PHOTOCHEMICAL FORMATION OF SMOG Photochemical Reactions in Atmosphere What is Smog ? Formation of Photochemical smog Probable Mechanism for Smog formation

1. PHOTOCHEMICAL FORMATION OF SMOG
SUBMITTED BY:
Keshav Kumar
Singh
Y19266023
Department of Chemistry
Dr. Harisingh Gaur Vishwavidyalaya (A Central University)
Sagar, M.P.

2. Natural photochemical phenomena have contributed to the
evolution of life and have allowed its continued existence on
the Earth. let us discuss atmospheric structure because
photochemical reactions depend on atmospheric structure.
Region Altitude range
(Km)
Temperature
Range (° C)
Important
Chemical
Species
1) Troposphere 0-11 15 to -56 N2 , O2 , CO2 , H2O
2) Stratosphere 11-50 -56 to -2 O3
3) Mesosphere 50-85 -2 to -92 O2
+ , NO+
4) Thermosphere 85-500 -92 to 1200 O2
+ , NO+ , O+
Photochemical Reactions in Atmosphere

3. What is Smog ?
 Hydrocarbons and other organic compounds in the
atmosphere are susceptible to oxidation through a series of
steps of chemical and photochemical reactions. As a result
many noxious secondary pollutant products and
intermediates are produced, which belong to the category of
photochemical smog.
 Smog is often seen as brown haze above large cities.
 Frequency and severity depends on local topography,
climate, population density, fossil fuel use.
 Deforestation and burning may also contribute to smog

4. Two types of pollutants which produce
photochemical smog are primary pollutants and
secondary pollutants.
 Primary Pollutant :
Harmful substances
put directly into air by
human activities.
These include oxides
of nitrogen, volatile
organic compounds
and carbon
monoxide.
 Secondary
Pollutant : These
include ozone,
Nitrogen Dioxide,
hydrogen
peroxide,
peroxyacetyl
nitrate(PAN)

5. Formation of Photochemical smog

6. • Hydrocarbons do not react readily with sunlight,
but they are reactive towards other substances
produced photochemically.
• An important characteristic of atmosphere which
are loaded with large quantities of automobile
exhausts, trapped by an inversion layer and at
the same time exposed to intense sunlight, is the
formation of photochemical oxidant in the
atmosphere. This gives rise to the phenomenon
of Photochemical smog.
• Photochemical smog is an oxidizing smog having
high concentration of oxidant (i.e., O3 and NO2 )

7. Probable Mechanism for Smog
formation

8. REACTIONS
INVOLVED

10. REFERENCES:
1) Photochemistry and pericyclic reactions by Jagdamba Singh and Jaya
Singh.
2) https://www.google.com/search?q=health+effects+due+to+photochemi
cal+smog&rlz=1C1RXQR_enIN928IN928&sxsrf=ALeKk017ePkVhLaQ
C3A0ns_hHTbHW8mxAA:1621597588089&source=lnms&tbm=isch&s
a=X&ved=2ahUKEwjviNPh2drwAhWIxzgGHYV7CDYQ_AUoAXoECA
EQAw&biw=1536&bih=666#imgrc=VhzeDj37C1W_vM
3) https://www.epa.sa.gov.au/files/8238_info_photosmog.pdf
4) https://chem.libretexts.org/Ancillary_Materials/Exemplars_and_Case_
Studies/Exemplars/Environmental_and_Green_chemistry/Photochemi
cal_Smog
5) https://www.sciencedirect.com/science/article/pii/S0166111608717928
6) https://www.sciencedirect.com/science/article/abs/pii/S1389556703000
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