Air Pollution is the introduction of contaminants into the natural environment that can cause adverse changes in the environment. It takes the form of chemical substance or energy (light, noise or. According to Creilson and Balek 2002); The introduction of harmful particles, biological or chemical molecules into the earth’s atmosphere which alters such environment by affecting the air quality and oxygen content of the air is referred to as pollution. The troposphere which is an area where the weather can be determined is defined as the lowest layer of the atmosphere which extends from the earth’s surface to a height of about 6-10km. It is in between the troposphere and the stratosphere. Air pollution in the environment has an adverse effect on our daily activities because of weather and climate help in regulating the biospheric, atmospheric and hydrospheric environments.

1. UNIVERSITY OF PORT HARCOURT
FACULTY OF SCIENCES;DEPARTMENT OF GEOLOGY
2016/2017 ACADEMIC SESSION
SERMINAR TOPIC
ON
AIR POLLUTION DISPERSION MECHANISM IN THE TROPOSPHERE
PRESENTED BY
OMOKPARIOLA ELSHALOM CHIOMA
MATRICULATION NUMBER: U2013/5565012
COURSE TITLE: SERMINAR
COURSE CODE: GLY 415.2
SUPERVISOR: DR. F.D GIADOM
JULY, 2017

2. CONTENTS:
 INTRODUCTION
 LITERATURE REVIEW
 BODY CONTENT
 CONCLUSION AND SUMMARY
 TERMINOLOGY
 REFERENCES

3. What Is Air Pollution?
The introduction of harmful particles, biological or chemical molecules
into the earth’s atmosphere which alters such environment by affecting the
air quality and oxygen content of the air is referred to as pollution .
 According to Creilson and Balek 2002); The introduction of harmful
particles, biological or chemical molecules into the earth’s atmosphere
which alters such environment by affecting the air quality and oxygen
content of the air is referred to as pollution.
An Air Pollution Problem Involves Three Parts:
• The pollution source
• The movement or dispersion of the pollutant
• The recipient
What Is A Troposphere?
The troposphere which is an area where weather can be determined is
defined as the lowest layer of the atmosphere which extends from the
earth’s surface to a height of about 6-10km.
Figure 1: Showing a Pollution source, Dispersion Mechanism and 2 recipients.

4. TYPES OF AIR POLLUTION
CAUSES OF AIR POLLUTION
1: Power Plants: From fossil fuel emissions contain the major greenhouse gases, including carbondioxide, methane, nitrous oxide and fluorinated
gases.
2: Vehicle Emissions: Through the emission of carbon monoxide from exhaust pipes of vehicles given a rise of about 10% carbon print.
3: Industry: Industry contributes to air pollution greatly. Industrial processes release pollutants such as nitrous oxide and hydro fluorocarbons into
the air
4: Smoking: Tobacco smoke contains 40 carcinogens, pods contains 59 carcinogens making it an especially lethal form of air pollution.
5: Deforestation: Forests act as sinks for carbondioxide through a process called carbon sequestration. Trees store carbon dioxide in their tissue as
they in this gas to undergo food-making. In effect, this action removes carbon dioxide is removed, increasing the concentration of atmospheric
carbondioxide.
 Primary Pollutants: They are usually produced from a process such as ash from a volcanic eruption. Examples are Sulfuroxide, Nitrogen
Oxides, Carbondioxide, Volatile Organic Compounds( VOC)
 Secondary Pollutants: They are gotten from the by-products of Primary Air Pollutants. Examples are Bimolecular Reaction, Thermal
Decomposition, Photolysis Reaction and Three Body Reaction
SOURCES OF AIR POLLUTION
 Point Source
 Line Source
 Area Source
 Volume Source

5. MECHANISMS OF AIR POLLUTION DISPERSION
Mechanism of air pollutants circulate the same way in the air as the troposphere circulates. Air movement is caused by solar radiation and
the irregular shape of the earth and its surface, which causes unequal absorption of heat by the earth's surface and atmosphere 1.3
Mechanisms of Air Pollutant Dispersion (Sub-Head) Pollutants circulate the same. This differential heating and unequal absorption creates
a dynamic system.
Types of Mechanisms Of Air Pollution Dispersion Includes;
Atmospheric Dispersion: Dispersion is the process by which contaminants move through the air and a plume spreads over a large area,
thus reducing the concentration of the pollutants it contains. The plume spreads both horizontally and vertically. If it is a gaseous plume,
the motion of the molecules follows the laws of gaseous diffusion.
1: Horizontal dispersion of pollutants: This is the dispersion of pollutants in a horizontal motion. Heat is transferred from the earth's
surface by radiation, conduction, and convection. Horizontal dispersion of pollutant is caused by eddies and random shifts of wind
direction; key parameters are physical stack height (h) i.e. plume rise (∆h) and effective stack height (H) i.e. wind speed, the rotation of the
earth continually presents new surfaces to be warmed, so that a horizontal air pressure gradient
Figure 2: Showing a Plot of Horizontal Dispersion of pollutants Vs Distance from Source

6. 2: Vertical dispersion of pollutants: This expansion lowers the temperature of the air parcel, and therefore the
air cools as it rises. The rate at which dry air cools as it rises is called the dry adiabatic lapse rate and is independent of
the ambient air temperature. The term "adiabatic" means that there is no heat exchange between the rising parcel of air
under consideration and the surrounding air. . However, the rotation of the earth continually presents new surfaces to
be warmed, so that a horizontal air pressure gradient.
CONT’D FROM MECHANISMS OF AIR POLLUTION DISPERSION
Figure 3: Showing a Plot of Vertical Dispersion of pollutants Vs Distance from Source

7. WHERE DO AIR POLLUTION DISPERSION OCCURS IN THE ATMOSPHERE?
Air pollution dispersion occurs at the troposphere because it is the region where the weather/ climates are organized. The earth’s surface is the
troposphere. It extends from sea-level to a height of about 17km and contains about 80% of the mass of the overall atmosphere is needed to
understand where airborne pollutants disperse in the atmosphere. (Ziemke, et al.,1998)
The stratosphere is the next layer and extends from 18km to about 50km. the third layer is the mesosphere which extends from 50km to about
85km. There are other layers above 85km, but they are insignificant with respect to air pollution dispersion modelling.
Air Pollution Trends
Air pollution trends are strongly affected by atmospheric conditions such as temperature, pressure, and humidity, and by global circulation
patterns. For example, winds carry some pollutants far from their sources across national boundaries and even across the oceans.
Types Of Air Pollution Trends
Primary Air Pollutants: Are emitted directly into the air from sources. They can have effects both directly and as precursors of secondary air
pollutants (chemicals formed through reactions in the atmosphere). Examples are Sulphur dioxide, Nitrogen Oxide, Carbondioxide and
Volatile Organic Compounds (VOC)
Secondary Air Pollutants: Are gotten form when primary pollutants react in the atmosphere. For reactions to take place, molecules must
collide. However, gases are present in the atmosphere at considerably lower concentrations than are typical for laboratory experiments or
industrial processes, so molecules collide infrequently. Examples includes; Ground-Level Ozone, Aerosols, Smog, Acid Deposition, Mercury
Dispersion.
Fig 4: Source from Google; Depicts Mercury Deposition on Land and Sea Fig 5:Source from Google; Depicts the Chlorine-catalysed ozone depletion mechanism.

8. LAYERS WHERE DISPERSION OF POLLUTION
DISPERSION FACTORS IN TROPOSPHERIC AIR POLLUTION
Dispersion is the name given to the spread and movement of pollutants.
Pollution dispersion depends on
 Wind speed and direction
 Plume rise, and
 Atmospheric turbulence
 Dispersion in neutral & stable boundary layers.
 Dispersion in unstable boundary layers
(Convective Mixed layers).

9. DISPERSION OF POLLUTANTS
1: Coning
2: Looping
3: Fanning
4: Lofting
Figure 6: Showing a Coning Dispersion Pollutants
Figure 8: Showing a Fanning Dispersion Pollutants
Figure 7: Showing a Looping Dispersion Pollutants
Figure 9: Showing a Lofting Dispersion Pollutants

10. SOURCES OF AIR POLLUTION EMISSION
These Includes:
I: Sources By Shape: Pont Source, Line Source, Air Source, Volume Source.
II: Sources By Motion: Mobile Source, Stationary Source-flue Gas.
III: Sources By Duration: Puff Or Intermittent Sources, Continuous Source.
IV: Sources By Urbanization Level: Urban Source, Rural Source.
HOW TO MEASURE POLLUTION DISPERSION MECHANISM
Atmospheric Dispersion Modelling System (ADMS): This model is used for calculating concentration of atmospheric
pollutants emitted both continuously from point, line, volume and area sources.
Figure 10; Source from SAGE Tropospheric Ozone Residual (TOR) JJA 1979-91 showing the tropospheric ozone at different layers.

11. VARIOUS MODELS OF AIR POLLUTION DISPERSION
1: Gaussian Model
Figure 11: Showing a Gaussian Model.
2: Box Model:
2: Langrangian Model
Figure 12: Showing a Langrangian Model
3: Density Gas Model:
Figure 13: Showing a Box Model

12. NATIONALAMBIENT AIR QUALITY STANDARDS
POLLUTANT STANDARD VALUE† STANDARDTYPE
1:Carbon Monoxide (CO)
8-hour Average 9,000 ppb (10 mg/m3)** Primary
1-hour Average 35,000 ppb (40 mg/m3)** Primary
2: Nitrogen Dioxide (NO2)
Annual Arithmetic Mean 53 ppb (100 μg/m3)** Primary & Secondary
3: Ozone (O3)
1-hour Average* 120 ppb (235 μg/m3 Primary & Secondary
8-hour Average 80 ppb (157 μg/m3)** Primary & Secondary
4: Lead (Pb)
Quarterly Average 1.5 μg/m3 Primary & Secondary
5: Particulate < 10 micrometers (PM-10)
Annual Arithmetic Mean 50 μg/m3 Primary & Secondary

13. CONT’D FROM NATIONALAMBIENT AIR QUALITY STANDARDS
POLLUTANT STANDARD VALUE† STANDARDTYPE
24-hour Average 150 μg/m3 Primary & Secondary
6: Particulate < 2.5 micrometers (PM-2.5)
Annual Arithmetic Mean 15 μg/m3 Primary & Secondary
24-hour Average 65 μg/m3 Primary & Secondary
7: Sulfur Dioxide (SO2)
Annual Arithmetic Mean 30 ppb (80 μg/m3)** Primary
24-hour Average 140 ppb (365 μg/m3)** Primary
3-hour Average 500 ppb (1300 μg/m3)** Secondary

14. SUMMMARYAND CONCLUSION
Polluted air results from both emissions into the air and meteorological conditions that control the dispersion of those emissions. Pollutants
are moved predominantly by wind, so that very light wind results in poor dispersion. Other conditions conducive to poor dispersion are:
• Little lateral wind movement across the prevailing wind direction,
• Stable meteorological conditions, resulting in limited vertical air movement,
• Large differences between day and night air temperatures, and the trapping of cold air in valleys, resulting in stable conditions,
• Fog, which promotes the formation of secondary pollutants and hinders the sun from warming the ground and breaking inversions, and
• High-pressure areas resulting in downward vertical air movement and absence of rain for washing the atmosphere.
Air pollution episodes can now be predicted, to some extent, on the basis of meteorological data. Many local air pollution control agencies are
implementing early warning systems, and acting to curtail emissions and provide emergency services in the event of a predicted episode.

15. THANK YOU…