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Introduction
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Introduction
• Air pollution may be described as contamination of theatmosphere by gaseous, liquid, solid wastes or by-products
that can endanger life, attack materials and reduce visibility.
• Air pollution worldwide is a threat to human health and the
natural environment.
• It may also be defined as the presence of matter in
atmosphere at concentrations, durations, and frequencies
that adversely affect human health and environment.
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Introduction
• Air pollution can be caused due to the burning of wood, coal,
oil, petrol, or by spraying pesticides.
• Some of the questions which might come to mind while
thinking about air pollution are:
– Are we doing something about solving these problems?
– Do we know enough about the conditions under which a pollution
episode occurs?
– What are the regulations?
– How to control emissions?
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Should we worry about Air Pollution?
• Air pollution affects every one of us.
• Air pollution can cause health problems and in an extreme
case even death.
•
Air pollution reduces crop yields and affects animal life.• Air pollution can damage monuments.
• Air pollution can cause significant economic losses.
• In short, air pollution does not only damage air; it also
damages environment on earth’s surface and theirinhabitants.
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History of Air Pollution in the US• The problems of air pollution in Los Angles, New York city, and
Chicago during the fifties drew attention of regulators in the United
States.
• Conventional pollutants due to auto emissions and smoke stacks
were the major thrusts of air pollution during the sixties and
seventies.• Invisible emissions of toxic pollutants were recognized in the late
seventies.
• In early eighties scientists observed a slow down in growth of red
spruce in the mountain areas of north-eastern US as a result of acid
rain.
• In early nineties standards for ozone air pollution and sulfur dioxide
has been revised
• In late nineties standard for particulate matter pollution was
strengthened.
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History of Air Pollution in the US
• In 2000, EPA passed a new rule for diesel, capping sulfur levels
in diesel fuel at 15 parts per million by 2007.
•
In 2005, EPA issued the Clean Air Interstate Rule (CAIR), toachieve the largest reduction in SO2 & NOX from the
atmosphere in the eastern United States.
• In 2006, EPA issued the strongest National Air Quality
Standards for particle pollution in the country’s history.
• In 2010 (January 6th), EPA has proposed to strengthen the
National Ambient Air Quality Standards for ground-level
ozone.
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Air Quality Standards Achievement
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Accidents and Episodes
• 1930 -3 day fog in Meuse Valley, Belgium
• 1931 -9 day fog in Manchester, England
• 1948 -Plant emissions in Donora, Penn, US
• 1952 -4 day fog in London, England
• 1970 -Radionuclide emissions, Three Mile Island, US
• 1984 -Release of Methyl isocynate in Bhopal, India
• 1986 -Radionuclide releases, Chernobyl, Ukraine
• 1997 – Haze disaster in Indonesia
• 2001 – Wildfires in Sierra Nevada, US
•
2001 – Enormous clouds of dust in New York during Collapse of World Trade Center, US• 2002 – Violent dust storm in Queensland, Australia
• 2005 - Jilin chemical plant explosions, Jilin city, China
• 2007 – Wildfires in TALLAHASSEE Florida, US
• 2008 - Kingston Fossil Plant coal fly ash slurry spill, Kingston, US
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Pre-Industrial EraEarly-Industrial Era
Early 20th Century Late 20th Century
Eras of Air Pollution
Early 21st Century
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Air Pollutant
• Contaminant that affects human life, plant life, animal life and
property could be termed as an air pollutant.
• Air pollutants are classified into two categories:
Primary pollutants: These pollutants are
emitted from a source directly into the
atmosphere.
e.g. Sulfur dioxide and Hydrocarbons
Secondary pollutants: These are formed
due to the chemical reaction among two or more pollutants.
e.g. Peroxyacetyl nitrate (PAN )
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How to Define an Air Pollutant?
• Basis: Chemicals present in the environment
• Process:
– Use composition of the clean air as a bench mark.
–
When the concentration of a chemical in air is above the benchmark, it is termed as an air pollutant .
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Chemical Composition of Dry Air
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Common Air Pollutants
→ Indoor
• Radon
• Combustion by-products
• CO, CO2, SO2, Hydrocarbons, NOx
• Particulates, Polyaromatic
hydrocarbons
• Environmental Tobacco Smoke
(ETS)
•Volatile organic compounds
• Asbestos
• Formaldehyde
• Biological contaminants
• Pesticides
→ Outdoor
• SO2
• CO, CO2
• Oxides of Nitrogen
• Ozone
• Total Suspended particles
• Lead
• Particulates
• Volatile organic compounds
• Toxic Air pollutants
The air pollution problem is encountered in both indoor as well as outdoor.
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Sources of Air Pollutants
Indoor Outdoor
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Physical Forms of an Air Pollutant
• Gaseous form
o Sulfur dioxide
o Ozone
o Hydro-carbon vapors• Particulate form
o Smoke
o Dust
o Fly asho Mists
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Toxic Air Pollutants
• Toxic air pollutants may originate from natural sources as well
as from manmade sources such as stationary and mobile
sources.
• The stationary sources like factories and refineries serve as
major contributors to air pollution.
• The Clean Air Act of 1990 provides a list of 189 chemicals to
be regulated under the hazardous air pollutant provisions of
the act.
• The list of hazardous air pollutants can be found in the EPA
website.
(http://www.epa.gov/ttn/atw/188polls.html)
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Sources of Toxic Air Pollutants
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Toxic Air Pollutants•
The toxic air pollutants released from industrial facilities, in theUnited States, are reported to the public via the Toxic Release
Inventory (TRI)
USEPA• “Major” sources are defined as sources that emit 10 tons per year of any of the
listed toxic air pollutants, or 25 tons per year of a mixture of air.
• “Area” sources are defined as sources that emit less than 10 tons per year of a
single air toxic, or less than 25 tons per year of a mixture of air toxics.
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Units for measurement of Air Pollution
There are two units of measurement. They are as follows:
• µg/m3 and ppm (parts per million)
At 25°C and 1 atm
• At 00 C and at a pressure of 76 cm of Hg, volume of the air is 22.41 l/mol.
• To obtain volume at any temperature, use gas law
P1V1/T1 = P2V2/T2
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Sources of Air Pollution
Natural Sources• Volcanoes
• Coniferous forests
• Forest fires
• Pollens
• Spores
• Dust storms• Hot springs
Man-made Sources• Fuel combustion - Largest contributor
• Chemical plants
•
Motor vehicles• Power and heat generators
• Waste disposal sites
• Operation of internal-combustionengines
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Natural Sources vs. Man-made Sources
• Pollutants released from natural sources like volcanoes,
coniferous forests, and hot springs have a minimal effect on
environment when compared to that caused by emissions
from man-made sources like industrial sources, power and
heat generation, waste disposal, and the operation of internalcombustion engines.
• Fuel combustion is the largest contributor to air pollutant
emissions, caused by man, with stationary and mobile sources
equally responsible.
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Source Classification
Sources may be classified as:
(A) Primary
Secondary
(B) Combustion
Non-combustion
(C) Stationary
Mobile
(D) Point: These sources include facilities that emit sufficientamounts of pollutants worth listing
Area: all other point sources that individually emit a small
amount of pollutants are considered as area sources.
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Problems
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Exercise
The exhaust from a 2001 Honda contains 2.5% by volume
of carbon monoxide. Compute the concentration of CO in
milligrams/m3 at 25°C and 1 atm of pressure.
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Exercise
Problem :The exhaust from a 2001 Honda contains 2.5% by volume of carbonmonoxide. Compute the concentration of CO in milligrams/m3 at25°C and 1 atm of pressure.
Solution :
Step 1 1 percent by volume = 104 ppm.
2.5 percent by volume = 2.5*104 ppm.
Molecular Weight of CO is 28 g/mol
Step 2
= 2.8 x 107 mg/m3
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Exercise
Determine the actual volumetric flow rate in acfm
assuming that pressure is constant, when the actual
temperature is 400 F. The standard conditions are 70 Fand 2000 cfm.
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Exercise
Problem :
Determine the actual volumetric flow rate in acfm assuming that
pressure is constant, when the actual temperature is 400 F. The
standard conditions are 70 F and 2000 cfm.
Solution :
Step 1
Temperaturestd = 70 F = 530 R.
Temperatureact = 400 F = 860 R.
Step 2 qact = qstd*(Tempact / Tempstd).
= 2000*(860 / 530).
= 3245.28 acfm
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Exercise
Calculate the density of a gas whose molecular weight is 29
at 1 atm, absolute and 50°F.
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Exercise
Problem :
Calculate the density of a gas whose molecular weight is 29 at 1 atm,
absolute and 50°F.
Solution :
Step 1
80 F = 50 + 460 = 510 R
R = 0.73 atm-ft3 /lb mol-R.
Step 2
density = P * mol.wt/RT
density = (1*29)/(0.73*510)
= 0.0779 lb/ft3.