ce 260 2013- lecture 22- air quality

7/30/2019 CE 260 2013- Lecture 22- Air Quality.

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Lecture 22

Air quality.

Civ. Env. 260: Fundamentals ofEnvironmental Engineering

Nazaroff Ch. 8


2/26

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)


3/26


http://www.dailymail.co.uk/news/article-563975/Amazing-pictures-The-lightning-storm-engulfed-erupting-volcano.html

Chaiten Volcano in southern Chile


4/26


Redoubt Volcano, Alaska

http://www.skimountaineer.com/ROF/ROF.php?name=Redoubt


5/26

Typical plume shapes


6/26

Typical plume shapes

http://oceanworld.tamu.edu/resources/oceanography-book/atmosphere.html


7/26

Acid rains...


8/26

Acid rains...


9/26

Acid rains...


10/26

Acid rains...


11/26

Air temperature profiles


12/26

Temperature

inversions

http://www.xweather.org/temperature-inversionhttp://earthsci.org/education/teacher/basicgeol/air_pollution/air_polution.html


13/26

Effects of temperature inversions in LA

and Phoenix

http://oceanworld.tamu.edu/resources/oceanography-book/atmosphere.htmlhttp://www.nebraskaweatherphotos.org/Phoenix2009.html


14/26http://weblogs.sun-sentinel.com/news/weather/hurricane/blog/fog/

http://www.anatreptic.com/archives/outdoors/

http://www.flickr.com/photos/fundance/2763357733/


15/26

Inversion and (photochemical) smog...

O2

+ N2

NOx

NOx + VOC + light O3

Causes severe respiratory issues.

Combined with particultates, increased severity


16/26

Plume transport models


17/26

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


19/26

Plume Boundary


20/26

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)


21/26

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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23/26

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


25/26

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


26/26

Indoor contamination:CSTR approach for modeling.

Sorption and dead zones :

ce 260 2013- lecture 22- air quality

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