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• 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

Pre-Industrial EraEarly-Industrial Era

Early 20th Century Late 20th Century

Eras of Air Pollution

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

→ 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.

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

o Smoke o Dust o Fly ash o 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• “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 PollutionNatural 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-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

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.

(E) Classification for reporting air emissions to the public:

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.

ExerciseProblem :

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/molStep 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 RR = 0.73 atm-ft3 /lb mol-R.

Step 2 density = P * mol.wt/RT density = (1*29)/(0.73*510)

= 0.0779 lb/ft3.