Page 364 - Fundamentals of Air Pollution 3E

Questions 319

3. At a particular downwind distance, a dispersing plume is approximately 40 m wide. Which
of the following three turbulent eddy diameters—5 m, 30 m, or 100 m—do you believe
would be more effective in further dispersing this plume?
4. A pollutant is released from an effective height of 50 m and has a ground-level concentration
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of 300 fjt,g m~ at a position directly downwind where the cr z is 65 m. How does the
concentration at 50 m above this point, that is, the plume centerline, compare with this
ground-level concentration?
5. At a downwind distance of 800 m from a 75-m source having an 180-m plume rise, cr y is
estimated as 84 m and erj is estimated as 50 m. If one considers buoyancy-induced dispersion
as suggested by Pasquill, by how much is the plume centerline concentration reduced at
this distance?
6. Consider the parameters that need to be measured and the instrumentation needed to
make the measurements for monitoring dispersion of effluent from a 30-m stack.
7. A tracer experiment includes sampling on an arc at 1000 m from the source. If the horizontal
spread is expected to result in a cr y between 120 and 150 m at this distance, and if the
wind direction is within ±15° azimuth of that forecast, how many samplers should be
deployed and what should be that spacing? It is desirable to have above seven measure-
ments within ±2(T y of the plume centerline and at least one sample on each side of the
plume.
8. For a tracer release that can be considered to be at ground level, approximate the vertical
dispersion cr z at the downwind distance where measurements indicate that the concentra-
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8
tion peak is 7 x 10~ g m~ , the horizontal cr y is 190 m, and the crosswind integrated
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5
1
concentration is 3.16 x 10~ g m" . The tracer release rate is 0.01 g s* and the wind speed
is 3.7m s~ . ]
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9. The maximum 1-h concentration at an urban monitoring station is 800 /tg m~ . If the
concentration varies with averaging time with a power law relation when the power is
- 0.3, what is the expected maximum concentration for a 1-week averaging time?