Transcript Ozone Depletion in the Stratosphere Indoor Air Pollution Global

Mrs. Sealy APES
VII. Acid Deposition
• 1. “dilution solution” to air-pollution: to
reduce local air pollution and meet
government standards without having to
add expensive pollution control devices,
most coal-burning plants, ore smelters,
etc. use taller smokestacks to emit
sulfur dioxide high into atmosphere
• 2. increases pollution downwind
VII. Acid Deposition
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3. chemicals reach ground:
a. Wet: acid rain, snow, fog, cloud vapor
b. Dry:acidic particles
c. mixture causes acid deposition (acid
rain)
VII. Acid Deposition
• 4. pH: a numerical measure of the
concentration of hydrogen ions in a solution
(1 digit change equals 10X change in acidity)
• a. levels less than 7 - acid (natural
precipitation)
• b. levels greater than 7 - Base
• c. typical rain in east US
is now about 10 times
more acidic (pH 4.3)
Wind
Transformation to
sulfuric acid (H2SO4)
and nitric acid (HNO3)
Windborne ammonia gas
and particles of cultivated soil
partially neutralize acids and
form dry sulfate and nitrate salts
Nitric oxide (NO)
Acid fog
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)
Farm
Ocean
Lakes in
deep soil
high in limestone
are buffered
Lakes in shallow
soil low in
limestone
become
acidic
Fig. 17.9, p. 428
5. What areas are most affected
by acid deposition?
• occurs on a local rather than global basis b/c
acidic components only remain in the air for a
few days
• areas downwind from coal and oil burning
power plants, industrial plants and urban
areas
• ecosystems containing acidic soils without
natural buffering of bases
• growing problem in China (40% of its land),
former Soviet Union, India, Nigeria, Brazil,
Venezuela, Columbia
Potential problem areas
because of sensitive soils
Potential problem areas because
of air pollution: emissions leading
to acid deposition
Current problem areas
(including lakes and rivers)
Fig. 17.11, p. 429
6. What are the effects of acid
deposition?
• medium-risk ecological problem, high-risk to
human health
• human respiratory diseases (bronchitis,
asthma), damages statues, buildings, metals,
plastics and paints
• damages tree foliage, makes trees more
susceptible to cold temps, disease, insects,
drought, fungi
• harmful to aquatic species
Effects of Weather
Emissions
Acid
deposition
Dry
weather
SO2
H2O2
NOX
O3
PANs
Others
Low
precipitation
Increased
susceptibility
to frost,
pests, fungi,
mosses,
and disease
Increased
evapotranspiration
Direct damage
to leaves
and needles
Increased
transpiration
Water
deficit
Bark damage
Acids
Potassium
Calcium
Aluminum
Magnesium
Sulfate
Nitrate
Lake
Kills certain
essential soil
microorganisms
Release of toxic metal ions
Acids
and soil
nutrients
Damage to
fine roots
Reduced
photosynthesis
and growth
Nutrient
deficiency
Soil acidification
Leaching of
soil nutrients
Dead leaves
or needles
Damage
to tree
crown
Tree death
Disturbance
of nutrient
uptake
Disturbance
of water
uptake
Groundwater
Fig. 17.14, p. 432
D. What can be done to reduce
acid deposition?
• prevention
• 1) reducing energy use & thus air-pollution by
improving energy efficiency
• 2) switching from coal to cleaner-burning natural gas
• 3) removing sulfur from coal before it is burned
• 4) burning low-sulfur coal
• 5) removing SO2 particles, particulates, and nitrogen
oxides from smokestack gases
• 6) removing nitrogen oxides from combustion
engines
D. What can be done to reduce
acid deposition?
• reducing coal use is economically &
politically difficult
• clean-up approaches are expensive and
mask symptoms w/ out treating causes
• acidified lakes can be neutralized by treating
them or the surrounding soil with large
amounts of limestone or lime. This is an
expensive and temporary remedy