Air%20Quality%20and%20Pollution

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Air Quality and Pollution

• The challenge to manage our atmospheric resources
  well

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Outline

• Atmospheric stability and pollution dispersion
• Vertical stability
• Adiabatic lapse rate
• Thermal Inversions
• Survey of criteria pollutants
• Emissions and concentrations
• Atmospheric reactions
• Effects

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Seeking Vertical Equilibrium

• As hot air rises, the pressure decreases, the
  temperature drops and the density drops.
• When it reaches air of the same temperature (and
  density), it stops rising.

T2
Tair2
T1
gt Tair1
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Atmospheric Stability Part II

• A vertically stable atmosphere is one in which
  denser air is below and less dense air, above.
• BUT, if the air below is heated, it will become
  less dense, and will tend to rise until it
  reaches air of the same density.
• Because of the suns heating and the earths
  cooling, the air is constantly rising and
  falling, seeking vertical equilibrium.

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Adiabatic Lapse Rate
h
stable

• Air cools as it rises.
• ALR -0.65 C / 100m
• The surrounding air can be cooler or warmer as
  you go up.
• If it is warmer, the rising hot air ( e.g.
  pollution) is trapped.
• Inversion

ALR
unstable
hs
320K
290K
270K
T
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Thermal Inversions
h
Subsidence Inversion

• Radiation Inversion
• On clear, winter nights, the earth cools off
  faster than the air.
• Lasts the morning hours.
• Subsidence Inversion
• High Pressure region subsides onto air below,
  compressing and heating it.
• Lasts up to several days.

Radiative Inversion
T
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Atmospheric Temperature
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Atmospheric Dispersion

• Polluted air tends to be hot, initially.
• As it rises, it tends to cool and disperse.
• Turbulence due to vertical and horizontal
  instabilities speed up dispersion, until the
  pollution is well mixed.
• Dilution is the solution to pollution!
• Tall stacks designed to increase dispersion.

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Pollution Concentrations

• Pollution levels are measured in either PPM
  (parts per million) or in ?g/m3.
• 1 mole of anything contains NA 6.02 x 1023
  particles.
• 1 mole of gas at STP occupies 0.0224 m3 .
• The particle density is then 2.69 x 1025
  particles per m3.
• A pollutant concentration of 1 ppm tells us that
  for every 1 MILLION of those particles, ONE of
  them is the pollutant.
• It means that in 1 m3, 2.69 x 1019 molecules of
  pollutant are present.
• To convert to ?g/m3, we just need to know the
  mass per mole

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6 Criteria Pollutants

• The federal EPA has identified 6 critical
  pollutants which are monitored nationwide.
• CO, SOx, O3 (VOCs), NOx, Pb, Particulates
  (PM10).
• NAAQS National Ambient Air Quality Standards.
• These standards set limits on allowable
  concentrations over time periods from 1 hour to a
  year.
• http//www.epa.gov/airs/criteria.html

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The EPA website

• http//www.epa.gov/oar/aqtrnd97/brochure/sixprin.h
  tml
• The trend is positive, however
• 107 million Americans live in counties in
  violation of one of the standardsthats about
  40!
• Illinois, Indiana are in the top three for
  emissions of particulates, SO and NO.

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Other areas of concern

• Acid Rain
• Visibility
• Global warming
• Stratospheric Ozone depletion
• Radioactive wastes