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Air Pollution
Chapter 15, Part 1
PART 1 (thru p. 388)
Section 15-1
WHAT IS THE NATURE OF THE
ATMOSPHERE?
The earth’s atmosphere is a dynamic
system that includes 4 layers
T-S-M-T (The Sky Makes Thunder)
Know this
(O3) – global
“sunscreen”
Section 15-2
WHAT ARE THE MAJOR AIR
POLLUTION PROBLEMS?
Outdoor air pollutants
harm organisms, ecosystems, or human made materials, or to
alter climate.
Natural sources include
dust blown by wind,
pollutants from wildfires
and volcanic eruptions,
and volatile organic
chemicals released by
some plants.
Most human inputs come
from the burning of fossil
fuels in power plants and
industrial facilities (stationary
sources) and in motor
vehicles (mobile sources).
Some primary air pollutants may react with one another or with
other chemicals in the air to form secondary air pollutants.
Major Air Pollutants
*
Summary of most of these
and others on next slides –
review them online.
*
*
*
*
*
Pollutants with (*) in next
slides classified as Nat Amb
Air Qual Std - NAAQS
criterion pollutants.
*Regulated by Clean Air Act
Major Air Pollutants
• Sulfur dioxide (SO2) * and sulfuric acid:
– About one-third of SO2 in the troposphere occurs naturally
through the sulfur cycle.
– Two-thirds come from human sources, mostly combustion
(S+ O2 → SO2) of sulfur-containing COAL and from oil
refining and smelting of sulfide ores.
– SO2 in the atmosphere leads to INDUSTRIAL SMOG (gray
smog) &can be converted to sulfuric acid (H2SO4) and
sulfate salts (SO42-) that return to earth as a component of
acid deposition
– SO2 emissions have seen a sharp decrease with better
regulations in developed countries. – Cap & Trade in US
*=Nat Amb Air Qual Std criterion pollutant
Major Air Pollutants
• Nitrogen oxides (NOx) and nitric acid:
– Nitric oxide (NO) forms when nitrogen and oxygen
gas in air react at the high-combustion
temperatures in CAR engines and COAL-burning
plants. NO can also form from lightening and certain
soil bacteria.
• NO reacts with air to form NO2 (nitrogen dioxide) * which reacts
to form PHOTOCHEMICAL SMOG.
• NO2 reacts with water vapor in the air to form nitric acid
(HNO3) and nitrate salts (NO3-) which are components of
acid deposition.
• N2O Nitrous Oxide = greenhouse gas from fertilizers,
animal waste & fossil fuels
Major Air Pollutants
• Suspended particulate matter (SPM):
– Solid and liquid particles suspended in the air.
– 38% from humans
– The most harmful forms of SPM* are fine
particles (PM-10, with an average diameter <
10 micrometers) and ultrafine particles (PM2.5).
– According to the EPA, SPM is responsible for
about 60,000 premature deaths a year in the
U.S.
Major Air Pollutants
• Carbon oxides:
– Carbon monoxide* (CO) is a highly toxic gas that forms
during the incomplete combustion of carbon-containing
materials—esp. from CARS.
– 93% of carbon dioxide (CO2) in the troposphere occurs
as a result of the carbon cycle.
– 7% of CO2 in the troposphere occurs as a result of human
activities (mostly burning fossil fuels).
• It is not regulated as a pollutant under the U.S. Clean Air Act. But
the EPA has recognized its accumulation as dangerous.
Major Air Pollutants
• Lead (Pb):
– Lead can be emitted into the atmosphere as
particulate matter (PM*) from paint, smelters,
and manufacturing.
– Accumulates in the body to cause nervous
system damage, digestive problems, and
cancer
– Harms wildlife.
Major Air Pollutants
• Ozone (O3) *:
– Ozone a highly reactive gas that is a major
component of photochemical smog.
– It can
• Cause and aggravate respiratory illness.
• Can aggravate heart disease.
• Damage plants, rubber in tires, fabrics, and paints.
(“good” when in stratosphere)
Major Air Pollutants
• Volatile organic compounds (VOCs):
– Most are hydrocarbons emitted by the leaves
of many plants and methane. React with NOx
to form PHOTOCHEMICAL SMOG.
– About two thirds of global methane emissions
comes from human sources.
– Other VOCs include industrial solvents such
as trichlorethylene (TCE), benzene, and vinyl
chloride.
• Long-term exposure to benzene can cause cancer,
blood disorders, and immune system damage.
Major Air Pollutants
• Radon (Rn):
– Radon a naturally
occurring radioactive
gas found in some
types of soil and rock.
– It can seep into
homes and buildings
sitting above such
deposits.
Sources of Air Pollution
www.epa.gov/airtrends/2010/report/airpollution.pdf
Smog
• Industrial smog (“grey”) is a mixture of sulfur dioxide, droplets
of sulfuric acid, and a variety of suspended solid particles
emitted mostly by burning coal, etc.
– rarely a problem in most more-developed countries
– China (Bejing below) uses lots of coal → 16 of the world’s 20 most
polluted cities.
Smog
• Photochemical smog (“brown”) is a mixture of air pollutants formed by
the reaction of nitrogen oxides and volatile organic hydrocarbons under
the influence of sunlight.
• Mexico City (pictured) and Los Angeles are two of the
many cities in sunny, warm, dry climates with many
motor vehicles that suffer from photochemical smog.
Decreased outdoor air pollution
– Heavy particles settle
– Rain and snow help
cleanse
– Salty sea spray from
the oceans washes
out many pollutants
over the oceans.
– Winds sweep
pollutants away to mix
with cleaner air.
– Some pollutants
removed by chemical
reactions.
Increased outdoor air pollution
• Factors can increase outdoor air pollution.
– Urban buildings, hills, mountains slow wind speed and reduce dilution. Also lead
to inversions (below).
– High temperatures promote the chemical reactions leading to photoch. smog.
– VOCs can be emitted from certain plants.
– Grasshopper effect—air pollutants are transported by evaporation and winds to
be deposited in earth’s polar areas.
Acid deposition is a serious
regional air pollution problem
• From coal-burning power plants, ore smelters, and other
industrial facilities:SO2 and NOx → sulfuric acid, nitric acid
vapor, and particles of acid-forming sulfate and nitrate
salts.
• Descend to the earth’s surface in two forms (often far
away if smokestacks):
– Wet deposition consisting of acidic rain, snow, fog, and cloud
vapor, and dry deposition resulting in a mixture called acid
deposition, or acid rain.
– Dry acid deposition (sulfur dioxide gas and particles of sulfate and
nitrate salts).
• Mixture of wet and dry is called acid deposition—
sometimes called acid rain.
Acid deposition
Wind
Transformation
to sulfuric acid
(H2SO4) and nitric
acid (HNO3)
Windborne ammonia gas
and some soil particles partially
neutralize acids and form dry
sulfate and nitrate salts
Nitric oxide (NO)
Sulfur dioxide
(SO2) and NO
Dry acid deposition
(sulfur dioxide gas and
particles of sulfate and
nitrate salts)
Wet acid deposition
(droplets of H2SO4
and HNO3 dissolved
in rain and snow)
Acid
fog
Lakes in deep soil
high in limestone
are buffered
Lakes in shallow
soil low in
limestone
become acidic
• Acid deposition consists of rain (acid rain),
snow, dust, or gas with a pH lower than 5.6.
Fig. 15-5, p.
Current and potential regions where acid
deposition is a problem
Acid deposition has a number of
harmful effects
• Damages statues and buildings
• contributes to disease
• leaches toxic metals (such as lead
and mercury) from soils and rocks
into lakes used as sources of
drinking water.
• Toxic metals can accumulate: 45
U.S. states have issued warnings
telling people to avoid eating fish
caught from waters that are
contaminated with toxic mercury.
• Harms aquatic ecosystems
• Indirectly kills trees -- leaching
essential plant nutrients releasing
toxic metals.
Indoor air pollution
• Major problem where burning of biomass, coal, etc. used for
cooking and heat
• Urban people in MDCs (more devel. countries) and LDCs
spend 70–98% of their time indoors/vehicles- 2-5x more pollutants
indoors
- 18x more pollutants in cars
• The four most dangerous indoor air pollutants in
MDCs are:
–
–
–
–
tobacco smoke
Formaldehyde from building and household products
radioactive radon-222 gas from underground rock deposits
very small (ultrafine) particles
Numerous indoor air pollutants are
found in most modern homes
The distribution of premature deaths
from air pollution in the United States
150,000 to 350,000
people in the U.S. +
cancer, asthma
At least 2.4 million
people worldwide
die prematurely
each year from the
effects of air
pollution.
Physiological protection
Sneezing
and
coughing
help
Section 15-3
HOW SHOULD WE DEAL WITH AIR
POLLUTION?
Laws and regulations
• The U.S. Congress passed the Clean Air Acts
in 1970, 1977, and 1990. SUCCESS!
– The federal government established air pollution
regulations for key pollutants that are enforced by
states and major cities.
– For CO, NO2, SO2, Pb, O3, PM
• Combined emissions of six major pollutants
decreased by ~54% between 1980 and 2008
• 1990 CAA included cap and trade program for
SOx.
Reduce pollution
More cap and
trade programs
Reduce pollution
Prevention