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Lecture 22
Air quality.
Civ. Env. 260: Fundamentals ofEnvironmental Engineering
Nazaroff Ch. 8
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Plumes from smokestacks, clouds and volcanoes
http://www.ics.uci.edu/~eppstein/pix/josh2/SmokestackCloud.ht
m
Prunerov power station in the Czech Republichttp://www.wired.com/wiredscience/2010/04/climate-desk-exxon-lawsuit/
Cleveland Volcano, Chuginadak Island, Alaska
http://www.earthmountainview.com/volcanos.html Popocatepetl volcano, Mexico (AP photo)
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Plumes from smokestacks, clouds and volcanoes
http://www.dailymail.co.uk/news/article-563975/Amazing-pictures-The-lightning-storm-engulfed-erupting-volcano.html
Chaiten Volcano in southern Chile
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Plumes from smokestacks, clouds and volcanoes
Redoubt Volcano, Alaska
http://www.skimountaineer.com/ROF/ROF.php?name=Redoubt
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Typical plume shapes
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Typical plume shapes
http://oceanworld.tamu.edu/resources/oceanography-book/atmosphere.html
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Acid rains...
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Acid rains...
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Acid rains...
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Acid rains...
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Air temperature profiles
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Temperature
inversions
http://www.xweather.org/temperature-inversionhttp://earthsci.org/education/teacher/basicgeol/air_pollution/air_polution.html
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Effects of temperature inversions in LA
and Phoenix
http://oceanworld.tamu.edu/resources/oceanography-book/atmosphere.htmlhttp://www.nebraskaweatherphotos.org/Phoenix2009.html
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http://www.anatreptic.com/archives/outdoors/
http://www.flickr.com/photos/fundance/2763357733/
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Inversion and (photochemical) smog...
O2
+ N2
NOx
NOx + VOC + light O3
Causes severe respiratory issues.
Combined with particultates, increased severity
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Plume transport models
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Gaussian plume modeling
Where;
x = along-wind coordinate measured in wind direction from the source (longitudinal)
y = cross-wind coordinate direction (transverse)
z = vertical coordinate measured from the ground (vertical)
C(x,y,z) = mean concentration of diffusing substance at a point (x,y,z) [kg/m3]Dx,Dy,Dz = Diffusion coefficients in the x, y, and z directions[m2/s]
U = mean wind velocity along the x-axis [m/s]
Time rate of change and advection of the cloud by the mean wind
Turbulent diffusion of material relative to the center of the pollutant cloud.
( the cloud will expand over time due to these terms.)
( )
( ) ( ) ( )
+
+
=
+
z
CD
zy
CD
yx
CD
xCU
xt
Czyx
( )x
CU
t
C
+
( ).,etc
x
DxC
x
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Where M is the strength of the emission source, mass emitted per unit time
Gaussian plume modeling
Steady-state solution
( )
+=
x
U
Dz
z
Dy
y
DzDyx
MzyxC
4exp
4),,(
22
2/1
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Plume Boundary
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The lateral and vertical dispersion coefficients depend on the downwinddistance and the atmospheric stability class. These coefficients can be obtained
using Pasquill-Gifford-Turner estimates using the equations below
where has units of m.
s = an integer [1-6] representing the atmospheric stability
kx,x = empirical constants, values for each of the stability class defined in Green et al. (1960)
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Surface windspeed at 10 m(m/s)
Day Night
Incoming Solar radiation Cloud Cover
Strong Moderate Slight Thinly Overcast Mostly Cloudy
< 2 A (s = 1) A-B B (s = 2)
2-3 A-B B C (s = 3) E (s = 5) F (s = 6)
3-5 B B-C C D E
5-6 C C-D D (s = 4) D D
>6 C D D D D
Constants a,b,c,ddepend on Pasquill Stability categories defined by Turner (1995)
Atmospheric stability classes
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Superposition mirror solutions
for releases near the ground
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Where;
C(x,y,z) = mean concentration of diffusing substance at a point (x,y,z) [kg/m3]x = downwind distance [m],
y = crosswind distance [m],z = vertical distance above ground [m],Q = contaminant emission rate [mass/s],
= lateral dispersion coefficient function [m],= vertical dispersion coefficient function [m],
U = mean wind velocity in downwind direction [m/s],
H = effective stack height [m].
Steady state with stack height H
( ) ( )
++
=
2
2
2
2
2
2
2exp
2exp
2exp
2),,(
zzyzy
HzHzy
U
MzyxC
y
z
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Equivalent to source of 2M since the inability to transport across the boundarycauses concentrations to be twice what they would be without the boundary.
To get ground-level concentration, solve for z = 0
= 2
2
2
2
2exp
2exp
22),,(
zyzy
HyUMzyxC
==2
2
2
2
2exp
2exp)0,,(
zyzy
Hy
U
MzyxC
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Indoor contamination:CSTR approach for modeling.
Sorption and dead zones :