Air Quality: Qualifications
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Consulting services offered by AER in air quality include computer
model simulations, data analysis, project management, and litigation
support. These services cover a broad range of issues such as
air toxics, ozone (and other photochemical smog pollutants), particulate
matter, visibility degradation (including plume opacity), indoor
air pollution, and acid deposition.
The air quality standards for particulate matter (PM) were revised
by the U.S. Environmental Protection Agency (EPA) in July 1997.
The revised standards now include standards for fine particles
(PM2.5, particles less than 2.5 microns in diameter) in addition
to the standards for particles less than 10 microns in diameter
(PM10). Since these standards were remanded to EPA by a federal
court in May 1999, there will be some time before the exact form
of the standards is known. Nevertheless, PM2.5 is likely to be
a major air quality issue in the U.S. for the next decade. AER
staff are currently on the forefront of research, development,
and applications for PM issues, providing guidance to the U.S.
EPA, state agencies, and major industry groups. AER's expertise
includes the development of new state-of-the-science PM models,
application of research-grade and regulatory models, data analysis
and design of monitoring programs.
With the promulgation of the Clean Air Act Amendments of 1990,
air toxics have become an issue of concern as federal regulations
(and, in some cases, state regulations as well) require assessments
of the potential impacts of air toxics industrial emissions. AER
staff have been on the forefront of air toxics issues for both
scientific research and regulatory applications. For example,
AER staff have developed atmospheric chemical mechanisms for several
compounds including mercury, chromium, and arsenic. They demonstrated
that the carcinogenic hexavalent form of chromium is likely to
be reduced to noncarcinogenic trivalent chromium species in the
atmosphere. AER staff have also developed a regional air quality
model for air toxics that has been applied to several compounds,
including mercury and arsenic. They are currently investigating
the atmospheric travel distance of dioxins/furans emitted from
a variety of source categories.
Photochemical smog includes ozone and a myriad of other pollutants.
It is a major issue in many urban areas but it is also a regional
problem in some areas such as the northeastern United States and
Europe. The 8-hour average ozone standard may extend non-attainment
areas beyond urban centers into downwind rural areas. Because
the relationship between ozone and its precursors (nitrogen oxides
and volatile organic compounds) is complex, the development of
effective emission control strategies requires the use of sophisticated
computer models that can simulate the salient features of the
relevant atmospheric processes. AER staff have expertise in the
development, testing, evaluation, and application of such air
quality simulation models. The models developed by AER staff have
been applied in many U.S. urban areas, the California central
valley, Latin America, Canada, and northern Europe. AER staff
have also hands-on experience with all the photochemical smog
models currently used for regulatory applications. AER staff have
installed air quality models at the facilities of clients and
provided on-site training of future users. In addition, AER has
conducted extensive data analyses to understand the processes
that govern ozone formation.
The degradation of atmospheric visibility is regulated in the
United States both at the regional level (protection of National
Parks and Wilderness Areas) and local level (stack plume opacity
limits). AER staff have developed a variety of models to address
atmospheric visibility issues (including a model currently recommended
by the U.S. EPA), have applied these models to a wide range of
practical issues, have managed and participated in field measurement
programs, and have integrated results of measurements and modeling
programs to develop effective solutions to specific visibility
problems.
Indoor air pollution can occasionally arise in areas with significant
chemical emissions and/or poor ventilation. AER staff have conducted
several customized investigations using both monitoring and modeling
approaches to identify the cause of the problem and recommend
appropriate mitigation measures.
Acid deposition has been a major issue both in north America and
Europe and is now being recognized as a major issue in Asia. AER
staff have been very active in the development and application
of modeling techniques to study the formation, transport, and
deposition of atmospheric acids (e.g., sulfate and nitrate). These
studies have included local, regional, and continental modeling
efforts, data analysis, and fundamental research.
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Consulting services offered by AER in risk assessment include
the application of existing techniques for conducting public health
and ecological risk assessments of routine and/or accidental releases,
the development and use of more refined approaches to risk assessment
including probabilistic analyses, and litigation support.
Under Section 112 of the Clean Air Act, risk assessments must
be conducted for industrial facilities to assess if routine emissions
of hazardous air pollutants into the atmosphere may potentially
lead to significant adverse health effects. Some states such as
California have also promulgated legislation requiring similar
public health risk assessments (e.g., California Assembly Bill
2588). In addition, the assessment of public health risks associated
with new or modified industrial projects is required under the
California Environmental Quality Act (CEQA) and generally needs
to be considered under the National Environmental Protection Act
(NEPA). Risk assessments are also valuable in support of the reporting
of Toxics Release Inventory (TRI) data that are mandated under
the Emergency Planning and Community Right-to-Know Act (EPCRA).
AER staff have conducted regulation-driven health risk assessments
for a large variety of facilities including refineries, incinerators,
hazardous waste transfer, storage and disposal (TSD) facilities,
oil production fields, power plants, marine terminals, research
laboratories and hospitals. All those risk assessments have been
approved by the responsible regulatory agencies. If needed, AER
staff will meet with regulatory agencies and the public to present
and explain the results of the risk assessments.
AER staff have developed a comprehensive user-friendly multimedia
health risk assessment model, the Total Risk of Utility Emissions
(TRUE) model, under the sponsorship of EPRI. TRUE was used to
conduct several human health and ecological risk assessments of
power plant emissions. Several of these assessments are included
in the EPRI report to EPA that was prepared in response to the
Clean Air Act requirements for the assessment of the potential
health risks due to electric utility emissions. In addition, AER
staff have prepared customized health risk assessments, primarily
in support of litigation cases.
The potential health risks to the population due to accidental
releases of toxic or flammable chemicals need to be addressed
under federal regulations (e.g., Risk Management Plans of the
Clean Air Act) as well as some state regulations (e.g. California
Risk Management Prevention Program and CEQA risk of upset analyses).
AER staff have experience in conducting consequence analyses of
such industrial accidental releases for a variety of chemicals
including chlorine, ammonia, oleum, phosgene, and sulfuric acid.
In addition, AER staff have the expertise needed to participate
as expert witnesses in litigation cases.
Because of the uncertainties associated with the information used
to conduct health risk assessments and the natural variability
of many environmental and exposure parameters, it is often appropriate
to take into account this uncertainty/variability by conducting
a probabilistic risk assessment. Thus, the typical "single
point estimate" of a regulatory guideline assessment is placed
into perspective. AER staff have been on the forefront of developing
effective methodologies for conducting probabilistic risk analyses.
For example, a methodology developed by AER staff was used as
a major component of the overall methodology recommended by the
National Academy of Sciences in its report to EPA titled "Science
and Judgment in Risk Assessment."
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The Air Quality Group interacts on a variety of projects with
several of the other AER programs including the Numerical Weather
Prediction Group, the Atmospheric Chemistry and Dynamics Group,
the Radiation & Climate Group, and the Systems Engineering
Group. Brief descriptions of these programs are provided below.
Global Modeling and Chemistry
Under the leadership of Dr. N.D. Sze, AER Founder and Chairman,
and Dr. M.K.W. Ko, Group Director for Atmospheric Chemistry and
Dynamics, AER has been a leader in the development and application
of one-, two-, and three-dimensional numerical models that incorporate
chemical, transport, and dynamic processes of the atmosphere.
While the major emphasis of this program has been on the analysis
of the depletion of stratospheric ozone, AER staff have also studied
the chemistries and global cycles of sulfur, fluorine, and metals.
Dr. Ko's group worked in close interaction with air quality staff
to conduct simulations of the atmospheric fate and transport of
mercury using a global chemistry transport model. The results
of the global simulations are being used by the Air Quality Group
to develop global source/receptor relationships and obtain upwind
conditions for the simulation of the fate and transport of mercury
over North America.
Meteorological Modeling
Meteorological modeling studies are led by Dr. J.-F. Louis, who
is on the advisory board of the European Center for Medium-Range
Weather Forecasts (ECMWF) and Dr. Tom Nehrkorn. Capabilities of
AER staff in this area include simulations of atmospheric physical
processes in the planetary boundary layer, numerical weather prediction,
cloud forecasting, and data analysis (e.g., satellite data analysis
using variational methods). The Numerical Weather Prediction Group
has conducted meteorological simulations of the Los Angeles basin,
California and of the Nashville airshed, Tennessee using a prognostic
non-hydrostatic model (MM5); the results of those simulations
were subsequently used by the Air Quality Group to drive the air
quality model used to simulate ozone and particulate matter pollution.
A real-time forecast of New England weather performed with MM5
is available on AER's web page (http://www.aer.com/forecast).
Atmospheric Radiation
The AER Radiation and Climate Group focuses on the study of atmospheric
radiative processes and their relationship to the earth's climate.
Under the direction of Mr. S.A. Clough, this program is involved
in the development of detailed radiative transfer models, their
validation with atmospheric data, and their incorporation in general
circulation models. The Rapid Radiative Transfer Model (RRTM)
developed by Clough and co-workers was recently incorporated into
MM5 and is available in Version 3.3 released by the National Center
for Atmospheric Research (NCAR). RRTM has been validated with
observations from the Atmospheric Radiation Measurement program.
It will provide significantly improved longwave fluxes and cooling
rates to MM5 simulations. Mr. R. Isaacs, Senior Vice President
of Applied Research, has developed radiative transfer models that
are used to simulate multiple scattering in plume visibility models.
He worked with Dr. Seigneur of the Air Quality Group on the development
of a plume visibility model, PLUVUE II, that is currently recommended
by the U.S. Environmental Protection Agency (EPA).
Systems Engineering
The Systems Engineering Group of AER offers capabilities in the
design and implementation of robust and efficient systems blending
environmental sensing and monitoring technologies with data processing
hardware. Headed by Mr. J. Bennett, P.E., this program offers
technical expertise that complements the modeling and data analysis
capabilities of the Air Quality Group. Most relevant to air quality
studies are the experience and expertise of the group in meteorological
and air quality monitoring including design of networks, instrumentation,
and data acquisition, processing and analysis.
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