METEOROLOGY

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METEOROLOGY

• GEL-1370

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Chapter Twelve

• Air Pollution

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What we are going to learn?

• We are going to learn the answers to the
  following questions
• What are the major sources of pollution?
• What are primary and secondary pollutants?
• Why does PM-10 pose the greatest risk to human
  health?
• Health problems associated with CO, SO2, VOCs,
  NOx?
• What is Smog? London-type and Los Angeles-type
  smog?
• Stratospheric vs tropospheric zone which is
  beneficial?
• What is PSI scale?
• How does atmospheric stability influence the
  accumulation of air pollutants?

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Historical Background of air pollution

• Major sources of pollutants car exhaust,
  chimneys, power plants, factories, forest fires
  other anthropogenic activities
• 1/6th of world population in urban areas
  continuously exposed to health hazards from air
  pollutants
• Air pollution is as old as the invention of fire
  smoke problem
• King Edward I (1273) Declared a proclamation to
  stop using sea coal, a dirty form of coal (soot
  and SO2)
• 1850s London had serious pea-soup fog, a thick
  mixture of smoke and fog that hung over the city
• 1873 700 people died due to these fogs
• 1911 1150 people in London died of smog
  (combination of smoke and fog)
• 1952 Major smog lasting for 5 days leading to
  4000 peoples death
• 1956 Passage of Clean Air Act in London

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History of Air Pollution

• In US, industrial revolution brought air
  pollution
• By 1940s Air in some cities was polluted that
  the auto-mobile headlights had to be turned on
  during the day
• 1948 Donora (PA), industrial pollutants got
  trapped in the Monongahela River valley, gt20
  people died, thousands became ill
• 1960s Air pollution levels dangerously high in
  NY city
• In LA, heavy smog due to large petroleum-processin
  g plants automobiles first alert toward the
  end of WW-II
• 1970 Clean Air Act was passed emission
  standards were set
• 1977, 1990 Clean Air Act was updated (stricter
  emission standards incentives to encourage
  companies to lower emission standards)
• Amendments to the Act identified 189 toxic air
  pollutants

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Easterly winds blow smoke from many large fires
over a vast area of Southern Africa
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Sources of Air pollutants

• Air pollutants Airborne substances, either
  solid, liquid, or gases, that occur in high conc.
  Threatening the health of people, animals,
  vegetation and structures
• Natural Sources of pollutants Dust and soot from
  earths surface (forest fires), volcanic eruption
  releasing tons of ash and dust into the
  atmosphere
• Anthropogenic Pollutants
• Fixed sources Homes, office buildings,
  industrial complexes, power plants, etc
• Mobile sources Motor vehicles, ships, jet
  aircraft, etc.
• Primary Pollutants Enter atmosphere directly
  (from smokestacks and tail pipes)
• Secondary Pollutants Formed when a chemical
  reaction occurs between a primary pollutant and
  some other component of air, such as water vapor
  or another pollutant

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Some of the sources of Primary pollutants
Sources Pollutants
Natural Volcanic eruptions Forest fires Dust storm Ocean waves Vegetation Hot springs Particle (dust, ash), gases (SO2, CO2) Smoke, unburned hydrocarbons (CO2, NOx, ash) Suspended particulate matter Salt particles Hydrocarbons (VOCs), pollen Sulfurous gases
Human caused Industrial Personal Paper mills Power Plants coal oil Refineries Manufacturing-H2SO4 PO4 fertilizer Iron steel mills Automobiles, fireplaces, home furnaces, Particulate matter, sulfur oxides Ash, sulfur oxides, nitrogen oxides Sulfur oxides, nitrogen oxides, CO Hydrocarbons, sulfur oxides, CO SO2, SO3 and H2SO4 Particulate matter, gaseous fluoride Gaseous resin CO, NOx, VOCs, particulate matter

• .

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of the primary pollutants in US
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Primary sources of air pollutants in US
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Denver (CO) on a clear day
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Denver (CO) on a day when particulate matter and
other pollutants reduce the visibility
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Aerosols suspended particulate matter

• Aerosols A group of solid particles and liquid
  droplets that remain in suspension in the air
  usually not poisonous more substances include
  asbestos, fibers, arsenic, droplets of H2SO4,
  PCBs, oil, pesticides
• Some particulate matter containing Pb, Ni, Cu,
  etc can affect respiratory system make breathing
  difficult, particularly for those suffering from
  chronic respiratory disorders
• High accumulation of Pb in bones and soft tissues
  can cause brain damage, convulsion, and death at
  low concentrations, dangerous to fetuses, infants
  and children when exposed may suffer central
  nervous system damage
• PM-10 Fine particulate matter lt 10 mm diameter
• gt 10 mm SPM settle in lt 1-day lt 1 mm remain in
  air for several weeks

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Suspended particulate matter contd.

• Total SPM emitted over US 6.6 million tons 40
  emitted from industrial processes highway
  vehicles 17
• Arctic Haze Sooty particles formed over the
  arctic during late winter and early spring
• These find SPM serves as nuclei for cloud
  droplets ice crystals when the particles are
  in 0.1-1.0 mm size, haze particles effectively
  scatter incoming sunlight
• CO A major pollutant of city air odorless,
  poisonous gas formed during the incomplete
  combustion of carbon containing fuels most
  abundant primary pollutant
• Over 60 million metric tons/yr of CO enter the
  air in US CO levels have decreased by 40 since
  early 1970s
• CO is quickly removed from the atmosphere by
  microorganisms in the soil human hemoglobin
  prefers CO to oxygen, so if CO is present, brain
  will starve of oxygen leading to headache,
  fatigue, drowsiness, and even death may result

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SO2 VOCs

• Sulfur dioxide sources burning of sulfur
  containing fossil fuels (coal oil) primary
  source includes power plants, heating devices,
  smelters, petroleum refineries paper mills
  volcanic eruptions and sulfate particles from
  ocean spray other major sources
• Inhalation of high concentrations aggravate
  respiratory problems, such as asthma, bronchitis
  emphysema
• VOCs Organic compounds that are mainly
  hydrocarbons individual organic compounds
  composed of hydrogen and carbon occur as solids,
  liquids and gases at room temperature
• Methane is the most abundant Other VOCs include
  benzene, formaldehyde some chlorofluorocarbons

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VOCs NOX

• 18 million metric tons of VOCS emitted into the
  air in US 34 from vehicles used for
  transportation 50 from industrial processes
• Certain VOCs are carcinogens (cancer-causing
  agents) benzene, benzo-a-pyrene (a product of
  burning wood, tobacco barbecuing)
• Many VOCs are harmless, but combining with
  nitrogen oxides in the presence of sunlight to
  produce secondary pollutants that are harmful to
  human health
• NOX Oxides of Nitrogen, primarily Nitrogen oxide
  (NO2) and Nitric Oxide (NO) forms when some of
  the nitrogen in the air reacts with oxygen during
  the high-temperature combustion of fuel

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NOX Ozone

• NOx are produced by natural bacteria
  concentration in urban area is 10-100 times
  greater than nonurban areas
• In moist air, nitrogen dioxide reacts with water
  vapor to form nitric acid --- acid rain
• Sources of NOx motor vehicles, power plants, and
  waste disposal systems
• Problems Contribute to heart lung problems,
  lowering bodys resistance to respiratory
  infections may encourage the spread of cancer
  NOx are highly reactive gases plays a key role
  in producing O3 in the air
• Ozone (O3) Noxious substance with unpleasant
  odor
• Smog means smoke fog used to refer smog that
  forms in large cities (e.g., LA)

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Smog

• Photo-chemical smog (or LA smog) Smog formed by
  the chemical reactions in the presence of
  sunlight
• London-type smog When smog is composed of
  sufurous and foggy air
• Ozone forms naturally in the stratosphere through
  the combination of molecular oxygen and atomic
  oxygen stratospheric ozone provides a protective
  shield against suns harmful UV rays
• Tropospheric ozone Near the surface, in polluted
  air, ozone is formed from a complex series of
  chemical reactions (with sunlight) involving
  pollutants, such as NOx and VOCs normally higher
  during the afternoons and during the summer months

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Ozone

• Problems with ozone Irritates eyes mucous
  membranes of the respiratory system, aggravating
  chronic diseases, such as asthma and bronchitis
  exposure to low concentrations for 6-7 hrs during
  periods of moderate exercise can significantly
  reduce lung function other symptoms include
  chest pain, nausea, coughing, and pulmonary
  congestion
• Ozone Production Sunlight (lt 410 nm) breaks down
  NO2 into NO and atomic oxygen
• NO2 Solar Radiation -------- NO O
• O2 O M -------- O3 M (M third molecule)
• Ozone is destroyed by combining with nitric oxide
• O3 NO ----------- NO2 O2

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Average (2-yrs, 6 cities) hourly concentrations
of Ozone
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Ozone contd.

• Certain VOCs in polluted air allow ozone conc. to
  increase by preventing nitric oxide from
  destroying the ozone as rapidly as it forms
• VOCs react with oxygen and nitrogen dioxide to
  produce other desirable contaminants (such as
  peroxy-acetyl nitrate)--- harmful to vegetation
  irritates eyes
• Ozone production should decrease in most areas
  when emissions of NOx and VOCs are reduced
• Ozone is most dense at 25 km from earth surface
  at this altitude, 12 ozone molecules/million air
  molecules (12 ppm)
• UV radiation lt 300 nm has enough energy to cause
  cancer
• Decrease of ozone in the upper atmosphere leads
  to the following a) Increase in the number of
  cases of skin cancer eye cataracts and sun
  burning b) suppression of human immune system
  c) decrease in the ocean productivity d)
  cooling of the stratosphere changes in
  stratospheric wind pattern

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Average distribution of ozone above the earths
surface in the middle latitude
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Ozone - contd

• Nitrous oxide from fertilizers
  chlorofluorocarbons (CFCs) - drifting to the
  atmosphere through the breaks in the tropopause
  in the vicinity of jet streams during
  thunderstorms penetrating into the lower
  stratosphere
• One single chlorine atom released from CFCs
  removes as many as 100,000 ozone molecules before
  it is removed by combining with other substances
• Average lifetime of a CFC molecule 50-100 yrs
• After 1987 Montreal Protocol, 1 decrease in the
  total concentrations of ozone destroying chlorine
  bromine compounds
• gt5 billion kg of CFCs have been released into the
  troposphere
• Ozone layer thinned by 3 during the summer from
  1979-1991 over heavily populated areas of the
  Northern Hemisphere

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Ozone molecule adsorbing UV radiation
dissociates into molecular and atomic oxygen
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Ozone contd.

• Ozone levels dropped to record low levels over
  much of the globe mainly due to
  ozone-destroying chemicals and from the 1991
  Mt.Pinatubo volcanic eruption (tons of sulfur
  dioxide gas into the atmosphere, formation of
  H2SO4)
• Ozone Hole Sharp drop in the stratrospheric
  ozone level observed over the Antarctic during
  the spring
• Clean Air Act of 1970 Since then, most of the
  pollutant levels have fallen off substantially
  many amendments thereafter 198 million autos on
  the road in a day
• Primary ambient air quality standards are set to
  protect human health and secondary standards to
  protect human welfare
• Nonattainment Areas Areas that do not meet air
  quality standards (80 million Americans are
  breathing air that does not meet at least one of
  the standards)

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Emission estimates of six pollutants in the US
from 1940-1995
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Pollutant Standard Index

• Pollutant Standards Index (PSI) Measure of air
  quality in a particular region the highest value
  in one day is used pollutant (CO, SO2, NO2, O3,
  SPM) measurement is converted to a number that
  ranges from 0 to 500
• Pollutant value primary ambient air quality
  standard, then, the pollutant is assigned PSI
  number 100 gt100 unhealthful 50-100 moderate
  lt 50 Good
• Total emissions of toxic chemicals spewed out
  into the skies over US declined steadily since
  EPA began the inventory of chemicals

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Number of unhealthful days (by county) when PSI
gt100 (any of CO, SO2, NO2, O3 SPM)
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Factors that affect air pollution

• Role of wind in diluting the pollutants
• Most pollution occurs when the winds are light,
  skies are clear, mixing is shallow, atmosphere is
  stable and a strong inversion exists
• Urban areas are more polluted than the rural
  areas
• Urban areas tend to be warmer than urban areas
• Acid rain is a major problem
• Stability of atmosphere is determined by the way
  air temperature changes with height

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Smoke from the shorter stack is trapped within
the inversion while smoke from taller stack,
above inversion, rises and mixes
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Stability and Inversions

• An inversion (temp decreases slowly as we ascend
  or increases with height) represents extremely
  stable atmosphere where warm air lies over the
  cold air lid on the vertical motion
• Pollutants from a shorter stack does not rise
  very high, but spreads out, contaminating the
  area while longer stacks release and the
  pollutants get mixed well and travel farther
  distances (dilution is the solution to the
  pollution!)

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As vertical temp profile changes, the pattern of
emitted smoke also changes
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Inversion layer preventing the escape of
pollutants
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Thick layer of polluted air trapped in the valley
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Cold air pollutants drain downhill and settle in
the low-lying area
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A weak country breeze carries pollutants from the
outskirts into the city
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pH Scale
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Chapter Summary

• Smoke in London, CA
• CO, NOx, SPM, how CO affect our body
• Volcano source of what contaminant
• VOC, photochemical smog
• Primary and secondary pollutants
• Acid rain, pH of rain water
• Mixing depth
• PSI-scale
• Aerosols, VOCs, carcinogens, ozone, sulfur
  dioxide