This document discusses air pollution modeling and dispersion. It describes the purposes of air quality modeling such as policy analysis and state implementation plans. It also discusses atmospheric transport mechanisms like advection and dispersion. Different types of air quality models are presented including emission rate models and ambient concentration models. The basic segments of an elevated plume like the initial, transition, and diffusion phases are outlined. Factors that affect plume dispersion like meteorology, boundary layer height, and temperature profiles are summarized.

1. AIR POLLUTION AND
CONTROL
Prof.M.V.Sanas

90. Example

96. PURPOSE OF AIR QUALITY MODELING
o Policy Analysis
o Regional Planning
o Supplementary Control Systems/ Air Quality Prediction
System
o Emergency Preparedness/ Accidental Releases
o Long Range Transport (Acid Rain)
o State Implementation Plan Revisions/ New Source Review
o Prevention of Significant Deterioration ( PSD )

97. ATMOSPHERIC TRANSPORT
o Basic Mechanisms in the Movement of a Plume
• Advection
• Dispersion
o Treatment of Concentration Field
• Theoretical Approach
• Statistical theory
• Similarit y theory
• K-Theo ry Models
• Higher Order Closure Models
• Experimental Approach
Wind tunnel/ Water tank
• Field Studies (Expensive, Time Consuming & Limitation of Instrumentation )

98. TYPES OF AIR QUALITY MODELS
o Types of air quality models
• Emission rate Modeling
• Ambient Air Concentration Modeling
o Types of ground level concentration models
• Physical Model/ Mathematical Model
• Historical Model
• Trend Model
• Prototype Model

99. BASIC SEGMENTS OF AN ELEVATED PLUME
lliffusion Phasa
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Flow regimes of a plume

100. BASIC SEGMENTS OF AN ELEVATED PLUME
o Initial phase
• Vertical Jet : Effluents are not deflected immediately upon entering the cross flow if
(Vs/ U> 4)
• Bent-Over Jet Section : Entrainment of the cross flow is rapid because by this time
appreciable growth of vortices has taken place.
• Thermal Section : Self generated turbulence causes mixing and determines the
growth of plume.
o Transition phase
• Plume's internal turbulence levels have dropped enough so that the atmospheric
eddies in the inertial sub range determines the plume's growth.
o Diffusion phase
• The plume's own turbulence has dropped and energy containing eddies of
atmospheric turbulence determine the growth of plume

101. Coordinates of a plume
X
y
H
Origin

102. DISPERSION OF HEAVY GASES
o Initial Acceleration Phase
o Initial Dilution Phase
o Slumping Phase (internal buoyancy-dominated dispersion )
o Transition Phase
o Passive Phase ( atmospheric turbulence-dominated
dispersion )

103. o Types of Plume
• Continuous Plume: The release and the sampling time are long
compared with the travel time.
• Puff Diffusion/ Instantaneous Plume: The release time or
sampling time is short when compared with the travel time
o Types of Plume Rise
• Buoyancy Effect: Rise due to the temperature difference between
stack plume and ambient air.
• Momentum Rise: Rise due to exit velocity of the effluents
(emissions).

104. CONCEPT OF PLUME PENETRATION
o Meteorology plays an important role in the dispersion of
effluents.
o Various meteorological factors affect the dispersion of
emission into the atmosphere in a variety of ways.
o Convective boundary layer (or mixing height) is one of
the most important meteorological variables responsible
for high ground level concentrations.

105. CONCEPT OF PLUME PENETRATION
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Figured: Plume Mixii:,gAt 9 AM

106. EFFECT OF TEMPERATURE PROFILE ON PLUME RISE
E N V I R O N M E N T AL L AP S E R A T E
A D I A B A T I C L A P S E R A T E
L O O P I N G
--- C O N I N G
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F A N N I N G
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T R A P P I N G
TcIDp . Te m p .
N o t e : F o llo w in g H e n r y a n d H c i n c k c ( 19 9 6 )

107. PLUME RISE MODELS
o Semi empirical equations based on heat flux
o Analytical solutions
o Numerical models