of PPCPs Via the Web
  How the Internet can be used to further the Agency's re-
search goals while providing meaningful information to the
public is demonstrated by the  NERL Environmental Sciences
Division website "Pharmaceuticals and Personal Care Prod-
                  ucts." The web site organizes and displays detailed technical
                  and non-technical information effectively, including contact
                  information for scientists involved worldwide with the envi-
                  ronmental aspects of PPCPs, answers to frequently asked
                  questions about PPCPs, a summary of media coverage on the
                  topic, a slide show highlighting the multifaceted issues, and
                  links to relevant citations, scientific conferences, and websites.
                  By serving as an information clearinghouse, the website fo-
                  cuses attention on the emerging issues of PPCPs.
                     As Dr. Christian Daughton, the site's content manager and
                  author, can attest, the website saves him time and energy in
                  responding to numerous inquires from those interested in the
                  topic. Many questions are repetitive and can be addressed
                  most effectively via the web. Each person can review and
                  digest the content at their own pace before contacting him
                  with specific questions or comments not addressed by the
                  site.
                     Feedback to the site is frequent, uniformly positive, and
                  comes from a wide range of people across the globe: faculty
                  and teachers interested in using PPCPs to teach environmen-
                  tal science or for research projects; students interested in
                  learning more about the specific topic of PPCPs or about
                  environmental science; environmental activists and lawyers
                  interested in gaining a better understanding of the science
                  behind environmental issues; research scientists interested in
                  preparing grant proposals or in collaborating with us; media
                  interested in preparing news stories; and the public.
                     The topic of PPCPs has proven to be an
                     effective tool for raising public
                     awareness of the complex issues
                     surrounding environmental science,
                     including awareness that the actions,
                     activities, and behaviors of
                     individuals can directly impact the
                     environment.  This is especially
                     important during a time when the
                     public's overall knowledge of science
                     has been declining.
                    The following comments exemplify some of the e-mails
                  received.  The Chief of the Michigan Department of Envi-
                  ronmental Quality, Surface Water Quality Division, wrote,
                  'The web site is outstanding.  I've sent your web site address
                                                   PageS

-------
                                             Research
         Research
Top Side
 NERL
Notables
Feedback
to my staff and will send it out to the rest of the States via a
list server." A concerned citizen wrote, "I am really awed by
the whole issue...thank you for all your work in bringing this
important matter to public attention."
  All told, the web site immeasurably expands the number of
nontechnical and technical people the Agency can reach and
inform about topic. You can visit the website at www.epa.gov/
nerlesdl/chemistry/pharma/index.htm.
         Christian Daughton, NERL-Las Vegas, (702) 798-2207
                                     NEKL Task #6980

Now Internet Accessible —Virtual Field Refer-
ence Database for the Neuse River Basin
  The Neuse River Basin
(NRB) Virtual Field Refer-
ence Database (VFRDB) is
now accessible via the
Internet at: www.epa.gov/
nerlesdl/lcb/nrb/VFRDB/.  Three years in the making, the
VFRDB contains site characterization, field measurement,
and digital imagery (camera)  data for 1,390 sampling locations
within the NRB.  Sites include approximately 1,000 general
watershed sites and 390 riparian buffer zone sampling loca-
tions. The VFRDB was designed using a stratified, random
approach to provide a statistically robust source of reference
data to validate the results of satellite based land-cover map-
ping activities, and to establish baseline conditions for future
measurement efforts.  The database is currently being used in
support of non-point source nitrogen modeling efforts in the
NRB. For detailed database  description, and methods docu-
mentation and application examples, see the June 2001 issue
of Photogrammetric Engineering and Remote Sensing or contact
Ross Lunetta to receive a reprint of the article.
                   Ross Lanetta, NERL-RTP, (919)541-4256
                                     NERL Task #5445

Use of NEXRAD Stage IV Data in the Multime-
dia Modeling of Pollutant Transport
  As a leader in the environmental research community,  the
NERL Atmospheric Modeling Division is designing the Mul-
timedia Integrated Modeling System (MIMS) to model the
cycling of pollutants and nutrients between the  atmosphere
and the earth's surface, including water bodies and groundwa-
ter.  Our ability to accurately model atmospheric, hydrological
and surface processes that transport chemicals is highly de-
pendent on precipitation types, rates, and totals. Of special
interest are precipitation extremes and subsequent flooding,
which can greatly enhance the movement of such chemicals.
During such events, these chemicals can enter the surface
                   water bodies via groundwater recharge as well as overland
                   flow.  For example, the extreme flooding associated with Hur-
                   ricane Floyd, which made landfall in North Carolina during
                   September of 1999, transported tremendous amounts of
                   agricultural and industrial waste and pesticides into area estu-
                   aries and rivers. This hurricane, which made landfall shortly
                   after an earlier hurricane (Dennis), inundated sections of
                   eastern North Carolina with more than 20 inches of rain.
                      During the development of MIMS, NERL is investigating
                   the use of the National Weather Service NEXRAD (NEXt
                   generation RADar) State IV precipitation estimates in our
                   modeling efforts.  The purpose of this research will be to
                   evaluate the quality and identify limitations of the NEXRAD
                   data through a comparison with ground truth data  obtained
                   from  a network of ten closely spaced rain gages. The evalua-
                   tion, which will use visualization tools and statistical analyses,
                   will determine if the spatial resolution of NEXRAD data is
                   adequate to capture the variability of precipitation on the
                   watershed that is used in the surface hydrology models asso-
                   ciated with MIMS.
                                       Brian Eder, NERL-RTP, (919) 541-3994
                                                        NERL Task #3868

                   Physical Modeling of Flow and Dispersion in
                   Urban Areas
                      Scientists at the Fluid Modeling Facility, managed by the
                   NERL Atmospheric Modeling Division,  have completed a
                   wind-tunnel study of the flow and dispersion in idealized
                   urban areas, in collaboration with modelers at Los Alamos
                   National Laboratory and Lawrence Livermore National
                   Laboratory. Three-dimensional, turbulent flow fields were
                   measured with a pulsed-wire anemometer for both an array
                   of two-dimensional buildings and of cubical buildings.  For
                   the cubical buildings, a point source tracer located just down-
                   wind  of the most  upstream building determined the concen-
                   tration field from measurements at various locations within
                   the array. The goal was to develop a database for design and
                   evaluation of 3-D fluid dynamic codes for predicting the fate
                   of pollutants released near groups of buildings  in urban ar-
                   eas. A comprehensive report describing the experimental
                   techniques, and containing all raw and reduced data, and se-
                   lected features of the data has been completed and submitted
                   to the collaborators. The report and associated data are avail-
                   able on CD-ROM from the principal investigators.
                                    Roger Thompson, NERL-RTP, (919) 541-1895
                                       Steven Perry, NERL-RTP, (919) 541-1896
                                                       NERL Task # 3871
                                                     Page6

-------
                                            Research
         Research
Top Side
          NERL
         Notables
Feedback
Effect of Time Splitting on the Prediction of Ozone and Particulate Concentrations Simulated by
the Models-3 Community Multiscale Air Quality (CMAQ) Model
  The Models-3 Community Multiscale Air
Quality (CMAQ) model is a multi-pollutant
and multi-scale air quality model that con-
tains state-of-science techniques for simulat-
ing all atmospheric and land processes that
affect the transport, transformation, and
deposition of atmospheric pollutants at re-
gional and urban scales. It is a tool for
handling all the major pollutant issues in-
cluding photochemical oxidants, particulate
matter, acidic, and nutrient deposition in a
holistic fashion. CMAQ's design incorpo-
rates process modules representing different algorithms and
parameterizations of physical and chemical processes.  The
modules follow a time-splitting numerical integration method
where the effect of each science process is computed by up-
dating pollutant concentrations sequentially one at a time.
The final concentration at each computational time step is
obtained by cycling through all the science processes in-
        3-D image generated by
          Models-3 software
                volved. Unlike a model that utilizes an im-
                plicit numerical method where all the sci-
                ence processes are solved simultaneously,
                CMAQ's concentration predictions are af-
                fected by the sequence in which different
                science processes are called. With the cur-
                rent version of CMAQ, the level of science
                modularity is subordinated by the way the
                science process codes are archived in the
                Models-3 system.
                  At present we are continuously testing
                different CMAQ configurations to study
the effects of the time splitting and sequence of science pro-
cess calls to establish a better model configuration that pro-
duces accurate simulation results without incurring excessive
computational cost.
                  Daemon Bjun, NEKL-RTP, (919) 541-0732
                   Jerry Gtpson, NERL-RTP, (919) 541-4181
                                    NERL Task #3873
                                                    Page 7

-------