Atmospheric Pollutants

1
Atmospheric Pollutants

• Chapter 2
• Part 1

2
Air Pollution - Objectives

• Up to now, weve been discussing air quality,
  that is, what are some of the issues that make
  air acceptable to breathe.
• Now, we will take a look at air pollutants
• First, well examine the overall sources
  anthropogenic and natural
• Next, well examine the physical types of
  pollutants and,
• Last, well look at individual pollutants and
  their characteristics (Part II)

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What is Air Pollution?

• It must have something to do with a contamination
  of the atmospheric environment.
• Addition of a foreign substance
• A change in the normal concentration of
  atmospheric gases
• Does the contamination have to cause harm to
  something?

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Definition of air pollutants

• Air pollution may be defined as the presence in
  the atmosphere of substance(s) added directly or
  indirectly in such amounts as to affect living
  and non-living things adversely.
• What is classified as a pollutant therefore
  depends upon recognition of which substances
  cause adverse effects. It is an ever-changing
  definition.
• Centuries ago only soot or smelly gases may have
  been considered air pollutant. Now we recognize
  that pollutants can cause more subtle effects
  than producing unpleasant smells. Even CO2 is
  now considered a pollutant.

Air Pollution ?
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Common air pollutants

• Particulate matter
• PM10, particulate matter of size
• PM2.5, particulate matter of size
• Gaseous pollutants
• Primary gaseous pollutants SOx, NOx, CO,
  volatile organic compound (VOC), Pb
• Secondary gaseous pollutants peroxyacetylnitrate
  (PAN), ozone (O3)
• Photochemical pollutants
• VOC, O3, PAN, CFC, greenhouse gases (CO2, H2O)

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Air Contaminates

• Air contaminants include smoke, vapors, charred
  paper, dust, soot, grime, carbon fumes, gases,
  mist, odors, particulate matter, radioactive
  materials, or noxious chemicals, or any other
  material in the atmosphere.

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Natural Air Pollution

• Virtually all air pollution control techniques
  focus on anthropogenic air pollution.
• It is incorrect to assume that natural pollution
  is insignificant in some cases they are much
  more devastating
• Often, natural air pollution is not only of
  regional concern, but of global concern
• Nature Pollutes More Than Man!

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Natural Air Pollution

• Can you name some sources of natural air
  pollution?

Mexico City
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Volcanoes
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Forest Fires
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Dust Storms
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Electrical Storms
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Miscellaneous Natural Air Pollutants
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Anthropogenic Air Pollution

• Since, in most cases, man can do little to
  mitigate natural air pollution sources, the focus
  of air quality has been exclusively on
  anthropogenic sources of air pollution.
• Historically, since fire was first discovered,
  man-made air pollution was also born.
• As coal became a chief fuel source (14th century)
  coal by-products became the major air pollutant.

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Anthropogenic Air Pollution

• The industrial revolution of the 19th and early
  20th centuries ushered in the air pollution
  problems we still face today.
• The pioneers of industrial medicine (Ramazzini,
  Pott, Paracelsus, et al) recognized and reported
  on the hazards of contaminated air.

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Size Scales of Air Pollution

• Local (up to city/state)
• Urban Smog Personal Occupational Indoor air
  pollution
• Regional (state/continental)
• Acid deposition (rain) Regional smog transport
• Global (planetary)
• Global climate change Stratospheric ozone
  depletion

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SummaryAir pollutants sources and properties

• Natural pollutant sources
• Volcano eruption emitting smoke, particulate
  matter, SO2, H2S, CH4
• Fires emitting smoke, unburnt hydrocarbons, CO,
  CO2, NOx...
• Dust or sand storms dispersing dust
• Oceans are emitting corrosive salt aerosols
• Lightning produces NOx and O3
• Normal human respiration produces CO2
• Artificial or anthropogenic sources
• Stationary sources combustion, fuel usage, waste
  incineration, industrial processes
• Mobile sources all emissions and exhausts from
  transportation

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Issues
Pollution Control
Physical Science
Politics, Sociology, Economics
Public Health
Engineering, Technology
Meteorology, dispersion Climate change Chemistry
(acids, ozone, smog)
Regulation Lifestyle changes Costs of Regulation
Effects of Pollution Risk Assessment
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Smog
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Smog

• The term was originally meant to describe London
  coal emissions mixed with their famous fog from
  the North Sea (Smoke Fog Smog).
• Smog now refers merely to severe ambient air
  pollution conditions.
• Primarily, we think of smog as pollution that
  causes reduced visibility regardless of which
  pollutants are present

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London Smog
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Smog Los Angeles

• The best known smog problem in the U.S. (by far)
  is associated with Los Angeles, CA. Several
  factors contribute to LAs smog problem
• In the LA basin, a near permanent high pressure
  condition exists along the coast (leading to
  inversions) and mountains to the East prevent
  horizontal dispersion.
• LA residents are drivers over 6 million cars
  are driven daily.
• Abundant sunlight
• These factors produce an unhealthy, complex
  mixture of photochemical smog

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LA Smog
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St. Louis Smog
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Gases and Particles

• Represent all 3 phases of matter
• Solid
• Liquid
• Gas

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Gases and Particles

• When solid and liquid particles are dispersed in
  air we refer to this as an Aerosol
• Aerosols reduce visibility, dirty
  buildings/statues etc., and adversely affect
  human health

TEM of Cu Particles
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Types of Aerosols

• Fumes
• Condensation of various metal vapors in air
• Dusts
• Mechanical fragmentation of various matter
• Mists
• Atomization of liquids or condensation of vapors
• Smoke
• Incomplete combustion of organic matter

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What Are Pollution Sinks????
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Air Pollution Sinks

• Sink The removal of air pollutants from the air
  can be anthropogenic, dispersion, chemical
  reactions, or deposition/fall-out

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Sinks - Dispersion

• When pollutants are emitted into clean air, the
  clean and polluted air mix, diluting the
  contaminants.
• Over time, air movement (such as from wind) can
  dilute the pollution enough so that it will not
  be harmful to life

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Sinks Chemical Reactions

• When gases react, other substances are produced.
• The original pollutant(s) then disappear.
• It may be that the products of the reaction are
  also pollutants, so a chemical reaction could be
  a source of one or more pollutants while it is a
  sink for one or more other pollutants.

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Sinks Deposition and Fallout

• Solid aerosol particles eventually settle out of
  the atmosphere due to gravity.
• This category also includes the impaction of
  aerosols and gas molecules onto solid surfaces
  near the ground (the particles or gas molecules
  collide with the solid object and stick to the
  object).
• This is known as "deposition".
• Where have we heard this term?

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Sinks Anthropogenic Removal

• In this case, humans are responsible for removing
  the pollutants from the air.
• These are essentially the three processes already
  noted, but enhanced by humans.
• For example electrostatic precipitation - where
  electrostatic charges are placed on pollution
  particles and attracted to an oppositely charged
  collector.

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Pollutant Sources

• Primary pollutants directly emitted into the
  atmosphere
• Secondary pollutants formed in the atmosphere
  from primary emissions (e.g., photochemical smog,
  ozone)

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Primary Pollutant Sources

• A)
• Mobile (cars, trucks, planes, trains)
• Stationary (coal-fired power plant)
• B)
• Combustion (smoke stack)
• Non-combustion (vapors from chemical process)
• C)
• Area (an industrial park, or a city)
• Point (smoke stack, exhaust pipe)
• D)
• Direct (open burning)
• Indirect (baseball park which attracts cars)

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National Emissions
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National Emissions

• From 1970 to 1993, emissions of 5 primary
  pollutants (CO, Particulate matter, Hydrocarbons,
  NOx, SO2) increased in 3 source categories and
  decreased in 2 source categories
• 1970 1993
• Transportation 54.7 56.2
• Stationary Fuel 19.3 22.5
• Industrial processes 16.8 11.7
• Solid Waste Disposal 4.5 2.6
• Miscellaneous 4.5 6.9

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National Emissions

• Emission reductions from industrial processes and
  solid waste disposal have been significant.
• They are a reflection of regulatory action taken
  toward these source categories.
• Unfortunately, extensive regulatory action toward
  the transportation source category has not been
  as successful.

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Lead Emissions

• Lead emissions reduction is a success story
• 1970 1993 Reduction
• Transportation 180.3 1.59 99.2
• Stationary Fuel 10.62 0.50 95.3
• Industrial processes 26.40 2.28 91.4
• Solid Waste Disposal 2.20 0.52 76.4
• Total 219.47 4.89 97.8
• From USEPA 1994 Estimates of National Lead
  Emissions, 1970 and 1993 (103 short ton/year)

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Which Sources are Most Responsible for Emissions?

• Transportation
• Stationary Source Fuel Consumption
• Industrial Processes
• Solid Waste Disposal
• Miscellaneous

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Concentration Expression

• In the U.S., we express concentrations of
  atmospheric gases and vapors as a mixing ratio
  and is typically reported as parts per million
  volume
• 1ppmv 1 gas volume
• 106 air volumes

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Nature of Pollutants

• Automobile exhaust alone contains more than 400
  different gaseous components
• The ambient atmosphere may be contaminated with
  hundreds of pollutants however, only a
  relatively small number have been identified to
  be at a significant enough level to pose a human
  health threat.
• Over the rest of this presentation and the next,
  we will examine the more prominent ones

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Gases and Particles

• On a weight to weight basis, approximately 90 of
  man-made air pollution are gases.

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Next Section

• We will discuss specific pollutants in the next
  section of Chapter 2
• Read articles from the website regarding National
  Ambient Air Quality Standards