Introduction

Introduction Air pollution worldwide is a growing threat to human health and the natural environment. 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. 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.

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. In 2000 EPA passed a new rule for diesel, capping sulfur levels in diesel fuel at 15 parts per million by 2007.

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

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, Formaldehyde, Hydrocarbons, NOx, Particulates, Polyaromatic hydrocarbons Environmental Tobacco Smoke (ETS) Volatile organic compounds Formaldehyde Biological contaminants Pesticides → Outdoor   SO2   CO, CO2    Oxides of Nitrogen   Ozone   Total Suspended particles Lead Asbestos Particulates Volatile organic compounds

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)

Toxic Air Pollutants The toxic air pollutants released from industrial facilities, in United States, are reported to the public via the Toxic Release Inventory (TRI) According to EPA: “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

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.

Air Quality Index (AQI) AQI helps in understanding the level at which air is polluted and the associated health effects that might concern. EPA calculates the AQI for five major air pollutants : ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. For each of these pollutants, EPA has established national air quality standards to protect public health. The EPA has developed the pollutant standard index (PSI) for introducing consistency in providing information regarding the air quality throughout the US. The system is based on a scale of 0-500.

Air Quality Index (AQI) Source: http://www.airnow.gov/index.cfm?action=static.aqi Good: The AQI value for a community is between 0 and 50 then the air quality is considered satisfactory, and air pollution poses little or no risk. Moderate: The AQI is between 51 and 100 then the Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people. Unhealthy for Sensitive Groups: When AQI values are between 101 and 150, members of sensitive groups may experience health effects. This means they are likely to be affected at lower levels than the general public. Unhealthy: Everyone may begin to experience health effects when AQI values are between 151 and 200. Members of sensitive groups may experience more serious health effects. Very Unhealthy: AQI values between 201 and 300 trigger a health alert, meaning everyone may experience more serious health effects. Hazardous: AQI values over 300 trigger health warnings of emergency conditions. The entire population is more likely to be affected.

Air Quality Standards Clean Air Act has developed national ambient air quality standards to protect public health and environmental resources. The air quality standards are classified into two types. Primary standards: Protect public health, including the health of "sensitive" populations such as asthmatics, children, and the elderly. Secondary standards: Protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings.

National Ambient Air Quality Standards (Source: USEPA)

Air Quality Regions Any region within a state is designated as either attainment or nonattainment area. Attainment area is the region where the air quality exceed national ambient air quality standards. Nonattainment area is the region where the air quality is within the national ambient air quality standards. An area may fall into both categories for different pollutants. Permits are issued to the sources considering the amount of pollutants that are expected to emit per year.

Remedies and Solutions Efforts to reduce air pollution have largely fallen into three categories: a) Regulatory, b) Technological, and c) Economic or Market-based solutions. Regulatory Solutions: Regulatory solutions involve the passage of laws and the establishment of government agencies which attempt to reduce air pollution through government monitoring and punitive measures (usually fines but, in exceptional cases, criminal sentences as well). Technological Solutions: This includes the progress in emissions technology (e.g., reformulated gasoline), pre-warmed catalytic converters, and in the extension of emissions rules to trucks, pickups and SUVs. Market-based solutions: These solutions allow firms the flexibility to select cost-effective solutions to achieve established environmental goals. Source: A.Kumar and S. Jampana, “Air Pollution”, 83-99, Vol. 1, Social Issues in America: An Encyclopedia, Edited by J. Ciment, M.E. Sharpe Inc., 2006.

Air Quality Monitoring Air quality monitoring helps us in better understanding the sources, levels of different air pollutants, effects of air pollution control policy, and exposure of various substances in the air we breathe. Air quality monitoring program assists us in improving and developing air pollution control programs to reduce the effect of air pollution. The purpose of air monitoring is not merely to collect data, but also to provide the information necessary for engineers, scientists, policy makers, politicians and planners to make informed decisions on managing and improving the air environment.

Air Quality Monitoring Monitoring stations continuously monitor and collect information about the presence and level of atmospheric contaminants as well as the meteorological indices. A typical monitoring station include sophisticated gaseous pollutant analyzers, particle collectors, and weather sensors that are continuously maintained and operated. In U.S., Environmental Protection Agency (EPA) with the help of state and local agencies monitors air pollutants.

Air Quality Monitoring In general air quality monitoring can be grouped into following types: Emissions Monitoring: This type of monitoring focuses on emissions coming out of natural and man made sources. Ambient Monitoring: The emphasis is on ambient air concentration of toxic as well as non-toxic contaminants. Deposition Monitoring: This type of network measures the dry and wet deposition of atmospheric contaminants. Visibility Monitoring: Ability to see things is primary focus of this type of monitoring. Upper Air Monitoring: A look at ambient concentrations in upper atmosphere with the help of satellites, airplanes etc. Health Monitoring: Recognizes the importance of risk assessment and risk management in public health studies.

Air Quality Monitoring Networks Different types of air quality monitoring networks operating today in the world: Ambient Air Monitoring Program in the U.S. Atmospheric Integrated Research Monitoring Network in the U.S. Canadian Air Monitoring Network Mexican Network Emission monitoring at industrial plants Health monitoring program by WHO Satellite monitoring by NASA and USEPA Source: A. Kumar, H. G. Rao, S. Jampana, and C. Varadarajan, Air Quality Monitoring & Associated Instrumentation, Chapter 2, Environmental Technology Handbook (edited by N.P. Cheremisinoff), Government Institutes, Rockville, MD, 99-136, 2005.

Air Monitoring Instrumentation Air pollution instruments are available for the measurement of indoor and outdoor air pollution. The available instruments could be grouped into the following major categories: Concentration Measurement Instruments: This group includes the instruments available for gaseous and particulate sampling. Continuous Emission Monitoring Systems (CEMS): Real time monitoring of stack gases is the basic thrust behind such systems. Air Measuring Devices: This category includes volume meters, rate meters and velocity meters (Kumar et al, 2004). Meteorological Instruments: Basic devices used for measuring atmospheric variables are included in this category.

Emission Inventory Emission inventory is an estimate of the amount of pollutants emitted into atmosphere. Developed by:  Plant  Local environmental agency  National environmental agency Characterized by the following aspects: Type of activities that cause emissions, Chemical or physical identity of the pollutants included, Geographic location, and Time period over which emissions are estimated.

Emission Inventory Details for development of an emission inventory depend on:  Area of coverage  Nature of sources  Purpose Well known emission inventories in US Inventory of criteria pollutants    Toxic release inventory (TRI)

Emission Rate Emission rate is the weight of a pollutant emitted per unit time. Emission factor is an estimate of the rate at which a pollutant is released into the atmosphere per unit level of activity To calculate emission rate: EMISSION RATE = [INPUT] x [EMISSION FACTOR] x [APPLICABLE CORRECTION FACTORS] x [HOURS OF OPERATION] x [SEASONAL VARIATION]

Emission Inventory The EPA estimates emission levels ranging from counties to the nation level. The EPA has developed several models to estimate current and future emissions in the atmosphere from different sources. MOBILE6 NON-ROAD These models are computer based applications and are available for free from the EPA’s official website.

Steps to Develop Emission Inventory Steps Involved in development of an emission inventory are:  Planning  Data Collection   Data Analysis  Reporting Data

Planning Defines scope and purpose of inventory Major points considered during this step are: Pollutants to be enlisted in the inventory are specified along with the methods to collect or estimate data Use of data and geographical area involved are determined Legal authority and responsibility of specific groups to acquire data is considered along with an assessment of cost and resources

Data Collection Steps to be taken: Emissions are classified Pollutant sources are located and classified Quality and quantity of materials handled, processed, or burned is determined Collection Methods: During this stage data may be collected by Mail survey Plant inspection Field surveys Data from literature: Industrial files Government files Periodicals Trade journals Scientific publications

Information Collected During Data Collection General source information - location, ownership, and nature of business Activity levels - amount of fuel and materials (input) Amount of production - output of the plant Control device information - type of pollution control devices Information required to estimate emissions - temperature, tank conditions, hours of operations, seasonal variation and other data

Data Analysis Check accuracy Calculation of emission rate is done using: Monitoring data (most accurate & most expensive) Emission factors from AP-42 , Mass balance, and  Engineering calculation

Reporting Data Information can be filed with the following pollution control agencies: Local Regional National In US, data gathered by state agencies are reported to the USEPA   Emission data are available from the USEPA’s web site

Uses of an Emission Inventory The Emission Inventory developed may be used for: Identifying types of pollutants emitted from specific sources. Determining the magnitude or amount of emissions from those sources Developing the emissions distribution in time and space Calculating emission rates under specific plant operating conditions Finding out the relation of ambient air pollutant concentration with specific sources Input data for air quality modeling and risk Determine pollution control options for public health Estimating cost based on emissions

Air Pollution in Asia Asia represents a major source of air pollution as a result of rapid population growth, explosive industrialization, and few environmental regulations China: China is polluted with sulfur dioxide (15 million tons) and particulate matter (20 million tons) because of the use of the high sulfur coal used to generate energy.   Other Chemicals: 1. Carbon Dioxide from Industry 2. Greenhouse Gases from Industry 3. Nitrogen Oxides from Cars 4. Acid Rain With all these problems China has started implementing air pollution control technology.

Air Pollution in Asia India: Most common air pollutant: Suspended particulate matter is due to use of coal in power plants Use of low quality coal produces 45 million metric tons of ash annually When particulate matter ash is mixed with auto exhaust the emissions across limits resulting in an increase in respiratory diseases and allergies South Korea: SO2 is the major pollutant in South Korea, however, it is being controlled by using air pollution control equipment Hong Kong: Vehicular emissions contribute to air pollution problems with diesel powered engines being the prime culprit.

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 104 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 = 700 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.

Exercise Problem : A power plant proposes to burn coal with a sulfur content of 1.8% by weight. The heating value of fuel is 10750 BTU/lb. What percent SO2 removal is required to meet the performance standard of 1.2 lb of SO2/106 BTU.

Solution Step 1 : Performance standard 1.2 lb/106 BTU Fuel heating value 10750 BTU/lb 1.8% S content by weight Step 2 : lb of coal for 106 BTU= ? 1 lb = 10750 BTU (106 / 10750)lb = 93.02 lb Step 3: S + O2 = SO2 32+32 = 64 1 lb yields 2lb of SO2 93.02 lb of coal contains 93.02*0.018 of S = 1.67 lb of S

Step 4 : Rate of SO2 generated = 93. 02. 018. 2 = 3 Step 4 : Rate of SO2 generated = 93.02*0.018*2 = 3.35 lb SO2 /106 BTU % to be removed = (3.35-1.20/3.35)*100 = 64%

Exercise Problem : For an SO2 emission of 22000 kg/day and an exhaust gas flow rate of 5.0 million m3/hr (after the scrubber) measured at 150°C and 1 atm of pressure, calculate the concentration (ppm) of SO2 in the exhaust gases.

Solution Step 1 : n = {33000 kg/day x 1000 g /kg x g-mol /64 g } =  515625 g-mol/day Step 2: VSO2 =  (nRT)/P   =  {515625 (g*mol/day) x 0.08206 (L*atm/gmol*°K) x (200+273)°K } /1 atm     =  20013664.7 L/day

Step 3: Vexhaust gases =  (5.0 x 106 m3/hour x 1000 L/m3 x 24 hours/1 day) =  1.2 x 1011 L/day Step 4: For 1 day, Total volume = 1.2 x 1011 L Volume of SO2 = 2.0 x 107 L   Concentration SO2 =  (VSO2 ) / (Vexhaust gases ) =  {(2.0 x 107 L) / (1.2 x 1011 L)} * 106 ppm                               =  166 ppm

References Corbitt, R. A., Standard Book of Environmental Engineering, McGraw-Hill, 1998. USEPA, National Ambient Air Quality Standards (NAAQS), http://www.epa.gov/air/criteria.html, 2008 http://www.epa.gov/air/oaqps/eog/course422/ap3.html http://airnow.gov/index.cfm?action=static.aqi http://www.atsdr.cdc.gov/general/theair.html http://yosemite.epa.gov/R10/AIRPAGE.NSF/webpage/Emissions+Inventory http://www.epa.gov/airprogm/oar/oaqps/takingtoxics/p1.html#3