Air Quality Research and Development
Pollutants released into the air can impact air quality, as well as
terrestrial and aquatic ecosystems when the pollutants fall back to
Earth. The Nation spends tens of billions of dollars each year to reduce
air pollution in order to protect human health and the environment.
Effective targeting of air pollution controls depends on having good
scientific understanding of which sources and which regions are
contributing to air quality issues. ARL conducts a world-class Air
Quality Research and Development program that provides information and
products that directly support air quality decision-makers, air quality
forecasters, and the research community. Specifically, we focus our Air
Quality program on improving measurements and monitoring the exchange of
pollutants between the air and the Earth's surface and on developing and
applying the next generation of forecasting and assessment tools.
Air-Surface Exchange of Pollutants
Particles and gases released into the air are exchanged with the Earth's
surface — termed air-surface exchange. ARL focuses on specific
chemicals, including nitrogen, sulfur, and mercury compounds, which can
have a significant impact on our environment — and in the case of mercury — human health.
Acid Rain and Nitrogen Fertilization
Sulfur and nitrogen compounds contribute to the acidification of freshwater systems, and in the case
of nitrogen, to the over-fertilization of coastal and estuarine waters.
In coordination with the National Atmospheric Deposition Program (NADP),
we conduct long-term, research-grade deposition monitoring of these
and other compounds. Our research network, called the Atmospheric Integrated Research Monitoring
Network, or AIRMoN, provides data to better undertand the sources of these
compounds and to evaluate the effectiveness of existing regulatory
emission controls. To complement the research monitoring, we conduct
short-term field studies that test emerging chemical measurement
technologies and improve the understanding of the atmospheric and
terrestrial processes and factors (i.e., wind, temperature, surface
roughness) controlling air-surface exchange of these compounds. Data
from both the AIRMoN and our field studies are used to improve and evaluate
modeling products.
Mercury Contamination
Mercury is known to adversely
affect the nervous system, particularly those of fetuses and young
children. People are exposed to mercury primarily by eating contaminated
fish and shellfish. This contamination occurs primarily from atmospheric
mercury entering into aquatic ecosystems, which is then taken up by fish
and other aquatic organisms. Terrestrial animals are also exposed to
mercury. In coordination with the NADP, we operate five long-term
intensive ambient air mercury monitoring stations. These are part of a
national monitoring network designed to address total mercury deposition
across the country. We also conduct short-term intensive studies at
select locations around the world. Data collected are also used to
interpret and evaluate our mercury modeling system—a special version
of the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT)
Model—which tracks mercury emission sources, transport, and
deposition.
The HYSPLIT-Hg model starts with a mercury emissions inventory; then
utilizes meteorological data to estimate the atmospheric dispersion of
mercury from each source. Chemical reactions in the air, phase-
partitioning of the mercury, and wet and dry deposition are then
simulated by the model. A key feature of HYSPLIT-Hg is that it can
estimate the overall atmospheric concentrations and deposition arising
from mercury emissions and at the same time keep track of the individual
contributions of each source to the overall totals.
Air Quality Forecast Products
More than half of the people in the U.S. live in areas that do not meet
the health-based air quality standards established by the U.S.
Environmental Protection Agency. The primary air quality problems are
elevated levels of ground-level ozone (O3) and fine particulate matter
(PM2.5 ) that can lead to respiratory and cardiovascular problems and
tens of thousands of premature deaths each year. Accurate air quality
forecasts enable communities to take actions that can reduce the
severity of episodes of poor air quality and also enable individuals to
take protective actions that limit their own exposure to unhealthy air.
ARL scientists evaluate and improve air quality models used by NOAA's
National Weather Service (NWS) to operationally predict concentrations
of O3 and PM2.5. ARL performs rigorous comparisons of model predictions
with actual atmospheric measurements. Based on the knowledge gained from
these evaluations, ARL adds or enhances specific model processes or
input data sets to better represent emissions of air pollutants and the
physical and chemical complexities that occur in the atmosphere. The
continuous model evaluation and improvement cycle conducted by ARL
scientists leads to better NWS operational air quality forecast
products. This work supports air quality planners and managers, air quality forecasters, and the research community.
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