Unit 9 Test

What are some sources of the following air pollutants? Sulfur Dioxide (SO2)

About one third of the SO2 in the atmosphere comes from natural sources as part of the sulfur cycle. The other two-thirds (and as much as 90% in some urban areas) come from human sources, mostly combustion of sulfur-containing coal in electric power and industrial plants and oil refining and smelting of sulfide ores. Sulfur dioxide emissions feeding the Asian Brown Cloud have increased by over a third in the past decade, according to a 2007 U.S. National Academy of Sciences report. In the atmosphere, SO2 can be converted to aerosols, which are microscopic suspended droplets of sulfuric acid (H2SO4) and suspended particles of sulfate (SO4 2) salts that return to the earth as a component of acid deposition. Burning fossil fuels.

Know your body's natural lines of defense against air pollution

Air pollutants of all types can have severe effects as a result of chronic (long-term) exposure. Air pollutants primarily affect the respiratory system, though, because all body systems are connected, there can be other negative effects throughout other body systems. The human respiratory system has barriers in place to prevent foreign objects from entering the body in the air. When air enters you nose, there are hairs and mucus that will trap particles. Next air will begin to travel down your trachea to the lungs. The trachea is also lined with mucus that will capture many of the large particles that enter the body. This mucus can also dissolve some gaseous pollutants. The trachea is also lined with cilia that move back and forth to move the mucus and pollutants up to your throat. The pollutants and mucus can then be swallowed or coughed out later. From the trachea, the air will enter the lungs through the bronchi. The bronchi branch into bronchioles which end in alveoli. The alveoli are tiny bubble-like structures that are surrounded by capillaries. The alveoli function to increase the surface area of the lung that is in contact with the capillaries since this is how oxygen and carbon dioxide are exchanged between the lungs and the blood. Large particles are not able to move into the capillaries, but ultrafine particles, smaller than 2.5 micrometers in diameter (PM2.5), can move into the capillaries and so are the most dangerous.

What is the Asian Brown Cloud?

Air pollution is no longer viewed as mostly a localized urban problem. Satellite images, along with a 2002 study by the U.N. Environment Programme (UNEP), revealed a massive brown cloud of pollution—called the Asian Brown Cloud—stretching nearly continuously across much of India, Bangladesh, the industrial heart of China, and the open sea east of this area. The cloud is about 3 kilometers (2 miles) thick, hangs at an elevation of 2-5 kilometers (1-3 miles), and covers an area about the size of the continental United States. About a third of it is dust, smoke, and ash resulting from drought and the clearing and burning of forests for planting crops. The rest is made up of acidic compounds, soot, toxic metals such as mercury and lead, hundreds of organic compounds, and fly ash produced by the burning of coal, diesel, and other fossil fuels in industries, motor vehicles, and homes. Beneath the cloud, photosynthesis has been reduced in China by about 7-10% and in India by about 7% because less sunlight reaches the ground, according to a 2008 report by atmospheric scientist Veerabhadran Ramanathan, who heads the UNEP's Atmospheric Brown Cloud Project. Acids in the haze fall to the surface and damage crops, trees, and aquatic life in lakes. Instead of blue skies, many of the people living under this cloud see brown or gray polluted skies much of the year. UNEP scientists estimate that the pollution in the cloud contributes to at least 700,000 premature deaths every year. Originally, scientists thought that the brown cloud deflected sunlight and tended to cool the atmosphere above it. But a study of black carbon particles in the cloud, done in 2006 and 2008 by a team of climate scientists led by Ramanathan, found that these particles helped to warm the atmosphere above the cloud by about as much as CO2 and other greenhouse gases do. The Asian Brown Cloud is also bad news for other parts of the world because it doesn't stay put. In 2006, a U.S. satellite tracked the spread of a dense cloud of pollutants from northern China to Seoul, South Korea, and then across the Pacific Ocean to the United States. The U.S. Environmental Protection Agency (EPA) estimates that on certain days, nearly 25% of the particulate matter, 77% of the black carbon, and 33% of the toxic mercury in the skies above Los Angeles, California, can be traced to coalfired power plants, smelters, diesel trucks, and dust storms caused by drought and deforestation in China. Satellite measurements show that it takes about 2 weeks for long-lived air pollutants to circle the world. Thus, long-lived air pollutants from China, India, the United States, or anywhere can affect the entire world. Air pollution connects us all. The history of air pollution control in Europe and the United States shows that pollution such as that in the Asian cloud can be cleared up fairly quickly by setting strict pollution control standards for coal-burning industries and utilities and by shifting from coal to cleaner-burning natural gas in industries and homes. China is beginning to take such steps but has a long way to go. India's capital city of Delhi, under orders from India's Supreme Court, has also made progress in reducing air pollution.

How do CFCs speed up the degradation of ozone in the stratosphere? (know the three steps)

Chlorofluorocarbons (CFCs) and other chlorine‐containing compounds can destroy ozone in the stratosphere faster than it is formed. When UV light hits a CFC molecule, it causes the chlorine atom to break off. This chlorine atom will react with ozone, making chlorine monoxide (ClO) and O2. Chlorine monoxide will then react with another oxygen atom to form another O2 molecule, releasing the free chlorine atom into the atmosphere. Note that chlorine atoms are continuously regenerated as they react with ozone. Thus, they act as catalysts—chemicals that speed up chemical reactions without being used up by the reactions. (Bromine atoms released from bromine‐containing compounds that reach the stratosphere also destroy ozone by a similar mechanism.) These reactions are shown below:

What is the urban heat island effect?

Cities generally are warmer, rainier, foggier, and cloudier than suburbs and nearby rural areas. The enormous amount of heat generated by cars, factories, furnaces, lights, air conditioners, and heat-absorbing dark roofs and streets in cities creates an urban heat island that is surrounded by cooler suburban and rural areas. As cities grow and merge, their heat islands merge, which can reduce the natural dilution and cleansing of polluted air. In addition to changing local and regional climate, the urban heat island effect in hot climates puts heat stress on humans and many other organisms, can increase the formation of photochemical smog, and greatly increases dependence on air conditioning for cooling. This in turn increases energy consumption, greenhouse gas emissions, and other forms of air pollution in a positive feedback loop.

What pollutants cause industrial smog?

Consisting mostly of sulfur dioxide, suspended droplets of sulfuric acid, and a variety of suspended solid particles.

What are some sources of the following air pollutants? Particulate Matter (PM)

Consists of a variety of solid particles and liquid droplets small and light enough to remain suspended in the air for long periods. About 62% of the SPM in outdoor air comes from natural sources such as dust, wild fires, and sea salt. The remaining 38% comes from human sources such as coal-burning power and industrial plants, motor vehicles, plowed fields, road construction, unpaved roads, and tobacco smoke. Burning fossil fuels.

What are some sources of the following air pollutants? Lead

Does not break down in environment. Found in leaded gasoline and lead-based paints. Major sources are particles of peeling lead-based paint found in about 38 million houses built in the United States before 1960 and lead-contaminated dust in deteriorating buildings. In 2007, major U.S. toy companies had to recall various toys made in China that contained lead paint. Also in 2007, tests revealed that almost two-thirds of the red, long-lasting lipsticks manufactured in the United States contained surprisingly high levels of lead, although none of them listed lead as an ingredient. Lead can also leach from water pipes and faucets that contain it.

Know at least two problems with the Clean Air Acts.

Even though the Clean Air Act has been highly successful, there are a number of ways that environmental scientists would like to see it improved. Many of these improvements would be costly to industries, so these are controversial points. In general we rely on pollution clean-up rather than prevention in the United States. Prevention could require some changes in infrastructure, but would save money in the long run, in both clean up and health care costs. One drawback to the Clean Air Acts is that they have not required the federal government to raise fuel economy standards for vehicles. Fuel economy standards steadily increased through the late 70's into the 80's and then leveled off from 1990 to 2010. They were recently raised to 30 mpg and are set to increase 54 mpg by 2025. Ours are much lower than other countries. We will discuss this in depth later. Another drawback is that many sources of emissions are not regulated (or not regulated strongly enough). These sources include motorcycles, oceangoing ships and airports. Some pollutants aren't regulated at all by the clean air act. These include ultrafine particulates and CO2. More and more scientists are pushing for regulation of CO2, so this could be a future addendum to the legislation. Finally, another drawback to this law is that Indoor air pollution isn't regulated at all.

What are some sources of the following air pollutants? Volatile Organic Compounds (VOCs)

Exist as gases in the atmosphere. Most are hydrocarbons, such as isoprene (C3H8) and terpenes such as C10H15 emitted by the leaves of many plants, and methane (CH4), a greenhouse gas. About a third of global methane emissions come from natural sources, mostly plants, wetlands, and termites. The rest comes from human sources, primarily rice paddies, landfills, oil and natural gas wells, and cows (mostly from their belching). Other VOCs, including benzene, vinyl chloride, and trichloroethylene (TCE), are used as industrial solvents, dry-cleaning fluids, and components of gasoline, plastics, drugs, synthetic rubber, and other products. Benzene (C6H6) is found in motor vehicle and power plant emissions and tobacco smoke. Burning fossil fuels.

What are some of the symptoms of sick building syndrome? What types of buildings might become "sick?"

Extreme cases of indoor air pollution can lead to what is called "sick building syndrome." This is caused by chronic exposure to a number of indoor air pollutants. Symptoms of SBS are dizziness, headaches, coughing, sneezing, nausea, burning eyes, sore throat, chronic fatigue, shortness of breath, flu-like symptoms, rash, itchy, diahrrea, and depression. The EPA estimates that 1 out of 5 commercial buildings in the US are classified as sick because of high levels of numerous air pollutants. Although we know the effects of these pollutants separately, there are more harmful when they are mixed together- this is an example of synergy. The specific characteristics that make a building more susceptible to SBS are poor ventilation, sealed windows, buildings that use the AC and are completely sealed for extended periods of time.

What are some sources of the following air pollutants? Nitrogen oxides (NOx)

Forms when nitrogen and oxygen gas in air react at the high-combustion temperatures in automobile engines and coal-burning plants. Lightning and certain bacteria in soil and water also produce NO as part of the nitrogen cycle. In the air, NO reacts with oxygen to form nitrogen dioxide (NO2), a reddish-brown gas. Collectively, NO and NO2 are called nitrogen oxides (NOx). Some of the NO2 reacts with water vapor in the air to form nitric acid (HNO3) and nitrate salts (NO3 )—components of harmful acid deposition. Both NO and NO2 play a role in the formation of photochemical smog—a mix of chemicals formed under the influence of sunlight in cities with heavy traffic. Nitrous oxide (N2O), a greenhouse gas, is emitted from fertilizers and animal wastes and is produced by burning fossil fuels.

What are the major trends in urban population dynamics?

Four major trends in urban population dynamics do seem clear, and they are important for understanding the problems and challenges of urban growth. First, the proportion of the global population living in urban areas is increasing. Between 1850 and 2008, the percentage of people living in urban areas increased from 2% to almost 50% and could reach 60% by 2030. About 88% of this growth will occur in already overcrowded and stressed cities in developing countries, where 44% of the people live in urban areas. Second, urban areas are expanding rapidly in number and size. Each week 1 million people are added to the world's urban areas. Between 2008 and 2015, the number of urban areas with a million or more people is projected to increase from 400 to 564. And there are 18 megacities or megalopolises—cities with 10 million or more people—up from 8 in 1985. Fifteen of them are in developing countries. Such megacities will soon be eclipsed by hypercities with more than 20 million people each. So far, Tokyo, Japan, with 26.5 million people, is the only city in this category. But according to U.N. projections, Mumbai (formerly Bombay) in India, Lagos in Nigeria, Dakar in Bangladesh, and São Paulo in Brazil will become hypercities by 2015. Third, urban growth is much slower in developed countries than in developing countries. Still, developed countries, now with 75% urbanization, are projected to reach 81% urbanization by 2030. Fourth, poverty is becoming increasingly urbanized, mostly in developing countries. The United Nations estimates that at least 1 billion people in developing countries live in crowded and unsanitary slums and shantytowns within most cities or on their outskirts; within 30 years this number may double. If you visit a poor area of a typical city in a developing country, your senses may be overwhelmed by a chaotic but vibrant crush of people, vehicles of all types, congestion, noise, traffic jams, and smells, including smoke from burning trash and wood and coal cooking fires and raw sewage. Many people sleep on the streets or live in crowded, unsanitary, rickety, and unsafe slums and shantytowns with little or no access to safe drinking water or modern sanitation facilities.

Give two natural sources of air pollution

Hills and mountains can reduce the flow of air in valleys below them and allow pollutant levels to build up at ground level. High temperatures promote the chemical reactions leading to photochemical smog formation, which means that global warming could increase photochemical smog in many of the world's cities.

What did Rowland & Molina discover?

In 9173, a device was invented which could detect atmospheric gases with very low concentrations. Using this device, he detected CFCs in the atmosphere for the first time. Scientists incorrectly concluded that CFS are not harmful. These experiments inspired two chemists - Sherwood Rowland and Mario Molina from UC Irvine - to look into CFCs int he atmosphere further. Rowland and Molina began to investigate what CFCs do in the atmosphere. They published their results in 1974. As it turned out, the property that made CFCs so useful, also made them destructive. Their low reactivity prevented them from breaking down in the lower atmosphere, thus they could rise into the stratosphere intact. Because they are so unreactive, Rowland and Molina found that they are very persistant in the atmosphere. They hypothesized that one CFC molecule could remain in the stratosphere for more than 300 years. However, once in the stratosphere, they break down and speed up the conversion of O3 to O2 (upsetting the natural equilibrium conditions). Chlorofluorocarbons (CFCs) and other chlorine‐containing compounds can destroy ozone in the stratosphere faster than it is formed. When UV light hits a CFC molecule, it causes the chlorine atom to break off. This chlorine atom will react with ozone, making chlorine monoxide (ClO) and O2. Chlorine monoxide will then react with another oxygen atom to form another O2 molecule, releasing the free chlorine atom into the atmosphere.Note that chlorine atoms are continuously regenerated as they react with ozone. Thus, they act as catalysts—chemicals that speed up chemical reactions without being used up by the reactions. (Bromine atoms released from bromine‐containing compounds that reach the stratosphere also destroy ozone by a similar mechanism.) After discovering how this process works, Molina and Rowland called for an immediate ban on CFCs (substitutes were available). They faced opposition and attacks on their research from DuPont and other CFS manufacturers. Molina and Rowland finally won the Nobel Prize in Chemistry for their research in 1995.

What are CFC's used in?

In particular they were used in refrigerants (freon) in refrigerators & air conditioners, aerosol cans and in the manufacture of Styrofoam.

Know definitions & how each can be an advantage in creating sustainable cities: Cluster development

In recent years, builders have increasingly used a pattern, known as cluster development, in which high-density housing units are concentrated on one portion of a parcel, with the rest of the land (often 30-50%) used for commonly shared open space. When this is done properly, residents live with more open and recreational space, aesthetically pleasing surroundings, and lower heating and cooling costs because some walls are shared. And developers can cut their costs for site preparation, roads, utilities, and other forms of infrastructure.

What type of rock in soil or lake bottoms would help buffer acid deposition?

In some areas, soils contain basic compounds such as calcium carbonate (CaCO3) or limestone that can react with and neutralize, or buffer, some inputs of acids.

What is urban sprawl? What factors have contributed to urban sprawl in the US?

In the United States and some other countries, urban sprawl—the growth of low-density development on the edges of cities and towns—is eliminating surrounding agricultural and wild lands. It results in a far-flung hodgepodge of housing developments, shopping malls, parking lots, and office complexes that are loosely connected by multilane highways and freeways. Six major factors promoted urban sprawl in the United States. First, ample land was available for most cities to spread outward. Second, federal government loan guarantees for new single-family homes for World War II veterans stimulated the development of suburbs starting around 1950. Third, low-cost gasoline and federal and state funding of highways encouraged automobile use and the development of outlying tracts of land. Fourth, tax laws encouraged home ownership. Fifth, most state and local zoning laws favored large residential lots and separation of residential and commercial areas. And sixth, most urban areas consist of multiple political jurisdictions, which rarely work together to develop an overall plan for managing urban growth. In a nutshell, urban sprawl is the product of affordable land, automobiles, cheap gasoline, and poor urban planning. It has caused or contributed to a number of environmental problems. Because of nonexistent or inadequate mass transportation in most such areas, sprawl forces people to drive everywhere and, in the process, to emit greenhouse gases and other forms of air pollution. Sprawl has decreased energy efficiency, increased traffic congestion, and destroyed prime cropland, forests, and wetlands. It has also led to the economic death of many central cities as people and businesses moved out of these areas.

How is ozone created in the stratosphere (the GOOD ozone)?

In the stratosphere UV radiation from the sun causes oxygen molecules to break apart (and ozone molecules to break apart). O2 combines with these atoms of oxygen to form O3. This reaction is at equilibrium in the stratosphere and more ozone is being created than destroyed at any given time. (This is without human influence). The chemical equation for this reaction is: 3O2 + UV ->-< 2O3. The levels of ozone with altitude are shown in the graph. (Note that the ozone layer varies in thickness with latitude and season)

How can indoor air pollution be prevented & cleaned up?

Little effort has been devoted to reducing indoor air pollution, even though it poses a much greater threat to human health than does outdoor air pollution. Air pollution experts suggest several ways to prevent or reduce indoor air pollution. In developing countries, indoor air pollution from open fires and leaky and inefficient stoves that burn wood, charcoal, or coal could be reduced. People could use inexpensive clay or metal stoves that burn bio fuels more efficiently, while venting their exhaust to the outside. They could use stoves that run on biogas (mostly methane) produced in biodigesters from animal and other organic wastes, or they could use stoves that use solar energy to cook food. This would also reduce deforestation by cutting demand for fuelwood and charcoal. In developed countries, where VOCs present the greatest indoor air pollution threats, houseplants may provide some relief. Scientists have found that some common houseplants—such as the Boston fern, peace lily, rubber plant, and bamboo palm—absorb VOCs and use them as nutrients. (Refer to reducing air pollution notes)

What are some sources of the following air pollutants? Ozone (O3)

Major component of photochemical smog

What environmental problems are faced by Mexico City?

Mexico City suffers from severe air pollution, close to 50% unemployment, deafening noise, overcrowding, traffic congestion, inadequate public transportation, and a soaring crime rate. More than one-third of its residents live in slums called barrios or in squatter settlements that lack running water and electricity. At least 3 million people have no sewer facilities. As a consequence, huge amounts of human waste are deposited in gutters, vacant lots, and open sewers every day, attracting armies of rats and swarms of flies. When the winds pick up dried excrement, a fecal snow blankets parts of the city. This bacteria-laden fallout leads to widespread salmonella and hepatitis infections, especially among children. Mexico City has one of the world's worst air pollution problems because of a combination of factors: too many cars, polluting factories, a sunny climate and thus more smog, and topographical bad luck. The city sits in a high-elevation, bowl-shaped valley surrounded on three sides by mountains—conditions that trap air pollutants at ground level. Breathing its air is said to be roughly equivalent to smoking three packs of cigarettes per day, and respiratory diseases are rampant. The city's air and water pollution cause an estimated 100,000 premature deaths per year. Writer Carlos Fuentes has nicknamed it "Makesicko City." Large-scale water withdrawals from the city's aquifer have caused parts of the city to subside by 9 meters (30 feet) during the last century. Some areas are now subsiding as much as 30 centimeters (1 foot) a year. The city's growing population increasingly relies on pumping in water from as far away as 150 kilometers (93 miles) and then using large amounts of energy to pump the water 1,000 meters (3,300 feet) uphill to reach the city.

Know what acid deposition is and what some effects can be

Most coal-burning power plants, ore smelters, and other industrial plants in developed countries use tall smokestacks to emit sulfur dioxide, suspended particles, and nitrogen oxides high into the atmosphere where wind can mix, dilute, and disperse them. These tall smokestacks reduce local air pollution, but can increase regional air pollution downwind. The primary pollutants (sulfur dioxide and nitrogen oxides) emitted high into the troposphere may be transported as far as 1,000 kilometers (600 miles) by prevailing winds. During their trip, they form secondary pollutants such as droplets of sulfuric acid (H2SO4), nitric acid vapor (HNO3), and particles of acid-forming sulfate (SO4 2) and nitrate (NO3) salts. These acidic substances remain in the atmosphere for 2-14 days, depending mostly on prevailing winds, precipitation, and other weather patterns. During this period, they descend to the earth's surface in two forms: wet deposition consisting of acidic rain, snow, fog, and cloud vapor with a pH less than 5.6 (Unpolluted rain is acidic with a pH of about 5.6 because of the reaction of CO2 and water to form carbonic acid (H2CO3) and dry deposition consisting of acidic particles). The resulting mixture is called acid deposition—sometimes termed acid rain. Most dry deposition occurs within 2-3 days fairly near the emission sources, whereas most wet deposition takes place within 4-14 days in more distant downwind areas. Acid deposition has been occurring since the Industrial Revolution. In 1872, British chemist Robert A. Smith coined the term acid rain after observing that rain was eating away stone in the walls of buildings in major industrial areas. Acid deposition occurs when human activities disrupt the natural nitrogen and sulfur cycles by adding excessive amounts of nitrogen oxides and sulfur dioxide to the atmosphere. Acid deposition is a regional air pollution problem in areas that lie downwind from coal-burning facilities and in urban areas with large numbers of motor vehicles. Such areas include the eastern United States and other parts of the world. In some areas, soils contain basic compounds such as calcium carbonate (CaCO3) or limestone that can react with and neutralize, or buffer, some inputs of acids. The areas most sensitive to acid deposition are those with thin, acidic soils that provide no such natural buffering and those where the buffering capacity of soils has been depleted by decades of acid deposition. In the United States, older, coal-burning power and industrial plants without adequate pollution controls in the Midwest emit the largest quantities of sulfur dioxide and other pollutants that cause acid deposition. Because of these emissions, and those of motor vehicles and other urban sources, typical precipitation in the eastern United States is at least 10 times more acidic than natural precipitation is. Some mountaintop forests in the eastern United States and east of Los Angeles, California, are bathed in fog and dews as acidic as lemon juice—with about 1,000 times the acidity of normal precipitation. Many acid-producing chemicals generated in one country are exported to other countries by prevailing winds. For example, acidic emissions from the United Kingdom and Germany blow into Switzerland, Austria, Norway, and neighboring countries. Some SO2 and other emissions from coal-burning power and industrial plants in the United States end up in southeastern Canada. The worst acid deposition occurs in Asia, especially in China, which gets 70% of its total energy and 80% of its electricity from burning coal. According to its government, China is the world's top emitter of SO2. The resulting acid precipitation is damaging crops and threatening food security in China, Japan, and North and South Korea. In addition, air pollution that contributes to acid deposition is produced by the greatly increased use of cheap diesel generators to provide electricity for rural villages and to run irrigation pumps in China, India, and other developing countries. All of this contributes to the Asian Brown Cloud. Acid deposition causes harm in several ways. It contributes to human respiratory diseases, and damages statues, national monuments, buildings, metals, and car finishes. Also, acidic particles in the air can decrease visibility. One of the most alarming and often unseen effects of acid deposition is that it can leach toxic metals (such as lead and mercury) from soils and rocks into lakes used as sources of drinking water. These toxic metals can accumulate in the tissues of fish eaten by people, other mammals, and birds. Currently, 45 U.S. states have issued statements warning people (especially pregnant women) not to eat fish caught from some of their waters because of mercury contamination. Acid deposition harms aquatic ecosystems. Most fish cannot survive in water with a pH less than 4.5. Acid deposition can also release aluminum ions (Al3), which are attached to minerals in nearby soil, into lakes. These ions asphyxiate many kinds of fish by stimulating excessive mucus formation, which clogs their gills. Because of excess acidity, several thousand lakes in Norway and Sweden contain no fish, and many more lakes there have lost most of their acid-neutralizing capacity. In Ontario, Canada, at least 1,200 acidified lakes contain few if any fish, and fish populations in thousands of other lakes are declining because of increased acidity. In the United States, several hundred lakes (most in the Northeast) are threatened in this way. And scientists are just beginning to study the effects of the Asian Brown Cloud on oceans. Aerosols in the cloud get pulled into thunderstorms that dump acid rain into the Indian and Pacific Oceans, possibly harming marine life and ecosystems. Acid deposition (often along with other air pollutants such as ozone) can harm crops, especially when the soil pH is below 5.1. It reduces plant productivity and the ability of soils to buffer or neutralize acidic inputs. An estimated 30% of China's cropland suffers from excess acidity. Acid deposition can affect forests by leaching essential plant nutrients, such as calcium and magnesium, from soils and releasing ions of aluminum, lead, cadmium, and mercury, which are toxic to the trees. This rarely kills trees directly, but it can weaken them and leave them vulnerable to stresses such as severe cold, diseases, insect attacks, and drought. Mountaintop forests are the terrestrial areas hardest hit by acid deposition. These areas tend to have thin soils without much buffering capacity. And trees on mountaintops (especially conifers such as red spruce and balsam fir) are bathed almost continuously in highly acidic fog and clouds. However, uncontrolled emissions of sulfur dioxide and other pollutants can devastate the vegetation in an area. Most of the world's forests and lakes are not being destroyed or seriously harmed by acid deposition. Rather, this regional problem is harming forests and lakes that lie downwind from large car-dominated cities and from coal-burning facilities without adequate pollution controls. Also, acid deposition has not reduced overall tree growth in the vast majority of forests in the United States and Canada, partly because of significant reductions in SO2 and NOx emissions from coal-fired power and industrial plants under 1990 amendments to the U.S. Clean Air Act. However, acid deposition has accelerated the leaching of plant nutrients from soils in some areas, which has hindered tree growth, as researchers found in the on-going Hubbard Brook studies. Scientists estimate that an additional 80% reduction in SO2 emissions from coal-burning power and industrial plants in the midwestern United States will be needed before northeastern lakes, forests, and streams can recover from past and projected effects of acid deposition. Science focus: In the Core Case Study for Chapter 2 (p. 28), we discussed controlled experiments by scientists in the Hubbard Brook Experimental Forest in the White Mountains of the northeastern U.S. state of New Hampshire—an area where forests are suffering the effects of acid deposition. Ecologist Gene Likens and his colleagues considered the effects of acid deposition on the experimental forest. They noticed that after SO2 and particulate levels in the atmosphere declined as a result of pollution controls mandated by the Clean Air Acts, damaged trees in the forest did not recover as expected. One hypothesis they considered to explain this was that nutrients required for tree health and growth—particularly calcium and magnesium—had been stripped from the soil by acid precipitation. It takes decades for soil to rebuild these nutrients, which would explain the lag in recovery of the trees. The scientists first turned to data they had collected since the 1950s and found that, since that time, most of the calcium ions (Ca2) in the soils had been leached into streams, which carried them away. They hypothesized that acid rain and snow had stripped the soils of these nutrients, and that, by the 1990s, this had essentially stopped the growth of trees and other vegetation. In 1998, Likens and his team began a new experiment to further test this hypothesis. For 2 years, they made measurements in control and experimental forests. Then they used a helicopter to drop quantities of a calcium salt into the experimental forest to add calcium to the soil. Subsequent examination of the soil showed that soil nitrate concentrations increased significantly, along with soil pH (showing lower soil acidity) in the experimental forest. The researchers projected that changes to plant growth patterns would not be recorded for several years. But in 2003, they found that during the winter, red spruce trees in the untreated forest lost about three times more of their needles than did the red spruce in the calcium-treated forest. These studies support the hypothesis that trees do not suffer from direct contact with acid precipitation, but rather from in sufficient nutrients in depleted soil. The researchers also concluded that, in order for damaged forests to recover, their soil nutrients must be restored, and that it could take decades for natural processes to repair the damage to these forests from acid precipitation.

What are noise & light pollution?

Most urban dwellers are subjected to noise pollution: any unwanted, disturbing, or harmful sound that impairs or interferes with hearing, causes stress, hampers concentration and work efficiency, or causes accidents. Noise levels are measured in decibel-A (dbA) sound pressure units that vary with different human activities. Sound pressure becomes damaging at about 85 dbA and painful at around 120 dbA. At 180 dbA it can kill. Prolonged exposure to sound levels above 85 dbA can cause permanent hearing damage. About one of every eight children and teens in the United States has some permanent hearing loss, mostly from listening to music at loud levels. Also, the artificial light created by cities hinders astronomers from conducting their research and makes it difficult for casual observers to enjoy the night sky. Light pollution also affects some plant and animal species. For example, endangered sea turtles lay their eggs on beaches at night and require darkness. And each year, large numbers of migrating birds, lured off course by the lights of high-rise buildings, fatally collide with the buildings.

Know the advantages & disadvantages of cars use

Motor vehicles provide mobility and offer a convenient and comfortable way to get from one place to another. They also are symbols of power, sex appeal, social status, and success for many people. And much of the world's economy is built on producing motor vehicles and supplying fuel, roads, services, and repairs for them. Despite their important benefits, motor vehicles have many harmful effects on people and the environment. Globally, automobile accidents kill approximately 1.2 million people a year—an average of nearly 3,300 deaths per day—and injure another 15 million people. They also kill about 50 million wild animals and family pets every year. In the United States, motor vehicle accidents kill more than 40,000 people per year and injure another 5 million, at least 300,000 of them severely. Car accidents have killed more Americans than have all wars in the country's history. Motor vehicles are the world's largest source of outdoor air pollution, which causes 30,000-60,000 premature deaths per year in the United States, according to the Environmental Protection Agency. They are also the fastest-growing source of climate-changing carbon dioxide emissions. In addition, they account for two-thirds of the oil used in the form of gasoline in the United States and one-third of the world's oil consumption. Motor vehicles have helped to create urban sprawl and the car commuter culture. At least a third of urban land worldwide and half in the United States is devoted to roads, parking lots, gasoline stations, and other automobile-related uses. This prompted urban expert Lewis Mumford to suggest that the U.S. national flower should be the concrete cloverleaf. Another problem is congestion. As the number of cars increases in an urban area, at some point they contribute to immobility not mobility. If current trends continue, U.S. motorists will spend an average of 2 years of their lives in traffic jams, as streets and freeways, begin to look like parking lots. Traffic congestion in some cities in developing countries is much worse. Commuter distances increase as cities sprawl out. Building more roads may not be the answer. Many analysts agree with economist Robert Samuelson that "cars expand to fill available concrete."

What is a temperature (thermal) inversion? What areas are most susceptible to enhanced pollution due to a temperature inversion?

Occurs in troposphere. Normal temperature pattern reverses (air gets warmer as you go up). Caused by a variety of weather conditions. Can trap pollutants (but is not caused by pollution). One of six factors that increases outdoor air pollution. Temperature inversions can cause pollutants to build to high levels. During daylight, the sun warms the air near the earth's surface. Normally, this warm air and most of the pollutants it contains rise to mix and disperse the pollutants with the cooler air above it. Under certain atmospheric conditions, however, a layer of warm air can temporarily lie atop a layer of cooler air nearer the ground. This is called a temperature inversion. Because the cooler air is denser than the warmer air above it, the air near the surface does not rise and mix with the air above. This allows pollutants to build up in the stagnant layer of cool air near the ground. Two types of areas are especially susceptible to prolonged temperature inversions. The first is a town or city located in a valley surrounded by mountains where the weather turns cloudy and cold during part of the year. In such a case, the surrounding mountains and the clouds block much of the winter sunlight that causes air to heat and rise, and the mountains block the wind. As long as these stagnant conditions persist, pollutants in the valley below will build up to harmful and even lethal concentrations. The tragic pollution event in Donora, Pennsylvania, was partly the result of such a temperature inversion. The other type of area vulnerable to temperature inversions is a city with several million motor vehicles in an area with a sunny climate, light winds, mountains on three sides, and an ocean on the other side. Here, the conditions are ideal for photochemical smog worsened by frequent thermal inversions, and the surrounding mountains prevent the polluted surface air from being blown away by sea breezes. This describes the U.S. state of California's heavily populated Los Angeles basin, which has prolonged temperature inversions, mostly during summer and fall (refer to diagrams on review layers of the atmosphere).

Know definitions & how each can be an advantage in creating sustainable cities: Zoning

Once a land-use plan is developed, governments control the uses of various parcels of land by legal and economic methods. The most widely used approach is zoning, in which various parcels of land are designated for certain uses. Zoning can be used to control growth and protect areas from certain types of development. For example, cities such as Portland, Oregon (USA), and Curitiba, Brazil, have used zoning to encourage high-density development along major mass transit corridors to reduce automobile use and air pollution.

What is the Montreal Protocol?

Once the scientific evidence was clear that the ozone layer was being depleted and that humans were the cause, 36 countries met & signed a treaty in Montreal. These countries committed to reducing CFC emissions by 35% by 2000. This treaty is called the Montreal Protocol. Later, the treaty was extended to reduce other ozone depleting chemicals. Currently 191 countries have agreed to reduce CFCs and other ozone depleting chemicals (some were adopted as substitutes for CFCs, but also caused some ozone depletion). Recent research in 2012 has shown that because of the Montreal protocol, the ozone layer is recovering and it is recovering faster than we initially expected it to. Ozone levels are expected to be restored to 1980 amounts by 2045‐2060, about 10 years earlier than we expected. This is an incredible success story of countries working together to solve an environmental problem for which there was abundant scientific evidence. It is a model for solving future environmental problems.

What is the grasshopper effect?

One of six factors that increases outdoor air pollution. Occurs when volatile air pollutants are transported by evaporation and winds from tropical and temperate areas through the atmosphere to the earth's polar areas, where they are deposited. This happens mostly during winter. It explains why, for decades, pilots have reported seeing dense layers of reddish-brown haze over the Arctic. It also explains why polar bears, sharks, and other top carnivores and native peoples in remote arctic areas have high levels of toxic pollutants in their bodies.

Know definitions & how each can be an advantage in creating sustainable cities: Urban growth boundary

One way to preserve open space outside a city is to draw an urban growth line around each community and to allow no urban development outside those boundaries. This urban growth boundary approach, is used in the U.S. states of Oregon, Washington, and Tennessee. However, the Seattle region of Washington state found that using growth boundaries to increase housing densities inside the boundaries had the unintended effect of encouraging low-density housing and sprawl in rural and natural areas just beyond the growth boundaries.

What are some health problems related to air pollution (particularly breathing in fine and ultrafine particulates)?

Prolonged exposure to these ultrafine particles (including through smoking) can lead to bronchitis, emphysema, lung cancer, asthma, heart attack or stroke. Can also cause irritation to the eyes, nose, and throat. The WHO estimates 3 million premature deaths per year worldwide from air pollution related causes. In the US there are an estimated 350,000 premature deaths per year related to air pollution. Many are related to breathing particulates from coal-burning power plants or diesel fumes from trucks or ships.

How can water (from precipitation or sea spray), winds and chemical reactions reduce outdoor air pollution?

Rain and snow help cleanse the air of pollutants. Salty sea spray from the oceans wash out much of the particulates and other water-soluble pollutants from air that flows from land over the oceans. Winds sweep pollutants away, diluting them by mixing them with cleaner air, and bringing in fresh air. Some pollutants are removed by chemical reactions. For example, SO2 can react with O2 in the atmosphere to form SO3, which reacts with water vapor to form droplets of H2SO4 that fall out of the atmosphere as acid precipitation.

What's the main difference between primary & secondary pollutants?

Scientists classify outdoor air pollutants into two categories. Primary pollutants are harmful chemicals emitted directly into the air from natural processes and human activities. While in the atmosphere, some primary pollutants react with one another and with the basic components of air to form new harmful chemicals, called secondary pollutants.

Know definitions & how each can be an advantage in creating sustainable cities: Greenbelt

Some cities provide open space and control urban growth by surrounding a large city with a greenbelt—an open area reserved for recreation, sustainable forestry, or other nondestructive uses. Satellite towns are often built outside these greenbelts. Ideally, the outlying towns are self-contained, not sprawling, and are linked to the central city by a public transport system that does minimal damage to the greenbelt. Many cities in western Europe and the Canadian cities of Toronto and Vancouver have used this approach. Seattle, Washington, could have minimized urban sprawl just beyond its urban grow boundary by establishing a greenbelt outside the boundary. Greenbelt areas can provide vital ecological services such as absorption of CO2 and other air pollutants, which can make urban air more breathable and help to cut a city's contribution to climate change.

How can cities encourage people to reduce automobile use? (think about economic methods, alternative modes of transportation etc)

Some environmental scientists and economists suggest that one way to reduce the harmful effects of automobile use is to make drivers pay directly for most environmental and health costs of their automobile use—a user-pays approach, based on honest environmental accounting. One way to phase in such full-cost pricing would be to charge a tax on gasoline to cover the estimated harmful costs of driving. According to a study by the International Center for Technology Assessment, such a tax would amount to about $3.18 per liter ($12 per gallon) of gasoline in the United States (p. 404). Gradually phasing in such a tax would spur the use of more energy-efficient motor vehicles and mass transit and decrease dependence on imported oil, thereby increasing economic and military security. It would also reduce pollution and environmental degradation and help to slow climate change. Proponents of this approach urge governments to use gasoline tax revenues to help finance mass transit systems, bike lanes, and sidewalks as alternatives to cars. They also urge reduction of taxes on income, wages, and wealth to offset the increased taxes on gasoline. Such a tax shift would make higher gasoline taxes more politically acceptable. Europe, Japan, Singapore, and some rapidly developing Chinese cities have developed rapid mass transit systems within and between urban areas and networks of sidewalks and bike lanes in urban and suburban areas. Analysts warn that countries such as the United States, which lags in developing such systems, will face great economic difficulties in the face of a projected decline in oil production and rapidly rising oil and gasoline prices. The end result could be mass abandonment of sprawling car-dependent suburbs and shopping centers as they become environmentally and economically unsustainable. Heavily taxing gasoline is difficult in the United States, for three reasons. First, it faces strong opposition from the public, which is largely unaware of the huge hidden costs they are paying for gasoline, and from powerful transportation-related industries such as oil and tire companies, road builders, car makers, and real estate developers. Second, fast, efficient, reliable, and affordable mass transit options and bike lanes are not widely available in most of the United States. And third, the dispersed nature of most U.S. urban areas makes people dependent on cars. These factors make it politically difficult to raise gasoline taxes. But U.S. taxpayers might accept sharp increases in gasoline taxes if a tax shift were employed, as mentioned above. Another way to reduce automobile use and urban congestion is to raise parking fees and charge tolls on roads, tunnels, and bridges leading into cities—especially during peak traffic times. Densely populated Singapore is rarely congested, because it auctions the rights to buy a car, and car owners must pay a high tax to use any of the roads leading into the city center. London, England, which has a similar road congestion fee of $49 per day on gas-guzzling cars (with no fee for fuel-efficient vehicles), has reduced the number of cars entering the city during the day. Stockholm, Sweden, and Milan, Italy, have also imposed stiff fees for motor vehicles entering their central cities. And in an effort to reduce fuel use, CO2 emissions, and local air pollution, the mayors of the U.S. cities of New York City and San Francisco, California, are considering such vehicle entry fees, and have announced that all taxis in their cities must be hybrid vehicles by 2012. Paris, France, one of Europe's most congested cities, has upgraded its mass transit system and created express lanes for buses and bicycles on main thoroughfares while reducing the lanes for cars. The city also established a program with almost 21,000 bikes available for rental at 1,450 rental stations throughout the city at a cost of just over $1 a day. In Germany, Austria, Italy, Switzerland, and the Netherlands more than 300 cities have car-sharing networks. Members reserve a car in advance or call the network and are directed to the closest car. They are billed monthly for the time they use a car and the distance they travel. In Berlin, Germany, car sharing has cut car ownership by 75%. According to the Worldwatch Institute, car-sharing in Europe has reduced the average driver's carbon dioxide emissions by 40-50%. Car-share companies have sprouted up in the United States since 2000 in cities such as Portland, Oregon, and San Diego and Los Angeles in California, among others. Bicycles; mass transit rail; buses; rapid rail. Mayors and urban planners in many parts of the world are beginning to rethink the role of the car in urban transportation systems and are providing a mix of other options, as they have in Curitiba, Brazil. Leaders in developing countries are recognizing that most of their people could never afford to own automobiles, and they are questioning the development of expensive car-oriented systems that mostly benefit the affluent minority. There are several alternatives to motor vehicles, each with its own advantages and disadvantages. One widely used alternative is the bicycle. Bicycles reduce congestion, promote physical fitness, emit no CO2 or other air pollutants, cost little to buy and operate, and reduce the need for parking space. Each year, the number of bicycles produced globally is about 2.5 times the number of cars produced. Also growing is the use of electric bicycles with lightweight electric motors. Bicycles are widely used for urban trips in many countries. Bicycling and walking account for about a third of all urban trips in the Netherlands and in Copenhagen, Denmark. Japan and the Netherlands strive to integrate travel by bicycle and by commuter rail by providing secure bicycle parking at rail stations. By contrast, bicycles account for only about 1% of urban trips in the United States. But one of five Americans say they would bicycle to work if safe bike lanes were available and if their employers provided secure bike storage and showers at work. Heavy-rail systems (subways, elevated railways, and metro trains) and light-rail systems (streetcars, trolley cars, and tramways) have their advantages and disadvantages. At one time, all major U.S. cities had effective light-rail systems, but they were dismantled to promote car and bus use. However, such systems are being built again in several U.S. cities. An outstanding example is the lightrail system in Minneapolis, Minnesota, which opened in 2005 and surprised planners by drawing 50% more riders than they had expected. The rail system in Hong Kong is one of the world's most successful, primarily because the city is densely populated, which means that half the population can walk to a subway station within 5 minutes. And owning a car is extremely expensive in this crowded city, which helps to make the rail system attractive to almost everyone. Buses are the most widely used form of mass transit within urban areas worldwide, mainly because they have more advantages than disadvantages. Curitiba, Brazil, has one of the world's best bus rapid transit systems, which carries about 2.3 million passengers a day. But the system is now feeling the strain of population pressures, and car use is increasing in Curitiba. Transportation officials there are considering building a light-rail system to help carry the rapidly growing passenger load. Similar bus rapid transit systems have been developed in Bogotá, Colombia, and are being planned for Mexico City; São Paulo, Brazil; Seoul, South Korea; Beijing and 20 other cities in China; Ottawa and Toronto in Canada; and the U.S. cities of Los Angeles, California; Minneapolis, Minnesota; and Las Vegas, Nevada. A rapid-rail system between urban areas is another option. In western Europe and Japan, high-speed bullet trains travel between cities at up to 306 kilometers (190 miles) per hour. Such trains began operating in Japan in 1964 and now carry almost a million passengers a day. Since 1964, there has not been a single casualty, and late arrivals average only 6 seconds, explaining why some analysts consider this system to be one of the new wonders of the world. In 2004, Shanghai, China, began operating the world's first commercial high-speed magnetic levitation train between its airport and downtown. The train, suspended in air slightly above the track and propelled forward by strong repulsive and attractive magnetic forces, travels much faster than bullet trains do. In the United States, a high-speed bullet train network could replace airplanes, buses, and private cars for most medium-distance travel between major American cities. Critics say such a system would cost too much in government subsidies. But this argument ignores the fact that motor vehicle transportation receives government (taxpayer) subsidies of $300-600 billion per year in the United States. The Urban Land Institute estimates that building a U.S. system comparable to the best European systems would cost $250 billion per year over 2 decades.

What are the sources & effect of these indoor air pollutants? Formaldehyde

Source of indoor air pollution in developed countries. Another common chemical that leads to indoor air pollution is formaldehyde. Which can be found in a number of products in the home like plywood, furniture stuffing, upholstery, drapes, insulation, nail polish and more. The American Lung Association has estimated that up to 40 million people have symptoms due to chronic formaldehyde exposure (breathing problems, dizziness, rash, headaches, sore throat, eye irritation, skin irritation, wheezing, nausea). There are suspected links to Lou Gehrig's disease (ALS). It is also a suspected carcinogen. However, having houseplants can help to remove formaldehyde and other chemicals from the air.

What are the sources & effect of these indoor air pollutants? Radon

Source of indoor air pollution in mainly developed countries. Another major indoor air pollutant is Radon-222, a naturally occurring radioactive gas. Radon forms from the natural radioactive decay of Uranium-238, which is found in small quantities in all rocks & soils. (Some rock types will have a higher concentration of uranium, however) Normally, Uranium will decay, producing radon-222. The radon will seep upward through the soil and be released into the air. If it is released outdoors it disperses quickly and decays so that the remaining levels are harmless. If a building is located above a source of radon-222, the radon gas can seep upward through cracks in the foundation or openings around drains and can accumulate in the building. Radon will continue to decay, but some of its decay products (ex. Polonium-210) are also radioactive. Breathing high concentrations of radon-222 over a prolonged period can lead to lung cancer. Consequently, the EPA recommends frequent monitoring of radon in the living spaces in your home. This can be done with a kit, detector, or by hiring a company. If high concentrations are detected, the situation can be fixed by sealing cracks and increasing ventilation.

Know about the layers of the atmosphere: Location of ozone layer & effect on temperature

Stratosphere; temperature increases in the stratosphere because the ozone absorbs UV radiation from the sun.

Know how emissions trading (cap-and-trade) programs work and what provisions ensure that they actually work to reduce pollution

The market can also be used to help regulate air pollution. The cap-and-trade or emissions trading program enables power plants to buy and sell rights to emit SO2 gas. Each plant is given a cap on how much it can pollute and can sell its "credits" if it pollutes less than this. This is similar to the discharge trading policy that is part of the Clean Water Act and has similar drawbacks. While many say an emissions trading policy is a cheaper & more efficient way for the government to control air pollution, others say that is a way for plants to get away with not improving their environmental standards. Also if the same plants are always buying credits, then it can create pollution hotspots and just move air pollution from one place to another. An important part of this plan is determining how high the cap is set and lowering it with time. Nevertheless, because of the cap-and-trade policy for SO2, levels of this gas were reduced by half from 1990-2006 at a much lower cost than was initially estimated. It is possible that this same system will be tried for other pollutants such as NOx gases or perhaps CO2.

Know what the following are: Electrostatic precipitators

The other is called an electrostatic precipitator. These use static electricity to remove particulates from the exhaust stream before it is emitted into the atmosphere.

Know some ways to reduce air pollution from both stationary sources and motor vehicle sources

There are two major sources of outdoor pollutants-stationary sources & motor vehicles and the method for pollution reduction varies with each source. To reduce pollution from stationary sources (power plants, factories, incinerators), one of the best ways is to use alternative energy sources such as wind, solar or hydroelectric power. We can also use cleaner burning fuels like natural gas instead of coal. We can also use technology that captures emissions before leaving the smokestacks. One method is called scrubbers or wet scrubbers. Wet scrubbers spray a liquid onto the exhaust which removes particles and some gases. Sometimes the liquid contains limestone to neutralize acids. These are effective at removing NOx in particular and also SOx. The other is called an electrostatic precipitator. These use static electricity to remove particulates from the exhaust stream before it is emitted into the atmosphere. To reduce air pollution from motor vehicle sources we can prevent the burning of fossil fuels that release most of the pollution. Using mass transit like buses or trains is one way. We can also encourage people to walk or bike instead of drive. Improving the fuel efficiency of cars also reduces pollution and can be accomplished though using alternative fuels or improving the efficiency of cars. We can also use technology to clean up pollution. In particular, we can use catalytic converters on cars to control the types of exhaust that are leaving the car. Catalytic converters use a catalyst to accelerate the reaction of CO, NOx, and unburned hydrocarbons into CO2, N2 and water. Both CO and NOx can contribute to the formation of smog, so removing these pollutants can greatly enhance air quality.

How does ground-level ozone/photochemical smog form?

There should be a high concentration of ozone in the stratosphere and a low concentration in the troposphere. However, humans are adding to tropospheric ozone when VOCs & NOx react in the presence of heat & UV light. This tropospheric ozone is considered a secondary pollutant and is a major component of photochemical smog. Ozone in the troposphere near ground level is often referred to as "bad" ozone, whereas we think of ozone in the stratosphere as "good" ozone that protects us from harmful UV radiation. Both are the same chemical. Much evidence indicates that some human activities are decreasing the amount of beneficial ozone in the stratosphere and increasing the amount of harmful ozone in the troposphere near ground level—especially in some urban areas.

How have emissions of major air pollutants changed since 1980 due to the Clean Air Acts?

This process of reporting has sharply reduced the amount of toxic chemicals that are being released since it was first required in 1988. Overall despite increases in GDP and population, we have seen decreases in the criteria pollutants (and other pollutants) since 1980.

Know about the layers of the atmosphere: Location of most air

Trophosphere

Know about the layers of the atmosphere: Location of most weather

Troposphere

Know about the layers of the atmosphere: Order

Troposphere, stratosphere, mesosphere, thermosphere

What problems are caused for humans and marine food chains by thinning of the ozone layer?

Two biggest issues with ozone depletion are the impacts of UV on human health and ecosystems. For humans increased UV can lead to sunburn and skin cancer. More UV can also lead to reduced populations of phytoplankton which will cause the collapse of some aquatic food webs and could reduce the amount of seafood available. Because more UV is getting through the stratosphere now, more is available to help create photochemical smog and ground level ozone, another drawback to ozone depletion. CFCs do act as a greenhouse gas, however, ozone depletion is a completely different problem from climate change.

How can buildings, mountains, high temperatures and the presence of some trees increase outdoor air pollution?

Urban buildings can slow wind speed and reduce dilution and removal of pollutants. Hills and mountains can reduce the flow of air in valleys below them and allow pollutant levels to build up at ground level. High temperatures promote the chemical reactions leading to photochemical smog formation, which means that global warming could increase photochemical smog in many of the world's cities. Emissions of volatile organic compounds (VOCs) from certain trees and plants such as some oak species, sweet gums, poplars, and kudzu in heavily wooded urban areas can play a large role in the formation of photochemical smog.

Know what the following are: Catalytic converters

We can also use technology to clean up pollution. In particular, we can use catalytic converters on cars to control the types of exhaust that are leaving the car. Catalytic converters use a catalyst to accelerate the reaction of CO, NOx, and unburned hydrocarbons into CO2, N2 and water. Both CO and NOx can contribute to the formation of smog, so removing these pollutants can greatly enhance air quality.

What do the Clean Air Acts do primarily? What are the National Ambient Air Quality Standards? What are criteria pollutants?

We have the technology to reduce air pollution, so the question is, how do we get people to utilize these methods? This can be done using the marketplace by giving people economic incentives to reduce air pollution and it can also be done through legislation. The US has been a model worldwide for using legislation to reduce air pollution. The main piece of legislation that regulates air pollution in this country is the Clean Air Act. Under the Clean Air Act, the EPA established the National Ambient Air Quality Standards (NAAQS) for 6 major outdoor air pollutants that are deemed to be most harmful to human health, property and the environment. These 6 pollutants are called criteria pollutants and include ozone, lead, carbon monoxide, sulfur oxides, nitrogen oxides and particulate matter. The standard sets the maximum allowable level of each pollutant over a specific amount of time. The EPA also has set standards for other air pollutants under the Clean Air Act (VOCs, heavy metals etc). Industries that produce a lot of air pollution (refineries, power plants, factories etc) are also required to report their releases for hundreds of chemicals. This information is listed on the internet so it is available to the public. This process of reporting has sharply reduced the amount of toxic chemicals that are being released since it was first required in 1988. Overall despite increases in GDP and population, we have seen decreases in the criteria pollutants (and other pollutants) since 1980.

What are some environmental hazards associated with shantytowns/ squatter settlements? How can governments improve these conditions?

When it rains, the usually unpaved alleys can become clogged with dead rats, garbage, and sewage. Poor people living in shantytowns and squatter settlements usually lack clean water supplies, sewers, electricity, and roads, and are subject to severe air and water pollution and hazardous wastes from nearby factories. Many of these settlements are in locations especially prone to landslides, flooding, or earthquakes. Many city governments regularly bulldoze squatter shacks and send police to drive illegal settlers out. The people usually move back in or develop another shantytown somewhere else. There are ways in which governments can address these problems. For example, they can slow the migration from rural to urban areas by improving education, health care, and family planning in the countryside and encouraging investment in small towns. Governments can also designate land for squatter settlements and supply them with clean water, as Curitiba, Brazil, has done. In addition to providing access to safe drinking water, they can place composting toilets, which require no water, at locations throughout such settlements. Guaranteeing regular bus service enables workers who live in such settlements to travel to and from their workplaces. In Brazil and Peru, governments legally recognize existing slums (favelas) and grant legal titles to the land. This is based on understanding that the poor will usually improve their living conditions and develop schools, day care centers, and other social improvements once they know they can stay there.

How has the percentage of the US population living in cities changed since 1800?

Between 1800 and 2008, the percentage of the U.S. population living in urban areas increased from 5% to 79%.

Know what the following are: Wet scrubbers

We can also use technology that captures emissions before leaving the smokestacks. One method is called scrubbers or wet scrubbers. Wet scrubbers spray a liquid onto the exhaust which removes particles and some gases. Sometimes the liquid contains limestone to neutralize acids. These are effective at removing NOx in particular and also SOx.

Which two gases exist in the greatest concentrations in the atmosphere? What are there approximate concentrations?

Nitrogen accounts for 80% of the atmosphere and oxygen 20%.

What are some sources of the following air pollutants? Carbon monoxide

Forms during the incomplete combustion of carbon-containing materials. Major sources are motor vehicle exhaust, burning of forests and grasslands, tobacco smoke, and open fires and inefficient stoves used for cooking. Burning fossil fuels.

Study unit 1-8 study guides

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What is an air basin?

An air basin is an area within a ring or partial ring of mountains that in the absence of winds holds air and smog within the area.

In what part of the world was the hole (or thinned area) of the ozone layer detected?

Antartica

What are some advantages & disadvantages to urbanization?

Urbanization has many benefits. From an economic stand point, cities are centers of economic development, innovation, education, technological advances, and jobs. They serve as centers of industry, commerce, and transportation. Urban residents in many parts of the world tend to live longer than do rural residents and have lower infant mortality rates and fertility rates. They also have better access to medical care, family planning, education, and social services than do their rural counterparts. However, the health benefits of urban living are usually greater for the rich than for the poor. Urban areas also have some environmental advantages. Recycling is more economically feasible because concentrations of recyclable materials and funding for recycling programs tend to be higher in urban areas. Concentrating people in cities helps to preserve biodiversity by reducing the stress on wildlife habitats. And central cities can save energy if residents rely more on energy-efficient mass transportation, walking, and bicycling. Half of the world's 6.8 billion people live in urban areas and each year, about 63 million people—an average of nearly 7,200 per hour—are added to such areas. Such intense population pressure makes most of the world's cities more environmentally unsustainable every year. Even in more sustainable cities such as Curitiba, Brazil, this pressure is taking its toll. Curitiba's once clear streams are often overloaded with pollutants. The bus system is nearing capacity, and car ownership is on the rise. While the recycling rate is still among the highest in the world, the region's only landfill will soon be full. Architect Jorge Wilheim, who helped to create Curitiba's master plan, points out that the city's population is now more than five times as large as it was in 1965 when the plan was drafted. With a metropolitan area population of 3.2 million, Wilheim believes it is time to adjust the plan. Although urban populations occupy only about 2% of the earth's land area, they consume 75% of its resources and produce 75% of all carbon dioxide emissions from human activities, according to the Worldwatch Institute. Because of this high resource input of food, water, and materials and the resulting high waste output, most of the world's cities have huge ecological footprints and are not self-sustaining systems. By concentrating people in a small area urbanization helps to preserve some of the earth's biodiversity. But at the same time large areas of land that must be disturbed and degraded to provide urban dwellers with food, water, energy, minerals, and other resources. This decreases and degrades the earth's overall biodiversity. Thus, urban areas have huge ecological footprints that extend far beyond their boundaries. Recent studies also reveal that most urban dwellers live in an artificial environment that isolates them from forests, grasslands, streams, and other natural areas that contain the world's biodiversity. As a result, many of them tend to have little passion for protecting biodiversity and other forms of natural capital that support their lives and the cities where they live. In urban areas, most trees, shrubs, or other plants are destroyed to make way for buildings, roads, parking lots, and housing developments. So most cities do not benefit from vegetation that would absorb air pollutants, give off oxygen, cool the air through transpiration, provide shade, muffle noise, provide wildlife habitats, and give aesthetic pleasure. As one observer remarked, "Most cities are places where they cut down most of the trees and then name the streets after them." As cities grow and water demands increase, expensive reservoirs and canals must be built and deeper wells must be drilled. This can deprive rural and wild areas of surface water and deplete groundwater. Flooding also tends to be greater in some cities, because they are built on floodplains near rivers or along low-lying coastal areas subject to natural flooding. And covering land with buildings, asphalt, and concrete causes precipitation to run off quickly and overload storm drains. In addition, urban development has often destroyed or degraded wetlands that have served as natural sponges to help absorb excess water. Many of the world's largest cities face another threat because they are located in coastal areas that could be partially flooded some time in this century as sea levels rise due to projected climate change. Other cities in arid areas that depend on withdrawing water from rivers and the reservoirs behind dams may face severe water shortages as global warming reduces the mountaintop glaciers and snow that melt each year to provide river flows and fill reservoirs. As a result, in some hotspot arid areas in the western United States fed by the Colorado River and California's water distribution system, irrigated agriculture may have to be abandoned. And urban populations in some of these areas may drop sharply as people are forced to move elsewhere because of a lack of water. Greater reliance on groundwater is not an option in many areas where aquifers are being depleted faster than they are being replenished. Because of their high population densities and high resource consumption, cities produce most of the world's air pollution, water pollution, and solid and hazardous wastes. Pollutant levels are generally higher because pollution is produced in a smaller area and cannot be dispersed and diluted as readily as pollution produced in rural areas. The concentration of motor vehicles and industry in urban centers, where about three-fourths of the world's CO2 from human-related sources are emitted, causes disruption of local and regional portions of the carbon cycle. This urban concentration also disrupts the nitrogen cycle because of emissions of large quantities of nitrogen oxides, which play a key role in the formation of photo chemical smog, and nitric acid and nitrates, which are major components of acid deposition in urban areas and beyond. And nitrogen nutrients in urban runoff and discharges from urban sewage treatment plants can disrupt the nitrogen cycle in nearby lakes and other bodies of water and cause excessive eutrophication. In addition, high population densities in urban areas can increase the spread of infectious diseases, especially where there are no adequate drinking water and sewage systems. Cities generally are warmer, rainier, foggier, and cloudier than suburbs and nearby rural areas. The enormous amount of heat generated by cars, factories, furnaces, lights, air conditioners, and heat-absorbing dark roofs and streets in cities creates an urban heat island that is surrounded by cooler suburban and rural areas. As cities grow and merge, their heat islands merge, which can reduce the natural dilution and cleansing of polluted air. In addition to changing local and regional climate, the urban heat island effect in hot climates puts heat stress on humans and many other organisms, can increase the formation of photochemical smog, and greatly increases dependence on air conditioning for cooling. This in turn increases energy consumption, greenhouse gas emissions, and other forms of air pollution in a positive feedback loop. Most urban dwellers are subjected to noise pollution: any unwanted, disturbing, or harmful sound that impairs or interferes with hearing, causes stress, hampers concentration and work efficiency, or causes accidents. Noise levels are measured in decibel-A (dbA) sound pressure units that vary with different human activities. Sound pressure becomes damaging at about 85 dbA and painful at around 120 dbA. At 180 dbA it can kill. Prolonged exposure to sound levels above 85 dbA can cause permanent hearing damage. About one of every eight children and teens in the United States has some permanent hearing loss, mostly from listening to music at loud levels. Also, the artificial light created by cities hinders astronomers from conducting their research and makes it difficult for casual observers to enjoy the night sky. Light pollution also affects some plant and animal species. For example, endangered sea turtles lay their eggs on beaches at night and require darkness. And each year, large numbers of migrating birds, lured off course by the lights of high-rise buildings, fatally collide with the buildings.