fundamentals of engineering supplied-reference handbook - Ventech!

For information about fluids, refer to the CIVIL
ENGINEERING and FLUID MECHANICS sections.
For information about geohydrology and hydrology, refer
to the CIVIL ENGINEERING section.
For information about ideal gas law equations, refer to the
THERMODYNAMICS section.
For information about microbiology (biochemical
pathways, cellular biology and organism characteristics),
refer to the BIOLOGY section.
For information about population growth modeling, refer to
the BIOLOGY section.
For information about sampling and monitoring (Student’s
t-Distribution, standard deviation, and confidence
intervals), refer to the MATHEMATICS section.
AIR POLLUTION
Activated carbon: refer to WATER TREATMENT in this
section.
Air stripping: refer to WATER TREATMENT in this
section.
Atmospheric Dispersion Modeling (Gaussian)
σy and σz as a function of downwind distance and stability
class, see following figures.
ENVIRONMENTAL ENGINEERING
143
Q
C =
2πuσ
y
σ
z
⎛
⎜ 1
exp −
⎜ 2
⎝
y
σ
2
2
y
⎞⎡
⎟
⎛
⎢ ⎜
1
exp −
⎟⎢
⎜
⎠⎣
⎝
2
( z + H )
( z − H )
⎛
⎜
1
+ exp −
⎜
⎝
2 2
σz
2 ⎞⎤
⎟⎥
⎟
⎠⎥⎦
where
C = steady-state concentration at a point (x, y, z)
(µg/m 3 ),
Q = emissions rate (µg/s),
σy = horizontal dispersion parameter (m),
σz = vertical dispersion parameter (m),
u = average wind speed at stack height (m/s),
y = horizontal distance from plume centerline (m),
z = vertical distance from ground level (m),
H = effective stack height (m) = h + ∆h
where h = physical stack height
∆h = plume rise, and
x = downwind distance along plume centerline (m).
Concentration downwind from elevated source
C
Q
( H ) ⎞
⎟
2
( max)
=
πuσ
yσ
z
exp⎜
⎜
−
2
2
σ z
where variables as previous except
C(max) = maximum ground-level concentration.
H
z
2
= σ for neutral atmospheric conditions
Atmospheric Stability Under Various Conditions
Day
Night
Solar Insolation
Cloudiness e
Surface Wind
Speed a (m/s)
Strong b Moderate c
Slight d
Cloudy Clear
(≥4/8) (≤3/8)
6
Notes:
C D D D D
a. Surface wind speed is measured at 10 m above the ground.
b. Corresponds to clear summer day with sun higher than 60° above the horizon.
c. Corresponds to a summer day with a few broken clouds, or a clear day with sun 35-60° above the
horizon.
d. Corresponds to a fall afternoon, or a cloudy summer day, or clear summer day with the sun 15-35°.
e. Cloudiness is defined as the fraction of sky covered by the clouds.
f. For A–B, B–C, or C–D conditions, average the values obtained for each.
* A = Very unstable D = Neutral
B = Moderately unstable E = Slightly stable
C = Slightly unstable F = Stable
Regardless of wind speed, Class D should be assumed for overcast conditions, day or night.
Turner, D. B., "Workbook of Atmospheric Dispersion Estimates," Washington, DC, U.S. Environmental Protection Agency, 1970.
⎛
⎝
1
⎠
σ
2
z
2
⎞
⎟
⎠