1. AIR POLLUTION
•Composition of Air
•Structure of atmosphere
• Ambient Air Quality Standards
• Classification of air pollutants
•Source of common air pollutants
•Effects of common air pollutants
2. Definition
The presence of unwanted and undesirable foreign
particles and gases in the air which may have adverse
effects on human, animals, plants or structures.
As per IS: 4167 (1966);
“Air pollution is the presence in ambient atmosphere of
substances, generally resulting from the activity of man, in
sufficient concentration, present for sufficient time and
causes the harmful effects on humans, plans and
animals”.
4. Composition of Air
Trace gases:
A gas (such as water vapor, ozone, nitrogen oxides,
sulphur dioxide, and carbon dioxide) that is present in the
atmosphere in only small amounts, either because of
its very reactive nature or because it is produced or
emitted at a very low rate.
5. Structure of Atmosphere
• The atmosphere consists of different layers with varying density
and temperature.
• Density is highest near the surface of the earth and decreases with
increasing altitude.
• The column of atmosphere is divided into five different layers
depending upon the temperature condition. They are;
• Troposphere
• Stratosphere
• Mesosphere
• Ionosphere
• Exosphere
7. Structure of Atmosphere
Troposphere:
• The troposphere starts at the
surface of the earth and goes up to
a height of 7 to 20 km.
• All-weather occurs within this layer.
• This layer has water vapor and
mature particles.
• Temperature decreases at the rate
of 1 degree Celsius for every 165 m
of height.
• Tropopause separates Troposphere
and Stratosphere
8. Structure of Atmosphere
Stratosphere:
• It extends up to 50 km of height.
• This layer is very dry as it contains little
water vapour.
• This layer provides some advantages
for flight because it is above stormy
weather and has steady, strong,
horizontal winds.
• The ozone layer is found in this layer.
• The ozone layer absorbs UV rays and
safeguards earth from harmful
radiation.
• Stratopause separates Stratosphere
and Mesosphere
9. Structure of Atmosphere
Mesosphere:
• It is the coldest of the atmospheric
layers.
• The mesosphere starts at 50 km above
the surface of Earth and goes up to 85
km.
• The temperature drops with altitude in
this layer.
• By 80 km it reaches -100 degrees
Celsius.
• Meteors burn up in this layer.
• The upper limit is called Mesopause
which separates Mesosphere and
Thermosphere
10. Structure of Atmosphere
Thermosphere / Ionosphere:
• This layer is found above Mesopause
from 80 to 400 km.
• Radio waves that are transmitted from
the earth are reflected by this layer.
• The temperature increases with height.
• Aurora and satellites occur in this layer.
• The lower Thermosphere is called the
Ionosphere.
• The ionosphere consists of electrically
charged particles known as ions.
• This layer is defined as the layer of the
atmosphere of Earth that is ionized by
cosmic and solar radiation.
11. Structure of Atmosphere
Exosphere:
• It is the outermost layer of the
atmosphere.
• The zone where molecules and atoms
escape into space is mentioned as the
exosphere.
• It extends from the top of the
thermosphere up to 10,000 km.
14. According to Origin
Primary pollutants:
The pollutants that are emitted directly from identifiable sources produced by
natural events. ( eg: dust storms and volcanic eruptions) and human activities
(eg: emissions from vehicles, industries etc.) are called primary pollutants. E.g.:
smoke, dust, oxides of sulphur & nitrogen, hydrocarbons and particulate matter
etc.
Secondary pollutants:
The pollutants that are formed in the atmosphere by chemical interactions
between primary pollutants and atmospheric constituents are known as
secondary pollutants. Eg. Sulphur trioxide, ozone, ketones, sulphuric acid, nitric
acid, carbonic acid etc.
15. According to state of matter
Gaseous air pollutants:
These pollutants exist in a gaseous state at normal temperature and
pressure. They are carbon dioxide, nitrogen dioxide, sulphur oxides etc.
Particulate air pollutants:
These are not gaseous substances. They are suspended droplets, solid
particles or mixtures of the two.
