Download Air Pollution

Chapter 20
 We
live at the bottom of a thin layer of
gases surrounding the earth
• Atmosphere
 The
Atmosphere is made up of several
layers
 We live in the troposphere
 Above the troposphere is the
stratosphere
Troposphere
 1st layer of atmosphere
 Extends 11 miles
above Earth
 78% N, 21% O
 Chemical cycling of
nutrients happens here
 Weather & Climate
happen here
 Water vapor present

Stratosphere
 2nd layer of atmosphere
 Extends from 11 – 30
miles above Earth’s
surface
 More ozone (O3)
present here
 Less water vapor

 Atmospheric
Pressure
• A measure of the mass per unit of air
 Pressure
of atmosphere increases at the
density increases
• A volume of air with a high density has more gas
molecules than air at a lower density (D = m/v)
• Atmospheric pressure decreases with altitude
 Ex: At sea level, your body is bombarded with more
gas molecules than your body would be at the top of a
mountain
In the
diagram,
notice that
as altitude
decreases,
the
atmospheric
pressure
increases.
Another graph: As altitude decreases, atmospheric pressure increases.
 Ozone
(O3)
• Found in 2nd layer of
atmosphere
(stratosphere)
• Filters our most of
the sun’s harmful UV
rays
 Ultraviolet rays –
dangerous to
organisms, can cause
cancer
• Created when
oxygen molecules
interact with UV
radiation emitted by
the sun
How ozone is created
 Air Pollution
• Presence of chemicals in the atmosphere in
concentrations high enough to affect climate and
harm organisms
• Range from annoying to lethal
 Sources
• Majority of air pollution comes from natural
sources
• Ex: dust blowing across the land; organic
chemicals released by plants, forest fires,
volcanic eruptions, and sea spray
 Primary
Pollutants
• Pollutants emitted directly into the troposphere
in a potentially harmful form
 Ex: soot, carbon monoxide (CO)
 Secondary
Pollutants
• When some primary pollutants react with one
another or with the air to form a new pollutant
 Ex: SO2, H3SO4
 U.S. cities
typically have higher outdoor
pollution levels than rural areas
 Due
to prevailing winds, the city
pollutants are spread to rural areas
 Indoor
air pollutants come from
infiltration of outdoor pollutions into the
building
 Most
people believe CO2 is a pollutant
 EPA
(Environmental Protection
Agency)disagrees
• Too much pressure from oil and coal companies?
• Repercussions if listed as pollutant by EPA?
CO2

IS a pollutant because:
1) It’s found in high concentrations in the air
• ANY chemical in high concentrations in the air can become a
pollutant

2) We have been increasing CO2 concentrations in the
troposphere by burning fossil fuels & clearing CO2absorbing trees faster than they can grow back
• No way to get rid of CO2
 3)
The troposphere is warming & there is
considerable evidence that additional CO2
added by humans is the cause
• Greenhouse gas – warms the Earth
 UV
Rays
 http://www.youtube.
com/watch?v=npBBJyl-go
 Air
Pollution
 http://www.youtube.
com/watch?v=e19Vo
A2SApM&feature=rel
ated
 Photochemical
reaction


Any chemical
reaction activated by
light (photo= light)
Ex: Photochemical
smog
 Photochemical
smog
• A mixture of air
pollutants formed
by the reaction of
nitrogen oxides
(NO and NO2 )and
volatile organic
hydrocarbons
• Activated by light
Photochemical
Smog formation
 Smog





pollutants:
NO2, NO3 (nitrogen
oxides)
Ozone
Nitric acid
Aldehydes
Peroxyacyl nitrates
(PANs)
 Sources
of smog
pollutants:




Automobile engines
Coal-burning plants
Industrial plants
Vegetation
 Certain
trees & plants
can contribute to
photochemical smog
 Ex: oak, sweet
gums,
poplars, kudzu
 They
release volatile
organic compounds
(VOCs)
• Ingredient in smog
 Trees
planted in nonurban areas release their
VOCs, which are dispersed into the
atmosphere
• They do not make a significant contribution to the
formation of photochemical smog
 Trees
planted in / near urban areas with high
levels of NOx (nitrogen oxides) and sunlight,
will create high levels of VOCs
 Environmentalists’ view: widespread planting
of trees in urban areas BUT only those who emit
low VOCs
 Industrial
smog
• A mixture of sulfur
dioxide, droplets of
sulfuric acid, and a
variety of particles
emitted by burning
coal and oil
• When burned, carbon
in coal and oil is
converted to CO2 and
CO
 Some of this ends up in
atmosphere as
ingredient of smog
 Industrial
smog
• Also known as: gray-air-smog
 Not
a big problem in developed
countries
• Good pollution control when coal & oil are
burned
 It
IS a big problem in industrialized
urban areas of:
• China, India, Ukraine, Slovakia, Poland, Hungary,
and Czech Republic
 Factors
that decrease outdoor air pollution:
• Precipitation
 Rain & snow help to cleanse the air, lowering pollution
• Sea Spray
 Can wash out particulates & water-soluble pollutants
from air that flows from land onto the oceans
• Wind
 Can sweep pollutants away or dilute them
 Pollutants are blown somewhere else
 Can be deposited onto surface waters, soil, buildings
 Factors
that increase outdoor air pollution:
• Urban buildings
 Slow wind speed
 Reduce dilution / removal of pollutants
• Hills and Mountains
 Reduced the flow of air in valleys below them
 Allows pollutants to build up at ground level
• High temperatures
 Promote chemical reactions leading to photochemical smog
• Grasshopper effect
 Transfers air pollutants from tropical / temperate areas to the
earth’s poles
 Reason for high levels of pollutants, decreasing ozone in poles
Keep in mind that the warm air rises in the temperate /
tropical areas and will condense once it reaches the
colder temperatures (earth’s poles).
 Temperature
Inversion
• Occurs when cool, dense air is trapped under a
warm, less dense air
• These two air masses do not mix
• As a result, pollutants in the air can be concentrated
in the lower layer of cool air (closest to the earth)
Effects of
temperature
inversion
 Asian
brown cloud (industrial smog)
 2 miles thick
 Caused by huge emissions of ash, smoke,
dust, acidic compounds (from burning
coal), burning trees (to plant crops), dust
blowing from desserts
 As the cloud travels it picks up many
pollutants
Impacts:
 Effects
the amount of solar energy hitting earth
• Impacts of crop production
• Damage trees
• Can kill organisms in lakes
 Illnesses
& premature deaths
• Respiratory diseases
 Particles
in cloud are causing climate change
• Changes temperature pattern, rainfall shifts
• Can effect El Nino (which could affect North & South
America)
South Asia’s
Brown Cloud

Acid deposition / acid rain:
• Mixture of wet deposition & dry deposition
• Wet deposition: acid rain, snow, fog, cloud vapor
 pH is less than 5.6
• Dry deposition: acidic particles

Composed of:
• Sulfur dioxide (SO2)
• Nitrogen oxides (NO2 and NO)
• Particulates
Acid Deposition / Rain
 Some
soils contain
chemicals which
buffer acidic
deposition / rain:
• Calcium carbonate
(CaCO3)
• Limestone
 Chemicals
neutralize
acids
• Bring pH closer to 7
 Harmful
effects of acid deposition / rain:
• Human respiratory diseases
 Bronchitis, asthma
• Can leach toxic chemicals into drinking water
 Lead, copper
• Damages statues, monuments, buildings, metals
 Including car finishes, eats away / dissolve certain types of rock
• Can kill aquatic life if pH drops too low
• Acid shock
 Damage to aquatic life due to runoff of large amounts of
highly acidic water
 Effects
of acid rain on plants and soil:
• Can deplete soil nutrients
 Calcium and Magnesium
• Release toxic ions into the soil
• Weaken plants
 If pH of soil drops below 5.1
• Calcium deficiencies in plants can be passed to the
organisms who eat them
 Ex: birds eating these plants could have problems with egg
production (shell made of calcium)
 Synergistic
effect
• When the interaction of two or more factors’
combined effect is greater than the sum of their
separate effects
 Clean
Air Act
• Has helped reduce
some of the harmful
impacts of acid
deposition
 Solutions

to acid deposition:
Prevention (BEST solutions)
• Improve energy efficiency
• Reduce coal use or burn low-sulfur coal
• Increase natural gas use and renewable energy
• Remove SO2 particulates and NOx from smokestack gases
• Fees for SO2 emissions
 Cleanup
• Add lime or phosphate fertilizer to neutralize acidified lakes
 Controlling
acid deposition / rain is a challenge:
• The people who cause acid rain and the people or
ecosystems affected by it are quite distant
• Countries with large supplies of coal (which produces
acid rain) want to use coal for energy
• Coal-burning power plants say it’s too costly to install
equipment to reduce harmful emissions
 Environmentalists
idea- Use alternative energy
sources (wind turbines, natural gas)
 Cleanup
of acid rain in lakes & soil
• Add limestone (or lime) to neutralize
• Called “liming”
• Problems:
 Expensive
 Needs to be repeated annually (temporary fix)
 Can kill some aquatic plants, plankton, wetland plants
• Possible solution:
 Add phosphate fertilizer to neutralize
 Effectiveness still being evaluated
Thermal Inversion demonstration
http://www.youtube.com/watch?v=LPvn9qhVFbM
 Thermal Inversion in the real world
http://www.youtube.com/watch?v=pkOuBUXwiyA
 Asia’s Pollution Super Cloud
http://www.youtube.com/watch?v=qYYK-2sDN4U
 Coal combustion & Acid Rain
http://www.youtube.com/watch?v=HE6Y0iEuXMQ



Go to hippocampus link
On the left-hand side of the screen click “Earth
Science”

Click “Environmental Science for AP”

Scroll down the middle of the page

Watch the following videos:
• Earth’s atmosphere
• Ozone
• Photochemical smog
• Air pollution