Chapter 23 Air Pollution

1. Chapter 23 Air Pollution

2. 23.1 A Brief History of Air Pollution • The atmosphere has long been a sink for waste disposal. • Long history of recognition of the existence of atmospheric pollutants • Natural photochemical smog recognized in 1550 • Acid rain first described in 17th century • Word smog introduced in 1905 • Mixture of smoke and fog • Two events sparked research on air pollution and regulations to control air quality. • Donora fog in 1948 • London smog event in 1952 • Both cause by pollutants being trapped by weather events. Both killed numerous people. • Could happen again in cities like Beijing or Mexico City

3. 23.2 Stationary Source of Air Pollution • Stationary sources are those that have a relatively fixed location. • Point sources emit pollutants from one or more controllable sites. • Fugitive sources generate air pollutants from open areas exposed to wind processes. • Area sources are well defined areas within which are several sources of air pollutants. • Mobile source of air pollutants move from place to place while emitting pollutants. • Automobiles, trucks, buses, aircraft, ships, and trains

4. Point source

5. Fugitive source

6. 23.3 General Effects of Air Pollution • Affects many aspects of our environment • Visual qualities, vegetation, animals, soil, water quality, natural and artificial structures • Significant factor in human death rate for many large cities • Affect human health in several ways • Toxic poisoning, cancer, birth defects, eye irritation, and irritation of respiratory system. • Increased susceptibility to viral infections, causing pneumonia and bronchitis. • Increased susceptibility to heart disease. • Aggravation of chronic diseases, such as asthma and emphysema. • Many air pollutants have synergistic effects • Do greater damage to the lungs in combination of the two pollutants than would be expected to do based on their separate effects

10. 23.4 Primary and Secondary Pollutants • Major air pollutants occur either in gaseous forms or as particulate matter. • Classified as primary or secondary • Primary pollutants- emitted directly into the air • Secondary pollutants- produced through reactions between primary pollutants and normal atmospheric compounds. • In addition to human sources, our atmosphere contains many pollutants of natural origin. • Release of sulfur dioxide from volcanic eruptions. • Release of hydrogen sulfide from geysers and hot springs and from biological decay in bogs and marshes. • Release of ozone in the lower atmosphere as a result of unstable meteorological conditions. • Emission of a variety of particles from wildfires and • windstorms. • Natural hydrocarbon seeps.

13. Total suspended particulates (TSP)

14. Air Toxics • Among pollutants that are known or suspected to cause cancer or other serious health problems. • Associated w/ long-term and short-term exposures • Gases, metals, and organic chemicals that are emitted in relatively small volumes • Cause respiratory, neurological, reproductive, or immune diseases • Standards have been set for more than 150 air toxics • E.g. hydrogen sulfide, hydrogen fluoride, chlorine gases, benzene, methanol, ammonia • EPA estimates that the average risk for cancer from exposure to air toxics is about 1 in 21,000

15. Three Others…. • Methyl Isocyanate • An ingredient of a common pesticide • known in the United States as Sevin. • Colorless gas • Causes severe irritation (burns on contact) to eyes, nose, throat, and lungs. • Breathing the gas in concentrations of only a few ppm causes violent coughing, swelling of the lungs, bleeding, and death. • Less exposure can cause a variety of problems, including loss of sight. • Benzene • Additive in gasoline and an important industrial solvent. • Produced when gasoline and coal undergo incomplete combustion. • Also component of cigarette smoke • Major environmental source on and off road vehicles • Arcolein • A volatile hydrocarbon that is extremely irritating to nose, eyes, and respiratory system. • Produced from • Manufacturing processes that involve combustion of petroleum fuels • Component of cigarette smoke

16. 23.6 Variability of Air Pollution • Problems vary in different regions of the country and the world. • LA pollution mainly from mobile sources • Ohio and Great Lakes point sources • Also varies w/ time of year • Smog a problem in summer when there is lots of sunshine • Particulates a problem in dry months • Particulates a problem in arid regions • Where little vegetation is present and wind can easily pick up and transport fine dust. • Brown haze over Las Vegas partly due to naturally occurring PM 10 • 60% of the dust comes from new construction sites, dirt roads, and vacant land.

18. Influences of Meteorology and Topography • Whether air pollution develops depends on topography and meteorological conditions • Determine the rate at which pollutants are transported away and converted to harmless compounds. • In the lower atmosphere, restricted circulation associated w/ inversion layers may lead to pollution events. • Atmospheric inversion- • Occurs when warmer air is found above cooler air • Cities situated in a valley or topographic bowl are more susceptible to smog problems than cities in open plains. • Surrounding mountains and inversions prevent pollutants from being transported by wind or weather systems. • E.g. Los Angeles

19. Occurs primarily in summer and fall. Occurs when cloud cover associated w/ stagnant air

20. Potential for Urban Air Pollution • Determined by the following factors: • 1. The rate of emission of pollutants per unit area. • 2. The downwind distance that a mass of air moves through an urban area. • 3. The average speed of the wind. • 4. The elevation to which potential pollutants can be thoroughly mixed by naturally moving air in the lower atmosphere.

23. Smog • Term first used in 1905 as mixture of smoke and fog that produced unhealthy air. • Two major types • Photochemical smog (LA type smog or brown air) • Sulfurous smog (London type smog, gray air, or industrial smog) • Photochemical smog reaction involves sunlight, nitric oxides and VOCs • Directly related to automobile use • Sulfurous smog is produced by the burning of coal or oil at large power plants.

27. Future Trends for Urban Areas • The optimistic view • Air quality will continue to improve • Because we know so much about the sources of air pollution and have developed effective ways to reduce it. • The pessimistic view • In spite of this knowledge, population pressures and economics will dictate what happens in many parts of the world, • The result will be poorer air quality in many locations.

28. Future Trends for Urban Areas; The United States • LA is a good area to look at for strategies for pollution abatement. • Air quality plan involving the entire urban region includes the following features: • Strategies to discourage automobile use and reduce the number of cars. • Stricter emission controls for automobiles. • A requirement for a certain number of zero-pollutant automobiles (electric cars) and hybrid cars with fuel cell and gasoline engines.

29. Future Trends for Urban Areas; The United States • A requirement for more gasoline to be reformulated to burn cleaner. • Improvements in public transportation and incentives for people to use it. • Mandatory carpooling. • Increased controls on industrial and household activities known to contribute to air pollution. • Less developed countries w/ growing populations are susceptible to air pollution • Don’t have the financial base necessary to fight air pollution • Attempts to reduce air pollution • Shutting down oil refinery • Ordering industrial plants to relocate • Air pollution however will continue to be a problem if unable to control vehicle use and LPG leaks.

30. 23.8 Pollution Control • The most reasonable strategies for control have been to reduce, collect, capture, or retain the pollutants before they enter the atmosphere. • Reduction of emissions through energy efficiency and conservation measures is preferred.

31. Particulates • Particulates emitted from fugitive, point or area stationary sources are much easier to control. • Point and area sources can be controlled by • Settling chambers or collectors which cause particulates to settle out • Fugitive sources • Protecting open areas, controlling dust, reducing effects of wind Automobiles • Control of pollutants such as carbon monoxide, nitrogen oxides, and hydrocarbons is best achieved through pollution control for automobiles. • Nitrogen oxides controlled by recirculating exhaust gas • CO and hydrocarbons reduced by catalytic converter

32. Sulfur Dioxide • Can be reduced through abatement measures performed before, during, or after combustion. • Cleaner coal technology available but makes fuel more expensive. • Switch to low-sulfur coal • But transportation is an issue • Washing it to remove sulfur • Iron sulfide settles out • Ineffective for removing organic sulfur • Coal gasification • Converts coal to gas in order to remove sulfur • Gas obtained is clean • Emissions from power plants can be reduced by removing the oxides from the gases in the stack • Scrubbing (flue gas desulfurization) • Occurs after coal is burned • Gases treated w/ a slurry of lime or limestone • Reacts to form calcium sulfite • Can then be process into building materials

34. 23.9 LegislationClean Air Act Amendments of 1990 • Comprehensive regulations enacted by the U.S. Congress that address acid rain, toxic emissions, ozone depletion, and automobile exhaust. • Buying and selling of sulfur dioxide emissions • One step back occurred in 2003 when the president and EPA allowed companies to upgrade w/o new pollution controls.

35. Clean Air Act Amendments of 1990 • Also calls for control of • Nitrogen dioxides • Reduced by 10 million tons • Toxins • Especially those causing cancer • Ozone depletion in the stratosphere • End production of all CFCs

36. Air Quality Index • AQI is used to describe air pollution on a given day. • AQI is determined from measurements of the concentration of five major pollutants: • Particulate matter, sulfur dioxide, carbon monoxide, ozone, and nitrogen dioxide. • An AQI value of greater than 100 is unhealthy. • Air pollution alert is issued if the AQI exceeds 200. • Air pollution warning is issued if the AQI exceeds 300, hazardous to all people. • If the AQI exceeds 400, an air pollution emergency is declared, and people are requested to remain indoors and minimize physical exertion

38. 23.10 Cost of Air Pollution Control • Cost for incremental control in fossil fuel-burning may be a few hundred dollars per additional ton of particulates removed. • For aluminum plant, may be several thousand per ton. • Also, a point is reached at which the cost of incremental control is very high in relation to additions benefits.

39. Cost of Air Pollution Control • Economic analysis of air pollution includes many variables, some of which are hard to quantify. We do know the following: • W/ increasing air pollution controls, the capital cost for technology to control air pollution increases. • As the controls for air pollution increase, the loss from pollution damages decreases. • The total cost of air pollution is the cost of pollution control plus the environmental damages of the pollution.