Research Highlight:
ARL to Conduct Roadside Tracer Study for Regulatory Model Improvements
Scientists from ARL’s Field Research Division are preparing to conduct a roadside barrier tracer study, anticipated to begin October 6 at the U.S. Department of Energy’s Idaho National Laboratory. The study, sponsored by the U.S. Environmental Protection Agency (EPA), is designed to quantify the effects of roadside barriers (e.g., sound walls) on the downwind dispersion of atmospheric pollutants emitted by roadway sources (e.g., vehicular transport). In this study, ARL will design a mock sound barrier and measure pollutant transport and dispersion using an atmospheric tracer gas (sulfur hexafluoride-SF6) as a pollutant surrogate. An identical tracer run will be conducted nearby without a barrier for data comparison. The study will be conducted over a wide range of atmospheric conditions during the day and at night. Study results will inform an EPA regulatory modeling system called AERMOD.
Background: AERMOD, developed through the American Meteorological Society/Environmental Protection Agency Regulatory Model Improvement Committee, incorporates air dispersion based on planetary boundary layer turbulence structure and scaling concepts, including treatment of both surface and elevated sources, and both simple and complex terrain. The model, however, does not account for roadway pollutant concentration adjustments if roadside barriers are present. This study is being conducted under the newly formed NOAA/Idaho National Laboratory, Meteorological Research Partnership, created in 2007 between the Department of Energy and NOAA in a Memorandum of Agreement. EPA strengthens this Partnership by becoming a supporting agency.
Significance: In recent years, studies have indicated that human exposure to air pollutants in the immediate vicinity of large roadways is associated with a range of health effects, including adverse respiratory effects. Approximately 36 million individuals live within 300 feet of a four-lane highway, railroad, or airport. NOAA’s science will be used to help guide the development of a new application of the AERMOD system that will correctly determine the concentration of roadway emissions downwind from roadside barriers. The study utilizes the world-class NOAA Tracer Test Facility located at the Field Research Division in Idaho Falls, Idaho.
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