Air Pollution - Effects and Origin of Major Pollutants

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Air Pollution - Effects and Origin of Major
Pollutants

• CE 511 - April 27, 2006

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Objectives

• Discuss effects of air pollution on materials and
  vegetation
• Discuss effects of air pollution on human health
• particulates (esp. PM10, 2.5), nitrogen dioxide,
  carbon monoxide, photochemical oxidants,
  hazardous air pollutants, sulfur oxides and lead
• Discuss the origin and fate of carbon monoxide,
  HAPs, lead, nitrogen dioxide, photochemical
  oxidants, sulfur oxides, and particulates in air

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Effects of Air Pollutants - Targets

• On materials
• On vegetation
• On human health

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Health Effects of Specific Pollutants

• Carbon monoxide
• colorless, odorless gas
• hemoglobin has stronger affinity for CO than O2
• lethal to humans at 5,000 ppmv
• CO concentration in cigarette smoke, 200-400 ppm
• Hazardous air pollutants (HAPs)
• most info. comes from work exposures
• effects of low concentrations unknown

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Effects of Specific Pollutants

• Lead
• cumulative poison (most air pollutants arent)
• both ingested and inhaled
• 120 micrograms /100g results in acute brain
  damage
• Nitrogen dioxide
• reddish brown gas
• 5-15 ppm cause cough URT irritation
• concentration in tobacco smoke 5ppm
• slight increase in respiratory illness at 0.10 ppm

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Effects of Specific Pollutants

• Photochemical oxidants
• major one is ozone
• indicator of total oxidants present
• 0.1 ppm irritates eyes, 0.3 ppm causes chest
  discomfort
• PM10
• particles this size not taken in lungs
• in 1997, EPA changed this standard to PM 2.5
• Sulfur oxides
• Problem on its own, but can also associate with
  particles

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Sources Fate of Carbon Monoxide

• Sources - natural
• Primarily, anaerobic oxidation of methane (CH4)
• 1.6 x 1014 grams CH4 produced by bacteria each
  year
• Sources - anthropogenic combusion
• motor vehicles
• burning fossil fuels
• solid waste disposal
• industrial processes
• burning leaves, brush, etc.
• Fate - No change in atmospheric CO in 20 years
• even though anthropogenic output doubled)

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Hazardous Air Pollutants (HAPs)

• Sources
• Direct - anthropogenic emissions
• Indirect - transformation of non-hazardous gases
  in atmosphere to hazardous ones
• Fate
• Many removed by addition of OH
• Often CO or CO2 formed
• 89 of 189 HAPs remain in atmosphere lt 1 day

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Lead

• Sources
• Natural
• Volcanic activity and airborne soil
• Anthropogenic
• Smelters and refineries
• Incineration of lead-containing wastes
• Leaded gasoline - no longer used
• Which source is larger?
• Fate
• Pb particles attach to other particles and settle
  out or wash out

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Nitrogen Dioxide

• Sources - natural
• Bacteria in soil produce nitrous oxide
• denitrification
• Forms upon reacting with molecular oxygen and
  ozone in upper troposphere and stratosphere
• Sources anthropogenic combustion at temps
  exceeding 1600K
• Which source is larger?
• Fate
• NO2 converted to NO2- or NO3- in particulate form
• Particles washed from air contribute to acid rain

?
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Photochemical Oxidants (Ozone)

• Called secondary pollutants - not directly
  released formed in atmosphere from other
  pollutants
• Source
• Release of NO and NO2
• VOC-catalyzed process
• Fate - highly reactive and typically doesn't
  persist in Troposphere
• X O3 ? XO O2
• Component of photochemical "smog"

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Sulfur Oxides

• Source
• As primary pollutants (SO2 or SO3)
• from power plants, industry, volcanoes
• As secondary pollutants
• from industrial and biological processes emitting
  H2S
• Which source is larger?
• Fate
• Converted to sulfate or sulfuric acid and settle
  or wash out
• Major contributor to acid rain

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Particulates

• Sources - Primary
• Natural
• Sea salt, soil dust, volcanoes, smoke from forest
  fires
• Anthropogenic
• Fossil fuel burning and industrial processes
• Source - secondary
• When H2S, SO2, NOx, etc. converted to
  particulates
• Which source is largest?
• Fate - settle out or are washed out