The air pollution regulatory process involves the permitting of sources of regulated pollutants. This process
requires sources to demonstrate that the National Ambient Air Quality Standards (NAAQS) are not exceeded as a result of
released pollutants. A determination of a facility’s compliance with the NAAQS is more frequently being based on dispersion
modeling estimates rather than ambient air sampling results. Current Gaussian-based dispersion models do not adequately
account for pollutant dispersion due to sub-hourly variations in wind speed and direction. This can result in overestimates
of downwind concentration and consequentially require costly additional control measures or denial of a construction or
operating permit. This research focuses on developing a methodology to analyze the theoretical degree of dispersion within
sub-hourly and hourly intervals. The methodology employed to develop the presently used Pasquill-Gifford (PG) dispersion
coefficients is explored and used in developing a new methodology for estimating theoretical dispersion coefficients based
on recorded meteorological data. This comparison allowed for an appropriate application time period of the PG dispersion
coefficients to be determined, which in general varied from 3 to 20 min. The most critical result of this research is that universal
application of the PG dispersion coefficients to a 1 h time period is incorrect. This misapplication will result in concentration
estimates based on insufficient plume spread, which will overestimate downwind concentrations and result in inappropriate
regulation of emitting sources.
[1]
F. Pasquill,et al.
Atmospheric diffusion;: The dispersion of windborne material from industrial and other sources
,
1974
.
[2]
M. T. Beychok.
Air-dispersion modeling and the real world
,
1996
.
[3]
Linda Mendez Williams.
Evaluation of the Industrial Source Complex Screen2 for regulatory purposes
,
1996
.
[4]
E. N. Lawrence.
Clean Air Act
,
1971,
Nature.
[5]
F. Gifford,et al.
Use of routine meteorological observations for estimating atmospheric dispersion
,
1961
.
[6]
D. B. Turner.
Workbook of atmospheric dispersion estimates : an introduction to dispersion modeling
,
1994
.
[7]
Milton R. Beychok,et al.
Fundamentals of Stack Gas Dispersion
,
2005
.
[8]
Rod Barratt,et al.
Atmospheric Dispersion Modelling: An Introduction to Practical Applications
,
2001
.
[9]
J. Seinfeld,et al.
Atmospheric Chemistry and Physics: From Air Pollution to Climate Change
,
1997
.
[10]
A. Venkatram.
An examination of the Pasquill-Gifford-Turner dispersion scheme
,
1996
.
[11]
U. Epa.
Air Quality Criteria for Particulate Matter
,
1996
.