Air Pollution
Chapter 19
Atmosphere Quiz
• Name the five layers of the
atmosphere
• What are the four main gases
found in air other than water?
• Name three primary air
pollutants
• Name three secondary air
pollutants
Five layers of the
atmosphere
• Troposphere
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Densest, 11 miles thick
Air cools with increased altitude
Ozone is poisonous here
Planes fly here
Weather occurs here
Five layers of the
atmosphere
• Stratosphere
– From 11 miles to 30 miles up from
earth
– Temperatures rise with increased
altitude
– Contains ozone layer
Ozone layer
• Blocks out 95% of UV radiation
– Allows life to exist
– Prevents sunburn/cancer of skin
– Prevents oxygen in troposphere
from converting into toxic ozone
Five layers of the
atmosphere
• Mesosphere – middle layer, air
cools with increased altitude
• Thermosphere – air warms with
increased altitude
• Exosphere – air cools with
increased altitude, blends to
space
What is in air
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78% nitrogen
21% oxygen
1% argon
< .1% carbon dioxide
What does our
atmosphere do?
• Two main natural processes
– Greenhouse effect – keeping the
planet warm through absorbing
long wave radiation from the planet
(water, CO2, CH4)
– Ozone shield – blocking unwanted
UV radiation
Primary pollutants
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CO – carbon monoxide
CO2 – carbon dioxide
SO2 – sulfur dioxide
NO – Nitric oxide
NO2 – Nitrogen dioxide
Hydrocarbons
particulates
Primary pollutants
• Can be natural (volcano) but most
are human released
• Cars, industrial plants and power
plants (especially coal) are main
sources
• When primary pollutants mix in air
some form new secondary pollutants
Secondary Pollutants
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SO3 – sulfur trioxide
HNO3 – nitric acid
H2SO4 – sulfuric acid
H2O2 – hydrogen peroxide
O3 - ozone
PANs – peroxyacyl nitrates
Human impact
• We are altering natural balance
of cycles in the atmosphere
– Add ¼ more carbon dioxide (global
warming)
– Burn fossil fuels and use fertilizers
releasing NOx into the air creating
more acid rain (nitric acid)
– Add sulfur to air from burning coal
and refining petroleum (sulfuric
acid)
That’s only the
beginning
• Heavy metals
– 2x the arsenic as nature releases
– 7x the cadmium
– 17x the lead
It is hard to judge the effect on
particulates, but we release large
amounts of ash and dust
Photochemical smog
• Brown smog
• Mostly Ozone, aldehydes, PANs
and Nitric acid formed from NOx
from cars/factories and volatile
organic compounds (CH4,
propane, benzene, CFCs) mixing
in the presence of sunlight
Smog chemistry
• N2 + O2 = 2NO (engine of car)
– Then in the air
• 2NO + O2 = 2NO2 (brown haze)
– Gives choking odor
• 3NO2 + H2O = 2HNO3 + NO
– Produces acid rain and some NO2
goes on to react this way
• NO2 + UV = NO + O which then
• O + O2 = O3 (ozone)
More smog
• Collectively NO2, O3, and PANs
are known as chemical oxidants
because they react easily with
other compounds or in your
lungs
• Very small (trace) amounts can
irritate respiratory tracts or
damage crops/vegetation
Industrial smog
• Known as gray-air smog
• Mostly SO2 and H2SO4 as well as
suspended particles (ash)
• Mostly caused by burning coal,
but can be prevented with
controls (scrubbers, etc.)
When smog is a real
problem
• Thermal inversion – a layer of
warm air sits on top of a cold
layer trapping pollutants that
would normally disperse. This
causes air pollutants to rise to
harmful or deadly levels
Ughh!
• Enough bad news for one day.
Industrial smog
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C + O2 = CO2 and CO and soot
S + O2 = SO2
2SO2 + O2 = 2SO3
SO3 + H2O = H2SO4
H2SO4 + 2NH3 = (NH4)2SO4 (salt)
+ soot give the gray color
Acid deposition
• Acid rain – wet acid
• Acid deposition – dry acid (solid
or a gas)
• Natural rain is pH 5 – 5.6
(without acid) CO2 is dissolved
from air forming weak carbonic
acid
Who/Where is affected?
• Areas that are downwind from
industrial or dense urban zones
are in greatest risk of damage
due to acid deposition
• Vegetation and aquatic life
receive most of the damage
Acid protection
• Natural buffers in soil – Ca+ and
Mg+ can react and neutralize
acids.
• Thin acidic soils offer no
buffering
Acid production
• Factories, power plants,
smelters and cars produce the
most acid
• Acid crosses large distances via
the wind and can still damage
“clean” nations/areas
Acid associated
problems
• Humans – respiratory (bronchitis
and asthma)
• Buildings – premature aging
• Trees – weakens leaves, disease
pest can then kill tree
• Soil – release metals (toxic) like
aluminum (3rd most abundant
element in crust) which can kill
fish by producing excess mucus
Acid associated
problems continued…
• Aquatic – release
methylmercury from natural
mercury which accumulates to
toxic levels in fish
Acid prevention
• Reduce energy use
• Switch from coal to cleaner
energy sources
• Remove sulfur from coal before
burning
• Remove SO2, NOx and
particulates from smokestacks
with scrubbers
• Remove NO2 from car exhaust
More acid cleanup
• Limestone can be added to
lakes to neutralize acid, but it is
hard to determine how much
and liming can kill some
organisms
Let’s step inside
• Indoor air pollution
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Carbon monoxide
Asbestos
Nitrogen oxide
Trichloroethane (aerosols, dry cleaning)
Chloroform (chlorine in hot water)
Radon (gas from uranium-238)
Tobacco smoke
Formaldehyde – particle board, furniture
Styrene – carpet, plastics
What does it do
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Smoke – cancer, asthma, bronchitus
CO – dizziness, headache, heart attack
Pm10 – respiratory disease, cancer
SO2 – restricted airway
NO – lung irritation, asthma,
encourage spread of cancer
• VOCs (benzene and formaldehyde) and
toxic particulates (lead, cadmium,
PCB, dioxins) – mutations,
reproductive problems
Ozone hurts trees
• As well as harming humans in
the troposphere, ozone affects
plants and trees
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Damage to leaves through pores
Reduced wax coating
Reduced photosynthesis
Reduced nutrient uptake
Regulation/protection
• Clean air act
– Sets nation limits for seven
pollutants – pm10, SO2, CO, Nox,
O3, VOCs, and lead
– Also prevents significant
deterioration in any area
– EPA set levels for 302 individual
compounds and 20 categories of
toxic compounds
Improving the Laws
• Switch from cleanup to
prevention
• Conservation/alternate energy
sources (no fossil fuels)
• Stricter emission standards
• Eliminate trash incineration
Emission controls for
smokestacks
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Electrostatic precipitator
Baghouse filter – good for pm10
Cyclone separator
Wet scrubber
• All collect toxic solids which
then must be disposed of as
hazardous waste
Reducing indoor air
pollution
• Better venting
• In developing countries – better
stoves, no smoke in the house
• Use natural fibers
• Reduce use of household
cleaners with harsh chemicals
• No dry cleaning