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

Eras of Air Pollution Pre-Industrial Era Early-Industrial Era Early 20th Century 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 → Outdoor → Indoor SO2 Radon CO, CO2 The air pollution problem is encountered in both indoor as well as outdoor. →  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   Sulfur dioxide   Ozone   Hydro-carbon vapors  Particulate form   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 “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 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 (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 : Step 2 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.