Introduction
Introduction
• Air pollution may be described as contamination of the
atmosphere 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.
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?
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 their
inhabitants.
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.
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), to
achieve 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.
Air Quality Standards Achievement
Accidents and Episodes
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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
Eras of Air Pollution
Early-Industrial Era
Early 20th Century
Pre-Industrial Era
Late 20th Century
Early 21st Century
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 )
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 bench
mark, it is termed as an air pollutant .
Chemical Composition of Dry Air
Common Air Pollutants
The air pollution problem is encountered in both indoor as well as outdoor.
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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
Sources of Air Pollutants
Indoor
Outdoor
Physical Forms of an Air Pollutant
• Gaseous form
o Sulfur dioxide
o Ozone
o Hydro-carbon vapors
• Particulate form
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Smoke
Dust
Fly ash
Mists
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)
Sources of Toxic Air Pollutants
Toxic Air Pollutants
• The toxic air pollutants released from industrial facilities, in the
United States, are reported to the public via the Toxic Release
Inventory (TRI)
USEPA
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“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.
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
Sources of Air Pollution
Natural Sources
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Volcanoes
Coniferous forests
Forest fires
Pollens
Spores
Dust storms
Hot springs
Man-made Sources
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Fuel combustion - Largest contributor
Chemical plants
Motor vehicles
Power and heat generators
Waste disposal sites
Operation of internal-combustion
engines
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 internal
combustion engines.
• Fuel combustion is the largest contributor to air pollutant
emissions, caused by man, with stationary and mobile sources
equally responsible.
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 sufficient
amounts of pollutants worth listing
Area: all other point sources that individually emit a small
amount of pollutants are considered as area sources.
Source Classification
(E) Classification for reporting air emissions to the public:
Transportation sources: Includes emissions from
transportation sources during the combustion process
Stationary combustion sources: These sources produce
only energy and the emission is a result of fuel
combustion
Industrial sources: These sources emit pollutants during
the manufacturing of products
Solid waste Disposal: Includes facilities that dispose off
unwanted trash
Miscellaneous: sources that do no fit in any of the above
categories like forest fires, coal mining etc.
Problems
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.
Exercise
Problem :
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.
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
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 F
and 2000 cfm.
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
Exercise
Calculate the density of a gas whose molecular weight is 29
at 1 atm, absolute and 50°F.
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.