Atmospheric Changes:
Climate Change and Air Pollution
Atmosphere is the thin layer of gases that surrounds the Earth
It supports life:
Absorbs dangerous solar radiation
Burns incoming meteors
Transports and recycles water and other chemicals
Drives Climate and Weather
Chemical Composition of Atmosphere
Major components
Minor variable components
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Although the atmosphere’s molecular
composition is largely similar
Certain characteristics change with altitude
Atmosphere is divided in layers
Ozone’s Distribution in the Atmosphere
Temperature and other characteristics vary
between layers
Stratosphere:
most ozone (0.00004%) found here
ozone layer: filters UV rays
Ozone layer
Troposphere:
ozone from human activities
causes health problems
Tropopause:
cap that prevents mixing between layers
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Addressing the problem of Air Pollution
In 1971 the newly-formed Environmental
Protection Agency regulated 6 “criteria”
pollutants…
…even though no conclusive evidence
proved a cause/effect relationship
between the pollutants and human health.
What are the six criteria pollutants in
Air Pollution?
-particulate matter (particles or droplets)
and 5 chemicals:
-sulfur oxides
-carbon monoxide
-nitrogen oxides
-ground-level ozone
-lead
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Addressing the problem of Air Pollution
In 1971, The EPA was following the
Precautionary,
Though you are not 100% sure of what is causing a
problem, there is a big risk to “doing nothing.”
All six pollutants have since been shown
to be harmful.
The EPA now lists another 187 hazardous
air pollutants—including carbon dioxide!
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Types of substances and their sources
Gases:
Oxides of carbon (CO, CO2)
Oxides of nitrogen (N2O, NOx)
Oxides of Sulfur (SO2)
VOC  Tropospheric Ozone
Ozone depleting substances (ODS)
Aerosols:
Particulate matter (soot, dust and smoke)
Metals (lead and mercury)
Transformation: Pollution Changes in the air
Primary pollutants
Emitted directly
from source
Secondary Pollutants
Form in the air
from primary pollutants
Note: Some chemicals can be considered primary and secondary
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Impact of Air Pollutants
• Change in Temperature:
Global warming (CO2 CH3 , HCFCs and N2O)
• Change in Water acidity:
Acid precipitation (SO2 and NOx)
• Depletion of stratospheric ozone:
ODP (chemicals with Bromide or Chloride atoms)
• Health problems:
Industrial smog SO, CO
Photochemical smog
NO2 and VOC (volatile organic compounds)
Lead and Mercury
(deposited in water, enter food chain, accumulate in tissue)
Industrial Smog or Gray Smog
Cause: combustion of coal and diesel
Chemistry:
Incomplete combustion  soot
Reaction of sulfur with
other elements in air  sulfur compounds
Products: Sulfur compounds and soot
Impact:
irritate respiratory tract
impair breathing
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Industrial smog in
London 1952
Industrial smog in
Pennsylvania in 1948
Picture taken at mid-day
Killing about 12000 people
Photochemical Smog or
Brown smog
Cause: gasoline combustion
on hot sunny days
Chemistry:
Reaction of light with NO2 and VOC’s
Products: Ozone and 100 more
Impact:
reduces photosynthesis
affects human health
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Topography and Climate in LA favors
photochemical smog conditions
Thermal inversion
The warm air holds down the cool air and
prevents pollutants from rising and scattering.
What are the health impacts to Los angelinos?
Stratospheric Ozone depletion
Cause: ODS (ozone depleting substances)
CFCs, its substitutes HCFCs, Halons
Methyl bromide (pesticide of strawberries)
ODS vary in
their in their life times and potential
Compare Halons with CFCs
Chemistry:
UV rays free Cl or Br atom
This atom destroys O3
Into O2 and O
Result:
Ozone layer gets thinner
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Impact of O3 depletion
International treaty for ODS
1987 Montreal Protocol
signed by 180 countries
Stop production of CFCs
Reasons for success of the Montreal Protocol:
- Government and industry cooperated on finding solutions
- Cheap replacement technologies
Future amendments have not been
as successful
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•
Issues to consider
Illegal trade of CFC on the raise
•
A large number of used CFC-based refrigerators are being exported to developing
countries by countries that have phased out CFCs.
•
Atmospheric halons continue to increase (production ended in 1994)
Halons in existing fire-fighting equipment emitted whenever there is a fire
Concern:
bromide in Halons is 50 x more potent than CFCs
•
Countries had promised to phase out methyl bromide 100% by 2005
Nov 2006, meeting agreed to allow US to produce of more pesticide
even though their stock piles have enough for farmers needs
Farmers allowed = 8,900 tons,
US stockpiles = 11,000 tons,
Allowed new production = 7,600 tons.
•
New estimates:
Ozone layer in mid latitudes will not return to pre-1980 levels until 2049
Antarctic ozone will only return around 2065
This year's Antarctic ozone "hole" was the largest ever recorded.
•
CFCs are being replaced by HCFCs, which have a large global warming potential.
Present and future
ozone levels
2011
Largest ozone
“hole” ever
recorded
above the
Arctic!
2050
Mid-latitude
areas back to
pre-1980
ozone levels
2075
Polar regions
back to
pre-1980
ozone levels
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Questions
• Is the depletion of the ozone layer over?
• Why are we concerned about the ozone layer?
• What are the differences between industrial
smog and photochemical smog?
Acid Rain
Cause:
Combustion of fossil fuels
Chemistry:
SO2 and NO reacts with water, oxygen, and oxidants  Nitric and Sulfuric acids
Result:
Acids can remain in atmosphere
They can be transported long distances
Eventually these fall as rain or snow
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Acid Rain Impact
Acid rain on soil
leaches basic minerals (calcium and magnesium)
no longer available to plants  us
Acid rain on lakes or rivers
increase acidity of water
harm fauna
Acid rain or fog on forests
damage plant tissue
Acid rain on buildings
eats away concrete
Why should air pollution be regulated
federally and internationally? Not just locally
Green House gases
ODS
Acids
Tropospheric ozone
They are transboundary problems
cross political borders
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Emissions reduction: Electricity
At the Industry level:
Improved technology at plants
Expansion of alternative sources
of energy
At the Consumer level:
Energy saving habits
Product choices
Emissions reduction: Transportation
At the Industry level:
Improve efficiency of cars
Improve exhaustion quality
At the Consumer level:
Consumer choices
Consumer habits
Walking briskly for just 2 miles
every day or cycling for five can
reduce your chances of heart
disease by 1/2
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