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PHOTOCHEMICAL SMOG

Swagath Navin Manohar

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Contents1. Smog

2. Physical Significance

3. Photochemical Smog

4. Topography & Meterology

5. Future Scope

6. 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 source-

Vehicle 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

• EffectsPlants - reducing or stopping the growthHumans - affects heart and lungs and even

genetic diseasesAffects 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 smog4.1 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/images/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 •Smoke & Fog•London Smog•Los Angeles Smog

Photochemical Smog •Pollutants (NOx ,O3, VOC, PAN)•Sources•Effects

Factors inflencing formation

•Topography•Meterology-Temperature Inversion

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