Air Quality
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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