Environmental Engineering Reference
In-Depth Information
turbulence, potential variation in source strength, and irregular distribu-tions of
canopy elements and flow obstructions. All of these can considerably complicate
the interpretation of results.
The Field Research Division (FRD) of the Air Resources Laboratory (ARL) of
the National Oceanic Atmospheric Administration (NOAA) conducted the Near
Roadway Tracer Study (NRTS08) experiment during October 2008. NRTS08 was
designed to quantify the effects of roadside barriers on the downwind dispersion
of atmospheric pollutants emitted by roadway sources (e.g. vehicular transport).
Pollutant transport and dispersion were measured during the field tests using
sulfur hexafluoride (SF
6
) tracer gas as a pollutant surrogate. The goal of the study
was to produce a roadside barrier dataset that (1) covered a range of atmospheric
stabilities, (2) minimized factors that could complicate data interpretation, and (3)
could be used to guide model development.
2. Methods
Roadway emissions were simulated by release of an atmospheric tracer (SF
6
) from
two 54 m long line sources in unstable, neutral, and stable conditions. A 90 m
long, 6 m high mock sound barrier constructed of straw bales (
Fig. 1)
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 at 1.5 m above ground level. An array of six
sonic anemometers was employed to measure the barrier-induced turbulence. The
pristine environment of the INL enabled a clearer and less ambiguous interpretation
of the data.
Fig. 1.
Straw bale mock roadside sound barrier
