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Tracer Studies to Characterize the Effects of Roadside Noise Barriers on Near-Road Pollutant Dispersion under Varying Atmospheric Stability Conditions
Citation:
Finn, D., K. L. Clawson, R. G. Carter, J. D. Rich, R. M. Eckman, S. G. PERRY, V. ISAKOV, AND D. HEIST. Tracer Studies to Characterize the Effects of Roadside Noise Barriers on Near-Road Pollutant Dispersion under Varying Atmospheric Stability Conditions. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 44(2):204-214, (2010).
Impact/Purpose:
The National Exposure Research Laboratory′s (NERL′s) Atmospheric Modeling and Analysis 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:
A roadway toxics dispersion study was conducted by the Field Research Division (FRD) of NOAA at the Idaho National Laboratory (INL) near Idaho Falls, ID to document the effects on concentrations of roadway emissions behind a roadside sound barrier in various conditions of atmospheric stability. The pristine environment of the INL, sans effects of vehicle emissions and turbulence and other manmade and natural barriers, enabled a clearer and less ambiguous interpretation of the data. Roadway emissions were simulated by the release of an atmospheric tracer (SF6) from two 54 m long line sources. A 90 m long, 6 m high mock sound barrier constructed of straw bales was installed on one grid while the other grid had no barrier. Simultaneous tracer concentration measurements were made with real-time and bag samplers on the identical sampling grids downwind from the line sources. An array of 6 3-d sonic anemometers was employed to measure the barrier-induced turbulence. Key findings of the study are: (1) the areal extent of the concentration footprint downwind of the barrier was a function of atmospheric stability with the footprint expanding as stability increased; (2) normalized concentrations were a function of atmospheric stability, increasing in magnitude as atmospheric stability increased; (3) a concentration deficit developed in the wake zone of the barrier with respect to concentrations at the same grid locations on the non-barrier side at all atmospheric stabilities; (4) lateral dispersion was significantly greater on the barrier grid than the non-barrier grid; and (5) the barrier tended to trap high concentrations in the "roadway" (i.e. upwind of the barrier) in low wind speed conditions, especially in stable conditions.
URLs/Downloads:
Tracer Studies to Characterize the Effects of Roadside Noise Barriers on Near-Road Pollutant Dispersion under Varying Atmospheric Stability (PDF, NA pp, 5863 KB, about PDF)Atmospheric Environment
