PHOTOCHEMICAL SMOG
Swagath Navin Manohar
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Contents
1.
2.
3.
4.
5.
6.
Smog
Physical Significance
Photochemical Smog
Topography & Meterology
Future Scope
Summary
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1. Smog
• Orginally phrased by Dr.Henry Antoine
Des Voeux
• Mixture of Smoke and Fog
• Famous Smogs
-London or The Classical Smog
-Los Angeles or The Photochemical Smog
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1.1 London Smog
• December 1952
• Huge amounts of coal
burning
• 4000 people died of
respiratory problems
• Followed by additional
8000 deaths in the
following months
www.martinfrost.ws/htmlfiles/smog4.gif
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1.2 Los Angeles Smog
• New kind of smog
• Primary sourceVehicle emissions
• First observed
in Los Angeles
http://www.physics.ohio-state.edu
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2. Physical Significance
•
•
•
Amount of pollutants released into the
atmosphere
Big problem in developing countries and
in many major cities
Effects
Plants - reducing or stopping the growth
Humans - affects heart and lungs and even genetic
diseases
Affects materials also
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3. Photochemical Smog
• Action of sunlight upon the exhaust gases
to form pollutants harmful at low altitudes
• Mixture of air pollutants
–
–
–
–
Nitrogen oxides (NOX)
Ozone
Volatile organic compounds (VOCs)
Peroxyacyl Nitrates (PAN)
• A major concern in urban cities-capable of
travelling with wind affecting huge
population
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3.1 Pollutants in Photochemical Smog
3.1.1 Ozone
•
•
•
Production at low altitudes
NOx from exhaust gases
Ozone production is dominant
when NO2/NO is greater than 3
Effects of Ground Level Ozone
• Damage to crops
• Irritates the respiratory tract and eyes
• High levels of O3 results in chest tightness, coughing and wheezing
• Increased hospital admissions and premature death
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3.1.2 Volatile Organic Compounds (VOCs)
• Carbon based molecules (aldehydes, ketones,
hydrocarbons)
• Short- and long-term adverse health effects
• Sources
– Paints; wood preservatives; aerosol sprays; cleansers
and disinfectants; moth repellents and air fresheners
etc.
• Health Effects
– Eye, nose, and throat irritation; headaches; damage
to liver, kidney, and central nervous system. Some
organics can cause cancer in animals; some are
suspected or known to cause cancer in humans.
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3.1.3 PAN
• Important contributor to photochemical smog
• Secondary pollutant-formed from other pollutants by
chemical reaction
• Contributor to production of groundlevel ozone, by
transporting NOx
• Powerful respiratory and eye irritants and toxic
• Higher concentrations lead to damage of vegetation
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4. Topography and Meterology
• Two factors influencing the formation of
photochemical smog
4.1 Topography
•
•
Very important for
formation of photochemical
smog
Restriction of air movement,
city in valley experience more
smog problem, than plains
http://www.uwsp.edu/geo/faculty/ritter/imag
es/atmosphere/misc/smog.jpg
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4.2 Temperature Inversion
• Increase of air temperature
with height for some distance
above ground causing the
smog trapped close to ground
• Consequences
– Air becomes still and dust
and pollutants are no
longer lifted from surface
• Serious problem in many cities
http://www.ec.gc.ca/cleanair-airpur
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5. Future Scope
Variations of different pollutants over the course of a smoggy day in Southern
California (From Finalyson-pitts, BJ & Pitts JN Jr. Adv. Environ. Sci. Technol. 7, 1977)
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•
•
•
•
Being reduced in large cities
Continuing to be a threat in more developing countries
Enforcement of more Environmental Protection Laws
Reduction of primary pollutants (NOx and VOC‘s)
NOx-catalytic converters in vehicles and industries
VOC-more than 700 chemicals found released by
VOCs
• Emmision controls are being devloped for manufactuers
• Still.....!!!! pose a great threat – evoporation of chemicals
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6. Summary
Smog
Photochemical Smog
Factors inflencing
formation
•Smoke & Fog
•London Smog
•Los Angeles Smog
•Pollutants (NOx ,O3, VOC,
PAN)
•Sources
•Effects
•Topography
•Meterology-Temperature
Inversion
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