Republic of the Philippines

CAGAYAN STATE UNIVERSITY

Carig Campus, Tuguegarao City
College of Engineering

Introduction
Environmental chemistry is a branch of chemical science which deals with the development,
transport, reactions, effects and fates of chemical species in the water, air, soil and biological
environment and the effects of human activities on them. It is an interdisciplinary field of research
including environmental engineering, chemistry, physics, biology, biotechnology, life sciences,
medical science, agriculture and public health.
There are many environmental problems currently that demand urgent consideration. There are many
environmental problems currently that demand urgent consideration. These traditional issues can be
dealt with from the chemical point of view
There are four environmental segments. These are:
a. Atmosphere - It is the protective blanket of gases, suspended liquids and solids that entirely
envelopes the earth, sustains life on earth, and saves it from the hostile environment of outer
space.
b. Hydrosphere – it consist of all types of water resources such as oceans, seas, rivers, lakes,
streams, reservoirs, polar ice caps and water below the earth’s surface which includes all
surface and ground water.
c. Lithosphere – it is the outer mantle or the soil of the solid earth, consisting of minerals occurring
in the earth’s crust.
d. Biosphere – it is the realm of living organisms and their interactions with the atmosphere,
hydrosphere and lithosphere.
. The relationship between these four environmental segments will be learned in this chapter.

I. THE CHEMISTRY OF THE ATMOSPHERE

A. ATMOSPHERE
The atmosphere is a vital mechanism that seeks to monitor and sustain the temperature of the
Earth, the balance of radiation by the absorption of electromagnetic radiation released by the sun
and re-emitted by the earth, as well as the transfer of heat across the globe It filters unhealthy
tissues that destroy ultraviolet (UV) radiation. It's even warming the world by day and cooling it by
night.

Chemical Engineering Department Page 1

 Republic of the Philippines
CAGAYAN STATE UNIVERSITY
Carig Campus, Tuguegarao City
College of Engineering

B. COMPOSITION OF THE ATMOSPHERE

According to NASA, the gases in Earth's atmosphere include:
  Nitrogen — 78 percent
  Oxygen — 21 percent
  Argon — 0.93 percent
  Carbon dioxide — 0.04 percent
 Trace amounts of neon, helium, methane, krypton and hydrogen, as well as water vapor

C. STRUCTURE OF THE ATMOSPHERE
The atmosphere is divided into four major regions on the basis of temperature profile. The different
atmospheric regions and their characteristics are summarized in the table below.
Altitude Important
Temperature
Region range chemical Description
range (ºC)
(km) species

the layer closest to Earth's surface

Contains half of Earth's atmosphere.
N2, O2, CO2,  Air is warmer near the ground and gets
Troposphere 0–11 15 to -56 H2O colder higher up.

Nearly all of the water vapor and dust
in the atmosphere are in this layer and
that is why clouds are found here.
 Ozone is abundant here and it heats
the atmosphere while also absorbing
harmful radiation from the sun .
Stratosphere 11–50 -56 to -2 O3  The air here is very dry, and it is about
a thousand times thinner here than it is
at sea level. Because of that, this is
where jet aircraft and weather
balloons fly.
 the top of the mesosphere, called the
mesopause, is the coldest part of
Earth's atmosphere
Mesosphere 50–85 -2 to -92 O2+,NO+  This layer is hard to study. Jets and
balloons don't go high enough, and
nitric oxide
satellites and space shuttles orbit too
high.

The thermosphere is considered part of
Earth's atmosphere, but air density is
so low that most of this layer is what is
normally thought of as outer space.
 This is where the space shuttles flew
and where the International Space
Station orbits Earth. This is also the
Thermosphere 85 – 500 -92 to 1200 O2+, O+,NO+ layer where the auroras occur. Charged
particles from space collide with atoms
and molecules in the thermosphere,
exciting them into higher states of
energy. The atoms shed this excess
energy by emitting photons of light,
which we see as the colorful Aurora
Borealis and Aurora Australis.

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 Republic of the Philippines
CAGAYAN STATE UNIVERSITY
Carig Campus, Tuguegarao City
College of Engineering

Has very high

Above 
temperature Also known as outer space.
Exosphere thermosph H2, He
due to
ere
radiation

Figure 1.

Figure 1 shows that the temperature and pressure of the Earth's

atmosphere change in function of altitude. Air pressure is decreasing
at altitude. https://www.thinglink.com/scene/343846388821393409

1. Air pressure decreases as we increase altitude. Why?

It is because the pressure of the air can be related to the weight of
the air in a given place. When we raise altitude through the
atmosphere, there is some air underneath us and some air above us.
Yet there is still less air above us than there was at a lower altitude.

2. The air temperature is highest near the surface and decreases

as altitude increases. Why?
It is because variations in the properties of the air reach outward from
the center of the Earth. The sun heats the earth's atmosphere, and part of this heat is heated by the
air near the surface. The hot air is either diffused or convected into the atmosphere. There's even
less air to breathe.

D. EARTH’S RADIATION/ENERGY BALANCE

The sun provides solar energy that is used within the world, even though much of the intensity
of the sun never hits the surface of the earth.

Figure 2.
Shows that the Earth absorbs a part of this energy while the rest is emitted back into the space.
https://www.worldatlas.com/articles/what-is-the-earth-s-energy-budget.html

The earth receives solar energy in the form of short-wave radiation and consumes about 70% of the
sun. Although the Earth constantly receives solar energy or radiation, it will not begin to heat up;
the Earth releases the remaining 30% of solar radiation in the form of long-wave radiation into
space, which allows the Earth to cool down. The proportion of solar radiation that is absorbed and
distributed out into space is also known as Albedo.

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 Republic of the Philippines
CAGAYAN STATE UNIVERSITY
Carig Campus, Tuguegarao City
College of Engineering

The sum of solar energy per unit time flowing through the unit area at right angles to the path of
the solar beam measured just outside the Earth's atmosphere is known as the solar flux, also known
as the solar constant. The solar radiation hitting the upper Earth's atmosphere is roughly 1340 watts
/ m2•min.
II. GREENHOUSE EFFECT
Sun rays comprise of UV rays, visible light and IR radiations. Ozone layer absorbs damaging UV
radiations and allows visible and IR radiations to pass through it towards the Earth.
The gases in the atmosphere are Carbon dioxide, water vapor, methane, tropospheric ozone, and
chlorofluoro carbon (CFC).
Although carbon dioxide is just a trace gas in the Earth's atmosphere, with a concentration of
approximately 0.033 per cent by volume, it plays a vital role in regulating our environment. The
so-called greenhouse effect explains the absorption of heat above Earth's surface by atmospheric
gases, in particular carbon dioxide. The glass roof of the greenhouse transmits visible sunlight and
collects some of the outgoing infrared (IR) radiation, trapping the heat.
The sinks of CO2 are:
1. Oceans: Which dissolves CO2 as carbonates

2. Biomass: Living green plants use CO2 in photosynthesis

→

These sinks are responsible for only 50% of the expected increase in the CO2 content in
atmosphere.
Carbon dioxide behaves much like a glass cover, except that the raise of temperature in the
greenhouse is mostly due to the reduced passage of air within. Calculations indicate that if the
atmosphere didn’t contain carbon dioxide, the Earth would be 30 °C cooler! Without CO2, the
earth would be as cold as moon.

Figure 3 . http://geologylearn.blogspot.com/2015/07/what-cause-global-warming-effect.html

Green house is a body which allows the short wavelength incoming radiations but does not allow
long wave radiations to escape.

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 Republic of the Philippines
CAGAYAN STATE UNIVERSITY
Carig Campus, Tuguegarao City
College of Engineering

GREENHOUSE GASES AND THEIR SOURCES

Table 2. Relative contributions of greenhouse gases and their uses
% Contribution
Gases towards Major Sources
greenhouse effect
Fossil fuel combustion, Deforestation,
I CO2 49 %
Respiration, Fermentation
Wet lands, Marshy places, Anaerobic
2 CH4 18%
decomposition of organic wastes, Forest fires
Refrigerant, Aerosol propellent,
CFC 17%

·
Manufacturing foams
Natural soils, fertilizers, fossil fuel
N 2O 6%
combustion, burning of biomass
A
Photochemical reaction in stratosphere and
O3 8%
diffusion into troposphere
4 H 2O 2%` Vapourisation process
With rapid manufacturing and technical developments, the production of greenhouse gasses is
rising at an unprecedented pace, which has a detrimental impact on the global environment.

III. OZONE LAYER

Ozone (O3) is concentrated in stratosphere at various heights from 16 – 40km at different
latitudes. This layer of atmosphere enveloped by ozone is known as ozone layer. It is also known
as ozonosphere or ozone umbrella.
The thickness of ozone layer is measured in Dobson units (DU). 1 DU = 0.01 mm of the
compressed gas at 0°C and 760mm Hg pressure.
A. Formation of Ozone.
It is formed naturally in stratosphere by the action of ultraviolet radiation.
→ (1)
(2)
Where ‘M’ is a third body (O2 or N 2) which absorbs the excess energy liberated by the
reaction (1) and thereby stabilize the ozone molecule.

B. Advantage of Ozone Layer.

 It acts as protective shield as is absorbs the UV-radiation responsible for DNA
mutation and skin cancer. The UV – radiation may also cause global warming, faster
degradation of plastics, fabrics, etc.

C. Depletion of Ozone Layer
The three main reasons where human activity has influenced the ozone layer are the
following:
1. Direct emission of NOx by supersonic transport. They just fly over the tropopause to
maintain their speed because of low resistance.
2. Use of cholofluorocarbons
3. Increased use of nitrogenous fertilizers.

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 Republic of the Philippines
CAGAYAN STATE UNIVERSITY
Carig Campus, Tuguegarao City
College of Engineering

If the thickness of ozone layer becomes less than 200 DU, it is known as ozone hole.

D. Mechanism of Ozone Depletion

i. Nitric Oxide converts ozone into O2 and NO2.

ii. NO2 formed reacts with nascent oxygen

iii. NO is regenerated which again reacts with
ozone and the depletion continues by the chain
reaction.

Figure. 4: Ozone depletion by NOx

CFC’s are inert in normal physical conditions.

But under the influence of UV-radiation they
form chloride radical and the following
reactions takes place.
→

Regenerated

The chloride free radical (·Cl) regenerated is

highly stable and one chloride free radical can
break 1 molecule of ozone.

E. Global Action against Ozone Depletion

1. Vienna Convention
  The convention laid a framework for global cooperation on arresting ozone depletion.
 20 nations, including most of the major CFC producers, signed the Vienna Convention
 in 1985
2. Montreal Protocol
  Then, in 1987, 43 countries signed the Montreal Protocol.
  The Protocol is ratified today by 197 Members.
 Ozone-depleting substances (as mentioned above) have been established for phase-out
 and are to be replaced by HFCs (Hydrofluorocarbons).
 With the introduction of the Montreal Protocol, CFC concentrations in the atmosphere
 have been undergoing a steady decline since peaking in 1994.
 Efficient Equivalent Chlorine (EECl) levels in the atmosphere had declined by around
10% by 2008.

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 Republic of the Philippines
CAGAYAN STATE UNIVERSITY
Carig Campus, Tuguegarao City
College of Engineering

IV. ACID RAIN

Every year, acid rain does hundreds of millions of dollars’ worth of damage to stone structures and
monuments all around the world. Some environmental chemists use the word "stone leprosy" to
describe the degradation of stone by acid rain. Acid rain is also harmful for crops and marine species.
Many well-documented cases demonstrate significantly how acid rain has ruined farm and timber land
and killed marine species.
Since atmospheric CO2 will not be expected to result in a pH lower than 5.5, sulfur dioxide (SO2) and,
to a lesser degree, auto-emission nitrogen oxides are thought to be responsible for elevated rainwater
acidity. Acid oxides, such as SO2, react with water to create the related acids.
There are a variety of sources of atmospheric SO2. Nature itself contributes a lot of SO2 in the form of
volcanic eruptions. Often, there are many metals in nature mixed with sulfur. The extraction of
metals also includes the smelting or roasting of ores— that is, the boiling of metal sulfide in the air to
form metal oxides and SO2.
Figure 6. Sulfur dioxide and other air pollutants being released into the atmosphere from a coal-
burning power plant.(Chang, R: Chemistry, 10th ed)
While smelting is a significant source of SO2, much of the SO2
released to the atmosphere is compensated for by the
combustion of fossil fuels in agriculture, power plants and
households. The sulfur content of coal varies from 0.5 to 5 per
cent by bulk, based on the source of the coal.
In the troposphere, SO2 is nearly always oxidized to H2SO4 in
the form of aerosol, resulting in heavy precipitation or acid
rain.

Figure 7.https://www.yourarticlelibrary.com/essay/essay-on-air-pollution-sources-causes-effects-and-control/30186

V. PHOTOCHEMICAL SMOG

The term "smog" was coined to describe the mixture of smoke and fog that engulfed London in
the 1950s. Today, though, we are more familiar with the photochemical smog produced by the
reactions of vehicle emissions in the presence of sunlight.

Chemical Engineering Department Page 7

 Republic of the Philippines
CAGAYAN STATE UNIVERSITY
Carig Campus, Tuguegarao City
College of Engineering

Automotive exhaust consists primarily of NO, CO and various unburned hydrocarbons. These gasses are
called major pollutants because they set in motion a series of photochemical reactions that create
secondary pollutants. The secondary pollutants — mainly NO2 and O3—are responsible for the
build-up of smog.
A. Mechanism of Photochemical smog
Hydrocarbon oxidation
produces various chemical
intermediates, such as
alcohols and carboxylic
acids, which are all less
fragile than the
hydrocarbons themselves.
These liquids are
gradually reduced into
tiny droplets of liquids.
The dispersion of these
droplets in the air, called
aerosols, disperses the
sunlight and decreases
visibility. This interaction
sometimes lets the environment seem hazy. As the mechanism for photochemical smog
formation has been better known, significant attempts have been made to reduce the
build-up of primary contaminants. Most cars are now fitted with catalytic converters
engineered to oxidize CO and unburned hydrocarbons to CO2 and H 2O and to reduce NO
and NO2 to N2 and O2.

References:

1. Goel, N. & Kumar, S. (2006). Concise Engineering Chemistry (2nd Ed). AITBS Publishers and
Distributors, India. ISBN 81-7473-233-2
2. Chang, Raymond (2010). Chemistry (10th ed). The McGraw-Hill Companies, Inc., 1221 Avenue
of the Americas, New York, NY 10020.

Self-Assessment Activity:

1. Describe the regions of Earth’s Atmosphere.

2. What processes give rise to aurora borealis and aurora australis?
3. Discuss briefly ozone hole and its effect on human health.
4. How to CFCs and nitrogen oxide destroy ozone in the atmosphere?
5. Why is more emphasis placed on the role of carbon dioxide in the greenhouse effect
than that of water?
6. Name the gas that is largely responsible for the acid rain phenomena.
7. List three detrimental effects of acid rain.
8. Suggest ways to minimize the formation of photochemical smog.

Chemical Engineering Department Page 8

AIR POLLUTION
CONTROL
Lecture 1: Atmosphere and Biochemical Cycle
Atmosphere
• is a dynamic system which is composed of thin layer of
gases that envelops the Earth

Component Concentration
Main Components
Nitrogen 78%
Oxygen 21%
Argon 0.9%
Carbon dioxide 0.03%
Trace Components
CH4, NOx, O3, H2S, SOx, CFC, HC, Aerosols
Layers of the Atmosphere
Temperature Profile of Atmosphere

Source: Vallero, Daniel. Fundamentals of Air

Pollution. 4th edition. figure 2.1, page 53.
Basic Concepts
• Density,  – ratio of mass and volume, kg/m3

• Weight Density or specific weight,  – ratio of weight and

volume, N/m3

• Specific volume,  – reciprocal of density, m3/kg

Basic Concepts
• Pressure – force divided by the perpendicular cross-
sectional area
𝑃 =𝑃 +𝑃
𝑃 =𝑃 −𝑃

• Pressure variation with respect to Altitude in terms of

specific weight

• Temperature – refers to the relative hotness or coldness

of materials
Basic Concepts: Mixtures
• Mole fraction – ratio of the number of moles of a
component to the total number of moles of the system
𝑛
𝑋 =
𝑛
• Total mole fraction

𝑋 =1

• Total mass of mixtures

𝑚 = 𝑚
Basic Concepts: Mixtures
• Mean molecular weight of the mixture
𝑚
𝑀𝑊 =
𝑛

𝑚 +𝑚 +𝑚 +⋯
𝑀𝑊 =
𝑛

∑ 𝑛 𝑀𝑊
𝑀𝑊 =
𝑛
Basic Concepts: Mixtures summary

Dobsbatm+Ogange num
of Formulas

MWave =

Mo

• Total Pressure of Mixtures

ideal gas

Pi =
MART ; from PV:NRT on PVMRT.

𝑃 =𝑃 +𝑃 +𝑃 +⋯
• For ideal gases,
𝑛 𝑅𝑇
𝑃 =
𝑉
• Total enthalpy of Mixtures

𝐻= 𝐻
Natural Processes that Removes Materials from
the Atmosphere
• Sedimentation – particles heavier than air settle out as a
result of gravitational attraction to the Earth

• Rain out – precipitation can physically or chemically

remove pollutants from the air

• Oxidation – reaction in which oxygen is chemically

combined with another substance

• Photodissociation – process by which solar radiation can

break down chemical bonds in a chemical process
Biogeochemical cycle
• is a circuit or pathway by which a chemical element or
molecule moves through both biotic ("bio-") and abiotic
("geo-") compartments of an ecosystem.

• Important Cycles
• Carbon
• Oxygen
• Water
• Nitrogen
• Sulfur
 18

The biogeochemical cycle

Atmosphere The biogeochemical

Biosphere cycle involves the
movement of elements
and compounds among
the land (lithosphere),
organisms, air
Hydrosphere (atmosphere) and the
oceans (hydrosphere).
Lithosphere
Human activities can
affect these cycles
BIOGEOCHEMICAL CYCLING OF
ELEMENTS: examples of major processes

Surface
reservoirs
Carbon Cycle
Oxygen Cycle
Water Cycle
Nitrogen Cycle
Sulfur Cycle
AIR DYNAMICS AND
METEOROLOGY
Lecture 2
CONCEPTS

 Air Dynamics – is
the study of the
motion of air

 Meteorology – is
the study and
forecasting of
weather changes
resulting from large-
scale atmospheric
circulation
ATMOSPHERIC CIRCULATION
PATTERNS
FACTORS AFFECTING SURFACE
CIRCULATION

Topography

Diurnal variation and seasonal variation in surface

heating

Variation in surface heating owing to the presence of

ground cover and proximity to large bodies of water
ATMOSPHERIC CIRCULATION
PATTERNS
 Source: https://addeyans-
geography.weebly.com/glo
bal-atmospheric-
circulation.html
 N

Hadley Cell

Yo -
Trade winds blow towards the
equator, then ascend near the
equator as a broken line of
- thunderstorms, which forms the
Inter-Tropical-Convergence
~ Zone (ITCZ).

From the tops of these storms,

the air flows towards higher
latitudes, where it sinks to
produce high-pressure regions
over the subtropical oceans and
the world's hot deserts, such as
the Sahara desert in North
Africa.
Source: https://www.metoffice.gov.uk/learning/learn-about-the-weather/how-weather-works/global-circulation-patterns

GLOBAL CONVECTION CURRENTS

 Ferrel Cell

Air converges at low altitudes to

ascend along the boundaries
between cool polar air and the
warm subtropical air that
generally occurs between 60 and
70 degrees north and south.

At the surface, air flowing

poleward is deflected to the east
by the coriolis force, resulting in
westerly surface winds.

Source: https://www.metoffice.gov.uk/learning/learn-about-the-weather/how-weather-works/global-circulation-patterns
 Polar Cell

Air in this cell sinks over the

highest latitudes and flows out
towards the lower latitudes at the
surface.

Source: https://www.metoffice.gov.uk/learning/learn-about-the-weather/how-weather-works/global-circulation-patterns
GLOBAL TEMPERATURE
PATTERNS

Source: https://addeyans-geography.weebly.com/global-atmospheric-
circulation.html
GLOBAL PRESSURE PATTERNS

Source: https://addeyans-geography.weebly.com/global-atmospheric-
circulation.html
GLOBAL WIND PATTERNS

Source: https://addeyans-geography.weebly.com/global-atmospheric-
circulation.html
WIND VELOCITY PROFILE

𝑣 𝑧
=
𝑣 𝑧

Where:
v2 = wind velocity at elevation z2, m/s
v1 = wind velocity at elevation z1, m/s
z = elevation, m
n = stability coefficient
n  0.35 for very stable condition
n  0.15 for very unstable condition
n ~ 0 . 20 for slightly unstable
WIND DIRECTION PROFILE

Wind direction normally changes in a

clockwise manner as elevation increases.

Veering – clockwise change in direction

Backing – counterclockwise change in

direction
 LOCAL CIRCULATION EFFECTS
 Land-sea breeze

Source: http://facweb.bhc.edu/academics/science/harwoodr/GEOG101/Study/Images/Sea-Land%20Breezes.jpg
 LOCAL CIRCULATION EFFECTS
 Land-sea breeze

Source: http://facweb.bhc.edu/academics/science/harwoodr/GEOG101/Study/Images/Sea-Land%20Breezes.jpg
 MOUNTAIN-VALLEY WINDS

Source: https://i.ytimg.com/vi/kMISOalQfpQ/maxresdefault.jpg
WIND
ROSE
 A wind rose diagram
is a tool which
graphically displays
wind speed and
wind direction at a
particular location
over a period of
time.
WIND ROSE
REQUISITES FOR AIR
POLLUTION PROBLEM
 There must be a pollutant emission into the atmosphere.

 The emitted pollutant must be confined to a restricted

volume of air.

 The polluted air must interfere with the well-being of

people.
ATMOSPHERIC STABILITY AND
VERTICAL MIXING
 Atmospheric Stability
 resistance to vertical mixing
 resistance of the atmosphere to
vertical motion

 Vertical Mixing (Atmospheric

Turbulence)
 an upward and downward movement
of air that occurs as a result of the
temperature gradients
ATMOSPHERIC STABILITY

 Visual Indicators of Stable Air

 Clouds in layers, no vertical movement
 Stratus-type clouds
 Smoke column drifts apart after limited
rise
 Poor visibility in lower levels due to
accumulation of haze and smoke
 Fog layers
 Steady winds
 ATMOSPHERIC STABILITY

Stratus Smoke Column

Clouds

Haze and smoke Fog

ATMOSPHERIC STABILITY

 Visual Indicators of Unstable Air

 Clouds grow vertically and smoke rises
to great heights
 Cumulus-type clouds
 Upward and downward currents
 Gusty wind
 Good visibility
 Dust whirls
 ATMOSPHERIC STABILITY

Smoke rises Cumulus clouds

Good visibility Dust whirl

QUANTITATIVE BASIS OF
STABILITY

 Air parcel is an imaginary body of air to which may be

assigned any or all of the basic dynamic and
thermodynamic properties of atmospheric air.
 Characteristics:
 Large enough to contain great number of molecules
 Properties are approximately uniform within

 Air parcel is assumed to be:

 Thermally insulated from its environment
 In hydrostatic equilibrium with the surrounding air
 Slow moving
QUANTITATIVE BASIS OF
STABILITY
 Heat Content
𝑄 = 𝐶 𝑑𝑇 + 𝑉𝑑𝑃
Where:
Q = heat content of air
CP = heat capacity at constant pressure
dT = differential change in temperature
V = volume
dP = differential change in pressure
QUANTITATIVE BASIS OF
STABILITY
 Hydrostatic Equilibrium
𝑑𝑃 = 𝜌𝑔𝑑𝑧
Where:
dP = differential change in pressure
 = air density
g = gravitational acceleration
dz = differential height
 QUANTITATIVE BASIS OF
STABILITY
 Dry Adiabatic Lapse Rate, d

𝑔 𝑑𝑇
𝛾 = =−
𝐶 𝑑𝑧

𝟓. 𝟒 ℉
𝜸𝒅 =
𝟏𝟎𝟎𝟎 𝒇𝒕
 Wet Adiabatic Lapse Rate, w

∆𝑌𝑑𝐻
𝛾 =𝛾 +
𝐶 𝑑𝑧

𝟑 ℉
𝛾 =
𝟏𝟎𝟎𝟎 𝒇𝒕
QUANTITATIVE BASIS OF
STABILITY

Lapse Rate Stability Condition

𝜸 > 𝜸𝒅 Unstable
𝜸 = 𝜸𝒅 Neutral
𝜸 < 𝜸𝒅 Stable
QUANTITATIVE BASIS OF STABILITY
QUANTITATIVE BASIS OF STABILITY
QUANTITATIVE BASIS OF STABILITY
MECHANISMS
THAT FORCES
AIR TO RISE
 Surface Heating
and free convection
Some surfaces better
absorb radiation
from the sun and
become warmer
than surrounding
surfaces. Parcels of
hot air form above
these "hot spots" on
the surface and
begin to rise upward.
MECHANISMS THAT FORCES AIR
TO RISE
 Surface Convergence and/or Upper-level Divergence (Dynamic
Lifting)

Convergence is an atmospheric condition that exists when there is

a horizontal net inflow of air into a region. When air converges
along the earth's surface, it is forced to rise since it cannot go
downward.

Divergence is an atmospheric condition that exists when there is a

horizontal net outflow of air from a region. When air diverges just
below the top of the troposphere, air from below is forced to rise
up and take its place.
MECHANISMS THAT FORCES AIR
TO RISE
 Surface Convergence and/or Upper-level Divergence
(Dynamic Lifting)
MECHANISMS THAT FORCES AIR
TO RISE
 Lifting Due to Topography

When air moving along the surface of the Earth is confronted

by a mountain, it is forced up and over the mountain, cooling
as it rises. If the air cools to its saturation point, the water
vapor condenses and a cloud forms.
MECHANISMS THAT FORCES AIR
TO RISE
 Lifting Due to Topography
MECHANISMS THAT FORCES AIR
TO RISE
 Lifting Along Frontal Boundaries

A front is defined as the transition zone between two air

masses of different density.

All fronts slope in the vertical so that the warmer (less dense)
air mass sits on top of the colder (more dense) air mass. In
other words, the warmer air mass is forced to rise over the
colder air mass. As air from the warm air mass rises, it cools,
leading to the development of clouds and maybe
precipitation.
MECHANISMS
THAT FORCES
AIR TO RISE
 Lifting Along
Frontal Boundaries
Atmospheric Temperature Inversion
 Temperature Inversion
• temperature inversion
is a thin layer of the
atmosphere where
the normal
decrease in
temperature with
height switches to the
temperature
increasing with
height. An inversion is
present in the lower
part of a cap.
Air near the ground cools more quickly than air aloft.
This is most likely when the sky is clear and the wind is
light/calm. Cooling will occur the most readily in low
places (such as valleys sheltered from the wind)
This often happens in the late
afternoon/early evening (before sunset) and
lingers into the next morning (after sunrise)
for a few hours.
THE
PROBLEM
Since warm air rises, air under
the inversion cannot escape
because it is cooler than farther
aloft. Smoke and pollution get
trapped.
Ideal conditions for
temperature inversion
• Long nights, so that the outgoing
radiation is greater than the incoming
radiation.
• Clear skies, which allow unobstructed
escape of radiation.
• Calm and stable air, so that there is no
vertical mixing at lower levels.
• Low elevation areas such as valleys and
basins where cool air can sink and collect
– Inversions will begin sooner, last longer,
and be more intense in these areas.
Clues a Temperature
Inversion Exists
Mist, fog, dew or frost are present

Smoke or dust hang in the air; may move

horizontally just above the surface.

Cumulous clouds disperse as evening

approaches/clear skies

Distant sounds become easier to hear

Distant smells are more distinct during the

evening than during the day
 • Temperature Inversion in
Intermountain Valley
Types of  this kind of temperature inversion
Temperature is very strong in the middle and
higher latitudes.
Inversion
 It can be strong in regions with
high mountains or deep valleys
also.
 Types of Temperature Inversion
• Temperature
Inversion in
Intermountain
Valley
 this kind of
temperature
inversion is very
strong in the middle
and higher latitudes.
 It can be strong in
regions with high
mountains or deep
valleys also.
Types of
Temperature
Inversion
• Frontal Inversion
 Inversion that is
developed when a warm
air mass overruns a cold
air mass below
 This kind of inversion has
considerable slope,
whereas other inversions
are nearly horizontal.
 humidity may be high,
and clouds may be
present immediately
above it.
 • Subsidence Inversion
 Associated with either a stagnant high-
pressure cell or a flow aloft of cold dry air
Types of from an ocean unto a land mass
surrounded by mountains.
Temperature  common over the northern continents in
Inversion winter (dry atmosphere) and over the
subtropical oceans
 these regions generally have subsiding air
because they are located under large high-
pressure centers.
Types of
Temperature
Inversion
• Subsidence Inversion
 Associated with either a
stagnant high-pressure cell
or a flow aloft of cold dry
air from an ocean unto a
land mass surrounded by
mountains.
 common over the northern
continents in winter (dry
atmosphere) and over the
subtropical oceans
 these regions generally
have subsiding air because
they are located under
large high-pressure
centers.
Types of Temperature Inversion
• Radiation Inversion
 Occurs during periods of clear weather and light to calm
winds and is caused by rapid cooling of the ground by
radiation of heat out of space.
Types of Temperature Inversion
Effects of Temperature Inversion
• The Great Smog of 1952 (London, England)
 For five cold December days, a heavy fog combined with sulfurous
fumes from coal fires, vehicle exhaust and power plants, blocking
out the sun and creating a public health disaster.

• The "Big Smoke"

was the worst air
pollution crisis in
European history,
killing an
estimated 8,000 to
12,000 people.
 Effects of
Temperature
Inversion
• The1962 Smog
(London, England)
 The transition away
from coal as the city’s
primary heating source
toward gas, oil and
electricity took years,
and during that time
deadly fogs periodically
occurred, such as one
that killed about 750
people in 1962.
 • Donora Smog of 1948 - Donora,
Effects of Pennsylvania (October 27-31, 1948)
Temperature  20 people were asphyxiated and over
7,000 were hospitalized or became ill as
Inversion the result of severe air pollution over
Donora, Washington County, the
Monongahela River town of 14,000.
PLUME BEHAVIOR
• Plume behaviour refers to the
dispersal pattern of gaseous
pollutants in atmosphere depending
upon wind conditions, atmospheric
stability and vertical temperature
profile. It shows seasonal as well as
diurnal variations
 Concept of Maximum Mixing Height
• Maximum mixing Depth (MMD)
 Altitude at which vertical mixing
stops
 Altitude at which the dry/wet adiabatic
lapse rate crosses the actual air
temperature profile

• Ventilation Coefficient, 
 Indicator of the atmosphere’s dispersive
capability
 If ventilation coefficient < 6,000 m2/s,
air pollution potential is considered to be
high

 = 𝑴𝑴𝑫 𝒙 𝑽 Where:
 = ventilation coefficient, m2/s
MMD = maximum mixing height, m
V = average velocity of air below MMH, m/s
Examples:
• Suppose the following atmospheric altitude versus air temperature
data have been collected.

Altitude 0 100 200 300 400 500 600

(m)
Temp 20 18 16 15 16 17 18
(0C)

a. What would be the mixing depth?

b. How high would you expect a plume to rise if it is emitted at 21

0C from a 100-m stack if it rise at the dry adiabatic lapse rate?

c. If the maximum daytime surface temperature is 22 0C, and a

weather station anemometer at 10 m height shows winds
averaging 4 m/s, what would be the ventilation coefficient? The
stability coefficient can be taken as 0.20.
 • Suppose the ambient atmospheric
Examples: temp profile of an area is given by
the following equation:
𝑇 ℃ = 30 − 0.005𝑧
where z = altitude in m. If the
maximum surface temperature is
34°C and average wind speed is
5.7 m/s, estimate the ventilation
coefficient and comment on the
pollution potential.
6 I VEN :
~
C
-
Ym
To C = 30-0 8052 .
/

y =
MX + b
· C o
G
To (C) =
34 + DALR 2 =
34 -
0 01 -
.
2 2
m

average wind speed = 5 7 m

.
s =
Z

using eq . 1 and 2 :

-
0 .
01" m2 + 34 C
°
: -0 005 .
"4m + 30 "C

z = 800 m =
MMD
& or u (same sila)

Ventilation
Coefficient VC ,
:
MMD x z =
800 m x 5 7 .

M/S
= 4560m2/S

4560- 6000m2 :
the area has a high pollution potential

Bale nakita
a vent Coef - Jung Kong formula en
.

MMD x
Y yung
"C =

velocity
Pero sa ginamit sa ex .
2
,

B = MMD X
↳ velocity
↓
vent .

Coef

yung U kasi sa
formula ni ma'am
, equivalent +o '2' " 'm' unit
.
; Yung ,

Tapos , puede mong Kunin V Kung hindi given .

Hassnasatabe e
>
-
n

1 (2) :
 • Atmosphere is stable with a
Homework lapse rate of -0.2 0C per 100
meters. The surface air
temperature is 15 0C. A
parcel of air is released at
the ground with a
temperature of 25 0C.
Calculate the maximum
mixing height in meters.
 • The atmosphere temperature profile
during a certain of a certain day is
Homework: given by

−80𝑇 + 1600, 0 ≤ 𝑧 ≤ 800

𝑧 = 50𝑇 + 300, 800 ≤ 𝑧 ≤ 900
−150𝑇 + 2700, 900 ≤ 𝑧

• Determine the maximum mixing

height. If the average wind speed in
the area is 40 km/h, determine
ventilation coefficient.
 IBD/Lecture Notes

Maximum Mixing Depth

The amount of air available to dilute pollutants is related to the wind speed
and to the extent to which emissions can rise into the atmosphere.

The maximum mixing depth (sometimes called the mixing height) is

obtained by projecting the dry adiabatic lapse rate line to the point of
intersection with the atmospheric temperature profile.

Neutral

Stable
Height
Maximum
mixing
depth

Unstable

Temperatur Tmax
e

The product of the maximum mixing depth and the average wind speed
within the mixing depth is sometimes used as an indicator of the
atmosphere’s dispersive capability. This product is known as the ventilation
coefficient (m2/s). Values of ventilation coefficient less than about 6000 m2/s
are considered indicative of high air pollution potential (Portelli and Lewis,
1987).

Sample Problems

EX1. Suppose the following atmospheric altitude versus temperature data

have been collected.

Altitude, 0 100 200 300 400 500 600

IBD/Lecture Notes

Temp. OC 20 18 16 15 16 17 18

a) What would be the mixing depth? for coming siya

. Pero sa
graph dapat titing in

b) How high would you expect a plume to rise if it is emitted at 21 OC

from a 100-m stack if it rises at the dry adiabatic lapse rate? Would
you expect the plume to be looping, coning, fanning, or fumigating?

the figure above

. Bale fumigationa
check

EX2. For the temperature profile given in the previous problem, if the
maximum daytime surface temperature is 22 OC, and a weather station
anemometer at 10 m height shows winds averaging 4 m/s, what would be
the ventilation coefficient? Assume stability class C and use the wind at the
height halfway to the maximum mixing depth.
IBD/Lecture Notes

eq
.
Step 1 :

600 ·

Ground level temp

.: 20
°
C
50g ·

max temp = 18 C
°

400 ·

300 ·

y
=
mx + b
200 &

100 &
T =

d 2 + b

O
14 15 I7
16 1819202

dT 18 -
20

d2
I

600 0
= - 0 .
0033 "m using eq. .
122 :

oc/m
-

° %
0 81 /M2 -0 %
°
+
21 C
=
0095
-

dT dT
.
.
-

b = T -
=
20 % -
Om °
dz az 2+ 18 C

di na sinulat Kasi z =
447 76 m .

times O lang din .

4 M2
° °
T = -0 .
0063 + 20 C

d
T/dz = -108/0 980r1 X
.
? by definition
b =
21
°
C or 180C ?

T= -

is z + 18
°
2

21 C
GIVEN :

TMax: 22
°
C

U, = 18 m > according to the table

↓ = 4 M/S
Class C =
slightly unstable = 0 20. =
n

600 ·

50g · 500m /intersection) =

MMD
400 ·

300 ·

200 &

100 &
cheight halfway ng MMD

O
14 15 16 17 18 19 20 21 a2

= 0 20

i
n 250m 6 20
.

Y2
.

22
I =
Y = 7 .

6/M/s
2
, 4 m/s 10m

B
= MMB X V =
500m x 7 .
6 m/s =
3800m2/6
sample Problem 3 :

GIVEN :

°
↑ =
30 C
max

ground level temp =

18 °
C

& 700 m '

& 700m the temp is 15 C

°
T = 15 C ,

2 :
2100m > ito at a answer

15-18

y: my
for
A =

700 -
O
= - 0 0043
. :
M
+ b
18 ° =
1-0 .
0043 ((OM) + b
°
b =
18 C

envi T = -0 .
0043"/m 2 + 18 ° C I

adiabatic
At :
-

to m
= -0 . 01" m

T = -
0 .

01 2 + 30 % 2

using ed. .
1 22 :

-
0 . 01 m2 + 30 %: -
0 .

0048
°
C/m2 + 18
°
C

2 = 2105 26 .
M

& =
2100 sa video

sample Problem I

600 ·

50g ⑳

400 ⑳
·

300 ·

200 &

100 &

O
14 15 It
16 18 192021

a) maximum mixing depth

= 400 m

b 21 C
°
,
100 m height
MMD = BOOM

Fumigation
TYPES AND CATEGORIES
OF AIR POLLUTANTS
Unit IV
Air Pollutants
• Any substance in air that could, in high enough
concentration, harm animals, humans, vegetation,
and/or materials.
Primary Pollutants
• Pollutants
which are emitted directly into the
atmosphere from the source

• Types of Primary Pollutants

• Carbon monoxide
• Oxides of sulfur
• Oxides of nitrogen
• Methane
• Volatile organic carbons
• Greenhouse gases
• Odor generating gases
Types of Primary Pollutants
• Carbon monoxide
• a poisonous, colorless, odorless, and tasteless gas
• a common industrial hazard resulting from the incomplete burning
of natural gas and any other material containing carbon such as
gasoline, kerosene, oil, propane, coal, or wood
Types of Primary Pollutants
• When inhaled it deprives the blood stream of oxygen, suffocating
its victim

• Symptoms of CO Poisoning
• tightness across the chest
• headache, fatigue, dizziness, drowsiness, or nausea
• Sudden chest pain may occur in people with angina
• Angina is a type of chest pain caused by reduced blood flow to the
heart
• For prolonged or high exposure: vomiting, confusion, and collapse
in addition to loss of consciousness and muscle weakness
Types of Primary Pollutants
Level of Remarks
Carbon
monoxide
(ppm)
0 Normal, fresh air
9 Maximum recommended indoor CO level
10-24 Possible health effects with long-term exposure
25 Max TWA Exposure for 8 hour work-day.
50 Maximum permissible exposure in workplace
100 Slight headache after 1-2 hours.
200 Dizziness, nausea, fatigue, headache after 2-3 hours of
exposure.
400 Headache and nausea after 1-2 hours of exposure.
Life threatening in 3 hours.
Types of Primary Pollutants
Level of Remarks
Carbon
monoxide
(ppm)
800 Headache, nausea, and dizziness after 45 minutes; collapse
and unconsciousness after 1 hour of exposure.
Death within 2-3 hours.
1,000 Loss of consciousness after 1 hour of exposure.
1,600 Headache, nausea, and dizziness after 20 minutes of exposure.
Death within 1-2 hours.
3,200 Headache, nausea, and dizziness after 5-10 minutes; collapse
and unconsciousness after 30 minutes of exposure.
Death within 1 hour.
6,400 Death within 30 minutes.
12,800 Immediate physiological effects, unconsciousness.
Death within 1-3 minutes of exposure.
Types of Primary Pollutants
• Cases of Carbon monoxide Poisoning
Types of Primary Pollutants
• Sulfur oxides (SOx)
• are compounds of sulfur and oxygen molecules

• Sulfur dioxide (SO2)

• is the pre-dominant form found in the lower atmosphere.
• It is a colorless gas that can be detected by taste and smell in the range
of 1,000 to 3,000 micrograms per cubic meter (μg/m3)
• At concentrations of 10,000 μg/m3, it has a pungent, unpleasant odor
• Soluble in water

• Major Sources
• Burning fuels containing sulfur
• Roasting of metal sulfide ores
• Volcanic eruption (35-65% of the total sulfur dioxide emission)
Types of Primary Pollutants
• Health
Level Effects
of Sulfur of SO2
Remarks
dioxide (ppm) lung function
• Reduced
0.3 – •1.0 Detected of
Increased incidence byrespiratory
taste symptoms and dieseases
More •than 1.0 of the
Irritation Injurious
eyes, to plant
nose andfoliage
throat
3 • Premature mortality
Noticeable odor
5 Immediate irritation to nose and throat
6-12 Irritation to eyes
20 Suggested maximum allowable concentration for 30 to 60
minutes' exposure
400-500 Immediately dangerous to life
Types of Primary Pollutants
• Oxides of nitrogen
• mixture of gases that are composed of nitrogen and oxygen
• consist primarily of nitric oxide (NO) and nitrogen dioxide (NO2)

• Nitrogen dioxide is a yellowish-orange to reddish-brown gas with a

pungent, irritating odor, and it is a strong oxidant

• Sources of NOx
• Combustion at high temperature
• Lightning
• Volcanic activities
• Anaerobic biological processes in soil and water
Types of Primary Pollutants
• Health Issues
• inflammation of the airways at high levels
• Long term exposure can decrease lung function, increase the risk
of respiratory conditions and increases the response to allergens
Types of Primary Pollutants
Level of
• Health Remarks
Effects of SO2
Nitrogen
• Reduced lung function
dioxide (ppm)
• Increased incidence of respiratory symptoms and dieseases
0-50 No health impacts are expected when air quality is in this range
• Irritation of the eyes, nose and throat
51-100 Individuals who are unusually sensitive to nitrogen dioxide
• Prematureshould
mortality
consider limiting prolonged outdoor exertion
101-150 The following groups should limit prolonged outdoor exertion:
• People with lung disease, such as asthma
• Children and older adults
151-200 The following groups should avoid prolonged outdoor exertion:
• People with lung disease, such as asthma
• Children and older adults

Everyone else should limit prolonged outdoor exertion.

201-300 The following groups should avoid all outdoor exertion:
• People with lung disease, such as asthma
• Children and older adults

Everyone else should limit outdoor exertion.

Types of Primary Pollutants
• Methane
• colorless, odorless, and extremely flammable gas that can be
explosive when mixed with air
• Tert-butylthiol – added to methane as a safety measure

• Sources
• production and transport of coal, natural gas, and oil
• decay of organic waste in municipal solid waste landfills
Types of Primary Pollutants
• Methane
• colorless, odorless, and extremely flammable gas that can be
explosive when mixed with air
• Tert-butylthiol – added to methane as a safety measure

• Sources
• production and transport of coal, natural gas, and oil
• decay of organic waste in municipal solid waste landfills

• Health Effects
• High levels of methane can displace oxygen in the air and cause
oxygen deprivation, which can lead to suffocation.
• Breathing high levels of the gas can also lead to agitation, slurred
speech, nausea, vomiting, flushing and headache. In severe cases
breathing and heart complications, coma and death may occur
Types of Primary Pollutants
• Volatile Organic Carbon (VOC)
• Organic chemicals that have a high vapor pressure at ordinary
room temperature
• large group of organic chemicals that include any compound of
carbon (excluding carbon monoxide, carbon dioxide, carbonic acid,
metallic carbides or carbonates, and ammonium carbonate)
• Ex: Gasoline, benzene, formaldehyde, toluene, xylene\

• Sources of VOC
• Burning fuels such as gasoline, wood, coal or natural gas
• Oil and gas fields
• Solvents, paints, glues, air fresheners
Types of Primary Pollutants
• Health Effects
• Acute/Short term Effect (hours to days)
• Eye, nose & throat irritation
• Headaches
• Nausea/vomiting
• Dizziness
• Worsening of asthma symptoms

• Chronic Effect (years to lifetime)

• Cancer
• Liver and kidney damage
• Central nervous system damage
Types of Primary Pollutants
• Odor Generating Gases
• Hydrogen Sulfide
• a colorless gas with the characteristic odor of rotten eggs
• very poisonous, corrosive, and flammable
• heavier than air and may travel along the ground

• Sources
• Anaerobic decomposition of organic matter
• Sewage sludge
• Sulfur hot spring
• Volcanic eruption
• Petroleum and Gas industry
Types of Primary Pollutants
• Health Effect of Hydrogen Sulfide
• Mucous membrane and respiratory tract irritant
• pulmonary edema
• Acute Exposure: nausea, headaches, delirium, disturbed
equilibrium, tremors, convulsions, and skin and eye irritation
• Inhalation of high concentrations of hydrogen sulfide can produce
extremely rapid unconsciousness and death
Types of Primary Pollutants
Level of
• Health Remarks
Effects of SO2
Hydrogen
• Reduced lung function
Sulfide (ppm)
• Increased incidence of respiratory symptoms and dieseases
0.00011- Typical background concentrations
• Irritation of the eyes, nose and throat
0.00033
• PrematureOdor
0.01-1.5 mortality
threshold (when rotten egg smell is first noticeable to some).
2-5 Prolonged exposure may cause nausea, tearing of the eyes,
headaches or loss of sleep. Airway problems (bronchial constriction) in
some asthma patients.
20 Possible fatigue, loss of appetite, headache, irritability, poor memory,
dizziness.
50-100 Slight conjunctivitis ("gas eye") and respiratory tract irritation after 1
hour. May cause digestive upset and loss of appetite.
100 Coughing, eye irritation, loss of smell after 2-15 minutes (olfactory
fatigue). Altered breathing, drowsiness after 15-30 minutes. Throat
irritation after 1 hour. Gradual increase in severity of symptoms over
several hours. Death may occur after 48 hours.
Types of Primary Pollutants
Level of
• Health Remarks
Effects of SO2
Hydrogen
• Reduced lung function
Sulfide (ppm)
• Increased incidence of respiratory symptoms and dieseases
100-150 Loss of smell (olfactory fatigue or paralysis).
• Irritation of the eyes, nose and throat
200-300 Marked conjunctivitis and respiratory tract irritation after 1 hour.
• PrematurePulmonary
mortality edema may occur from prolonged exposure.
500-700 Staggering, collapse in 5 minutes. Serious damage to the eyes in 30
minutes. Death after 30-60 minutes.
700-1000 Rapid unconsciousness, "knockdown" or immediate collapse within 1 to
2 breaths, breathing stops, death within minutes.
1000-2000 Nearly instant death
Types of Primary Pollutants
• Greenhouse Gases
• Gases that trap heat in the atmosphere
• CO2
• CH4
• N2O
• H2O
• Fluorinated gases
Types of Primary Pollutants
Types of Primary Pollutants
AIR POLLUTION DISPERSION,
DIFFUSION AND DEPOSITION
Factors in the Accumulation of Pollutant in an Area

• Emission rates
• Generation and destruction rates
• Dispersion rates
Atmospheric Dispersion Modeling
• Need for Dispersion Modeling
• It is impossible to measure the impact from a facility that will be
built in the future.
• Comprehensive measurement programs could be 1000 times
more expensive than modeling and are also subject to errors.
• Modeling is the only practical approach when there are many
sources and when we wish to isolate the potential effects of just
one source.
• Modeling may not be 100% accurate but it is precise (reproducible)
Physical Explanation of Dispersion
+z
-y

Wind, u -x +x

+y
Plume Centerline -z
h

H
h Plume Edge

Ground Level
Behavior of a Plume
• Pollutant concentration at a particular source is usually
measured in terms of averaging time.

• Time-averaged pollutant concentration at a given

distance, x0, is normally distributed in the + y direction
(Williamson, 1973).

• Spreading plume in the vertical has a normally distributed

concentration.

• Thus, distribution of pollutant is termed binormal.

Two Approaches to Air Pollution Modelling
• Fickian Diffusion Equation
• Second order differential equation and uses average eddy
diffusivities and constant average wind speed as the inputs.

𝜕𝐶 𝜕 𝐶 𝜕 𝐶 𝜕 𝐶
=𝐷 +𝐷 +𝐷
𝜕𝑡 𝜕𝑥 𝜕𝑦 𝜕𝑧

• Gaussian Dispersion Equation

1
𝑔 𝑥 = 𝑒
2𝜋𝜎
The Gaussian Model
• The binormal behavior of pollutants is best modeled by a
Double-Gaussian equation (Pasquill, 1961).

• This equation models the dispersion of non-reactive

gaseous pollutants from an elevated source.

• The steady-state concentration at a point (x,y,z) located

downwind from the source is given by,

1
𝑔 𝑥 = 𝑒
2𝜋𝜎
The Gaussian Model
• The steady-state concentration at a point (x,y,z) located
downwind from the source is given by,

𝑄
𝐶= 𝑒 𝑒 +𝑒
2𝜋𝑢𝜎 𝜎
Where:
C = steady-state concentration at a point (x,y,z), g/m3
Q = emission rate, g/s
y, z = horizontal and vertical spread parameters, m
u = average wind speed at stack height, m/s
y = horizontal distance from the centerline, m
z = vertical distance from ground level, m
H = effective stack height, m
 Atmospheric Stability Classes
Day Night
Surface Wind Speed (m/s)
a Incoming Solar Radiation Cloudiness e
Strong b Moderate c Slight d Cloudy Clear
(>4/8) (< 3/8)
<2 A A-B f B E F
2-3 A-B B C E F
3-5 B B-C C D E
5-6 C C-D D D D
>6 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 600 above the
A = very unstable horizon
B = moderately unstable c Corresponds to a summer day with a few broken clouds, or a clear day
C = Slightly unstable with sun 35-600 above the horizon
D = Neutral d Corresponds to a fall afternoon, or a cloudy summer day, or clear summer

E = Slightly stable day with the sun 15-350

e Cloudiness is defined as the fraction of sky covered by clouds
F = Stable
f For A-B, B-C, or C-D conditions, average the values obtained for each.

Regardless of wind speed, Class D should be assumed for overcast

conditions, day or night.
Estimating Spread Parameters
• The general equations given by Martin (1976) are as follows:

For the horizontal spread parameter,

𝜎 = 𝑎𝑥

For the vertical spread parameter,

𝜎 = 𝑐𝑥 + 𝑓

Where:
x is the distance from the stack, km
a, b, c, d and f = constants that are dependent on the stability
class
Estimating Spread Parameters
Stability x < 1 km x > 1 km
Class a b c d f c d f

A 213 0.894 440.8 1.941 9.27 459.7 2.094 -9.6

B 156 0.894 106.6 1.149 3.3 108.2 1.098 2.0
C 104 0.894 61.0 0.911 0 61.0 0.911 0
D 68 0.894 33.2 0.725 -1.7 44.5 0.516 -13.0
E 50.5 0.894 22.8 0.678 -1.3 55.4 0.305 -34.0
F 34 0.894 14.35 0.740 -0.35 62.6 0.180 -48.6
Wind Speed Variation with Elevation
Power Law,
𝑢 𝑧
=
𝑢 𝑧

Stability Exponent (n)

Class
Rough Surface Smooth Surface
(Urban) (Rural)
A 0.15 0.07
B 0.15 0.07
C 0.20 0.10
D 0.25 0.15
E 0.30 0.35
F 0.30 0.35
The Dependence of Concentration on Averaging Time

• For averaging times between 10 minutes to 5 hr, the averaging

time is related to concentration as follows (Hino 1968),

.
10
𝐶 =𝐶
𝑡
Where:
t = averaging time, min
Ct = concentration for averaging time, t
C10 = concentration for 10-minute averaging time

Note: if averaging time < 10 minutes, replace the exponent 0.5

by 0.2.
Example 1
• Nitric oxide (NO) is emitted at 110 g/s from
a stack with physical height of 80 meters.
The wind speed at 80 meters is 5 m/s on
an overcast morning. Plume rise is 20
meters.
a. Calculate the ground-level centerline
concentration 2.0 km downwind from the
stack
b. Calculate the concentration at 100 m off
the centerline at the same x distance.
Example 2
• Consider the same data as in Example 1 except that the
meteorology is such that the wind speed at 10 meters is 4
m/s and it is midafternoon on a hot summer day. Calculate
the ground-level centerline concentration at x = 2.0 km,
assuming rough terrain. Determine also the concentration
at an averaging time of 1.5 hours.