AIR POLLUTION CONTROL course material by Prof S S JAHAGIRDAR,NKOCET,SOLAPUR for BE (CIVIL ) students of Solapur university. Content will be also useful for SHIVAJI and PUNE university students

1. What do you
think why such a
difference is
there?

3. L-30 UNIT-VI
Photochemical smog
Air Pollution and Control
(Elective - I)

4. Unit- VI
L-29 Chemistry of air pollution, Chain
reactions of hydrocarbons, nitrogen
oxide, Sulphuric oxides and
intermediates, photochemical smog
formation
L-30 Air pollution indices -aerosols,
fog, smog index.

5. Smog
 The word ‘smog’ comes from two words:
smoke and fog.
 Characterize visible combination of smoke and
fog
 Occurs in highly motorised areas and where
inversion conditions prevail in the
atmosphere.
e.g. – Los Angeles
 It is because of action of sunlight on H-C
(Hydrocarbons) and Nitrogen Oxides (NOx)
emitted from the automobiles

6. smog
primary
pollutants


volatile
hydrocarbons VOC
nitrogen oxides
secondary
pollutants





ketones,
aldehydes,
PANs,
peroxides,
ozone,

7. Smog Formation
Sun

9. Composition of smog






Nitrogen oxides
Ozone
Aldehydes
Unreacted carbon
Particular matter
Peroxyaceyl nitrate (PAN)

10. Chemical compounds involved
Molecule Name
and Formula
Nitric Oxide, NO
Nitrogen Dioxide,
NO2
Ozone, O3
ThreeTwo-Dimensional
Dimensional
Representation
Representation

11. Acetaldehyde,
C2H4O (an example of
an Aldehydes)
Peroxyacetyl Nitrate,
C2H3O5N
1,3-Butadiene,
C4H6 (an example of a
volatile organic
hydrocarbon)

12. smog: variation in day

13. 


Early morning traffic increases the emissions
of both nitrogen oxides and VOCs as people
drive to work.
Later in the morning, traffic dies down and
the nitrogen oxides and volatile organic
compounds begin to be react forming nitrogen
dioxide, increasing its concentration.
As the sunlight becomes more intense later in
the day, nitrogen dioxide is broken down and
its by-products form increasing
concentrations of ozone.

14. 

At the same time, some of the nitrogen
dioxide can react with the volatile organic
compounds to produce toxic chemicals such
as PAN.
As the sun goes down, the production of
ozone is halted. The ozone that remains in
the atmosphere is then consumed by several
different reactions.

15. Colour


Nitrogen dioxide is responsible for the brownish
colour of the haze.
The particulates formed and the brown colour of
nitrogen dioxide give the air a dirty, ‘smoggy’
appearance.

18. Los Angeles
Photochemical smog / LA smog
18

19. Photochemical smog / LA smog
LA
Santiago
Las Vegas

20. Reaction with NO2






UV light energy is absorbed by NO
It moves into high energy state and becomes
unstable.
Then decomposes in to NO and O (nascent oxygen)
Nascent oxygen quickly reacts with atmospheric
oxygen to form ozone.
This reaction takes place in presence of third body
(X).
If nitric oxide is present it reacts with ozone to form
NO2 and O2

21. Chemical reactions :NO2 + hv

NO*

O + O2

O3
O3 + NO

NO2 +O2
NO2 behaves like catalyst
NO + O

24. Aldehydes
Peroxyacyl radical
Acetyl radical

25. Acetaldehyde
Acetone
Methyl
Methyl
Formyl radical
Acetyl

26. Factors affecting photochemical
reactions






Light intensity
Hydrocarbon reactivity.
Ratio of H-C to nitric oxide
Presence of light absorbers
Meteorological variables
Height and intensity of atmospheric
inversion

27. smog: effects

Effects on human health




Headaches
Eyes, nose and throat irritations
Impaired lung function
Coughing and wheezing

28. 

PAN’s cause eyes to water and respiratory
problems, also catalyses formation of
sulphuric acid,
ozone in the troposphere is:






an eye irritant and also irritates respiratory system
causes deterioration of rubber as it breaks –C=Cand bleaches dyes
affects leaves and therefore growth/damages crops
reduced visibility
secondary pollutants are toxic to plants
corrosion of building materials by acids
and ozone.

29. Objective Questions
1.
2.
3.
4.
5.
_________________ is main driving factor
for photochemical smog formation.
NO2 acts as ________________.
Increase in ozone concentration during day
time indicates _____________________
formation.
Cracking of rubber takes place because of
______.
Photochemical smog occurs in highly
_________area.

30. Theory Questions
Q1. Write detailed short note on ‘Photo-chemistry of
air pollution’
OR
Explain ‘Photochemical reactions’ in detail.
Q2. Explain effects of photochemical smog.

31. Video Clip-1

32. Video Clip-2