What is "Air"?

Air is a non-homogenous mixture of gases, solid particles, and liquids.

Air is characterized as an aerosol.

Gases and particles with small settling velocity that exhibit stability in a gravitational field.

Recall atmosphere layers

Troposphere 0-17 kilometers (¾ 11 miles)
Stratosphere 17-50
Mesosphere 50-90
Ionosphere 90-100

95% of the air by weight is contained in the Troposphere.


Nominal Composition

Major Components
(99%) in % by w or fraction of total molecules*
Component Percentage by Weight Fraction of Total Molcules
N2 75.51 0.7808
O2 23.14 0.2095
40Ar 1.28 0.0093
Water Vapor 0.0004
* Fractions of total molecules


Minor Components
Component ppm (parts per million**)
Carbon dioxide CO2 325.0
Ne 18.0
He 5.0
CH4 2.0
Kr 1.0
H2 0.5
N2O 0.5
Xe 0.1
** 325 ppm means that 325 of each 1 million particles is CO2


Outdoor Air Pollutants

Sources and Types:

  1. Carbon Oxides
    Carbon Monoxide (CO) & Carbon Dioxide (CO2)

  2. Sulfur Oxides
    Sulfur Dioxides (SO2) & Sulfur Trioxide (SO3)

  3. Nitrogen Oxides
    Nitric Oxide (NO), Nitrogen Dioxide (NO2), & Nitrous Oxide (N2O)

  4. Volatile Organic Compounds (VOCs)
    Most organic compounds - Example: Methane (CH4), Methanol (CH3OH), Benzene (C6H6), Chlorofluorocarbons (CFCs), formaldehyde (CH2O), Propane (C3H8).

  5. Suspended Particulate Matter (SPM)
    Solid and Liquid Particles both suspended in air. Example: dust soot, pollen, asbestos, ash, conglomerates, soil, salts, etc.

  6. Photochemical Oxidants
    Ozone (O3), Peroxide (H2O2), Hydroxide radicals (HO), aldehydes, etc. induced by electromagnetic energy from the Sun.

  7. Radioactive Isotopes
    Radon-222, Iodine-131, Strontium-90, Plutonium-239, Potassium-40, as gases and suspended particles.

  8. Heat
    Waste energy from fossil fuels; most energy sources and uses produce waste energy as heat, Example: cars, power plants, factories, homes.

  9. Noise
    A byproduct of energy used in airplanes, cars, industry, lawn mowers, mechanical byproduct, radios, wind, electrical power line discharge, communications (electromagnetic overlap and clutter in communications).

Primary Pollutants (Anthropogenic)

Secondary Pollutants

Partial Size Significance

Large Size Particles -
Defined as ¾ 10 micrometers (µm) in diameter.
Do not remain in suspension and settle from Troposphere in < 1 day

Medium Size Particles -
Defined as > 1 < 10 micrometers (µm) in diameter.
Remain in suspension for Several days

Fine Size Particles -
Defined as < 1 micrometer in diameter.
Remain in Troposphere for 1-2 weeks and in Stratosphere for 1-5 years
Generally these will be distributed over the entire earth


Outdoor Air Pollutants

Greenhouse Gas Emissions

Anthropogenic compositional alterations to the atmosphere:
From 1989 Compilation (from United Nations Reference)

Carbon Dioxide (C02)
Emissions from Industrial Processes
(Anthropogenic Sources)
Total Metric Tons Per Capita (Metric Tons)
World 21,863,088,000 4.21
By World Region :
Asia 5,812,064,000 1.93
North and Central America 5,760,830,000 13.60
Europe 4,347,794,000 8.74
USSR 3,804,001,000 13.30
Africa 647,352,000 1.03
South America 557,298,000 1.91
Oceannia (Australia, Fiji, etc.) 291,248,000 11.20


Methane CH4
Greenhouse Gas Emissions
from Anthropogenic Sources
Total Metric Tons
World 270,000,000
By World Region :
Asia 130,000,000
North and Central America 45,000,000
Europe 26,000,000
USSR 34,000,000
Africa 19,000,000
South America 18,000,000
Oceannia (Australia, Fiji, etc.) 6,200,000


Emissions of Chlorofluorocarbons (CFCs)
Total Metric Tons
World 580,000
By World Region :
Asia 140,000
North and Central America 150,000
Europe 180,000
USSR 67,000
Africa 16,000
South America 15,000
Oceannia (Australia, Fiji, etc.) 9,000
Ozone depletion is the main effect, remember on average
each Cl atom destroys 100,000 (105) O3 molecules.


Emissions of Other
Common Anthropogenic Pollutants
The U.S. for 1989 (In Metric Tons)
CO Particulates Hydrocarbons
60,900,000 6,900,000 18,500,000


Why is CO a pollutant? a hazard?

Notes on importance:

Carbon Monoxide (CO) permanently binds with the Fe in Hemoglobin and permanently destroys that group

Particulates contribute to Smog and Lung disorders including cancer, haze, etc.

Hydrocarbons are greenhouse gases, contribute to Smog, are potentially toxic, and contribute to Smog and Lung disorders, haze, etc.

Local or Global Pollution -

Why is particulate pollution usually, local and gaseous pollution usually, global?

Sulfur Dioxide (SO2) Emissions
1989 1980
North & Central Am. 20,700,000 23,900,000
Asia ? 1,263,000
Europe ~23,000,000 ?
USSR 9,318,000 12,800,000


Atmospheric Sources

Primary forms are SO2, H2S, in the gas phase and SO4-2 in the condensed phases. From the burning of sulfur containing fuels. From bacterial reduction of SO4-2to H2S and sulfur containing proteins. Natural sources are volcanoes which produce large quantities of SO2 and biological processes.

Notes on significance:

SO2 and NO2 (NOx) in the presence of water contribute to acid precipitation (acid rain) and photochemical smog. Acid Rain adversely effects agriculture, forests, aquatic habitats, and the weathering of building materials. SO2 and NO2 aerosols impair visibility.

SO2 concentrations as low as 0.1-0.2 ppm can incapacitate asthma or emphysema patients.

SO2 combines with water to form sulfuric acid H2SO4

Primary methods of preventing SO2 is removal of "S" compounds prior to combustion of carbon or hydrocarbon "desulfurization" of Coal or Fuel Oil.
Scrubbing (bubble through solution of calcium oxide CaO (lime) forming CaSO4


Nitrogen Dioxide (NO2) and
Nitrous Oxide (N2O)
Emisions
1989 1980
North & Central Am. 21,600,000 22,300,000
Asia 1,400,000 ?
Europe ~15,000,000 ?
USSR 4,190,000 ?


Principle source of NOx compounds is from combustion processes:

Then NO combines with O2 in air to convert NO to NO2 within a few hours under normal conditions.

All Oxides of nitrogen with water form nitric acid HNO3

Primary method of prevention is reduced temperature oxidation. The oxidation reaction


is very temperature dependent and is favored to the right at high temperatures.

Scrubbing with various bases can be used if the process permits.


Smog and Acid Deposition

Photochemical Smog is the interaction of electromagnetic radiation from the Sun and Primary Pollutants to form photochemical smog.

Sulfate particles are a major cause of haze and smog.


pH of rain is 5.0 to 5.6 due to CO2 and water interaction as previously described, recall carbonate equilibrium.

Average eastern US precipitation is 4.3 with pHs < 3 and 2.5.

What are the consequences of "Acid Rain"?

Effects may cross borders and thus are exported to other countries.


Indoor Air Pollution

This is the source of one of the most significant pollution exposures facing humans.

Duration of exposure
We spend 70 to 90% of our time indoors.

Intensity of exposure
Levels reach 10 to 40 times those of outdoor air concentrations.

Estimates of 6,000 excess cancer deaths each year (excluding radon) and 20,000 excess cancer deaths from Radon alone.

Industrial exposure is estimated by the author and EPA to be 100,000 to 200,000 premature deaths each year to workers from indoor air in industrial settings.

Specific indoor air problems


Relationships between


What is the "Sick Building Syndrome"?
Why does it exist?


Effect of Air Pollution on Living Organisms

Humans

Cumulative effect of all of these pollutants is:

Estimates:

Office of Technology Assessment estimates 50,000 premature deaths in US each year from respiratory or cardiac problems as result of air pollutants

American Lung Association estimates 120,000 US deaths each year from air pollution

EPA estimates air pollution costs $150 billion yearly in health care
$100 billion from indoor air pollution
$40 billion from automobiles

Plants

Chronic exposure to ozone, acid rain, sulfur, and nitrogen oxides may be most significant and synergistic.

Damage to leaves, roots, microorganisms (nitrogen fixing bacteria) etc. all weaken plant resistance to insects, frost, fungi, mosses, and disease.

Equilibration shifts in nutrients, aluminum ions, etc.

Aquatic Organisms Are Also At Risk

Acid precipitation is a major threat.

Low buffering capacity permits acid shock.

Why?

Hint: What is physiological pH and what does it control?

Aluminum soil leached by acid precipitation kills fish by interfering with gill oxygen exchange

Liming is a temporary fix.

> ~ 75,000 lakes or streams world wide have been acidified to a substantial loss of aquatic life or are stressed.


Air Pollution Control and Clean Air Act of 1977 as revised in 1990

Established national ambient air quality standards (NAAQS) for 7 outdoor pollutants:

Toxic Air Pollutants

A list of 600 toxic air pollutants was proposed

EPA has emission standards of 7 of the 600 toxic air pollutants:

Goals for CFCs, CO2, NOx, Auto emission Standards etc.


Methods of Pollution Control

Control of

Pollutants in general
Sulfur dioxide
Nitrogen oxides
Particulate matter emissions
Motor vehicle emissions
Troposphere ozone
Indoor air pollutants
+ 600 other pollutants (189 prime)


Prevention

Set limits, provide technology, provide incentive

Conservation of energy use in general and recycling and mass transit

Cleaner (low S fuel) and alternative Fuels and electric motors as alternative (batteries), Nuclear (fission, fusion?)

Modifying industrial plants and the engines for cleaner burning lower operating temperatures for NOx for example or collection devices in conjunction with reduced emission processes

Convert coal to gas first (eliminate particulate and S at same time)

Eliminating SO2 and NOx will reduce O3 in Troposphere from Photochemical reactions

Control Population?

Prevent indoor air pollutant buildup using air-to-air heat exchangers

Materials evaluation prior to use as building materials (indoor +) Methods of Pollution Control

Introduction of CaO (lime) into burning chamber for industrial burning

why?

To form Ca salts with SO4-2 and NO3- (chemical modification, neutralization & conversion to salts and products {gypsum CaSO4} {CaSO4 and H2O used in plaster and wall board}

Higher smoke stacks to get above the inversion layer reduce local particulate, smog and pollution but let it fall elsewhere

Capture particulate and some pollutants using Electrostatic Precipitators, Baghouse Filters, Cyclone Separators, Wet Scrubbers.

Chemical Modification - example NOx and HCNO (isocyanic acid converts 99% of NOx to N2 and water {not yet technically feasible commercially}.

"Rule of Thumb"
Cleanup vs. Prevention - Prevention is always cheaper in the long run.



Notes Table of Contents

Introduction to Environmental Science Home Page

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Revised 8/12/98.