Earths Changing Environment Lecture 2

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Earths Changing EnvironmentLecture 2

• Air Pollution

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• Those who contemplate the beauty of the earth
  find reserves of strength that will endure as
  long as life lasts.
• - Rachel Carlson

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The Atmosphere

• N2 780900 ppm (78.09)
• O2 209400 ppm (20.94)
• Argon 9300 ppm (0.93 )
• CO2 372 ppm (0.037)
• Everything else is less than 0.003 or 30 ppm

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Layers of the Atmosphere

• Stratosphere begins at about 10 miles above the
  surface.
• Pressure drops with altitude.
• So, less oxygen with altitude.

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Air Pollution Sources

• Most air pollution is emitted from fixed and
  mobile sources at ground level.

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Buoyant Force

• The density of air is proportional to its
  Temperature.
• Hot polluted air is less dense than the cooler
  air around it.
• So, hot polluted air will rise, expand, cool, and
  disperse

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Temperature vs. Altitude

• Hot air released at ground level will loose
  temperature as it rises and expands. The rate at
  which its temperature drops is the adiabatic
  lapse rate (ALR) and equals 3.5F per 1000 feet.

• The environmental lapse rate (ELR) is typically
  equal to the ALR.

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Unstable Air

• If the ELR ALR, then hot polluted air will rise
  and disperse.

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Temperature Inversion

• If the there is a temperature inversion (a warm
  layer above the cool surface layer), the air will
  not rise.
• This may lead to a severe pollution episode.
• Temperature inversions are frequently caused by
  radiative cooling of the ground at night.

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Subsidence Inversion

• Descending air compresses and warms, creating an
  inversion layer

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Global Air Circulation

• The combination of air density, uneven solar
  heating, and the Earths rotation explains global
  air circulation and climate zones.

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Hadley Cells
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Pollutants

• Gases CO, SOx, O3, NOx, and VOC
• SPM (suspended particulate matter) particulates
  and aerosols

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Primary vs. Secondary
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CO

• Primarily due to auto emissions.

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SO2

• Primarily from power plants coal and oil.

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VOC

• In rural areas, natural sources dominate.
• In urban areas, transportation dominates.

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NOx

• Primarily from power plants and transportation
• Emitted as NO and oxidized to NO2

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Particulates

• From Industry, power plants, and transportation

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Photochemical Smog

• Main harmful ingredient in smog is ozone.
• Ozone is formed when UV radiation, high
  temperatures, Nitrogen oxides, and VOCs combine.
• Automobiles are the main problem.

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Ozone

• Ozone is primarily a summer problem in the US.
• Higher temperatures and higher ozone levels are
  need to drive the reactions.
• VOCs have many sources.
• NOx is primarily from cars.

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Acid Rain

• Acid rain is formed from SO2 and NO2 pollution.

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Acid Rain

• Sulfuric acid (H2SO4) and nitric (HNO3) acid are
  formed and precipitated on vegetation in lakes
  and streams.

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pH

• Normal rainwater is slightly acid because of
  carbonic acid (H2CO3) and nitric (HNO3). pH 5.6
• pH values between 4.0 and 4.5 are common in NE,
  Canada, northern Europe

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Health Effects Outdoor Air Pollution

• Kills 200,000 - 570,000 annually globally.
• Kills 20,000 people annually in US.
• Particulates and ozone are the biggest problem
• Major sources are coal-burning power plants and
  vehicle emissions

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Worse Air Pollution Disaster

• London, England, 1952
• From December 5 to 8, 1952
• The meteorological conditions were ideal for a
  pollution. Anti-cyclonic or high pressure weather
  with stagnating continental polar air masses
  trapped under subsidence inversions produced a
  shallow mixing layer with an almost complete
  absence of vertical and horizontal air motion.
• Fireplaces and industries supplied the
  hygroscopic condensation nuclei into the air to
  form dense fog.
• Deaths from bronchitis increased by a factor of
  10, influenza by 7, pneumonia by 5, tuberculosis
  by 4.5, other respiratory diseases by 6, heart
  diseases by 3 and lung cancer by 2.
• 4,000 Londoners perished.

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Health Effects Indoor Air Pollution - Global

• Kills 2.8 million annual globally
• In developing countries, burning wood and other
  materials for heat and cooking is the major
  source.

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Health EffectsIndoor Air Pollution - US

• Kills 100,000 people annually in US.
• Cigarette smoke, formaldehyde, and radon-222 are
  primary indoor pollutants.