Basics of Air pollution, Various air pollutants and its impact, lapse rate and Plume behaviour.

1. Mr. Manoj H Mota
Department of Civil Engineering
SITCOE, Yadrav

2.  Air pollution may be defined as the presence in the air
(outdoor atmosphere) of one or more contaminants or
combinations thereof in such quantities and of such
durations as may be or tend to be injurious to human,
animal or plant life, or property, or which
unreasonably interferes with the comfortable
enjoyment of life or property or conduct of business.

3. A pollutant can be solid (large or sub-molecular),
liquid or gas
It may originate from a natural or anthropogenic
source (or both).
It is estimated that anthropogenic sources have
changed the composition of global air by less than
0.01%.
However, it is widely accepted that even a small
change can have a significant adverse effect on the
climate, ecosystem and species on the planet.
Examples of these are acid rain, ozone in the lower
atmosphere, and photochemical smog.

4. Major primary pollutants produced
by human activity
Sulphur oxides (SOx)
Nitrogen oxides (NOx)
Carbon monoxide (CO)
Carbon dioxide (CO2)
Volatile organic compounds
Particulate matter
Secondary pollutents……..
Sulphuric acid(H2SO4),ozone(O3), formadehides,
peroxy-acyl-nitrate(PAN)

5.  Sulphur oxides (SOx) - especially sulfur dioxide, a
chemical compound with the formula SO2. SO2 is
produced by volcanoes and in various industrial processes.
Since coal and petroleum often contain sulfur compounds,
their combustion generates sulfur dioxide. Further
oxidation of SO2, forms H2SO4, and thus acid rainThis is
one of the causes for concern over the environmental
impact of the use of these fuels as power sources.
 Nitrogen oxides (NOx) - especially nitrogen dioxide are
emitted from high temperature combustion, and are also
produced naturally during thunderstorms by electrical
discharge. Nitrogen dioxide is the chemical compound
with the formula NO2. It is one of the several nitrogen
oxides. This reddish-brown toxic gas has a characteristic
sharp, biting odor.

6.  Carbon monoxide (CO)- is a colourless, odorless,
non-irritating but very poisonous gas. It is a product
by incomplete combustion of fuel such as natural gas,
coal or wood. Vehicular exhaust is a major source of
carbon monoxide.
 Carbon dioxide (CO2) - a colourless, odorless, non-
toxic greenhouse gas also associated with ocean
acidification, emitted from sources such as
combustion, cement production, and respiration.
 Volatile organic compounds - VOCs are an important
outdoor air pollutant. In this field they are often
divided into the separate categories of methane (CH4)
and non-methane (NMVOCs). Methane is an
extremely efficient greenhouse gas which contributes
to enhanced global warming.

7. Particulate matter –
Particulates, alternatively referred to as particulate matter
(PM) or fine particles, are tiny particles of solid or liquid
suspended in a gas. In contrast, ‘aerosol’ refers to particles
and the gas together. Sources of particulate matter can be
man made or natural. Some particulates occur naturally,
originating from volcanoes, dust storms, forest and grassland
fires, living vegetation, and sea spray. Human activities,
such as the burning of fossil fuels in vehicles, power plants
and various industrial processes also generate significant
amounts of aerosols. Averaged over the globe,
anthropogenic aerosols—those made by human activities—
currently account for about 10 percent of the total amount of
aerosols in our atmosphere. Increased levels of fine particles
in the air are linked to health hazards such as heart disease,
altered lung function and lung cancer.

8. The worst short term civilian pollution crisis in India was
the 1984 Bhopal Disaster. Leaked industrial vapours from
the Union Carbide factory, belonging to Union Carbide,
Inc., U.S.A., killed more than 25,000 people outright and
injured anywhere from 150,000 to 600,000.
 The United Kingdom suffered its worst air pollution
event when the December 4 Great Smog of 1952 formed
over London. In six days more than 4,000 died, and 8,000
more died within the following
The worst single incident of air pollution to occur in the
United States of America occurred in Donora,
Pennsylvania in late October, 1948, when 20 people died
and over 7,000 were injured.

9. Health Effects of Nitrogen Oxides
Short-term exposure at concentrations greater than 3
parts per million (ppm) can measurably decrease lung
function.
Concentrations less than 3 ppm can irritate lungs.
Concentrations as low as 0.1 ppm cause lung irritation
and measurable decreases in lung function in
asthmatics.
Long-term lower level exposures can destroy lung
tissue, leading to emphysema.

10. Other effects….
Seriously injure vegetation at certain concentrations.
Effects include:
 Bleaching or killing plant tissue.
 Causing leaves to fall.
 Reducing growth rate.
Deteriorate fabrics and fade dyes.
Corrode metals (due to nitrate salts formed from nitrogen
oxides).
Reduce visibility.
Oxides of nitrogen, in the presence of sunlight, can also
react with hydrocarbons, forming photochemical oxidants
or smog.

11. Sulfur Dioxide
 Sulfur dioxide not only has a bad odor, it can irritate the
respiratory system.
 Exposure to high concentrations for short periods of time can
constrict the bronchi and increase mucous flow, making
breathing difficult.
 Children, the elderly, those with chronic lung disease, and
asthmatics are especially susceptible to these effects.
 Immediately irritate the lung and throat at concentrations
greater than 6 parts per million (ppm) in many people.
 Impair the respiratory system's defenses against foreign
particles and bacteria, when exposed to concentrations less than
6 ppm for longer time periods.
 Apparently enhance the harmful effects of ozone.

12. Sulfur dioxide easily injures many plant species and
varieties, both native and cultivated. Some of the most
sensitive plants include various commercially valuable
pines, legumes, red and black oaks, white ash, alfalfa and
blackberry. The effects include:
Visible injury to the most sensitive plants at exposures as
low as 0.12 ppm for 8 hours.
Visible injury to many other plant types of intermediate
sensitivity at exposures of 0.30 ppm for 8 hours.
Positive benefits from low levels, in a very few species
growing on sulfur deficient soils.
Increases in sulfur dioxide concentrations accelerate the
corrosion of metals, probably through the formation of
acids

13. Dispersion of air pollutents
 Lapse rate…… Rate of change of temr. w.r.t. height.
 Environmental lapse rate……..15 0
c/km
 Adiabatic lapse rate…..6.0(dry) to 9.8(wet) 0
c/km
height ELR
ALR
tempr.

14. ELR > ALR ……unstable environment.
ELR < ALR ……stable environment.
ELR = ALR ……neutral environment.
Negative lapse rate…..
Tempr .of environment increase with altitude.
1. Radiation inversion…unequal cooling of air and
earth.
2. Subsidence inversion…sinking of air in high pressure
area surrounded by low pressure area.

16. Plume behavior
 Looping
Under super-adiabatic condition, both upward and
downward movement of the plume is possible. Large
eddies of a strong wind cause a looping pattern,
Although the large eddies tend to disperse
pollutants over a wide region, high ground level
concentrations may occur close to the stack.

17. Fanning
A fanning plume occurs in the presence of a
negative lapse rate when vertical dispersion is
restricted, The pollutants disperse at the stack
height, horizontally in the from of a fanning plume.

18. Fumigation
when the emission from the stack is under an inversion
layer,
the movement of the pollutants in the upward
direction is restricted. The pollutants move
downwards. The resulting fumigation can lead
to a high ground level concentration downwind of
the stack.

19. Lofting
When the stack is sufficiently high and the emission is
above an inversion layer, mixing in the upward
direction is uninhibited, but downward motion is
restricted. Such lofting plumes do not result in any
significant concentration at ground level. However,
the pollutants are carried hundreds of kilometers from
the source.

20. Effective height of stack
Δh
h
Emited smoke

21.  Δh = (vs . D/u) * (1.5+ 2.68*10-3
* P*D (Ts-Ta)/Ts)
……………………Holland equation.
 Δh…. Rise of plume above the stack.
 vs ….. Stack gas velocity (m/sec)
 D …… inside exit dia. of stack (m)
 u….. Wind speed (m/sec)
 P ….. Atmospheric pressure in millibars.
 Ts….. Stack gas tempr.(oK)
 Ta…… air tempr (oK)

22. Predicting pollutants concentration
thro’ dispersion model and eqn.
∂c = ∂ ( Kx .∂c ) + ∂ ( Ky. ∂c) + ∂ ( Kz .∂c) + Q x,y,z
∂t ∂x ∂x ∂y ∂y ∂z ∂z
Fick’s law of turbulent diffusion
 Kx,Ky,Kz…. Eddy diffusitive coefficient.
 Q x,y,z ….. Source or sink.


23. Gaussian distribution

24.  Maximum ground level conc. occures at σz = 0.707H.

25. References:
 Environmental Engineering….. Peavy, Rowe
 Environmental engineering (Vol II)…. S.K. Garg