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Accounting for Heterogeneous-Phase Chemistry in Air Quality Models - Research Needs and Applications
Citation:
LUECKEN, D. J. AND R. MATHUR. Accounting for Heterogeneous-Phase Chemistry in Air Quality Models - Research Needs and Applications. EM: AIR AND WASTE MANAGEMENT ASSOCIATION'S MAGAZINE FOR ENVIRONMENTAL MANAGERS. Air & Waste Management Association, Pittsburgh, PA, September, 2012:45-47, (2012).
Impact/Purpose:
The National Exposure Research Laboratory′s (NERL′s)Atmospheric Modeling Division (AMAD) conducts research in support of EPA′s mission to protect human health and the environment. AMAD′s research program is engaged in developing and evaluating predictive atmospheric models on all spatial and temporal scales for forecasting the Nation′s air quality and for assessing changes in air quality and air pollutant exposures, as affected by changes in ecosystem management and regulatory decisions. AMAD is responsible for providing a sound scientific and technical basis for regulatory policies based on air quality models to improve ambient air quality. The models developed by AMAD are being used by EPA, NOAA, and the air pollution community in understanding and forecasting not only the magnitude of the air pollution problem, but also in developing emission control policies and regulations for air quality improvements.
Description:
Understanding the extent to which heterogeneous chemical reactions affect the burden and distribution of atmospheric pollutants is important because heterogeneous surfaces are ubiquitous throughout our environment. They include materials such as aerosol particles, clouds and fog, snow, dust particles, building surfaces, snow packs, and even vegetated surfaces such as grass and leaves. While heterogeneous surfaces have long been known to be important reaction matrices for atmospheric chemistry, 1,2 emerging laboratory, field, and computational studies continue to demonstrate additional routes for atmospheric chemical reactions on heterogeneous surfaces. From a regulatory perspective, heterogeneous chemistry has the potential to affect several criteria pollutants, including ozone (O3), nitrogen dioxide (NO2), and fine particulate matter (PM2.5), as well as the formation of acidic and toxic air pollutants. While there is evidence that heterogeneous reactions occur, how much do they impact the chemical composition of the atmosphere, and where are the greatest impacts likely to be seen? This is difficult to answer because large uncertainties exist not only in characterizing the area and characteristics (e.g., size, age, composition, etc.) of reaction surfaces, but also the kinetics of surface reactions. The experimental set-up for measuring heterogeneous chemistry is challenging due to the need to introduce and characterize surface properties, as well as gas-phase and wall chemistry. The wide variety of surface types also adds to the difficulty—building exteriors are very different than water droplets, for example. These surfaces may also be temporally variable; clouds are one example of an ephemeral medium. For regulatory air quality model (AQM) applications, we need to know how uncertainties and inaccuracies in describing heterogeneous chemical reactions might affect predictions of harmful air pollutants.
URLs/Downloads:
Accounting for Heterogeneous-Phase Chemistry in Air Quality Models - Research Needs and Applications (PDF, NA pp, 1701 KB, about PDF)EM Magazine
