PHOTOCHEMICAL SMOG

By AKASH BISWAL

3rd Semester ,MSc ENVIRONMENTAL

SCIENCE DEPT-BOTANY

WE KNEW THAT :

A smog is a mixture of Smoke + fog

Name Industrial Smog

Photochemical Smog

Weather Cool,Damp SunnyContent Particulate,S

O2

Nox,O3,Hydrocarbon

Chief Sourse Coal Combustion

Gasoline Combustion

Smog

Industrial SmogOr

London Smog

Photochemical SmogOr

Los Angels Smog

If so,then what is a photochemical smog

Photochemical Smog is an air pollution ,formed when photons of sunlight hit molecules of different kinds of pollutants in the atmosphere

AIR POLLUTANT

Primary Air PollutantNOx , VOCs

Secondary Air Pollutant

Ozone(O3) , PAN

Process Involving Formation Of Photochemical Smog

Formation of Oxides of Nitrogen

N2+O2→2NO2NO+O2→NO2

NO2+hν→NO+O

Photolysis

Formation of Tropospheric Ozone

Nitrogen Oxide

O∙+O2→O3NO+O3→NO2+O2

O3+RH→RCO2∙+RCHO+R2CO

HydrocarbonO+RH→R∙ + RCO∙ (acyl

radical)RCO∙ +O2 →RCO3

∙ (peroxyacyl radical)RCO3

∙+ NO2 → RCO3NO2R=CH3,CH3 + NO2→ CH3CO3NO2

Effect on Human Health

&Plants

Smog can irritate and inflame pulmonary membranes, causing chest pains, coughing, and throat irritation.  Other illnesses such as colds and pneumonia can also be brought on by exposure to smog.

People with asthma problems are under an even greater threat.  Even minor exposure to smog may cause these people to get asthma attacks.

Smog slowly ruins people's lungs to an extent as great as that of cigarettes.

SOURCES AND EFFECT OF PHOTOCHEMICAL

SMOG

CHEMICAL SPECIES

ANTHROPOGENIC

SOURCES

ENVIRONMENTAL HEALTH & EFFECTS

COMMENTS

Nitrogen Oxides(NO2,NO,)

• Combustion of gasoline in Automobiles

• Gasoline , Coal, Gas Industry

• Decrease visibility due to yellowish nature of NO2

• Eye irritation • NO2 responsible

for suppressing growth of plants

• Prolong exposure to Nitrogen Dioxide increases respiratory infection

• May increase the cases of cancer

• Only 5% of the total concentration of NO2 results From combustion and most is formed from reaction involving NO from lightening, Bacterial action in soil.

Volatile Organic compound(VOCs)

Evaporation of solvents

Incomplete combustion of fossil fuel

Evaporation of fuels

Eye irritation

Respiratory irritation

Decreased visibility due to Blue-brown haze

VOCs in the atmosphere includes naturally occurring compounds such as Terpenes from vegetation

Ozone(O3)

• Formed From Photolysis of NO2

• Harsh Odour• Bronchial

constriction• Coughing and

Wheezing• Damage Plastics• Retard Plant

Growth• Decrease yield of

crop

• People with asthma and respiratory problems mostly affected by it.It’s 0.1 PPM concentration can reduce half of total photosynthesis

Peroxy acyl nitrate(PAN),and other related compounds

• Formed by reaction of NO2 with VOCs

• Eye and respiratory irritation

• Cause damage to proteins

• Was not detected until recognized in smog,Cause more damage to plants than ozone

Factors affecting Formation of Photochemical Smog

Formation of Different content of photochemical smog in different time of day

Pollutants are rinsed out of the atmosphere with rainfall

Photochemical Smog can be blown away by wind

Temperature Inversion increases photochemical smog

Role of Topography in smog formation

Mitigation measures

ForPhotochemical

Smog

Catalytic Converter

Free Radical Trap

Free Radical Traps

When Sprayed in the atmosphere

Produce Free

radical

Combine with free radical

O*,R*,RO* radicals

Free radical traps slows down the reaction

N2+O2→2NO

2NO+O2→2NO2

2-6 Hr

6-12 hr

Diethyl HYdroxylamine

Petrol reformati

on

1/10 Aromatic hydrocarbon

Oxygenated fuel

C(CH3)3OTertiary butyl

ether

Emission of oxides of Nitrogen is reduced

Petrol containing oxygenates atLow temperature

Emission of VOCs and NOxSupresess smog formation

How to save environmentby preventing Smog???!!!

i. Try to use the vehicles at minimal level and check the engine’s smoke emission frequently

ii. Prevent high usage of coals,which result in heavy smog

iii. Reduction of fumes from metal-working and other industrial plants;

iv. Buy green electricity-produced by low-or even zero-pollution facilities.

v. Reduce pesticide use.

vi. Consumers can reduce VOC emissions by avoiding paints with labels that clearly indicate VOC limits are high. Switching to water-based paint is also useful.

Lets start living and stop existingAnd save our mother earth

THANK YOU!!!