Atmospheric Pollution

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Atmospheric Pollution

• Text.Chp. 21
• I. Background
• II. Major pollutants
• III. Sources
• IV. Focus on acid rain
• V. Control strategies
• I.Background
• Air pollutants are certain gases and aerosols in
  the
• atmosphere that have harmful effects.
• Level of air pollution is determined by
• -- amount entering air
• -- volume of air pollutants are dispersed in
• -- removal mechanisms

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• Current levels gt natural systems cant
  assimilate, remove and recycle pollutants
• Threshold level gtabove that, damaging effects.
• The OH radical is a natural scavenger, but
  excessive scavenging
• acid rain
• Smoggtderived from smoke and fog. Two kinds
  industrial photochemical.
• Seasonal variationsgttemperature inversions in
  spring and autumn
• can trap pollutants

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The Threshold Level
Dose concentration x exposure.
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Temperature inversion
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II.Major Pollutants (Table 21-1)

• Suspended particulate matter
• VOCs
• CO
• NOX

• SOx
• Heavy metals
• O3
• Air toxics (asbestos, vinyl)

• Pollution effects hard to detect because of
  synergistic effects.
• Three categories of impact on human health
  chronic, acute,
• carcinogenic.

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• Impact on agriculture and forest gt die-off from
  acid rain, O3 and smog.
• Aesthetic impacts
• III. Sources
• Primary pollutants vs. secondary pollutants
• EPA tracks emissions from source to correlate
  with ambient
• concentrations.

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Major Primary Pollutants

• Particulates
• Hydrocarbons
• CO
• NOX
• SO2

• Major Secondary Pollutants
• O3
• PANs
• Acids H2SO4 HNO3
• OZONE is the champion in non-compliance.

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Emission Trends
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IV. Focus on acid rain

• Def. Rain, fog or mist that is more acidic than
  usual (pH 5.6).
• Sources of acid ppt
• SO2, NOX
• Natural sources vs. anthropogenic sources
• Ecosystem damage if pH shifts by 1
• Buffer, the acid slayer add limestone to raise
  pH.

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pH Scale
pH measurement of H ions in solution
Acid precipitation pH lt 5.5
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Acid Deposition
Four forms
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General Effects of Acid Deposition

• Alteration of plant and animal reproduction
• Leaching of toxic elements, e.g., Al, Hg, Fe

• Effects of Acid Precipitation on Forest
  Ecosystems
• Leach nutrients
• Al goes into solution
• ? soil chemistry
• Reduced growth and plants and animals die.
• Increased plant vulnerability to disease
• Soil erosion ?
• Sedimentation of rivers
• Flooding ?

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Clean Air Act of 1970, 1977, 1990

• Identifies most widespread pollutants e.g.,
  particulates, SO, CO, NO, lead criteria
  pollutants.
• Set national ambient air quality standards.
• Set national emission standards.

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Control Strategies

• Command-and-control regulate air pollution so
  criteria pollutants remain below primary standard
  level
• Results
• Lack of enforcement and compliance
• 37 reduction of air pollutants
• Work with state implementation plan (SIP)

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Title IV Clean Air Act 1990

• Reduce SO to 50 lt 1980 levels
• Improve methods of reducing SO emissions
• Emissions allowances trading purchases
• Reduce NO emissions

• Industries Response to Title IV
• Fuel switching
• Scrubbers
• Emissions allowance trading
• Using low-sulfur coals

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Future Responses to Air Pollution Control

• Increase fuel efficiency
• Emission-free vehicles
• Improving mass transit
• Reduce commuting