Mrs. Sealy APES

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Ch. 17 Notes Air Pollution

• Mrs. Sealy APES

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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

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VII. Acid Deposition

• 3. chemicals reach ground 
• a. Wet acid rain, snow, fog, cloud vapor
• b. Dryacidic particles
• c. mixture causes acid deposition (acid rain)

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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)

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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
Wet acid deposition (droplets of H2SO4 and HNO3
dissolved in rain and snow)
Dry acid deposition (sulfur dioxide gas and
particles of sulfate and nitrate salts)
Sulfur dioxide (SO2) and NO
Nitric oxide (NO)
Acid fog
Farm
Ocean
Lakes in shallow soil low in limestone become acid
ic
Lakes in deep soil high in limestone are buffered
Fig. 17.9, p. 428
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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

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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
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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

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Effects of Weather
Emissions
Dry weather
Low precipitation
SO2
NOX
Acid deposition
Increased susceptibility to frost, pests,
fungi, mosses, and disease
H2O2
O3
Increased evapotranspiration
PANs
Others
Direct damage to leaves and needles
Dead leaves or needles
Increased transpiration
Water deficit
Reduced photosynthesis and growth
Bark damage
Nutrient deficiency
Soil acidification
Damage to tree crown
Tree death
Kills certain essential soil microorganisms
Nitrate
Sulfate
Acids
Aluminum
Calcium
Magnesium
Potassium
Release of toxic metal ions
Leaching of soil nutrients
Disturbance of nutrient uptake
Damage to fine roots
Acids and soil nutrients
Disturbance of water uptake
Lake
Groundwater
Fig. 17.14, p. 432
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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

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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