Transcript APES 15 Air Pollutionx

The atmosphere is the key symbol
of global interdependence.
Margaret Meade
Air Pollution
Unit 14
Nature of the Atmosphere
• Thin layer of gases surrounding earth
• Density (air mass/air volume) is greater at sea
level than in mountains
• Atmospheric pressure (force/area) decreases
with altitude
• 78% nitrogen, 21% oxygen (water vapor,
argon, CO₂)
Layers of Atmosphere
• Troposphere: layer closest to earth (extends
11 miles above surface)
-responsible for weather, climate,
greenhouse effect
• Stratosphere: layer surrounding troposphere
(extends 30 miles above troposphere)
-ozone layer: protects earth from too much
of sun’s UV radiation
Atmospheric pressure (millibars)
Temperature
Pressure
Thermosphere
Heating via ozone
Mesosphere
Stratopause
Stratosphere
Altitude (miles)
Altitude (kilometers)
Mesopause
Tropopause
Ozone “layer”
Heating from the earth
Troposphere
(Sea
level)
Temperature (˚C)
Pressure = 1,000
millibars at ground level
Fig. 19-2, p. 440
Air Pollution
(all environmental problems involve the air)
• Primary air pollutants: released directly from
a source into the atmosphere
-natural sources: dust, wildfires, volcanoes
-manmade sources: primarily burning of fossil
fuels, burning of biofuels
-may be stationary or moving
CO
CO2
SO2 NO NO2
Most hydrocarbons
Most suspended particles
Sources
Natural
SO3
HNO3 H3SO4
H2O2 O3 PANs
Most NO3– and SO42– salts
Stationary
Mobile
Fig. 19-3, p. 442
Air Pollutants (cont’d)
• Secondary pollutants: product of reactions
between primary pollutants and other
chemicals in the atmosphere
-prevailing winds carry pollution from source
to other areas
-responsible for hundreds of millions of lung
problems (WHO)
FYI: Exam Tip
• Be specific in identifying types of pollution.
Simply stating that an activity results in
“pollution” won’t earn you points.
Exemplar: Burning wood for fuel produces CO
and is a major source of indoor air pollution in
developing countries.
Major Air Pollutants
Carbon oxides: colorless, odorless, toxic
(prevents O₂ from binding with red blood cell)
• Carbon monoxide (CO)
-incomplete burning of carbon-based matter
(tobacco, forest fires, vehicles, factories)
-catalytic converters remove CO from vehicle exhaust
• Carbon dioxide (CO2)
-93% results from carbon cycle
-7% results from human activities (mostly burning
fossil fuels)
Health issues: asthma, COPD, heart attacks, headache,
death
Major Air Pollutants (cont’d)
Nitrogen oxides: gas which forms when N₂
combines with O₂
• Nitrogen dioxide: reddish brown gas
-forms photochemical smog in cities
• Nitric acid
-”acid rain”/acid deposition
• Nitrous oxide (N₂O)
-greenhouse gas emitted from burning animal
waste, fossil fuel
Major Air Pollutants (cont’d)
(Human issues: discussed later)
(Environmental issues: discussed later)
Major Air Pollutants (cont’d)
Sulfur dioxide; sulfuric acid
• ⅓ comes from sulfur cycle
• ⅔ comes from combustion of coal, oil refining
• Scrubbers: remove SO₂ from coal smoke by
combining it with calcium carbonate (sludge
deposited in landfills)
(Health issues: discussed later)
(Environmental issues: discussed later)
Major Air Pollutants (cont’d)
Ground-level (tropospheric) Ozone (O₃)
• Secondary pollutant
• Major part of photochemical smog
• Unstable, strong oxidant (sheds O to become O₂)
Health issues: irritates eyes, lungs, heart
Environmental issues: damages plants, fabrics,
paints, rubber in tires
(Remember: ozone in the stratosphere is good;
ozone in the troposphere is harmful)
Major Air Pollutants (cont’d)
Suspended Particulate Matter (SPM/PM-10)
• Primary pollutant- solid, liquid “droplets” less than
10mm in diameter
• Emitted from burning coal/dung, plowing, tobacco
smoke, vehicles
• Includes mercury, cadmium (toxic heavy metals)
• Electrostatic precipitator: removes particles from
smoke (negative charge on particle makes it stick to a
positive plate; sludge is dumped in landfill)
Health issues: irritates eyes, lungs, can cause
mutations, cancers (mercury, heavy metals)
Environmental issues: reduces visibility, corrodes metals
Major Air Pollutants (cont’d)
FYI: According to EPA, SMA is responsible for
about 60,000 premature deaths/year in the
US alone
Major Air Pollutants (cont’d)
Volatile organic compounds (VOCs):
• Primary pollutant; most are hydrocarbons
emitted by natural and anthropogenic sources
• ⅔ of global VOC methane emissions come from
fossil fuel leaks, rice paddies
• others sources include solvents- trichlorethylene
(TCE), benzene, and vinyl chloride (dry-cleaning,
paints)
Health issues: cancer, blood disorders, immune
system damage
Major Air Pollutants (cont’d)
Lead (Pb)
• Primary pollutant; doesn’t break down in
environment
• Released from lead additives in gas, peeling leadbased paint (both banned in US in ‘70’s)
Health issues: brain damage, mental retardation,
partial paralysis, blindness, death
(WHO estimates that 130-200 million children are at
risk of lead poisoning worldwide)
Core Case Study:
When Is a Lichen Like a Canary?
• Lichens can warn us
of bad air because
they absorb it as a
source of
nourishment.
Figure 19-1
Core Case Study:
When Is a Lichen Like a Canary?
• Some lichen species are sensitive to specific airpolluting chemicals.
• After Chernobyl, more than 70,000 reindeer had
to be killed because they ate highly radioactive
lichens
• Because lichens are widespread, long-lived, and
anchored in place, they can help track pollution
to its source.
Acid Deposition
(Remember, oxides of sulfur and nitrogen can be
further oxidized in the atmosphere to form acid
precipitation- snow, sleet, rain, fog- and dry
fallout in the form of particulates)
• Sulfuric acid-H₂SO₄/sulfate salts-SO₄²
• Nitric acid-HNO₃/nitrate salts-NO₃²
Acid Deposition (cont’d)
• Source: coal-burning plants, ore smelters
• Create regional air pollution downwind from
source (hundreds of miles away)
• Wet deposition: acidic rain, fog, snow with
pH less than 5.6
• Dry deposition: acidic particles
• Buffers: some lime-containing soils that can
neutralize acids, minimize effects of acid rain
Wind
Transformation to
sulfuric acid (H2SO4)
and nitric acid
(HNO3)
Nitric oxide (NO)
Windborne ammonia gas and
particles of cultivated soil partially
neutralize acids and form dry
sulfate and nitrate salts
Sulfur dioxide
(SO2) and NO
Dry acid deposition (sulfur
dioxide gas and particles of
sulfate and nitrate salts)
Wet acid depostion
(droplets of H2SO4 and
HNO3 dissolved in rain
and snow)
Acid fog
Farm
Ocean
Lakes in deep soil
high in limestone
are buffered
Lakes in shallow soil
low in limestone
become acidic
Fig. 19-6, p. 448
Acid Deposition
Figure 19-8
Effects of Acid Deposition
Health issues: damages respiratory system,
irritates eyes, threatens food security
(concentrates heavy metals in fish, dissolves
shells of mollusks, harms crops)
Environmental issues: can leach aluminum,
lead, cadmium from soil, which enters aquatic
ecosystems, can leach nutrients out of soil
*thin mountain soils are most vulnerable to damage
Emissions
SO2
Acid H O
2 2
deposition
PANs
NOx
O3
Others
Reduced
photosynthesis and
growth
Direct damage to
leaves & bark
Tree death
Soil acidification
Leaching
of soil
nutrients
Acids
Susceptibility
to drought,
extreme cold,
insects,
mosses, &
disease
organisms
Release of
toxic metal
ions
Root
damage
Reduced nutrient &
water uptake
Lake
Groundwater
Fig. 19-9, p. 451
Results of Acid Deposition on
Producers
• Soil acidification: root damage, reduced
nutrient/uptake
• Direct damage to bark, leaves
• Susceptibility to drought, cold, predation by
insects
Reducing Acid Rain
• Reduce coal use (increase alternate fuels)
• Use of scrubbers to reduce emissions from
factories, vehicles
• Add lime or phosphates to neutralize acidified
lakes (expensive)
Smog
• Industrialized/Gray-air smog: suspended
droplets of salts, soot that hangs in urban air
-source: burning coal
-major problem in China (16 of 20 most
polluted cities)
• Photochemical/Brown-air smog: mix of
ozone, VOCs, NO, PANS (peroxyacyl nitrates) in
urban air
Smog (cont’d)
• Photochemical/Brown-air smog: mix of
ozone, VOCs, NO, PANS (peroxyacyl nitrates) in
urban air
-UV from sun causes NO to react with plant
VOCs
-increases with hotter, drier air
FYI: Sunlight plus Cars Equals
Photochemical Smog
• Mexico City is one of
the many cities in
sunny, warm, dry
climates with many
motor vehicles that
suffer from
photochemical smog
• LA , Salt Lake City
also has smog issues.
Figure 19-4
Factors Influencing Outdoor Pollution
Reducing pollution:
1. Density of particles (settle out)
2. Rain, snow (partially cleanse air)
3. Sea spray (washes ocean air)
4. Winds (mix polluted and unpolluted air)
5. Chemical reactions (sulfur, nitrates form
acids, which fall to earth)
Factors Influencing Outdoor Pollution
Increasing pollution:
1. Heat island: urban buildings block air flow
(reduce dilution of pollutants)
2. High temperatures (pc smog)
3. VOCs from urban forests (pc smog)
4. Grasshopper effect- movement of pollutants
from tropics to poles
Factors Influencing Outdoor Pollution
5. Temperature inversion: layer of warm air sits
over cooler, polluted air; prevents air from
rising and dispersing pollutants
- occurs in cities surrounded by mountains
(think L A)
Warmer air
Inversion layer
Descending warm air mass
Inversion layer
Case Study:
South Asia’s Massive Brown Cloud
• Huge cloud of industrial smog, caused by coalburning in countries such as China and India,
• Covers much of southeastern Asia.
– In areas beneath cloud, photosynthesis is reduced,
interfering with crop development.
– Fine particles and droplets in the cloud appear to be
changing regional climates (including rainfall).
• May have contributed to floods in 2002 and 2005 which
killed thousands of people.
Indoor Air Pollution
• Usually a greater threat to health than outdoor
air pollution
• Increases with poor ventilation
Major Indoor Pollutants
4 most dangerous indoor pollutants (according
to EPA):
• Tobacco smoke
• Formaldehyde
• Radioactive radon-222 gas
• Very small fine and ultrafine particles
FYI Tobacco Smoke
• Contains 70 carcinogens (including filter), 250
toxins
• 2nd-hand smoke is considered to be a leading risk
to human health (from cigarettes)
• Risk is magnified within enclosed spaces
Health issues: cancer, heart disease, birth defects,
emphysema
Remediation: quit smoking, ban smoking in
buildings, improve building ventilation
Economic health cost in US: ≈$72 billion
Formaldehyde
• Found in common building materials
(plywood, particleboard, wallpaper, carpet)
• Known carcinogen
Health issues: headaches, respiratory tract ,
irritation, sore throats, dizziness, nausea, cancer
Remediation: use formaldehyde-free materials,
increase building ventilation
Radon-222
• Colorless, odorless gas
• Radioactive decay of uranium 238
• Seeps from ground into foundations
Health issues: alpha particles damage lungs,
leads to lung cancer (2nd leading cause of cancer)
Remediation: Sealing cracks in foundations,
increase ventilation
FYI: Radioactive Radon
• Radon-222, a
radioactive gas
found in some soils
and rocks, can seep
into some houses
and increase the risk
of lung cancer.
Sources and paths of entry
for indoor radon-222 gas.
Figure 19-13
Fine Particles
Bacteria, viruses, pollen, dust, mildew, mold,
• Circulate in heating, cooling systems
• Can create sick-building syndrome
Health issues: infectious disease, allergic
reactions, headaches, irritated eyes and lungs,
chronic fatigue
Remediation: replace, disinfect air ducts or
condemn building
(1 in 5 commercial buildings in US is considered
“sick”)
FYI: Indoor Air Pollution
• Household dust mites
feed on human skin and
dust; live in materials such
as bedding and furniture
fabrics.
– Can cause asthma attacks/
allergic reactions in
sensitive people.
Figure 19-12
Other Pollutants
• Carbon monoxide
-results from inefficient combustion in gas
appliances
Health issues: headache, nausea, death
• Asbestos
-mineral once used in insulation, ceiling and
floor tiles
Health issues: skin and lung irritant, lung cancer
Global Climate Change
4 major anthropogenic greenhouse gases:
• CO₂
• Nitrous oxide (N₂O)
• Methane (CH₄)
• Chlorofluorocarbons (CFCs)
***global temperature increase 1°F***
Global Climate Change (cont’d)
CO₂
Source: burning hydrocarbons
-biggest contributor to greenhouse gases
Remediation:
-conservation of fossil fuels
-switch to alternate fuels
-sequester CO₂ in ground, plant trees, reduce
deforestation
Global Climate Change (cont’d)
N₂O
Sources: inorganic fertilizers, fossil fuels,
sewage treatment, decomp of biowaste
-lingers long time in atmosphere
Remediation:
-conservation of fossil fuels
-decrease use of fertilizers
Global Climate Change (cont’d)
CH₄
Sources: cattle, fossil fuel mining, landfills, rice
cultivation
-primary pollutant & VOC
-more potent than CO₂
Remediation:
-capture for fuel
-burning it
Global Climate Change (cont’d)
CFCs- molecules of chlorine & fluorine
-Cl⁻ + O₃ → ClO + O₂
(1 Cl⁻ ion may react with 1 x 10⁵ ozone molecules)
Sources: used in refrigerants, fumigants, propellants
in aerosol cans
-deplete ozone
-not water soluble (stays in atmosphere)
Remediation: Montreal Protocol phased out CFCs
Effects of Climate Change
• Sea level rise: thermal expansion of water,
melting of land-based glaciers
-degrades coastal wetlands, estuaries, reefs
-saltwater intrusion
-coastal flooding
-positive feedback loop: exposed soil absorbs
more heat, melts more snow…
Effects of Climate Change (cont’d)
• Melting of permafrost: (ground under tundra
is a sink for CO₂, CH₄)
-positive feedback loop: melting permafrost
releases gases, increases heat in atmosphere…
(TransAlaska pipeline is already showing signs of
sustained damage due to permafrost melting)
Effects of Climate Change (cont’d)
• Extreme weather: severe drought,
desertification, unusual snow events
-positive feedback loop: fewer plants means
more CO₂ in atmosphere…
• Change in ocean currents: meltwater from
Arctic circle may disrupt conveyor belt
currents in N Atlantic (Gulfstream currents
warm climate in Europe)
Effects of Climate Change (cont’d)
• Changing vegetative zone: temperature
increases will move zones northward.
-threatens food security
-increase plant extinction rates
• Biodiversity loss:
-animals must find vegetation- migrate or die
(arctic species are most vulnerable since there
is nowhere to migrate)
FYI: Atmosphere-Ocean Link
• CO₂ is dissolved in huge amounts in the
oceans
• CO₂ forms carbonic acid in water so acidity in
ocean increases
• Increased acidity inhibits production of
mollusk shells, coral
• Warmer oceans will dissolve less CO₂, which
means more in the atmosphere…
Stratospheric Ozone and UV Rays
• 3 types of UV radiation: A, B, C (A is least
energetic, C is most energetic)
-UV B/C is of most concern to us
• Ozone shields earth from UV radiation
-O₂ + UV → 2O (single oxygen)
-O + O₂ → O₃
(back and forth exchange of O and O₃ shields
earth from UV radiation)
Ozone Depletion
• First proposed by Rowland & Molina, 1970
-ozone measured in Dobson units (DU):
1 DU = ozone column 0.01 mm thick at O⁰C
• Polar stratospheric clouds: South pole winds
amplify “hole” in ozone in spring
Hazards of Depletion
Human issues: sunburns, cataracts, skin cancer,
crop damage, reduction in fish populations
Environmental issues: damage to phytoplankton,
UV-sensitive trees
Legislation
• Clean Air Act (1970): est. national standards for
allowable concentration of 6 outdoor/industrial
pollutants
• Montreal Protocol (1987): international
agreement to reduce CFCs, halons, methyl
bromide (to reduce ozone depletion)
• Kyoto Protocol (2005): proposed a reduction in
greenhouse gases, by 2012 (disagreements over
developed and developing countries’
responsibilities have quashed efforts to reach an
agreement)
FYI: Exam Tip
• Global warming and stratospheric ozone
depletion are not the same environmental
issue!
Be sure you know the similarities and
differences
Exam Focus
• Layers of atmosphere
-which one traps heat radiated from earth
(greenhouse layer)
-which one has ozone layer (not smog)
-which one has photochemical smog
-location of mesosphere
• Primary pollutants- traits, sources, effects
-CO, CO₂
-SO₂
-N₂, NO₂
-VOCs
Exam Focus
• Secondary pollutants- traits, sources, effects
-ozone/photochemical smog *highest in morning
-sulfuric, nitric acids
-PANS
-CFCs/Montreal Protocol
• Indoor air pollutants- sources, effects
-radon
-asbestos
-CO
Exam Focus
• Reducing acid deposition
• Prevention of pollutants
-scrubber (function)
• Heat island, temperature inversion (typical
location)
• Anthropogenic greenhouse gases
• Effects of increased UV radiation
• Legislation: Clean Air, Kyoto Protocol
goal/failure