Environmental Engineering Reference
In-Depth Information
Briefly, other key findings of the study include: (1) the magnitude of the
concentration footprint expanded or contracted in stable and unstable conditions,
respectively, and (2) very high concentrations were measured in the roadway
upwind of the barrier in stable, light wind speed conditions.
Acknowledgments and Disclaimer
We wish to thank Alan Vette and S.T. Rao from the EPA
and Shane Beard, Tom Strong, and Neil Hukari from FRD for the contributions they made to the
study. This work was completed under Interagency Agreement DW-13-92274201-0 between the
National Oceanic and Atmospheric Administration and the U.S. Environmental Protection
Agency. Although it has been reviewed by EPA and NOAA and approved for publication, it does
not necessarily reflect their policies or views. U.S. Government right to retain a non-exclusive
royalty-free license in and to any copyright is acknowledged.
References
Baldauf., RW., Thoma, E., Hays, M., Shores, R., Kinsey, J., Gullett, B., Kimbrough, S., Isakov,
V., Long, T., Snow, R., Khlystov, A., Weinstein, J., Chen, F., Seila, R., Olson, D., Gilmour,
I., Cho, S., Watkins, N., Rowley, P., Bang, J., 2008a. Traffic and meteorological impacts on
near-road air quality: summary of methods and trends from the Raleigh near road study.
Journal of the Air and Waste Management Association 58, 865-878.
Baldauf, R.W., Thoma, E., Khlystov, A., Isakov, V., Bowker, G., Long, T., Snow, R., 2008b.
Impacts of noise barriers on near-road air quality. Atmospheric Environment 42, 7502-7507.
Bowker, G.E., Baldauf, R., Isakov, V., Khlystov, A., Petersen, A., 2007. The effects of roadside
structures on the transport and dispersion of ultrafine particles from highways. Atmospheric
Environment 41, 8128-8139.
Nokes, W.A., Benson, P.E., 1984. Carbon monoxide concentrations adjacent to sound barriers.
Office of Transportation Laboratory, California Department of Transportation, Report FHWA/
CA/TL-84/04.
4. Questions and Answers
Steve Hanna:
How did you decide on how long the barrier would be, and
wouldn't the results depend on this length? Was this investigated by the EPA
wind tunnel tests?
Answer:
We were concerned about having a barrier long enough to ensure that
edge effects would be minimal or nonexistent. We used the EPA wind tunnel
study to guide us in determining the length of the barrier. Obviously, an infinite
length barrier would have been ideal. Construction costs ultimately limited the
length to 90 m. In some of the test periods, edge effects were visible when the
data were plotted as shown in
Fig. 2
above. However, in the majority of
individual tests periods, which is when the wind was essentially perpendicular
to barrier, edge effects were usually negligible. This is demonstrated by the fact
that the areas of peak concentrations were located behind the barrier, even if
not directly centered. It was when the peak concentrations were clearly located
