Air Pollutants

1
Air Pollutants

• Substances that are present in air at
  concentrations sufficient to cause harm to
  humans, other life-forms, vegetation, and/or
  materials

2
Atmosphere is divided into regions based on
changes in temperature. Pollution is concerned
with troposphere and stratosphere (99.9 of mass
of atmosphere)
Cunningham/Saigo, Environmental Science,
6th,McGraw-Hilll, NY, 2001, 376
3
Layers of the Earths Atmosphere
http//telstar.ote.cmu.edu/environ/m3/s2/03earthat
mos.shtml
4
http//www.geog.ouc.bc.ca/physgeog/contents/7a.htm
l
5
Types of Pollutants

• Primary pollutants - those emitted directly into
  the atmosphere CO, CO2, NO2, SO2, VOC (volatile
  organic compound), PM (particulate matter) - most
  come from use of fossil fuels
• Secondary pollutant - formed in the air as a
  result of reactions with primary O3
• Tertiary pollutant - formed in the air as a
  result of reactions with secondary aldehydes

6
Carbon Monoxide

• Anthropologic sources combustion of fossil fuels
  especially for transportation - burning gasoline
  in limited amount of air produces CO rather than
  CO2
• 2 C8H18 17 O2 18 H2O 16 CO
• Adverse effect CO binds to iron in hemoglobin to
  hinder transport of oxygen to cells

7
CO Contd

• Laws Clean Air Act (1970) and amendments (1990)
  defined standards for lowering CO emissions of
  cars
• Remediation technology CO output of cars is
  reduced by the catalytic converter that uses
  Pt/Pd to catalyze the reaction
• 2 CO O2 2 CO2

8
Catalytic Converter
Pt/Pd catalyst converts 96 of CO to CO2
http//www.air-quality.org.uk/images/25a.jpg
9
Particulate Matter

• Particulate matter - solid or liquid particles of
  greater than molecular size
• Large particles are visible as dust and smoke
  while small particles of 1 ?m (called aerosols)
  are invisible
• Particulate size indicated by a subscript such as
  PM10 for 10 microns or micrometers

10
Sizes of Particulate Matter
Stoker/Saeger, Environmental Chemistry, 2nd,
Scott, 1976, 90
11
Visible PM
Hill/Kolb, Chemistry for Changing Times, 7th,
Prentice Hall, NJ,1995, 347
12
Adverse Effects of PM

• Anthropogenic source incomplete burning of a
  fossil fuel producing particles of carbon. Also
  minerals that do not burn but form small
  particles that are carried out in smoke as fly
  ash
• Adverse effects PM5 filtered by nasal passage
  but smaller are deposited in lungs where could
  cause damage

13
Adverse Effects of PM (contd)

• Particles may carry substances on surface that
  cause damage to lungs
• Particles may be toxic themselves such as
  particles of Be, Ni, Cd, Sn, Sb, Pb, Bi, and Hg
• Particles may block natural expulsion of other
  toxic substances from lungs

14

• Laws Clean Air Act (1970) and amendments (1990)
  defined standards for lowering PM emissions
• Remediation technologies Electrostatic
  precipitation and bag filtration

15
Removal of PM from Effluents
Remove 98 of particles but not
Electrostatic Precipitator
Bag Filtration
Buell/Girard, Chemistry, Prentice Hall, NJ, 1994,
410
16
Sulfur Oxides

• Anthropologic sources production of electricity
  by burning coal mined in Eastern US that contains
  3 S
• S burns to produce SO2 S O2 SO2
• Further air oxidation produces SO3
• 2 SO2 O2 2 SO3
• SO3 ultimately produces sulfuric acid
• SO3 H2O H2 SO4

17
Adverse effects London Smog

• Smog is the combination of the words, smoke and
  fog
• When smog is produced by burning of coal (C and
  3 S and minerals) it is called London or
  Industrial Smog
• Named after city of London where in a 5 day
  period in December of 1952 it contributed to
  deaths of 8000 people

18
Adverse Effects of London Smog

• PM, sulfur oxides and sulfuric acid can cause
  severe lung damage
• The alveoli lose their resilience making it
  difficult to expel the CO2 - leads to emphysema,
  which can be fatal
• Sulfur compounds also damage plants, farm crops
  and produce acid rain

19
SO2 Contd

• Law Clean Air Act (1970) and amendments (1990)
  defined standards for lowering SO2 emissions of
  power plants to 10 M tons/yr by 2000. Each plant
  has emissions allowance and can sell unused
  portions.
• Remediation technologies switch to low S coal
  (expensive and negative impact on coal mining in
  Ohio and WV) or install efficient scrubbers

20
Removal of SO2 from Effluent Stream
Allowed developed countries to cut SO2 emissions
30-50 but developing countries have doubled
their output.
Limestone and lime must be added continuously
The waste CaSO3 must be disposed of in a landfill
Chang, Chemistry, 5th, McGraw Hill, NY, 1994, 727
21
Volatile Organic Substances (VOC)

• Anthropogenic sources escape of gasoline (a
  mixture of hydrocarbons represented by HC) when
  gas is pumped, during filling of storage tanks at
  gas stations, and as unburned gas in automobile
  exhaust
• Adverse effect tertiary pollutants (see
  photochemical smog)

22
Nitrogen Oxides

• Anthropogenic source union of nitrogen and
  oxygen from air at high temperatures either in
  car engine or power plant
• N2 O2 ? 2 NO (colorless gas)
• NO reacts spontaneously with O2
• 2 NO O2 ? 2 NO2 (dark brown gas)

23
Downtown LA on a Smoggy Day
Hill/Kolb, Chemistry for Changing Times, 7th,
Prentice Hall, NJ,1995, 352
24
Secondary and Tertiary Pollutants in LA Smog

• Sunlight causes the production of ozone
• Ozone reacts with hydrocarbons in air (VOC) to
  produce aldehydes (tertiary pollutants - formed
  by reactions of secondary pollutants)
• Hydrocarbons also react with NO2 and O2 to
  produce peroxyacetylnitrates (PAN) CH3COO-ONO2

25
Formation of Photochemical Smog
Hill/Kolb, Chemistry for Changing Times, 7th,
Prentice Hall, NJ,1995, 354
26
Conc.of Air Pollutants vs Time in Los Angeles
Chang, Chemistry, 5th, McGraw Hill, NY, 1994, 729
27
Adverse Effects of Photochemical Smog

• Aldehydes and PAN are severe eye and lung
  irritants
• Ozone is capable of impairing the elasticity of
  lungs causing death if sufficient exposure
• PAN is sufficiently stable that it is carried by
  wind for up to 100 miles before it decomposes and
  pollutes

28
Effect of Ozone on Elastomers
Ozone breaks the double bond between carbon atoms
in elastomers such as rubber causing tires to
lose elasticity and to crack
Chang, Chemistry, 5th, McGraw Hill, NY, 1994, 727
29
Remediation Technology Catalytic Converter
Pt/Pd catalyst converts 98 of HC to CO2 H2O
and Rh catalyst converts 95 of NOx to N2 O2
http//www.air-quality.org.uk/images/25a.jpg
30
Acid Rain

• Acid rain results from the use of fossil fuels
  for production of electricity and/or for
  transportation

31
Acidity of Pure Water
http//gcsechemistry.com/aa8.htm
32
Acidity of Aqueous Solutions

• Acidity refers to H of a solution
• Acidity of solution is defined relative to H
  of water, 1.0 x 10-7 M
• Acidic H 1.0 x 10-7 M
• Neutral H 1.0 x 10-7 M (Water)
• Basic H

33
Acidity Expressed as pH

• pH is a logarithmic scale for expressing acidity
  of a solution
• pH - log10 H
• Acidic pH
• Neutral pH 7
• Basic pH 7

34
H
H 10 - pH
Tro, page 327
35
Acid Rain

• Natural rainwater has a pH 5.6 due to reaction
  of carbon dioxide (acid anhydride) with water in
  air
• CO2 H2O ? H2CO3 ? H HCO3 -
• Acid rain is rain that has a pH more acidic than natural rain
• Two sources of acid rain natural (volcanoes and
  lightning) and anthropogenic (human activities)

36
pH of some common substances
37
Source of Rain Containing Sulfuric Acid, H2 SO4

• Power plant using coal containing S is an
  anthropogenic source of acid rain
• S O2 ? SO2
• SO2 OH ? HOSO2
• From solar photolysis H2O ? H OH
• HOSO2 O2 ? SO3 HO2
• SO3 H2O ? H2 SO4 (acid rain)

38
Sources of Rain Containing Nitric Acid, HNO3

• Power plants or car engines are anthropogenic
  sources of HNO3
• Produce high temperatures which cause reaction of
  nitrogen and oxygen
• N2 O2 ? 2 NO (colorless gas)
• 2 NO O2 ? 2 NO2 (dark brown gas)
• NO2 OH ? HNO3 (acid rain)

39
Formation of Acid Rain
http//www4.ncsu.edu/vpaneja/images/gpc.jpg
40
Annual emissions of gases causing acid rain
Schwartz et al, Chemistry in Context, ACS, DC,
1994, 163
41
Anthropogenic Sources of Acid Rain
Hill/Petrucci, General Chemistry, Prentice Hall,
NJ, 1996, 546
42
pH of Rainfall
Buell/Girard, Chemistry, Prentice Hall, NJ, 1994,
230
43
Effects of Acid Rain on Soil

• Soil containing limestone is protected by the
  reaction
• CaCO3 H ? Ca2 HCO3 -
• Soil not containing limestone, acid reacts with
  clay (Al2Si2O5(OH)4 ) to free Al3 which can kill
  trees and fish
• Al2Si2O5(OH)4 6 H ? 2 Al3 2 SiO2 5 H2O

44
Buell/Girard, Chemistry, Prentice Hall, NJ, 1994,
232
45
Dissolving of Soil Components by Acid Rain
http//www.geog.ouc.bc.ca/physgeog/contents/table.
html
46
Adverse Effect of Acid Rain on Trees
Raven et al, Environment, Saunders, NY, 1995, 449
47
Adverse Effect of Acid Rain on Trees in Blue
Ridge Mountains, NC
Buell/Girard, Chemistry, Prentice Hall, NJ, 1994,
232
48
Adverse effect of acid rain on fish in Lake
Michigan
Schwartz et al, Chemistry in Context, ACS, DC,
1994, 171
49
Adverse effects of Acid Rain on materials
Acid dissolves marble
CaCO3 H ? Ca2 HCO3 -
Shown is a tomb-stone that was carved in 1817 in
England
Raven et al, Environment, Saunders, NY, 1995, 450
50
Remediation Technology for Acid Rain
Application of Agricultural Limestone to Soil
CaCO3 H ? Ca2 HCO3 -
Chang, Chemistry, 5th, McGraw Hill, NY, 1994, 727
51
Remediation Technology for Acid Rain
Liming an Acid Lake in Sweden
CaO H Ca2 H2O
Stanitski et al, Chemistry in Context, 3rd, ACS,
DC, 2000, 251
52
Buell/Girard, Chemistry Fundamentals, 2nd,
Jones/Bartlett, MA, 350
53
Laws on Acid Rain

• Congress created the Acid Rain Program in Title
  IV of the 1990 Clean Air Act Amendments. The Acid
  Rain Program has the goals of lowering the
  electric power industrys annual emissions of
• Sulfur dioxide (SO2) to half of 1980 levels,
  capping them at 8.95 million tons starting in
  2010, and

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• Nitrogen oxide (NOX) to 2 million tons lower than
  the forecasted level for 2000, reducing annual
  emissions to a level of 6.1 million tons in 2000.
• In 2003, Acid Rain Program emission controls on
  the electric power industry resulted in? SO2
  emissions of 10.6 million tons, a reduction of 38
  percent from 1980 levels.

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Trends in SO2 Emissions
http//www.epa.gov/airmarkets/cmprpt/arp03/so2_emi
ssions_reductions.gif
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Trends in NOx Emissions
http//www.epa.gov/airmarkets/cmprpt/arp03/nox_emi
ssions_reductions.gif
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• NOX emissions of 4.2 million tons, which were
  close to 4 million tons less than the emissions
  forecasted for 2000