Industrial and Environmental Chemistry, DSE-III for U. G. CBCS course. The ppt describes about types of air pollutants, it's effects. Constituents and photochemistry of smog, Environmental effect of ozone etc.

1. Air Pollution
DSE-III
Dr. Banita Pattnaik
Faculty in Chemistry,
Rama Devi Women’s University
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2. o Major regions of Atmosphere
o Atmosphere as a Resource
o Types and Sources of Air Pollution
• Major Classes of Air Pollutants
• Sources of Outdoor Air Pollutants
• Urban Air Pollution
o Chemical and photochemical reactions in
atmosphere
o Photochemical smog: its constituents and
photochemistry
o Effects of Air Pollution
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3. Major Regions of Atmosphere: On the basis of temperature:
What is atmosphere? Discuss the different zones of atmosphere.
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4. Troposphere (Tropo = turning or changing)
• Bottom layer 🡪 from Earth’s surface to about 12
kilometers altitude (0 to 7.5 miles)
• Where we live & weather happens, clouds form, air
moves a lot here 🡪it’s turbulent and well-mixed
• gets colder with increasing altitude…to about -550 C (-
670 F) at the top (tropopause) (Temperature range 150C to
-560C)
Think about how it gets colder on a mountain?
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5. Troposphere
o most of atmosphere’s
mass is here 🡪 the
densest layer because
gravitational pull is
stronger here
o Jet stream is in
upper troposphere &
lower stratosphere…
o Airplanes do not fly
higher than about 11
km …~7 miles up
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6. Stratosphere: Strato = layer or “spreading
out” ...air does not move a lot here
o above the troposphere
o You can see where it begins
because large cumulonimbus
storm clouds reach into and
stop at the lower stratosphere
o Extends to ~50 km (31 mi)
o Way less air pressure
here…less mass above, less
density and less gravitational
force
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7. Stratosphere
o OZONE is formed in this
layer….O3 absorbs most UV
radiation from sun
o temperatures increase with
altitude in the stratosphere
because of ozone.
As ozone molecules absorb UV they
get energized, move faster and
produce heat
Is ozone
good or
bad?
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8. Mesosphere
o ~50-90 km (31 – 50 mi)
o meso = middle
o 99.9% of mass lies below the
mesosphere
o Not enough oxygen to
breathe but % is still the
same (What % is that?)
o Most meteoroids burn up
here…. the air is very thin,
but still dense enough to
slow down meteoroids due
because of friction
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9. Mesosphere
o There is not an ozone layer to cause heating
so, temperatures decrease with altitude in
the mesophere
o Coldest layer! down to -1480 F (-1000C ) at
the mesopause…
What is a
“pause”?
What is a “pause”?
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10. Thermosphere
o Above the mesosphere to ~690 km
(430 miles)….with no real upper limit
🡪 space!
o least dense of all layers …. few
molecules are far apart & moving
fast because of radiation absorption
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11. Thermosphere
o temps can reach 2,0000
C (3,6000 F) … but would
feel very cold…too few
hot molecules to transfer
heat
o Temperatures can vary greatly
here because of solar activity
o Thermo = heat
o Sometimes divided into
two layers : ionosphere
and exosphere
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12. Ionosphere
o lower part of thermosphere
o solar radiation very strong here & is absorbed by
the few oxygen & nitrogen molecules resulting in
electrically charged gas particles (ions) that cause
heat (O2
+, O+
, NO+)
o AM radio waves bounce off these ions and back
to earth
o Aurora Borealis(Northern Lights) ….glowing ions
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13. Exosphere
o ” Outer thermosphere & outermost layer
of the atmosphere
o Exo = “outer(To infinity & beyond! )
o Satellites orbit here
o Atoms & molecules
escape into space here
o TV & cell phone signals
travel to satellites here
and are bounced back
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14. Atmosphere as a Resource
o Atmospheric Composition
• Nitrogen 78.08%
• Oxygen 20.95%
• Argon 0.93%
• Carbon dioxide 0.04%
o Ecosystem services
• Blocks UV radiation
• Moderates the climate
• Redistributes water in the
hydrologic cycle
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15. Air Pollution
Chemicals added to the atmosphere by natural events or
human activities in high enough concentrations to be
harmful.
or
It is the direct or indirect changes in one/more components
of biosphere that are harmful for living entities.
Air Pollution
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16. Types and Sources of Air Pollution
Two categories:
oNatural
• Forest fire by lightening
• Soil erosion
• Volcanic eruption
• Decomposition of organic matter and natural
radioactivity
o From human activity
• U V radiation due to Ozone layer depletion
• Nuclear fall out radioactive materials
• From industries
• From burning of fossil fuel
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17. Two categories
o Primary Air Pollutant (Contributes ~ 90%)
• Harmful substance that is emitted
directly into the atmosphere
o Secondary Air Pollutant
• Harmful substance formed in the
atmosphere when a primary air pollutant
reacts with substances normally found in
the atmosphere or with other air
pollutants
Types and Sources of Air Pollution
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18. Major Air Pollutants
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19. 19

20. Chemical and Photochemical
Reactions
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21. Major Classes of Air Pollutants
o Carbon Oxides
o Hydrocarbons
o Nitrogen Oxides
o Sulfur Oxides
o Particulate Material
o Ozone
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22. Carbon Oxides and Hydrocarbons
o Carbon Oxides
• Gases carbon monoxide (CO) and carbon
dioxide (CO2)
• Greenhouse gases
o Hydrocarbons
• Diverse group of organic compounds that
contain only hydrogen and carbon (ex: CH4-
methane)
• Some are related to photochemical smog and
greenhouse gases
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23. Nitrogen and Sulfur Oxides
o Nitrogen Oxides
• Gases produced by the chemical interactions
between atmospheric nitrogen and oxygen at
high temperature
• Problems
• Greenhouse gases
• Cause difficulty breathing
o Sulfur Oxides
• Gases produced by the chemical interactions
between sulfur and oxygen
• Causes acid precipitation
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24. Particulate Material
o Thousands of different solid or liquid
particles suspended in air
• Includes: soil particles, soot, lead, zinc,
asbestos, sea salt, and sulfuric acid droplets
o Dangerous for two reasons
• May contain materials with toxic or
carcinogenic effects
• Extremely small particles can become lodged in
lungs
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25. Ozone
o Tropospheric Ozone
• Man- made pollutant in the lower atmosphere
• Secondary air pollutant
• Component of photochemical smog
o Stratospheric Ozone
• Essential component that screens out UV
radiation in the upper atmosphere
• Man- made pollutants (ex: CFCs) can destroy it
O2 plays an important role in Troposphere and O3 in Stratosphere
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26. Sources of Outdoor Air Pollution
o Two main sources
• Transportation
• Industry
o Intentional forest
fires is also high
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27. Urban Air Pollution
o Photochemical Smog (ex: Los Angeles below)
• Brownish-orange haze formed by chemical reactions
involving sunlight, nitrogen oxide, and hydrocarbons
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28. Two very important Factors on
Atmospheric chemistry
Important Gaseous Atmospheric Chemical Species
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29. Gaseous atmospheric Chemical Species
o Sunlight of U V region and Hydroxyl radicals (OH.)
are important as it provides a way to pump high level
of energy into a single gas molecule to start a series
of Chemical reactions.
o Hydroxyl free radicals are the most reactive
intermediate and currency of day time atmospheric
phenomena where as NO3 radicals are important
intermediate in night time atmospheric chemistry.
o Both solid and liquid particles in atmospheric aerosols
and clouds serve as sources and sinks for gas-phase
species, as sites for surface reactions.
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