1. Introduction

2. 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.

3. 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?

4. 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.

5. 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.

6. Accidents and Episodes
1930 -3 day fog in Meuse Valley, Belgium
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

7. 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 )

8. 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

9. Chemical Composition of Dry Air

10. 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

11. Physical Forms of an Air Pollutant
Gaseous form
  Sulfur dioxide
  Ozone
  Hydro-carbon vapors 
Particulate form
  Smoke
  Dust
  Fly ash
  Mists

12. 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. (

13. 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.

14. 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 l/mol.
To obtain volume at any temperature use gas law
P1V1/T1 = P2V2/T2

15. Sources of Air Pollution

16. 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

17. 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.

18. 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.

19. 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.

20. 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

21. Air Quality Index (AQI)
Source:
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.

22. 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.

23. National Ambient Air Quality Standards
(Source: USEPA)

24. 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.

25. 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.

26. 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.

27. 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.

28. 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.

29. 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, , 2005.

30. 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.

31. 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.

32. 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)

33. 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]

34. 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.

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

36. 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

37. 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

38. 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

39. 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

40. 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

41. 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

42. 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.

43. 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.

44. Problems

45. 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.

46. 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

47. 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.

48. 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). = acfm

49. Exercise
Calculate the density of a gas whose molecular weight is 29 at 1 atm, absolute and 50°F.

50. Exercise Problem : Step 2
Calculate the density of a gas whose molecular weight is 29 at 1 atm, absolute and 50°F.
Solution :
Step F     = = 510 R
R = 0.73 atm-ft3 /lb mol-R.
Step 2
density = P * mol.wt/RT  
density = 1*29/0.73*510
=  lb/ft3.

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

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

53. 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)*100 = 64%

54. Exercise
Problem : For an SO2 emission of 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.

55. Solution Step 1 : n = {33000 kg/day x 1000 g /kg x g-mol /64 g }
=  g-mol/day
Step 2:
VSO2 =  (nRT)/P  
=  { (g*mol/day) x (L*atm/gmol*°K) x ( )°K } /1 atm    
=  L/day

56. 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

57. References
Corbitt, R. A., Standard Book of Environmental Engineering, McGraw-Hill, 1998.
USEPA, National Ambient Air Quality Standards (NAAQS),