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Air Pollution from Combustion Sources All substances are poisons. There is none, which is not a poison. The right dose differentiates a poison from a remedy. ~ Paracelsus (1493-1541) Concentrate on what cannot lie. The evidence… ~ Gil Grissom (1956-) CHAPTER 8 Two of the main consequences of the second law of thermodynamics that must be taken into account when burning fossil fuels are the release of large amounts of waste heat and the emission of toxic pollutants into the surrounding air and water. Thermal pollution arises because the full energy content of the fuel cannot be converted to useful work and electricity. Chemical contaminants are produced because the combustion process cannot go entirely to completion. Environmental pollution does not only affect human health, but also endangers plant and animal life, damages materials, affects visibility, and contaminates air, water, and soil. These effects cost billions of dollars in cleaning, repair, replacement, prevention, and lost productivity. According to the World Health Organization (WHO), an estimated 1.5-6 million people die of air pollution related diseases annually, mostly in developing countries where health care facilities are often inadequate, environmental laws are seldom enforced, and the high costs of air pollution control equipment are largely prohibitive. In Chapter 5, we discussed the laws of thermodynamics and how they can be used to design power plants and other useful devices. In these devices, either heat is used to produce shaft work (automobile) and electricity (power plants), or work is used to move heat from a colder to a hotter space (refrigerators and heat pumps). In all cases, some heat must be discarded into the atmosphere in a process known as thermal pollution. Thermal pollution is not limited to mechanical devices, however. Any human activity, even the simple act of breathing, involves the dissipation of a substantial amount of heat to the surrounding air. Other phenomena attributed to emissions from combustion sources are smog formation, ozone depletion, and acid rain. Global Warming The earth’s climate has undergone great changes over time. Until recently, these changes were solely a result of natural variation in the atmosphere. Human activities in the last century, particularly the burning of vast amounts of fossil fuels, have been responsible for alterations in atmospheric composition, changes in weather patterns, and an increase in global temperature of about 0.6oC. During the past 25 years, however, the rate of temperature increase has been even greater and totals to about 2oC if extrapolated over 100 years. In fact, the ten warmest years since 1860 (at which point measurements started) have occurred after 1998. According to data recently released by NASA, the earth is becoming hotter than it has been in the last 12,000 years, and if the current global warming pattern continues, by middle of this century, temperatures will exceed the highest level ever in the last million years. Burning fossil fuels releases large amounts of carbon dioxide, nitric oxides, methane, and other pollutants acting as the culprits for global warming. These are collectively termed “greenhouse gases”. Greenhouse Gases The link between carbon dioxide and atmospheric temperatures was presumed as early as the 19th century, but it remained merely speculation until the 1980s when enough data had been collected to show strong correlation between the two. In order to understand the global warming phenomenon, we must understand the greenhouse effect. Greenhouses heat to temperatures exceeding their surroundings because window glass (and some plastics) is transparent to incoming solar radiation but blocks most of the reflected infrared radiation from the plants and surroundings. Certain gases such as water vapor, carbon dioxide, methane, nitrous oxides, and CFCs behave in a similar fashion; they allow solar radiation to pass through to reach and heat up the ground and air above it but absorb and reradiates the reflected terrestrial (IR) radiation, blanketing the earth. Because no air is present outside the atmosphere, heat cannot escape by conduction and cooling can only occur by radiation. Carbon dioxide is the main product of the combustion of fossil fuel. Methane is leaked into the air from coal mines and pipelines, but is mostly produced by cattle and termites, or in wetlands, municipal waste dumps, and rice patties. Nitric oxides come primarily from fertilizers and animal waste. CFCs are non-toxic, inexpensive, and energy-efficient substitutes for highly toxic, potentially explosive ammonia and, until recently, were marketed under the trade name Freon, being widely used in fire extinguishers, refrigeration systems, and aerosol spray cans. The degree to which greenhouse gases contribute to global warming depends not only on the nature of the gases and their concentrations, but also on the length of time that they remain in the atmosphere. Some gases remain for short periods of time while others, such as CFCs, may remain there for several hundred years.1 Contrary to what some may suspect carbon dioxide is not the most damaging greenhouse gas. Methane traps 20 times more heat per molecule than carbon dioxide, nitric oxide 200 1 SUN Re ected back to space Infrared emission escaped back into space Absorbed by the earth Trapped by atmosphere Infrared emission by the earth’s surface . Figure 8-1 Global Warming For example, CFC-12, common in many refrigeration systems, has a half-life of 100-150 years. CFC-115 can stay in the atmosphere for up to 800 years. 174 Chapter 8 - Air Pollution times more, and CFCs could be 10,000 times more damaging than carbon dioxide. Carbon dioxide has been cited as the most important greenhouse gas merely because it is the most abundant; it is responsible for roughly one-half of measurable global warming. Question: Water vapor is an effective greenhouse gas. Why isn’t it cited as the main cause of global warming? Answer: Indeed, water vapor is the largest contributor to greenhouse gases in the atmosphere. When we burn fossils, we are producing about twice as much water vapor as carbon dioxide; however, its emission is directly linked to the emission of carbon dioxide. Unfortunately, some politicians and lobbyists cite the role of water vapor as proof that global warming is a natural phenomenon having nothing to do with human activity. An analysis of air bubbles trapped in Antarctic ice caps provides evidence that, for thousands of years, carbon dioxide concentrations in the atmosphere has been essentially constant at around 280 parts per million (ppm). Only in the last two hundred years, following industrialization and the rapid increase in the rate of consumption of fossil fuels, has manmade carbon dioxide caused these levels to increase.2 The concentration is now roughly 370 ppm and is expected to rise to over 500 ppm by the middle of this century. As Figure 8-2 shows, the increase in carbon dioxide emission in the last few decades closely correlates with the consumption of fossil fuels. The seasonal variation of the background carbon dioxide concentration can be explained by noting that in spring and summer (in the northern hemisphere), when photosynthesis is more predominant, plants use some atmospheric carbon dioxide as food. It is returned to the atmosphere in fall and winter as plants die. Until now, most greenhouse gases have been released by industrial countries, mainly the United States, and distributed roughly equally among the transportation, residential and commercial heating and cooling, and industry sectors (Figure 8-3). As developing countries become more industrialized and their consumptions of fossil fuels increase, it is expected that the percentage of greenhouse gases contributed by these countries will increase, causing global warming to accelerate in the foreseeable future.3 Question: Estimate the volume of carbon dioxide released into the atmosphere as a result of fossil combustion in the United States. Answer: The latest data indicates that the US consumes about 112 quads4 of energy annually. A simple calculation can be made to convert this to the total mass of fossil fuel consumed. Referring to the 2 3 (a) (b) Figure 8-2 World carbon dioxide emission 1970-2020. (a) Total emission, and (b) Background concentration Cars and light trucks Trucks and Buses Aircrafts Boats and Vessels Rail Motorcycles Total Transportation 20.2% 5.4% 3.6% 1.3% 0.7% 1.8% 33% Industrial 30% Commercial 17% Residential 20% Figure 8-3 US carbon dioxide emissions from energy sources by sector in 2000. Source: DoE/EIA-0573, 2000. http://www.eia. Neftel, A., E.,et al., “Evidence From Polar Ice Cores for the Increase in Atmospheric CO2 i n the past Two Centuries”. (Nature, 315, 45. 1985) R ecent data suggests that for the first time China surpassed the United States in total emission of greenhouse gases. Per capita production remains well below US, however. (International Herald Tribune, June 20, 2007) 4 E ach quad is one quadrillion BTU, each BTU is 2.51x10 -7 barrels of oil, each barrel of oil is 42 gallons, and each gallon is 3.785 liters. 175 energy conversion tables given in Appendix A, we have: 112 quads = 1.12x1017 BTU = 2.81x1010 barrels of oil = 1.18x1012 gallons of oil = 4.47x1012 liters of oil The United States satisfies about 86% of its energy needs with fossil fuels. Assuming a fuel specific gravity of 0.8, the total mass of fossil fuels consumed will be 4.16x1012x0.86x0.8 = 2.9x1012 kg fossil. Considering that, on average, hydrocarbon fuels produce about three times their mass in carbon dioxide, the total amount of carbon dioxide emissions is 9x1012 kilograms (9 billion tons). This figure accounts for about one quarter of all the carbon dioxide produced in the world. Factors Affecting Global Warming Various mechanisms affect the severity of global warming to different degrees. Among the mechanisms that increase the rate of global warming are: 1. Rising temperatures cause acceleration in the rate of decay of organic matter, producing methane, a major greenhouse gas. 2. Rising temperatures make forests drier and more vulnerable to pests, diseases, and fire. For example, it is estimated that by doubling of the carbon dioxide levels in the atmosphere, will raise earth’s surface temperature by about 3oC; the US alone will lose up to 40% of its forests.5 3. With rising temperatures, the Arctic permafrost and tundra will melt and release an enormous amount of methane into the atmosphere, accelerating global warming. Tundra and permafrost cover about one-fifth of all land. 4. Oceans are huge sinks of carbon dioxide. The solubility of water is highly temperature dependent -- the colder its temperature, the higher the capability of water to dissolve carbon dioxide. As ocean temperatures rise, some of the stored carbon dioxide is released back into the atmosphere. While most mechanisms act to amplify global warming, there are some that reduce the effect. Among the mechanisms responsible for reducing the rate of global warming are: 1. The burning of fossil fuel releases particles that act as condensation nuclei and increase cloud-cover, blocking sunlight from reaching the earth. 2. Higher temperatures increase rates of ocean water evaporation, thereby expanding low altitude cloud-cover.6 The role of clouds in C line, William R. 1992. “The Economics of Global Warming,” Washington D.C. Institute for International Economics. The decrease in solubility of carbon dioxide with temperature is also the main reason that soda, beer, and other carbonated beverages become flat shortly after they are opened. Soda c ans are filled under pressure. When opened, their pressure drops to atmospheric levels. Carbon dioxide is less soluble and leaves the beverage. Similarly, when the beverage warms up, its ability to dissolve carbon dioxide reduces and the beverage goes flat. 5 6 176 Chapter 8 - Air Pollution Global Warming: The Facts Did You Know That ...? A ccording to the Intergovernmental Panel on Climate Change (IPCC),i the UN’s scientific advisory body, as a result of global warming, • The current atmospheric concentration of carbon dioxide and methane, two important heat-trapping gases, “exceeds by far the natural range over the last 650,000 years.” • It is expected that by the end of the 21st century, the average sea level will eventually rise by up to half a meter or more, causing many countries like the Maldives and some of the Caribbean and Pacific Islands to disappear completely underwater. In the US, much of the coastline along the Gulf of Mexico and the entire Florida Everglades will be devastated. Many acres of public beaches, millions of birds, and many arctic animals like seals and polar bears will become extinct • Eleven of the last 12 years rank among the 12 hottest years on record. • Over the past few decades, the intensity of tropical cyclones (hurricanes) has increased, droughts have become longer, more intense and more widespread, and mountain glaciers and snow cover have declined worldwide. • The average temperature will increase between 2 to 11.5 degrees Fahrenheit (1.1 to 6.4 degrees Celsius) by the end of the century. Intergovernmental Panel on Climate Control (IPCC) ,Summary for Policy Makers: Economic and Social Dimensions of Climate Change IPCC Working Group III (2001), Revised in 2007. “Climate Change 2007:The Physical Science Basis). Available at i global warming is particularly complicated as clouds differ in thickness, composition; they can travel and may or may not result in rain. More water vapor contributes to increased blanketing effects, both to keep the reradiated terrestrial radiation in (positive effect), and incoming solar radiation out (negative effect). Clouds net contribution in heating or cooling the atmosphere is not certain. Consequences of Global Warming There is considerable disagreement as to the severity of global warming and its long-term effects on the environment. Although environmentalists and the scientific community blame human greed and non-restricted use of fossil fuels, many politicians, oil companies, and even some researchers claim that the natural variations of solar activity have a much larger influence on climate change.7 However, this point of view is the clear minority, and many discard it purely as a political ploy to support the hidden agendas of special interest groups. One thing that scientists agree on-- and data confirm-- is that global warming, whatever the cause, can lead to major changes in the regional climate, or local weather, increased frequency of extreme events, unprecedented hot summers, more intense heat waves, heavy rainfalls, and severe droughts.8 Among the potential consequences of global warming are: 1. The air temperature close to the earth’s surface increases, whereas the stratosphere cools. It is expected that, as a result of global warming, 7 8 See for example the article by Richard Lindzen in the Wall Street Journal , June 11, 2001. NOAA web site: see <>, April 18, 2000. 177 the earth will warm somewhere between 1.4-5.8°C by the end of the twenty-first century.9 The severity of the consequences can only be appreciated if we compare this to the last ice age, during which time the earth’s average surface temperature was only 5°C colder than it is today. 2. The ocean water gets warmer. Global warming also results in the warming of ocean waters and possibly even the collapse of the conveyor belt. The conveyor belt is a body of water that circulates between the Atlantic and Pacific oceans. It is shallowest in the Indian Ocean where the water is warmest. As water moves north it cools, becomes denser, and sinks to the bottom of the Atlantic near Greenland. The Gulf Stream is part of a conveyor belt in the south Atlantic that moves north, bringing mild weather to Europe; if weakened, it will cause the temperature in much of Europe to drop.10 Warmer oceans also affect the diversity of marine life. As oceans warm, fish body temperatures, and with it metabolism and oxygen consumption rates, will rise. Unfortunately, the solubility of gases is reduced at higher temperatures and less oxygen is available, causing many species of fish to disappear. Higher temperatures also increase the rate at which organic waste decomposes, a process that competes for the dissolved oxygen and consequently, oxygen levels drop even further. Furthermore, water viscosity and density are reduced, causing increases in the rate of settlement of suspended particles in the water – possibly affecting aquatic food supplies.11 Finally, warmer oceans mean fewer nitrates, an important ingredient for the production of carbon-absorbing phytoplankton. 3. Ice caps in northern latitudes and Antarctica break up and melt. Rising temperatures cause the melting of glaciers, thus further reducing the fraction of sunlight that is reflected to the sky. A rise in sea level of only a few feet will bury many of the smaller Pacific islands underwater. In low lying countries, such as Bangladesh and the Netherlands, millions of people will be displaced. Many coastlines and beaches including some in the United States, Australia, and Europe, will also be lost. As a result, atmospheric temperature rises even further, causing more ice to melt.12 4. The climate becomes even more unpredictable. Global warming does not mean all regions will experience warmer weather. As the upper layers of seawater warm, the intensity of hurricanes, typhoons, and tornadoes increases.13 The change in rainfall pattern will result in droughts in some regions and floods in others. Forests and other natural resources will suffer from changes in the climate. 5. Weather related diseases will increase. Global warming can 9 10 I ntergovernmental Panel on Climate Change, IPCC Working Group ,2001. “Scientists see threat of abrupt world climate,” Environmental News Network, December 13, 2001. Reuters article by Andrew Quinn, ( stories/2001/12/12132001/reu_45873.asp). 11 Hodges, L., Environmental Pollution, 2nd Ed., Holt, Rinehart and Winston, 1977. p.312. 12 I PCC, Climate Change 1995: The Science of Climate Change, Oxford, Cambridge University Press, 1996. 13 R ecent studies suggest that much of the violent weather behaviors of the last decade, such as the 1991 cyclone in Bangladesh, 1992 floods in Pakistan, China, and Australia, and 1990-1995 El Nino and La Nina in the United States are related to global warming. 178 Chapter 8 - Air Pollution The Greenhouse Effect FYI ... I t is interesting to note that life on our planet would not be possible if it were not for the greenhouse properties of the earth’s atmosphere. Without an atmosphere, almost all solar energy incident on earth’s surface would be reflected back to space, and earth would be a frozen planet with a global average temperature of -17oC (1oF). Various gases in the atmosphere, principally carbon dioxide and water vapor, are capable of absorbing the infrared radiation reflected from the surface, preventing heat from escaping. Nitrogen and oxygen do not absorb the infrared radiation and therefore are not greenhouse gases. As a result of presence of greenhouse gases, the actual global average temperature of our planet is around 15oC (59oF). dramatically increase pests and outbreaks of infectious diseases such as tuberculosis and malaria. 6. Agriculture will suffer. Salt water will damage much of the low-lying coasts and reduce farmland, thus affecting the grazing of farm animals and production of food. Drinking water will also be in short supply. Combating Global Warming To slow down global warming, the concentration of greenhouse gases, carbon dioxide in particular, must be lowered. This can be best achieved by reducing fossil fuel combustion and converting to technologies that reduce the emission of harmful gases to the environment. In absence of adequate support for cutting emissions, we need to lower carbon dioxide levels in the atmosphere either by reducing the carbon in fuel (decarbonization) or by preventing carbon dioxide’s release into the atmospheric air by storing it in other mediums (sequestration). Decarbonization can be accomplished by switching to alternative fuels with higher H/C ratios. Coal has no hydrogen, and is therefore considered to be the dirtiest of all fossil fuels. Natural gas has four hydrogen atoms for each carbon and is considered cleaner than other types of fossil fuels. Of course, the best option is to remove carbon altogether and use pure hydrogen as fuel. Hydrogen is, however, highly explosive and has a low density. Additionally, it must be kept at high pressure, which makes it even more dangerous. A good way of utilizing hydrogen is through fuel cells. Fuel cells are devices that combine hydrogen and oxygen in the air to produce electricity (see Chapter 14). The only product is water vapor, which is not a pollutant. Sequestration refers to the long-term storage of carbon underground or in oceans so as to prevent the buildup of carbon dioxide concentration in the atmosphere. Earth’s oceans have the capacity to hold 45 trillion tons of carbon - 60 times as much as the atmosphere. 2.4 trillion tons are contained within organic matter, such as trees and soil. Untapped fossil fuel reserves could add another 10 trillion tons.14 This means that the oceans alone can absorb all the carbon dioxide that will eventually be produced. However, there are problems with this scenario. As carbon 14 Savage, Neil, “Greenhouse Effects, R.I.P.,” Discover, August 2001. 179 dioxide dissolves in water, the water becomes more acidic. This could harm marine organisms, demonstrating that one environmental problem potentially leads to another equally important environmental problem. Question: W hat would have happened if oceans could not dissolve the carbon dioxide in the atmosphere? Answer: The amount of carbon dioxide in atmospheric air is a tiny fraction of that dissolved in ocean. Without water the atmospheric carbon dioxide concentration would have been much higher, making the atmosphere much hotter and unsuitable for most forms of life. In fact, the planet Venus apparently retains much of its carbon dioxide in its atmosphere, keeping its surface temperature at a searing 470oC (880oF), today (See box “Venus”). Carbon dioxide can also be sequestered by planting trees (Figure 8-4). Photosynthesis helps by removing carbon dioxide and converting it to carbohydrates and food (Chapter 6). This also improves air quality and beautifies the landscape. Unfortunately, trends point in the opposite direction. In the last few decades, much of the existing rainforests have been lost to logging and used as wood fuel or cut down to pave the way for urbanization. Another option is to inject the carbon dioxide back into coal mines, oil fields, and saline aquifers. This is being done to some extent in enhanced oil recovery and the reclamation of abandoned mines. Other less serious approaches have been proposed in which fleets of aircraft crisscross the skies releasing dust into the low atmosphere, millions of hydrogen-filled aluminized balloons are sent into the sky, or thousands of mirrors are put into orbit, all in order to reflect sunlight back to space.15 We could adjust the numbers to balance cooling as a result of reduced insolation with increased heating from emissions of greenhouse gases. The Kyoto Protocol Figure 8-4 Large amounts of carbon dioxide are trapped in vast forests and large bodies of water. In response to growing concern and mounting evidence of global warming, the United Nations hosted the 1992 Earth Summit in Rio de Janeiro, Brazil, where leaders of most industrialized countries agreed to adopt policies aimed at protecting biodiversity. Gases specifically targeted were carbon dioxide, methane, sulfur hexafluoride, HFCs, and CFCs. Furthermore, the Rio agreement established a legal ground to protect a country’s biological Venus FYI ... C ompared to the earth’s atmosphere which except for some trace gases is composed entirely of nitrogen and oxygen, Venus’ atmosphere is 96% carbon dioxide. Much of the carbon dioxide in earth is dissolved in ocean waters, sequestered in plants, or locked up in carbonated rocks, releasing only trace amounts of carbon dioxide to the atmosphere. Venus does not have any liquid water and almost all carbon dioxide has outgassed into its thick atmosphere. As a result, the runaway green house gases play a much more dominant role in Venus, maintaining its temperature in excess of 470oC. 15 Begley, S., “On the Wings of Icarus,” E nvironment, May 20, 1991. 180 Chapter 8 - Air Pollution assets by giving host countries the intellectual property rights on genetic information of their unique animals or plants. Unfortunately, because of the low price of petroleum and lack of enforcing authority, the use of fossil fuels and the emissions of carbon dioxide continued to increase. The failure of the Rio Summit prompted many to organize a meeting in Kyoto, Japan in 1997. This meeting was to devise plans to fight climate changes and their adverse consequences on the world’s weather, agriculture, and ecosystems. Many countries favored putting limits on fossil fuel consumption, phasing out CFCs and other chlorine and bromine-based products, banning future deforestation and planting new trees, increasing efficiency, and promoting renewable energy sources. The United States argued against the measure and considered the protocol to be biased, unfair, and politically motivated. If ratified, it puts unfair strain on the US economy, while giving unfair advantages to countries that are not covered under this treaty, like China and India. There will be more incentive for US companies to transfer their manufacturing to these and other less-industrialized countries that are inherently less efficient and thus the greenhouse gas problem will actually worsen. Developing nations opposed the US view, stating that the cost of cleanup should be borne solely by rich nations that had done the most damage over the past years and arguing that their fledgling economies should not pay the price for the petroleum-driven economic growth of developed nations. Specifically, most criticized the United States for being the biggest contributor to global warming. The US, with 5% of the world population, is responsible for one fifth of all carbon dioxide emissions. A compromise was finally reached, stipulating that by 2012, the so-called Annex 1 countries (the developed countries and the Eastern European countries Point/Counterpoint ... Global Warming Controversy* A minority of scientists take the view that there are unproved and insufficient evidence that links the global warming to man-made carbon dioxide emission. Some cite the poor measurements, inaccurate instruments and crude computer models, preconceived ideas, or biased interpretation of the theoretical or analytical data; others attribute the phenomenon to natural and cyclic fluctuations in the solar activity, cosmic rays, ocean currents, or other unknown causes; yet others see it as a response to political (or even academic) pressures on scientists, and in the US at least, a partisan issue. Even among those who believe that global warming is real and due to human impact, there are debates as to the extent of the problem, appropriate response and the time that it must be implemented. The ultimate judgement on whether the global warming is a natural phenomenon or a result of human activity might have to wait sometime, hopefully before it is too late. One thing is true however that overwhelming majority of reputable scientists, various professional societies and academies of science, as well as US National Academy of Science, and the American Association for the Advancement of Science have sided with the United Nations’ IPCC conclusions and consider climate warming as real and dangerous, and must be dealt with effectively and immediately. For an excellent review of scientific, political, and social aspect of the global warming controversy see the Wikipedia and references that follow ( * 181 of the former Soviet block) were to reduce their collective emissions to 5.2% below the 1990 benchmark. The non-Annex 1 countries would be exempt from these restrictions for a ten-year grace period. However, to induce other nations (notably China and India) to join the agreement, it required rich countries to establish funds to finance costs of replacing CFCs in poor countries by benign refrigerants. In addition, the protocol allowed the signatories to meet emission reduction requirements by devising an emission trading market, which allowed Annex-1 countries to receive emission credits for helping the non-Annex-1 countries reduce emissions. In order to be binding under international law, the treaty would need ratification by countries responsible for at least 55% of the global greenhouse gas emissions of 1990. In 2001, the United States officially pulled out of the treaty, effectively making the treaty enforceable only if Russia, responsible for 17% of the greenhouse gases, ratified the treaty. In February 2005, after some modifications, Russia agreed to sign the treaty and Kyoto Treaty officially went into effect. Thirty five industrialized countries have signed a binding commitment to curb their greenhouse gas emissions by 2012 to overall levels that are 5.2% below 1990 levels. The European Union has committed itself to cut emissions by 8%, Japan and Canada by 6%, while Russia has agreed to limit emissions to 1990 levels. Developing countries are exempt from this protocol, although many have expressed a desire to sign on and are planning to reduce emissions voluntarily. Australia was the last country who signed the agreement, leaving the United States the only developed country who has not ratified the treaty. By 2006, China had already overtaken the United States as far as total carbon dioxide emission. With China’s heavy reliance on coal for production of its massive amount of electricity, the situation is not getting any better soon. At the time of this writing China is producing 2.5 times greenhouse gases as it did in 1991 when Kyoto Protocol was initially drafted. India’s contribution has risen from 2.9% of the world emission in FYI ... The Killer Lakei o n August 21, 1986, a sudden release of over one billion cubic meters of carbon dioxide gas suffocated 1,800 people and numerous herds of cattle living near Lake Nyos in the African nation of Cameroon. Lake Nyos is thermally stratified; colder water at the bottom warms up as it gets closer to the surface. Due to the cold temperatures and high pressures at the bottom, the concentration of dissolved carbon dioxide can reach near saturation levels. Under normal conditions, the stratification limits vertical mixing, allowing the gradual release of the trapped gases. It is believed that a heavy storm triggered a thermal instability in the lake that brought the deeper, gas-rich water to surface. As water warmed up, its capacity to dissolve carbon dioxide decreased and gas bubbles began to form. This process is identical to the sudden opening of a can of soda or a bottle of champagne. When the cap is removed, there is no more pressure to keep the gas dissolved in the soda and the gas fizzes. The cloud of gas is estimated to have reached one hundred meters above the lake surface and extended out to 10 miles into the valleys near the lake, killing villagers while they slept. i Fialka, J. J., “Do Bubbles of Champagne Die? Alas, No,” Wall Street Journal, November 17, 1997, Section B. 182 Chapter 8 - Air Pollution 1991 to 4.4% in 2008.16 Carbon Abatement Strategies The major strategies used to meet the Kyoto benchmark are: 1. Emission Trading -- The establishment of an emission market where emission credits are traded. This way, companies and countries could continue producing pollutants as long as they could offset their higher emissions by buying credits from companies or countries that opted for cleaner technologies or deployed emission control strategies. The rationale for this option is that as long as the total emissions are reduced on a global scale, it does not matter where these reductions are made. US is the prime proponent of this approach. 2. Carbon Capture and Storage (CCS) -- This is the process by which the carbon dioxide produced at the power plant is captured and stored (sequestered) instead of being released into the atmosphere. 3. Carbon Tax -- Taxes are based on the amount of carbon emission per unit energy production (kg/kWh, or lb/Btu). This scheme is used in most European countries. 4. Renewable Resource Mix -- Proposed in Britain, electrical suppliers are obligated to acquire a certain fraction of their energy from renewable sources. The fraction is gradually increased until their obligations under Kyoto Treaty is met. Outdoor Air Pollution The major sources of outdoor air pollution are transportation, stationary sources, and industrial processes. Motor vehicles account for about a third of all carbon dioxide, 98% of all carbon monoxide, and about half of all nitrogen oxides and hydrocarbons emissions (Figure 8-5).17 Stationary sources such as large diesel engines, coal power plants, and refineries are major contributors to sulfur emission and particulates. Industrial pollution is mostly a result of manufacturing a huge number of new and non-biodegradable chemical compounds produced from petroleum products. The sources of pollution are many, and the detailed discussion of their harmful effects is outside the scope of this book. Air pollutants are divided into two categories: The so-called criteria air pollutants and hazardous (toxic) air pollutants. The criteria air pollutants are those common in mobile and stationary sources (tailpipe and smokestack emissions) which are thought to cause heart and respiratory problems and may cause cancer. They are particulates, sulfur dioxide, carbon monoxide, nitrogen oxide, ground-level ozone (smog) and lead. Carbon dioxide is not usually considered a pollutant, but because of its increased global background 16 17 Figure 8-5 Pollutants emitted by fossil power plants and cars are responsible for 2/3 of all pollution. The rest is from industries. Energy Information Administration website, w US Environmental Protection Agency, National Emission Inventory Air Pollutant Emission Trends website ( 183 Table 8-1. Total US Emission of Carbon Dioxide and Criteria Air Pollutants, 2002 CO2 Tons* Transportation Stationary Sources Industrial Others Total 1875 2250 1665 0 5790 % 32 39 29 0 100 86.6 4.4 2.7 18.3 112 CO Tons* % 77.3 4.0 2.4 16.3 100 11.5 8.3 0.9 0.4 21.1 NOx Tons* % 54.3 39.3 4.0 11.0 100 7.2 1.0 7.0 1.3 16.5 HC Tons* % 43.7 6.1 42.1 8.1 100 Particulate Tons* 1.0 2.5 1.1 24.3 28.9 % 3.5 8.7 3.8 84.0 100 * million short tons (a) Includes transit and intercity; (b) Certificated routes and general aviation; -- Data not available. Ref: Davis, S. C., Diegel, S. W., US Department of Energy, “Transportation Energy Data Book,” ORNL-6978, 2007. Tables 12.1. and its effect on global warming, it is sometimes treated as such. However, carbon dioxide emission is not regulated by the federal government. The hazardous air pollutants are less common air pollutants, but they are carcinogenic or may cause damage to the immune or neurological systems. These include volatile organic compounds (unburned hydrocarbons), ammonia, and a wide range of chemicals used as solvents, sterilizers, and components in industrial processes. Table 8-1 shows the total US emission of criteria air pollutants for various sectors in 1999. In addition to these pollutants, radio nuclides emitted from nuclear sources are also of great concern and will be discussed separately in Chapter 12. Depending on the source of the pollution, air pollutants can be considered as primary or secondary. Primary pollutants are those coming directly from the source and may be natural or anthropogenic (human caused). Natural sources include dust, pollen, sea salt nuclei, volcanic ash, smoke, and particulates from forest burning. The primary anthropogenic source of pollutants results from fossil fuel combustion and includes: carbon monoxide, the oxides of nitrogen (mainly NO and NO2), the oxides of sulfur (mainly SO2), unburned hydrocarbon, and particulates (mainly soot, ash, and metal traces). Because almost all air pollutants come from combustion sources, the amount of emission correlates closely with the amount of fossil fuel consumption.18 Volatile Organic Compounds (VOC)19 are the carbon containing compounds derived from living things. Fossil fuels are the main source of VOCs released to the atmosphere and include gasoline, industrial chemicals such as benzene, solvents such as toluene and xylene, and many other chemicals used as dry cleaning solvents. Carbon monoxide forms when there is not enough oxygen or time for the complete oxidation of carbon to carbon dioxide. When inhaled, 18 19 US Environmental Protection Agency, National Air Quality and Emissions Trends Report, Annual 2000. The EPA does not list VOCs as criteria pollutants, but because of their impact on the formation of smog they are included here. 184 Chapter 8 - Air Pollution Dinosaurs and Air Pollution* FYI ... D inosaurs dominated the earth for nearly 130 million years but became victims of an unthinkable mass extinction some 65 million years ago. In 1979, Luis and Walter Alvarez, a father-son scientist team, suggested that extreme pollution was in fact a major contributor to the dinosaurs’ demise. The scientists proposed that an asteroid or comet had smashed into the earth and caused a series of catastrophic events that wiped out the dinosaurs within a blink of a geological eye. A compelling piece of evidence discovered by the two scientists was an excess of iridium and other rare elements in a rock layer determined to be about 65 million years old. In 1992, further support for the hypothesis came in the form of a giant crater found in Mexico spanning about 300 km.i The asteroid that possibly produced the crater is estimated to have had a mass of approximately 2x1016 kg, which collided with the earth at a speed 10 km/s. This amounts to about 1024 J of kinetic energy, which is roughly equivalent to about 2 billion Hiroshima bombs. The debris from the impact might have risen as high as several kilometers into the atmosphere. In addition to polluting the air with dust and deadly acid rain, the impact caused huge tidal waves and earthquakes — much larger than anything experienced in recent history. And if that were not enough, the combined effect of a darkened, wintry sky and the release of vast quantities of greenhouse-prone carbon dioxide (normally trapped in the soil and water) would undoubtedly produce calamitous extremes of cold and/or heat in the climate. Such abrupt environmental changes evidently exceeded the ability of the dinosaurs — and certainly of many other living organisms — to adapt and condemned them to remain forever as spectacles of extinction. i Alvarez, L., Alvarez, W., “Giant Crater Linked to Mass Extinction,” Science News, Vol. 142, No. 7, p. 100, August 1992. * Excerpts from a physics text currently under preparation jointly by this author and Professor Igor Glozman, Department of Physics, Highline Community College, Des Moines, Washington 98198. it diffuses through the lungs into the blood stream where it reacts with the blood hemoglobin displacing the oxygen. Consequently, the body will be deprived of oxygen resulting in headaches, fatigue, impaired judgment, and in extreme cases, suffocation and death. The overwhelming majority of all carbon monoxide emissions are from cars. Other major contributors include stationary power plants and solid waste disposal. Nitrogen dioxide is emitted from a reaction between oxygen and nitrogen in the air at combustion temperatures. The main sources of nitrogen dioxide are transportation and stationary power plants, but some are also released from fertilizers and other chemical plants. The most important health effect associated with nitrogen dioxide is the reduction of the body’s resistance to infection. Nitrogen dioxide also limits plant growth, causes corrosion in metals, and is a major cause of global warming, acid deposition, and photochemical smog. In the presence of sunlight, nitrogen dioxide reacts with hydrocarbons to form ozone – a major lung irritant and contributor to bronchitis and asthma. Sulfur oxides (SO2) are generated by the combustion of sulfur-rich fuels in stationary power stations, refineries, and industrial processing plants. In the atmosphere, it can be further oxidized to form SO3 and eventually reacts with water to form sulfuric acid. Some of the sulfuric 185 acid will subsequently react with trace elements emitted alongside other pollutants to form submicron size sulfate particles – a major cause of acid fog, acid mist, and acid rain. The major impacts are reduced visibility and damage to vegetation, materials, and human health. Particulates include soot, lead, dust, ocean salt, and metal debris. The main sources of particulates are power plants and diesel cars, although smaller sources such as wood stoves, agricultural burning, and dust also contribute. Particulates can vary in size from a fraction of a micron to many hundreds of microns. Larger particles are responsible for reduced visibility and will eventually settle, whereas smaller particles become airborne and may be inhaled, diffuse, and be adsorbed and deposited on the interiors of the lungs, potentially contributing to lung damage and cancer. Particles larger than 10 microns are entirely blocked by the nose. Those below 10 microns (PM-10) pass through the upper respiratory system. Smaller particles in the range of 0.55 microns (PM-2.5) can travel as far as the bronchioles before they are deposited onto the inner walls. Depending on their physical and chemical structure, particles can be toxic (trace of metals such as lead, cadmium, mercury, etc.), or they can interfere with normal breathing (dust). Some particles, such as ocean salt and fine soot, can act as nuclei sites for water condensation and fog formation. Lead is a poisonous metal emitted from old automobile exhausts, paints, storage batteries, and pipes. The lead problem became particularly significant when it was routinely added to gasoline to reduce knocking and to allow for the construction of higher compression engines in the 1970s. Due to its adverse health effects, lead was eventually removed from gasoline. Depending on its concentration, lead can damage the lungs and may lead to convulsions, brain damage, and even death. Secondary pollutants result from the further interaction of the primary pollutants with the atmosphere. Ozone is considered the main secondary pollutant. Ground-level ozone is produced by the combination of pollutants from smoke stacks, cars, paints, and solvents in the presence of sunlight. Ozone is a pale blue gas with a pungent smell that allows it to be detected even in very low concentration. In fact, the word ozone is derived from Greek ozein meaning “to smell.” Major health problems associated with elevated levels of ozone in the atmosphere are coughing, headaches, nausea, and chest pains. Ozone also causes shortness of breath, asthma, chronic bronchitis, and fatigue. Asthma epidemics, especially in children in industrialized countries, can be directly attributed to ozone. 186 Chapter 8 - Air Pollution Effects of the Air Pollutants Depending on the nature of the contaminants, dose rate, and duration, air pollution can cause health complications in humans and animals, damage plants, deteriorate materials and property, and affect global climate. The health effects associated with air pollution are numerous and can vary from burning eyes and nose, irritated throat, and breathing difficulties to more severe effects such as cancer, birth defects, brain and nerve damage, and death. Gaseous pollutants can enter the body through the eyes, skin, or respiratory tract. Depending on the size of the particulate, debris can then be deposited in different areas of the respiratory tract such as the nose, mouth, or lungs. The effects of pollution on animals are similar to those in humans and result in respiratory and eye damage. Water pollutants have a similar effect on aquatic life. Depending on their types and concentrations, toxins and other air pollutants can have significant health consequences over a relatively short duration or even during onetime exposure. A testament to this is the notorious London episode of 1952 which, as a result of thick fog and a high concentration of carbon and sulfate particles, caused many thousands of people to become sick, 4,000 of whom eventually died. The 1984 release of methyl isocyanate from a Union carbide pesticide plant in Bhopal, India killed 2,500 people and injured numerous others. Another example is the Exxon Valdez oil spill in 1989. In this incident, the huge tanker carrying 1.2 million barrels of Alaskan crude oil ran aground and emptied its cargo into the Prince William Sound. Although no human life was lost in the accident the cost to the environment and local economy was enormous (Figure 8-6).20 Many of the emissions released into the atmosphere are directly or indirectly corrosive and attack buildings and materials at a great cost. Dust and soot particulates, especially in humid air, cause the erosion and soiling of buildings, paintings, and sculptures. Nitrogen and sulfur oxides cause deterioration of cottons and nylon, corrosion of metals, and fading of dyes. Atmospheric pollution can affect the environment by changing the climate and reducing the visibility. It damages plants by destroying their chlorophyll, which causes yellowing and the dropping of their leaves. It makes lakes, rivers, and aquifers toxic and corrosive, which kills fish and other marine species and damages crops. Smog Smog is a result of physical and chemical activities between various pollutants released from smoke stacks in the presence of fog (thus the word smog). Classical smog refers mainly to plume of sulfur oxides and particulate matter generated from the combustion of coals and 20 Figure 8-6 Oiled crow in the aftermath of the Exxon Valdez oil spill “ Valdez Spill Toll is Now Called Far Worst,” New York Times, April 18, 1992. 187 petroleum products. It is formed primarily in the early morning, during winter months, and in places of high humidity where condensation of water vapor over smoke particles is easier. The notorious London “fog” discussed above is a good example of this type of smog. Cooler air Cool air Warm air POLLUTION Photochemical smog is very different from classical smog because it is formed under specific meteorological conditions and only when a large amount of sunlight is available. It forms when nitric oxides and hydrocarbons react in the presence of sunlight to produce ozone; this ozone can be further oxidized to produce nitric dioxide and other photochemical oxidants. NO + 1/2 O2 NO2 + HC hν NO2 NO + O Normal Pa ern Cooler air Warm air Cool air O + O2 O3 POLLUTION ermal Inversion Figure 8-7 Thermal inversion The Los Angeles Basin is a prime location for photochemical activities because of the large number of cars and power stations, the availability of sunlight, and its proximity to water. Furthermore, the basin is surrounded on three sides by the San Fernando mountain range, which prevents the dispersion of the pollutants. To make the matter worse, Los Angeles has many days in which a thermal (or temperature) inversion layer blankets the basin and prevents the upward mixing of pollutants with atmospheric air. Thermal inversion refers to the condition where, as a result of a large amount of emissions from cars and smoke stacks, temperature increases rather than decreases with height (Figure 8-7). Under these conditions, a warm layer is sandwiched between a layer of cold air near the surface and another cold layer in the upper atmosphere. Thermal inversion is more severe when wind is calm and pollutants can stay in place for many hours or even days. The smaller the inversion’s height, the less volume is available where pollutants can mix and the greater their concentration. The situation can be visualized as having a pot (mountains) filled with Figure 8-8 The Los Angeles Basin 188 Chapter 8 - Air Pollution water (oceans) and other ingredients (pollutants) with the lid closed (the inversion layer) to prepare a stew (photochemical smog). All that is missing is the heat, which is provided by the abundant Southern California sun (Figure 8-8). Acid Rain Caused by air pollution, acid rain refers to any kind of acid precipitation such as acid fog, acid sleet, acid snow, acid mist, or any other acidic particles or aerosols that fall to the ground or remain suspended in the atmosphere. The main components responsible for the acidity of these particles are oxides of sulfur and nitrogen that are dissolved in water and deposited on the surfaces of suspended particles. Acid rain has a detrimental effect on human and animal health, endangers plant and marine life, and also degrades materials. The health problems associated with acid rain include lung diseases and respiratory ailments. Its primary effect on plants is the leaching and blocking of the uptake of nutrients and essential minerals, such as calcium and magnesium, from the plants’ roots. Acids are also highly corrosive and attack metals and other construction materials. The measure of the acidity of a solution is its pH value. The pH scale ranges between 0 and 14. Pure water has a pH of 7 and is considered to be neutral. Acids have pH values lower than 7, and alkalines have pH values higher than 7. The lower the number, the more acidic the substance is. The scale is logarithmic, which means a drop of one in the pH level represents a tenfold increase in the acidity. Thus a pH of 6 is 10 times more acidic than water; the pH of 5 is 100 times more acidic. Even unpolluted rainfall is normally slightly acidic, with a pH of around 5.6, because it includes dissolved carbon dioxides. Precipitation with a lower pH than this is considered acid rain. Acid rain affects lakes and ponds in an adverse way. The severity of the problem depends on the nature of the lake. In some parts of the world, lakes are in limestone (calcium carbonate), which neutralizes acid. The tendency to neutralize acid provides a buffer against acid rain. In other parts, including the northern US, Canada, and most of Europe, lakes are in granite and have less buffering capacity. Therefore, acid rain poses a greater threat to fish, salamanders, and frogs in these areas. At higher levels of acidity, bacteria and water plants also die. Under these conditions, lake water looks pure, while a healthy lake might have cloudy water because of the natural plant life in it. To increase the alkalinity of the soil and water, some people have proposed liming them; however, this process has proven prohibitively expensive. Many nations have enacted laws to limit their sulfur emission, mainly by installing scrubbers. Scrubbers remove sulfur dioxide by spraying powerplants’ exhausts with a watery, limestone mist to produce sludge that can be dumped or used to make boards suitable for home building.21 21 Moore, Curtis, “Green Revolution in the Marketing,” January/February issue of Sierra . 189 Oxygen Atom (O) Oxygen Molecule (O2) Ozone Molecule (O3) o o o o o o Figure 8-9 Molecular structures of oxygen and ozone Ozone A molecule of ozone contains three atoms of oxygen bound together (Figure 8-9). In the lower atmosphere (troposphere), ozone is formed from the reaction between nitrogen oxides and volatile hydrocarbons in the presence of sunlight. In the upper atmosphere (stratosphere), ozone is produced from the reaction of oxygen with ultraviolet radiation from the sun. Ozone is highly reactive, attacking and oxidizing almost anything it contacts. The Good Ozone and the Bad Ozone 35 Altitude (kilometers) 30 25 20 15 10 5 0 Ozone Layer Stratosphere ozone 20 15 10 Troposphere ozone 5 Altitude (miles) The ozone layer may be regarded as the earth’s sunglasses. It serves as a shield, protecting earth from the harmful effects of ultraviolet radiation. Most of the ozone is found at around 15-35 km above the ground (Figure 8-10). As a result of large-scale meteorological weather systems, the ozone layer somewhat varies in thickness from one day to the next and greatly fluctuates with the seasons. Depending on its frequency, ultraviolet light can be classified as UV-A (320-400 nm), UV-B (290-320 nm), or UV-C (100-290 nm). UV-A, also known as black light, is responsible for skin tanning and has the lowest energy. It is generally considered to be harmless, although some new studies have linked some damage to the retina with long term exposure to this type of radiation. UV-C has the most energy, but is entirely absorbed by the outer layers of the earth’s atmosphere and, under normal circumstances, is not of concern. Because it is highly effective in killing germs, bacteria, viruses, mold, fungi and spores, UV-C is used in hospitals and some industrial applications. UV-B has a lower energy than UV-C, and most is absorbed by the ozone layer in the upper atmosphere, however, even the small amount that reaches the ground results in long term cataracts, skin cancer (malignant melanoma), and breakdowns of the immune system in a large number of people (Figure 8-11). A 1% reduction in the thickness of the ozone layer will result in a similar increase in the intensity of UV-B radiation and a 2% increase in the probability of skin cancer. The effect is more severe at higher latitudes (such as in Scandinavian countries) and higher altitudes. In contrast to stratospheric ozone that is considered “good,” the ozone in the lower atmosphere is “bad.” As discussed in the previous section, it is formed mainly as a result of photochemical reactions between nitric oxides, hydrocarbons, and sunlight. Furthermore, ozone is a strong oxidant and easily attacks metals, rubber, and other materials. At high concentrations, ozone is harmful to plants. It damages crops and slows forest growth. In humans, ozone reduces immunity to various diseases, reduces lung capacity, and causes chest pain, coughing, and asthma. Ozone concentration UV-B Figure 8-10 Atmospheric Ozone: 90% of all ozone resides in the ozone layer in the stratosphere and only 10% in the troposphere. The increase in ozone UV-A concentration near the ground is a result of UV-B UV-C pollution from human activities.ayer Ozone l Figure 8-11 Ultraviolet radiation 190 Chapter 8 - Air Pollution Air Pollution: The Facts Did You Know That ...? • • • • Almost 50% of smog-producing pollutants come from cars. Every year, as many as 200,000 people die in the United States as a result of diseases related to air pollution. Air pollution costs Americans at least $150 billion a year in health care and lost work productivity. Radon is the second leading cause of lung cancer. Ozone Depletion The reduction in the amount of ozone in the stratosphere is another environmental problem widely attributed to the increased use of fossil fuels. This reduction, commonly referred to as the “ozone hole,” was first reported over Antarctica in 1985. Since then it has been recorded over the Arctic and elsewhere around the globe (Figure 8-12). Since 1978, in areas where ozone concentration has been routinely measured, there has been a 4-5% loss of stratospheric ozone over the continental United States. Among the chemicals most threatening to the ozone layer are chlorofluorocarbons (CFCs). CFCs are odorless, non-toxic, nonflammable and inexpensive chemicals originally used as a substitute to ammonia, which was the primary coolant in refrigerators. Marketed under the trade name Freon, it quickly found its way into a large number of other products such as paints, propellants, insulation, seat cushions, solvents, and a foam lowering agent for aerosol cans. In addition to CFCs, methyl bromide (a product mainly used in pest control and fire extinguishers) and nitrogen oxides (produced during combustion and a common component of fertilizers) are also shown to have similar destructive properties. Supersonic passenger aircrafts, rockets, and space shuttles release chlorine gases directly into the atmosphere and thus contribute to the depletion of the ozone layer. The mechanism responsible for ozone destruction was first investigated by Rowland and Molina,22 who showed that the depletion is a result of chlorine, fluorine, and bromine compounds transported from the lower to the upper atmosphere. Once in the stratosphere, these chemicals are broken down by high concentrations of ultraviolet rays which, in turn, decompose ozone molecules into molecular and monatomic oxygen. Although vehemently attacked by various manufacturers of CFCs, the experimental data became so convincing that the production and use of CFCs was eventually banned. Rowland and Molina received the 1995 Nobel Prize in chemistry for this pioneering work. Although ozone depletion is widespread over the entire globe, it is of particular significance in the Antarctic. The severity of depletion in the Antarctic is due to its extreme cold temperature (as low as -90oC in winters) and the presence of ice crystals that hover over Antarctica and act as catalysts to breakup CFCs and release chlorine needed to destroy 22 Figure 8-12 The Antarctican one hundred dollar bill signifies the ozone depletion problem over the continent. R owland, F. S., and Molina, M. J., “Ozone Depletion: 20 years after the Alarm,” Chemistry & Engineering News, August 15, 8-13, 1994. 191 Did You Know That ...? Ozone: The Facts • Ozone is thinnest at the equator and thickens toward the poles, so the farther from the equator you live the less radiation you’ll receive. • A single chlorine free radical reacts with as many as 100,000 molecules of ozone before it reacts with other molecules and becomes immobilized. • Even if the use of ozone-depleting agents altogether stops today, it will still take 50-100 years before the stratospheric ozone returns to its original concentration. • If we were to replace the ozone loss in the upper atmosphere, we would have to pump in 90 megatons of ozone. Even if we could produce this much ozone, the energy required for its delivery would be unthinkable. • Like carbon dioxide, ozone is a greenhouse gas, though ozone’s contribution to global warming is small compared to other greenhouse gases. • As a result of ozone depletion, in the United States alone, the incidence of melanoma has gone up from 1 in 1500 in 1935, to 1 in 150 in 1991, to 1 in 75 in 2000. ozone. There are no such ice clouds around the North Pole and so the ozone hole is relatively smaller.23 The Montreal Protocol The rapid increase in the rate of ozone depletion led to an international agreement -- known universally as the 1987 United Nations Montreal Protocol-- obliging the signatories to gradually phase out the production of CFCs and other ozone depleting compounds. According to this agreement and the subsequent amendments (London, 1990; Copenhagen, 1992; Vienna, 1995; Montreal, 1997 and Beijing, 1999), a set of interim steps were devised that put a cap on the production of ozone depleting materials. Responsibility for the implementation of the Protocol and subsequent mandates remains within individual countries and no reinforcement authority is assigned. As a first step, it was recommended that CFCs, halon, and other ozone depleting emissions should be substituted with hydrofluorocarbons (HFC) and hydrochlorofluorocarbons (hydrogenated CFCs or HCFCs). HFCs do not have chlorine and are therefore not ozone-depleting, but are not as efficient as a coolant, either. HCFCs have a much shorter lifetime in the atmosphere and are much less harmful than CFCs to the ozone layer. These products are scheduled to be phased out by 2030 and substituted with harmless alternatives. The preliminary results are encouraging, as the amount of CFCs released by major industrial countries has fallen by 99%.24 It should be noted, however, that despite a substantial decrease in the release of ozone depleting materials into the atmosphere, because of their long lifetimes, these chemicals remain in the atmosphere for many decades so repair to the ozone layer is very slow. It is expected that by 2050, stratospheric ozone concentrations will return to its original levels. 23 24 Fahey, D. W. et al., “Twenty Questions and Answers about the Ozone Layer,” 2002 Scientific Assessment of Ozone Depletion, Les Diablerets, Switzerland, 24-28 June 2002. National Renewable Energy Laboratory Fact Sheet, DOE/GO-102000-1048, May 2000. 192 Chapter 8 - Air Pollution Ozone Myths Point/Counterpoint ... P: There is no scientific evidence that the ozone hole actually exists. CP: Although there is no hole per se, there is enough data that indicates the thinning of the ozone layer. P: The Ozone hole exists only over Antarctica CP: Although the ozone hole is larger over Antarctica, recent measurements show similar but smaller effects over the Arctic and other locations, except the tropics. P: CFC molecules cannot reach the stratosphere because they are heavier than air. CP: Unlike the stratosphere, which is relatively calm, the troposphere is very turbulent. This turbulence ensures that all gases whether they are lighter or heavier than air, are well mixed in the troposphere. P: Sea salt is a much bigger source of chlorine than CFCs. CP: Unlike CFCs, sea salt particles are soluble in water and are washed out in the lower atmosphere within days or weeks. In fact, no sodium can be detected in the stratosphere. P: The chlorine from man-made CFCs is negligible compared to the chlorine gases released from occasional volcanic eruptions. CP: Although volcanic plumes are rich in hydrogen chloride, they also contain considerable amounts of water vapor. The chlorine is efficiently scavenged by rainwater and ice and removed from the lower atmosphere, and therefore is unlikely to be transported to the upper atmosphere. Indoor Air Pollution We spend over 90% of our lives indoors, so the quality of indoor air we breathe is particularly important. Unfortunately, over the past few decades indoor air quality has continuously deteriorated. In an effort to reduce heating and cooling loads, many newer buildings have been weatherproofed by insulating walls and ceilings and by sealing windows. Little did anyone realize that these cost and energy saving measures would cause a multitude of problems resulting in what is commonly known as the “sick building syndrome.” It is estimated that 20-30% of people are exposed to toxins, and losses of as much as $400 billion dollars are attributed to sick buildings. There are three basic sources of indoor contaminants: 1. People: People are carriers of many contaminants such as bacteria, germs, allergens, and not-so-obvious pollutants such as perfumes and fragrances. Even the simple act of breathing can emit many chemicals and shed millions of dead skin flakes. 2. Building materials: These include construction materials such as formaldehyde outgassing from particle boards, paints, glues, waxes, fiberglass, paper, dust, lint, carpet fibers, dirt, detergents and other cleaning materials, and, in the case of old buildings, asbestos from ceiling tiles. 3. Processes: Major contributing processes are tobacco smoking and indoor appliances, such as copying machines, computers, gas water heaters, gas stoves, and oven ranges. 193 The adverse effects of various gaseous pollutants were covered earlier when we discussed outdoor air pollution, so only those of other pollutants present mostly in indoor environments are given below: Radon is a naturally occurring gas derived from the radioactive decay of uranium-238. It diffuses through rocks and soil and enters through cracks into concrete and clay basements. When ingested, a small amount diffuses through the lungs causing ionization of molecules and other unwanted chemical reactions along its path that may cause lung cancer and other ailments. According to EPA estimates about 20,000 persons are developing lung cancer as a result of exposure to radon in the home. Areas with naturally high concentration of radon are Brazil, China, India and Iran. Ionizing radiation will be discussed in greater detail in Chapter 12. Tobacco smoking is a significant contributor to indoor air pollution. Worldwide, over 2-3 million people die annually of smoke-related diseases such as lung cancer, emphysema, and bronchitis. The number in the United States is around 400,000. It has been reported that even a single cigarette in an office can quickly raise the levels of particulate matter to over 30 times the EPA standards.25 In addition to tar and nicotine, tobacco smoke contains large amounts of carbon dioxide, formaldehyde, hydrogen cyanide, and benzene. The concern about smoking became significantly greater among the general populace when it was discovered that smoking was not only a hazard for the smokers themselves, but for people around them. As evidence on the dangers of secondhand smoking mounted, smoking was banned in public places such as office buildings, theatres, shopping malls, buses, and airplanes in many US and Canadian cities. Other countries are slowly following their leads. Asbestos is one of the most dangerous contaminants still found in older buildings. Because of its fire resistancy asbestos has been widely used in woven fiber mats, fireproof suits, gloves, gaskets, brake shoes, and even gas masks. The most popular applications of asbestos have been its use as insulating material in roof panels and corrugated walls. Reports of fibrotic lung damage (asbestosis) among textile workers and ship insulators, massive increases in the number of lawsuits, and pressure from labor unions have forced the EPA to ban the use of asbestos in most products. Today, asbestos is used in US Navy submarines, and space shuttles’ solid fuel boosters carry asbestosimpregnated rubber liners to protect the steel casings from the heat of takeoff. 25 Neumann, R. J., “Smoking and Air Pollution Standards,” Science, 182:335-336, 1973. 194 Chapter 8 - Air Pollution Pesticide is a general term that refers not only to insecticides (for killing insects), but also herbicides (for controlling weeds), fungicides, and fumigants and constitutes as a major contributor to indoor air pollution. Mold refers to the growth of microorganisms on damp surfaces. Much of the mold found indoors comes from outdoor sources. Other harmful substances found in everyday household products include formaldehydes, benzene, and chlorinated compounds. Formaldehyde, a component of many glues, resins, paints, surface coatings, particleboards, insulation foam, and wood paneling, is present in most furniture, shelving, and cabinetry. The major health effects associated with formaldehydes are headaches, dizziness, burning of the eyes and throat, nausea, and dermatitis. Benzene is known to cause leukemia and is present in most petrochemical products, tobacco smoke, and also many household products (such as glues and paints). Chlorinated substances are found in many dry cleaners, spray aerosols, and paint removers. PCB or polychlorinated biphenyl is used in insulation, lubricants, paints, and fluorescent lights. PCB is carcinogenic and is known to damage the liver, the skin, and to cause birth defects. There is no federal law to regulate or limit indoor air pollutants. Several states have enacted their own regulations in terms of building codes, and some industries have adopted standards and developed guidelines that are mostly voluntary. In the absence of federal laws, it is best that we use our common sense and implement strategies that safeguard our health and the health of our loved ones. To reduce complications associated with indoor air pollution and “sick building syndrome,” it is best to remove their source by eliminating or reducing the use of toxins and substituting them with more environmentally friendly chemicals, proper maintenance, and increased ventilation. The costs are somewhat higher, but considering the cost of exposure to indoor pollutants, many feel it is worthwhile. Control and Prevention The best way to control pollutants is to prevent them from forming in the first place. The obvious choice is to reduce fossil fuel consumption and switch to cleaner sources of energy. Short of that, cleaning the fuel and subsequently modifying combustion processes is probably our next best option. As a last resort, we may opt to remove gaseous and particulate pollutants from the exhaust before they are released into the atmosphere. Fortunately, technologies exist that can help reduce environmental impact at every stage in the process. New technologies have made many alternative and renewable sources of energy cheaper and, in some instances, competitive with fossil fuels. Several new processes have been developed that show the promise of more efficient combustion and reduced air pollution. Cogeneration and combined cycle combustion turbines have helped to improve efficiency and reduce pollution considerably. 195 Coal combustion has become cleaner as well. For example, in fluidized bed combustion, coal is pulverized and suspended on a bed of air, thus reducing combustion temperature which reduces nitric oxide emission. These technologies can reduce particulate and sulfur emissions to a great degree but still produce substantial amounts of gaseous emissions which must be removed before they are released into the atmosphere (end-of-the-pipe control technologies). Depending on the nature and size of the particulates, they can be removed by cyclones, bag houses, filters, scrubbers, or electrostatic precipitators. Gaseous pollutants can be removed by physical and chemical adsorption. Sulfur dioxide emission can be controlled by fuel desulphurization and limestone scrubbing. Nitric oxides and oxides of carbon are best removed by catalytic converters and other flue gas treatment techniques.26 Automobiles are another source of emission. Vehicular emission is controlled by catalytic converters, where small pellets of palladium and platinum transform carbon monoxide and nitric oxides into carbon dioxide and nitrogen. Automotive emission will be discussed in greater detail in Chapter 14. Air Pollution Standards There are no air pollution standards that are universally adopted by all countries. The World Health Organization (WHO) has provided Air Quality Guidelines for key pollutants (SO2, NO2, CO, O3, and lead) to enable countries to set their national or regional air quality standards within the context of existing environmental, social, economic, and cultural conditions. Because air pollution does not recognize any boundaries, various states and governments must establish guidelines that regulate interstate and inter-continent pollution transport. In the United States, the agency responsible for setting, monitoring, and enforcing air quality standards is the Environmental Protection Agency (EPA). Congress has empowered the EPA to enact the Clean Air Act (CAA), passed in 1963 and amended in 1970, 1977, and 1990, to develop National Ambient Air Quality Standards (NAAQS) to set criteria for improving average air quality at the federal level. Individual states can set more stringent standards if they desire. Furthermore, it is each state’s responsibility to develop state implementation plans that set the procedure to achieve the state and federal goals. As a result of more and more stringent regulations, US air quality has continuously improved since 1970 when the EPA was established (See Figure 8-13). Each of the criteria pollutants is assigned a primary standard intended to set limits that protect health and a secondary standard intended to protect public welfare by preventing environmental and property damage. For areas already cleaner than NAAQS, a three-tiered system 26 140 120 100 80 60 40 20 0 Million tons 250 1970 2000 200 150 100 50 Thousand tons CO (-25%) NOX (+20%) VOC (-43%) SO2 (-44%) PM (-88%) 0 Pb (-98%) Figure 8-13 Comparison of the emissions for six criteria pollutants in the United States for the period 1970-2000. Source: Environmental Protection Agency, Cooper, C. D., Alley, F. C., “Air Pollution Control-A Design approach,” Waveland Press, Inc., 1994. 196 Chapter 8 - Air Pollution has been established to prevent significant deterioration of air quality. In Tier 1 regions (mainly national parks), the emission levels were frozen at their 1997 level when the air quality standards were established. Tier 2 included most regions and allowed some reduction in air quality, whereas the quality of the Tier 3 regions could eventually deteriorate to the minimum air quality standards. Table 8-2 compares the current guidelines established by the WHO and the US EPA for various pollutant concentrations and exposure times. Example 8-1: A monitoring station near a coal power plant measures sulfur dioxide concentrations of 200 mg/m3 between the hours of 7:00 am and 5:00 pm. It drops to 60 mg/m3 at all other times. Determine whether this power plant satisfies the WHO’s guidelines. Solution: Within any 24-hour period, the power plant emits 200 mg/m3 for 10 hours of operation and 60 mg/m3 for the remaining 14 hours. The average 24-hour emission is calculated as: Average Daily Concentration = (10x200)+(14x60) = 118 mg/m3 24 Table 8-2. Guidelines for Common Pollutants WHO Pollutant CO Exposure time 15 min 30 min 1 hour 8 hours 1 hour 1 year 10 min 24 hour 1 year 1 hour 8 hour 24 hours 1 year 24 hours 1 year 1 quarter 1 year US EPA Concentration (µg/m3) 100,000 --60,000 --30,000 40,000 10,000 10,000 400 40 500 125 50 175 110 ----------0.5 --100 --365 80 235 157 65 15 50 50 1.5 --- NO2 SO2 O3 PM2.5 PM10 Lead Although the power plant does narrowly meet the WHO’s guidelines in any 24-hr average, unless there is a considerable downtime, the power plant is likely to exceed the 1-year average emission guidelines. Geographical areas that do not meet the emission standards are called non-attainment areas. Air Quality Index The Air Quality Index (AQI) was established by the EPA as a simple indication of how clean the air is on a given day and what precautions, if any, need to be taken in carrying out daily activities.27 The AQI can be viewed as a yardstick to measure the cumulative effects of the criteria air pollutants on human health. It is calculated based on a number of factors such as ambient air temperature, wind conditions, and concentrations of various pollutants. The value of 100 is arbitrarily assigned to air which barely meets the national air quality standards. A value lower than 100 means acceptable air quality and successively lower values mean comparatively cleaner air. Values above 100 signify unhealthy air. The higher the AQI number, the more health risks to individuals. Under these conditions, sensitive groups such as children, the elderly, and adults with heart disease, asthma and other respiratory complications are at higher risk and must limit their outdoor activities. When the AQI climbs above 200, everyone is affected. AQI above 300 is considered hazardous and everyone should avoid prolonged outdoor exposure (See Table 8-3). In the United States, the AQI is usually below 100 for most communities, but may exceed this value a few times a year. In recent years, the AQI has rarely gone beyond 200. Similar standards are set in other major cities around the world (Figure 8-14). 27 Table 8-3 Air Quality Index Figure 8-14 This billboard in a Tehran street, informs the drivers that all criteria pollutants are well within their safe allowable limits. E nvironmental Protection Agency, . 197 Summary Air pollution, both indoor and outdoor, is responsible for hundreds of thousands of deaths each year. Fossil fuels are responsible for thermal pollution and an overwhelming majority of the pollutants released into the atmosphere. Many of the products used indoors are petroleumbased and therefore can be eliminated only if they are replaced with more environmental-friendly materials. Even renewable energy technologies are not entirely “clean”. For example, it has been suggested that to generate the same amount of electricity with wind and solar plants, we still need some fossil fuels for manufacturing these devices. Furthermore, solar cells and batteries use large quantities of highly toxic materials (such as arsenic, cadmium, selenium, boron, etc.) that may prove even more harmful than contaminants associated with fossil fuel use. Since most of these products have a limited life, they must be disposed of and occasionally retrofitted with new systems, so finding cleaner manufacturing techniques is essential. The Kyoto Treaty is expected to have only a limited success unless it includes provisions that requires reducing greenhouse gas emissions by all countries. This will be possible, only if the industrialized countries help the less-developed countries with technologies that enable them to reduce their carbon footprint with no or little economic hardship. Additional Information Books 1. Gore, A., An Inconvenient Truth, Penguin Books, 2007. 2. Roleff, T., Pollution: Opposing viewpoints, Greenhaven Press, 2000. 3. Walsh, P. J., Dudney, C. S., Copenhave, E. D., Indoor Air Quality, CRC Press, 1984. Periodicals 1. Environmental Science and Technology, published by the American Chemical Society. Government Agencies and Websites 1. Environmental Protection Agency ( 2. Occupational Safety and Health Administration (OSHA) (http:// Non-Government Organizations and Websites 1. Intergovernmental Panel on Climate Control (IPCC), (http://www. 2. United Nations Environment Programme ( 3. World Health Organization (WHO) ( 198 Chapter 8 - Air Pollution Exercises I. Essay Questions: 1. What is the difference between weather and climate? What are the major factors that determine weather and climate? 2. What factor(s) determine(s) global temperature? Explain how. 3. Describe what the greenhouse effect is and how it contributes to global warming. 4. What are the sources of pollution? Which sector contributes most? 5. What does sequestration of carbon dioxide mean? Describe a few methods by which atmospheric carbon dioxide can be sequestered. 6. How does acid rain form? Where is the acid rain problem more severe and why? What are its effects on health, the environment, and water supplies? 7. Why do some highly polluted lakes appear to be clean? 8. Is a higher concentration of ozone in the lower atmosphere good or bad? In the upper atmosphere? Explain. 9. What is the difference between primary and secondary pollutants? Name a few pollutants in each category. 10. What are the criteria pollutants and why are they important? Which pollutants are considered criteria air pollutants and why? 11. What do primary and secondary pollutants refer to? What are the main primary and secondary pollutants in our atmosphere? 12. What is the air quality standard and how is it determined? What constitutes healthy air quality? W hat about hazardous? 13. What was the main purpose of the Rio Summit? The Kyoto Treaty? The Montreal Protocol? How have they been implemented? 14. What are the indoor air pollutants and how do they affect our health? 15. Sea salt actually puts more chlorine into the Earth’s atmosphere than anything else, but is not a contributor to ozone depletion. Why not? 16. How do you assess the outcome of Montreal and Kyoto Protocols? Name a few accomplishments and shortcomings. II. Multiple Choice Questions: 1. The increase observed in atmospheric levels of carbon dioxide over the past 100 years is most likely due to a. Variations in the rate of lunar eclipses b. Melting of thermafrost c. The burning of fossil fuels d. Deforestation e. The advent of nuclear reactors 2. What factor(s) determine(s) global temperature? a. Concentration of greenhouse gases in the atmosphere b. Earth’s albedo c. Seasonal variation d. Solar intensity e. All of the above 3. Ozone has the chemical formula _______, is generally __________ in the lower atmosphere, and is _____________ in the stratosphere. a. O3, beneficial, detrimental b. O3, detrimental, beneficial c. O3, detrimental, detrimental d. O2, beneficial, detrimental e. O2, detrimental, beneficial 4. The gas most responsible for the global warming at present is a. O3 b. CO2 c. CFC d. NOx e. SO2 199 5. On a per molecule basis, which of these gases is most effective in causing global warming? a. Carbon dioxide b. Methane c. Ammonia d. Nitric Oxides e. CFCs 6. The so-called “greenhouse effect” is mainly due to a. The opacity of ozone and CO2 to infrared radiation b. The transparency of CO2 and H2O to infrared radiation c. The opacity of CO2 and H2O to infrared radiation d. The transparency of ozone to ultraviolet radiation e. All of the above 7. Which of the following gases is not considered to be a greenhouse gas? a. Nitrogen b. Methane c. Nitric oxide d. Chlorofluorocarbon e. Water vapor 8. Carbon monoxide is considered a highly poisonous gas because a. CO can be oxidized to CO2 which is a strong greenhouse gas b. CO can cause extensive damage to DNA c. CO can diffuse and prevent air from entering the lungs d. Hemoglobin has a higher affinity for O2 than for CO e. Hemoglobin has a higher affinity for CO than for O2 9. Carbon monoxide is dangerous to human health because a. It causes suffocation because it can react with hemoglobin in the blood b. The greenhouse effect will warm up the earth to a point where life will be affected c. It will reside in the lungs and produce cancer d. It is an important ingredient of photo-chemical 200 smog e. CO can cause extensive damage to DNA 10. Which of the following statement is not correct? a. The severity of global warming problems depends on the nature, concentration, and their residence time in the atmosphere. b. We can use the concentration of air bubbles deep in the Antarctic to estimate the degree at which the earth has warmed up. c. In the worst case scenario, many Caribbean and Pacific Island countries will be buried underwater by the end of this century. d. Rising the global temperature results in increase in solubility of carbon dioxide in the ocean water. e. Rising temperature causes acceleration in rate of methane production by organic matters. 11. The primary source(s) of SO2 in the atmosphere of a large city is/are a. Waste disposal b. Incineration c. Automobiles d. Volcanic ash e. Power plants and other stationary sources 12. What is the most abundant gas in the universe? a. Hydrogen b. Oxygen c. Nitrogen d. Carbon dioxide e. Water vapor 13. Which of the following statement(s) is/are correct? a. 90% of all ozone resides in the ozone layer in the stratosphere. b. Transportation is the largest source of carbon monoxide, volatile organic matters, and nitrogen oxides. c. Nitrogen is the most common gas in the atmosphere. d. The largest source of photochemical smog in Los Angeles is automobiles. e. All of the above. Chapter 8 - Air Pollution 14. The most destructive photochemical pollutant in smog is a. Particulates b. Carbon monoxide c. Carbon dioxide d. NOx e. Ozone 15. Ozone depletion is a result of the a. Reaction between nitric oxides and hydrocarbons in the presence of sunlight b. Reaction between carbon dioxide and ozone on the upper atmosphere c. Leaching mechanisms that remove ozone from the lower atmosphere d. Reaction between chlorine and bromine compounds with ozone e. Reduction in photochemical activities in the stratosphere 16. The seasonal variation in background carbon dioxide concentration is a result of a. The uncertainties inherent in the CO2 monitoring devices b. The more energy use in winter than in summer c. The more energy use in summer than in winter d. The change in the level of photosynthetic activities e. None of the above 17. Photochemical smog has its name because a. The chemical industry in Los Angeles produces photons b. Sunlight converts O3 to NO c. Sunlight converts NO2 to sulfuric acid d. A combination of NO, HC, and sunlight leads to the formation of O3 e. A combination of SO2 and sunlight leads to the formation of O3 18. Thermal inversion refers to a. A condition in which cooler air sits on top of the warmer air b. A condition in which, as a result of a large amount of emissions from cars and smoke stacks, temperature increases rather than decreases with height c. Changes in temperature between summer and winter seasons d. Cooling of the atmosphere as we move to higher elevations e. Decrease in the concentration of pollutants in the upper regions of the atmosphere 19. The most environmentally harmful emissions from automobiles powered by gasoline engines are a. CO, SO2, and NOx b. Hydrocarbon, CO, and NOx c. CO2, SO2, and NOx d. CO, O3, and NOx e. Hydrocarbon, particulates, and CO 20. Which of the following statements is correct? a. The measure of the acidity of a solution is its pH value. b. The pH scale ranges between 0 and 14. c. Pure water has a pH of 7, and is considered to be neutral. d. Acids have pH values lower than 7, and alkalines have pH values higher than 7. e. All of the above. 21. The primary source of man-made SO2 is ______; it harms people, animals, vegetation, and material through the formation of _________. a. Gasoline burning, nitric acid b. Hot springs, sulfuric acid c. Coal burning, sulfuric acid d. Coal burning, hydrocarbons e. Automobiles, smog 22. Which of the following statements about sulfur dioxide emission is true ? a. More than two-thirds of all sulfur dioxide emissions in the US are from chemical smelting plants. b. The main consequences of large sulfur dioxide emissions are acid rain and ozone destruction. c. The primary source of sulfur dioxide emission is coal combustion. d. Due to the lack of environmental regulations, 201 the poorest countries are responsible for most sulfur dioxide emissions. e. All of the above. 23. It is feared that, with the use of many SSTs (supersonic transports) and the release of Freon, the _______ in the upper atmosphere will decrease, which in turn will cause an increase in the level of __________ at the surface of the earth. a. Ozone, ozone b. Ozone, ultraviolet c. Ultraviolet, ultraviolet d. Carbon dioxide, global warming e. Ozone, greenhouse effect 24. Which of the following statements about CFCs is (are) true? a. CFCs are more harmful than HCFCs. b. The most effective mechanism for removal of CFCs from the atmosphere is by rain. c. CFCs are the main cause of global warming. d. Stratospheric ozone is produced mainly by the incomplete combustion of fossil fuels. e. All of the above. 25. The reason skin cancer can be caused by an increase in ultraviolet radiation but not in visible light at earth’s surface is a. That the wavelength of UV is longer; hence, it is more destructive b. That there is much more UV than visible light at earth’s surface c. The greenhouse effect d. UV has more energy than visible light and can breakup (ionize) biological molecules more readily than light e. All of the above 26. Which of the following statements is correct? a. The most harmful type of UV radiation endangering our environment is UV-C. b. UV-C has been cited as the main cause of increase in skin cancer in humans. c. Almost all incoming UV-C radiation is blocked by the earth’s atmosphere. d. For better results, most tanning machines use UV-B radiation. 202 e. UV-A is completely blocked by the atmosphere and therefore is of no concern to humans. 27. You can easily feel the heat from the sun through a glass window, but behind a sheet of glass you do not feel much heat from a fireplace. This is because a. Glass is transparent to visible light and opaque to infrared b. The fireplace emits essentially pure ultraviolet radiation c. Glass is opaque to visible light and transparent to infrared d. The infrared component of solar radiation is more intense than that of fire e. None of the above 28. The 1987 United Nations’ Montreal Protocol a. Was drafted to limit consumption of fossil fuels to pre-1990 levels b. Obliged signatories to cut carbon dioxide emissions c. Was designed to gradually phase out the production of CFCs and other ozonedepleting compounds d. Established guidelines for initiating an “emission market” e. Provided incentives for voluntary reduction of greenhouse gases 29. Which chemicals are most responsible for breakdown of ozone molecules? a. Carbon dioxide and carbon monoxide b. Sulfur and nitrogen oxides c. Sulfur and carbon oxides d. Compounds containing chlorine or phosphorous e. Compounds containing chlorine or bromine 30. In which layer of the atmosphere is most of the earth’s ozone concentrated? a. Exosphere b. Mesosphere c. Thermosphere d. Stratosphere e. Troposphere 31. Which of the following chemicals have been Chapter 8 - Air Pollution banned in most of the world because of their role in destroying the ozone layer? a. DDT b. Peroxide c. Mercury and heavy metals d. Chlorofluorocarbon e. All of the above 32. Radon is a. A poisonous gas produced in many industrial processes b. Found in a naturally occurring radioactive gas derived from the decay of uranium-238 c. Mostly absorbed by the atmosphere and is not of particular interest except for certain regions in the United States. d. A strong rock mostly used in building foundations e. A reference to photons emitted in radio frequency range III. True or False 1. A perfect engine produces no thermal pollution. 2. The best strategy to slow down the rate of ozone depletion is to ban or reduce the use of products that contain chlorine or bromine. 3. The so-called “greenhouse effect” is due, at least partially, to the opacity of CO2 and H2O to infrared radiation. 4. The reason that skin cancer can be caused by an increase in ultraviolet radiation but not visible light at earth’s surface is that UV wavelength is longer; hence, it is more destructive. 5. The primary source of SO2 in the atmosphere of a large city is automobile exhaust. 6. The increase observed in atmospheric levels of carbon dioxide over the past 100 years is most probably due to the SST flights in the stratosphere. 7. The brownish color of Los Angeles smog is due to particulates from the many oil-burning plants in the area. 8. Acid rain is a severe problem found mainly in areas with high traffic congestion. 9. Deforestation is of grave concern because it enhances pollution levels and reduces the capacity to remove carbon dioxide. 10. No methane is put into the atmosphere by natural processes. 11. Even if no more ozone depleting materials were to be released into the atmosphere, it would take many decades before ozone concentration in the stratosphere returns to its pre 1950s level. 12. The seasonal variation in carbon dioxide concentration can be traced to changes in levels of photosynthesis activity in plants. IV. Fill-in the Blanks 1. Long-term storage of carbon underground or in oceans to prevent buildup of carbon dioxide concentration in the atmosphere is referred to as ____________. 2. The main ingredients of ______________ smog are sunshine, hydrocarbon, water, and nitric oxides. 3. It is widely believed that ozone destruction is a result of ___________ and ___________ compounds transported from the lower to the upper atmosphere. 4. There are three basic sources of indoor contaminants: ___________, __________, and processes. 5. In the United States, the _______ is the agency responsible for developing, monitoring, and enforcing the air quality standards. 6. As of 2006, _________ has overtaken _______ as the largest contributor of greenhouse gases. 203 V. Project I - Status of international treaties In this project you are asked to carry out a literature survey and comment on the status of various international treaties and what different countries have done to comply with the established guidelines and recommendations. 1. Highlight major milestones that are to be achieved by the Kyoto Treaty and Montreal Protocol. As of today, what should have been accomplished and by whom? 2. What were the responsibilities of the country of your birth in meeting these requirements? Have they been met? If not, why? 3. How do you rate the overall success of these treaties? Have they achieved their general goals? W hat were the shortcomings? Project II - Status of the air quality around the world. Much of the discussion in this chapter was centered around the air pollution problems in the United States and what the US is doing in terms of air quality standards. This project concentrates on air pollution problem in the countries other than the United States. Please conduct a literature search on the Internet and other resources and answer the following questions. 1. What country were you born in or resided in for a major part of your life? 2. How is the air pollution problem in the country different from that of the United States? Why? 3. What are the sources of pollution? Which sector contributes the most? The least? 4. How do the air quality standards differ in the country from those of the United States? Project III - Global Warming and Climate In the movie “An Inconvenient Truth,” Al Gore suggested that as a consequence of global warming there has been an increase in the number of hurricanes, tornado, and other violent storms over the past few decades. Check the internet and compile the data on the frequency of these events for the last 50 years. Discuss the data and verify whether such correlations exist. If you find such correlations, does that prove this increase is as a result of global warming? Can you give an alternative explanation? Project IV - Inventory of household chemicals Take an inventory of the chemicals found in your house (kitchen, laundry, garage, etc). Classify them by their applications as solvents, detergents, paints, etc. 1. List their chemical compositions and identify them as toxic, non-toxic, volatile, organic, or biodegradable. 2. Which of these chemicals are carcinogenic, poisonous, or flammable? 3. Which of these products are causing global warming? Which ones are ozone depleting? Which ones are considered to be health hazard? 4. Can you substitute any of these products with more environmentally friendly (green) products? List. 5. What are the proper methods of disposal for each of these products? 204