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Environmental Science A Study of Interrelationships Twelfth Edition Enger & Smith Chapter 16 Air Quality Issues Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Air Quality Issues Outline The Atmosphere Pollution of the Atmosphere Categories of Air Pollutants Control of Air Pollution Acid Deposition Ozone Depletion Global Warming and Climate Change Addressing Climate Change Indoor Air Pollution The Atmosphere The atmosphere is composed of 78.1% N, 20.9% O, and about 1% of other gases such as argon, carbon dioxide, methane, and water vapor. Most of the atmosphere is held close to the Earth by the pull of gravitational force, thus it gets less dense with increasing distance from the Earth. Air Quality Issues The Atmosphere The troposphere extends from the Earth’s surface to about 10 km above the Earth. The stratosphere extends from the top of the troposphere to about 50 km above the Earth. • Most ozone is located in a band between 15 and 30 km. The mesosphere extends from 50-80 km above the Earth. The thermosphere extends to about 300 km above the Earth. The Atmosphere The Atmosphere As the air absorbs heat from the Earth, it expands and rises. • When heat is radiated into space, air cools, becomes more dense, and flows toward the Earth. As the air circulates vertically, it also moves horizontally as the Earth spins on its axis. The combination of all air movements creates the wind and weather patterns characteristic of different regions of the world. Pollution of the Atmosphere Pollution is any addition of matter or energy that degrades the environment for humans and other organisms. Because human actions are the major cause of pollution, we can do something to prevent it. Automobile emissions, chemical odors, factory smoke, and similar materials are considered air pollution. Pollution of the Atmosphere Air pollution is directly related to the number of people living in an area and the kinds of activities in which they are involved. In urbanized, industrialized societies, there are dense concentrations of people that use large quantities of fossil fuels for manufacturing, transportation, and domestic purposes. These activities release large quantities of polluting byproducts into our environment. Pollution of the Atmosphere In urbanized areas, pollution cannot be sufficiently diluted before the air reaches another city. • Polluted air from Chicago is further polluted when it reaches Gary, Indiana; • is supplemented by wastes of Detroit and Cleveland; • and finally moves over southeastern Canada and New England to the ocean. Air pollution is not just an aesthetic problem; it also causes health problems. Pollution of the Atmosphere Air pollution and population centers Pollution of the Atmosphere Many of the megacities of the developing world have extremely poor air quality. The causes of this pollution are open fires, poorly maintained motor vehicles, and poorly regulated industrial plants. • Air pollution increases the death rate and lowers the general health of the population. – Chronic coughing and susceptibility to infections are common. Categories of Air Pollutants Five major types of materials are released directly into the atmosphere in unmodified forms in sufficient quantities to pose a health risk. These are called primary air pollutants. They are: • • • • • Carbon monoxide Volatile organic compounds (hydrocarbons) Particulate matter Sulfur dioxide Oxides of nitrogen Categories of Air Pollutants Secondary air pollutants form under reaction of primary pollutants and water or sunlight. • Ozone Criteria air pollutants are those pollutants for which specific air quality standards have been set. • • • • • • Nitrogen dioxide (NO2) Ozone (O3) Sulfur dioxide (SO2) Particulate matter (PM) Carbon monoxide (CO) Lead (Pb) Categories of Air Pollutants Carbon monoxide is produced when organic materials are burned with insufficient oxygen. • The single largest source is the automobile. – 60% from vehicles driven on roads – 20% from vehicles not used on roads – Remainder from burning, i.e., power plants, leaves, etc. • Carbon monoxide binds to hemoglobin in blood and makes the hemoglobin less able to carry oxygen. • It is most dangerous in enclosed spaces; several hours of exposure to air containing only 0.001% CO can cause death. Categories of Air Pollutants Carbon monoxide Categories of Air Pollutants Cigarette smoking is an important source because the person is inhaling CO directly. U.S. levels of CO have decreased by about 67% between 1970 and 2007. Categories of Air Pollutants Particulate matter consists of minute pieces of solid materials (< 10 microns) and liquid droplets dispersed into the atmosphere. • The EPA has set standards for particles smaller than 10 microns (PM10) and 2.5 microns (PM 2.5). • Larger than 2.5 microns are primary pollutants; smaller than 2.5 are mostly secondary pollutants. • Particulates can accumulate in lungs and interfere with the ability of lungs to exchange gases. Categories of Air Pollutants Amount of PM10 has decreased 28% between 1990 and 2007. U.S. EPA has been setting PM2.5 standards for a shorter period of time. • Amount decreased 11% between 2000 and 2007. Most communities now meet the standards set for PM10 but exceed the standards set for PM25. Categories of Air Pollutants Sulfur dioxide (SO2) is a compound of sulfur and oxygen produced when sulfur-containing fossil fuels are burned. • Burning coal releases SO2. • Today over 70% of SO2 released into the atmosphere is from coal-burning power plants. – U.S. levels of SO2 decreased 56% between 1990 and 2007. Nearly all communities meet the SO2 standards set by the U.S. EPA. Categories of Air Pollutants Oxides of nitrogen (NOx) are formed when fossil fuels are burned. The nitrogen and oxygen molecules in the air combine with one another when subjected to the high temperatures of combustion. • Nitrogen monoxide (NO) and nitrogen dioxide (NO2) are the most common. • Burning fossil fuels in internal combustion engines is the primary source of nitrogen oxides. – Automobiles produce 38% – Non-road motorized equipment produces 21% – Electrical generations produces 22% Categories of Air Pollutants About 75% of the NO produced by an automobile engine is converted back into N2 and O2 by the catalytic converter. • An increase in the number of cars and miles driven offsets the gains attributable to catalytic converters. Although all communities meet the EPA standards for nitrogen oxides, they remain a problem because they contribute to the development of photochemical smog. Categories of Air Pollutants Lead (Pb) can enter the body through breathing airborne particles or consuming lead deposited on surfaces. Lead accumulates in the body and can cause mental retardation and kidney damage. Leaded gasoline was primary source. • Currently, over 80% of gasoline sold in the world is unleaded. Those still using it plan to phase it out. • In the U.S. lead emissions peaked at about 258,000 tons per year. In 2007 they were about 1300 tons per year, a reduction of 99.5%, meeting EPA standards in the U.S. Categories of Air Pollutants Volatile organic compounds readily evaporate and become pollutants in the air. They are also known as hydrocarbons, a group of organic compounds consisting of carbon and hydrogen. The use of internal combustion engines accounts for 37% of VOCs released into the air. • Solvents contribute about 22% • Fires contribute about 15% Categories of Air Pollutants VOCs aid the production of secondary air pollutants found in smog. Some VOCs are toxic and are known as hazardous air pollutants. The EPA does not publish VOC reduction data. • VOC levels are reduced when ozone levels fall. VOC levels have fallen substantially in recent years. Categories of Air Pollutants Ozone (O3) is a molecule of three oxygen atoms bonded to one another. • It is an extremely reactive secondary pollutant that can: – Cause permanent lung damage – Irritate respiratory tissues – Damage plants – Reduce agricultural yields • Zone levels fell by only about 9% from 1990 to 2007 and are still a problem particularly in southern California and the U.S. Northeast. Categories of Air Pollutants Photochemical smog is a mixture of pollutants. It forms when nitrogen dioxide and VOCs interact in primary pollutants interact under the influence of sunlight. • Two most destructive components: – Ozone – Peroxyacetyl nitrates Categories of Air Pollutants Daily changes in photochemical smog Categories of Air Pollutants Cities with warm climates and lots of sunlight are more prone to develop photochemical smog. • Warm temperatures and sunlight are needed. • Smog is more likely to be a problem in the summer with higher temperatures and longer days. • Cities adjacent to mountains or in valleys tend to have trouble with photochemical smog because pollutants are trapped by thermal inversions. Categories of Air Pollutants Thermal inversions occur when warm air becomes sandwiched between two layers of cold air and acts like a lid on a valley. Warm air cannot rise, causing smog accumulation. • Ozone levels fell by about 9% from 1990 to 2007 and are still a problem, particularly in southern California and the U.S. Northeast. • Since ozone is produced by VOCs and Nox it is necessary to further reduce the levels of these two components to decrease the production of ozone. Categories of Air Pollutants Thermal inversion Categories of Air Pollutants Hazardous air pollutants (HAP), or air toxics, are compounds that can harm human health or damage the environment. • Some released from consumer activities: – Benzene escapes during automobile refueling. – Some consumer products such as glues and cleaners release toxic materials into the air. • The majority are released from manufacturing: – Perchloroethylene is released from dry cleaning processes. Control of Air Pollution All of the air pollutants examined thus far are produced by humans. Thus, their release into the atmosphere can be controlled. • In the U.S., implementation of the Clean Air Act has been the primary means of controlling air pollution. Engineering changes in autos have reduced the amount of VOCs that escape from the gas tank and crankcase. Modifications to the pumps at gas stations and filler pipes of cars has been beneficial. Control of Pollution In the U.S., implementation of the requirements of the Clean Air Act has been the primary means of controlling air pollution. • Under the Clean Air Act, a variety of pollution control mechanisms have been employed and the quality of air has improved significantly in the last 27 years. • The EPA is responsible for developing and meeting air quality standards. • Industry must meet a series of detailed control requirements with the goal of improving air quality. Control of Air Pollution Motor vehicles are the primary source of several important air pollutants: carbon monoxide, VOCs, and nitrogen oxides. • Catalytic converters reduce these emissions. Lead-free fuel has reduced the amount of lead in the atmosphere. Ozone levels depend on VOC and NO2 levels, and have fallen somewhat but still need improvement in some areas of the country, particularly California and the northeast U.S. Control of Air Pollution Mining, farming, transfer of grain or coal, and road dust are sources of particulate emissions. Forest fires, grass fires, leaf burning, fireplaces, and woodstoves are a significant source of particulate matter. • Some municipalities ban wood burning stoves and fireplaces, while high-efficiency wood stoves significantly reduce particulate emissions. Burning of fossil fuels is another source of particulate matter. Diesel engines are a source of particulate matter. Control of Air Pollution Improvement in air quality Control of Air Pollution Power plant emissions Particulates and sulfur dioxide are associated with electric power plants. • Filters and mechanical means control particulates. • The control of sulfur dioxide requires changes to the way electricity is produced. The EPA has set limits and allow the electric utility to decide which options are best for them. Control of Air Pollution Low-sulfur coal reduces sulfur emissions by 66%. Switching to oil, natural gas, or nuclear fuels further reduces sulfur emissions. 40% of sulfur can be removed before the fuel is used. Smokestack gases can be scrubbed before they are emitted. • The technology is available, but costly to install, maintain, and operate. Acid Deposition Acid deposition is the accumulation of potential acid-forming particles on a surface. When dry particles are deposited, an acid does not actually form until these materials mix with water. All of these sources of acid-forming particles are commonly referred to as acid rain. Acid Deposition Acid deposition is the accumulation of potential acid-forming particles on a surface. When dry particles are deposited, an acid does not actually form until these materials mix with water. All of these sources of acid-forming particles are commonly referred to as acid rain. SO2 + H2O H2SO4 (Sulfuric Acid) Acid Rain Limestone degradation:H2SO4 + CaCO3 CaSO4 (soluble in water) Limestone degradation Forest Decline Acid Deposition Sources of acid deposition Acid Drainage Acid Deposition Acid rain is a worldwide problem. Acid rains can have concentrations of acid 1000 times higher than normal. Harmful effects of acid rain include: • Property and structural damage – Limestone degradation • Damage to forests – Acidic soil results in reduced nutrient absorption • Lake acidification causes food chain disruption Ozone Depletion In 1985, it was discovered that a significant thinning of the ozone layer over the Antarctic occurred during the Southern Hemisphere spring. The stratosphere was being reduced, and this area became known as the “ozone hole.” Ozone in the outer layers of the atmosphere shields the Earth from the harmful effects of ultraviolet light radiation. Ozone Depletion Chlorofluorocarbons and similar compounds can release chlorine atoms which can lead to the destruction of ozone. It can take 10 to 20 years for chlorofluorocarbon molecules to get into the stratosphere. They can then react with the ozone for up to 120 years. Ozone Depletion Chlorofluorocarbons are strongly implicated in the ozone reduction in the upper atmosphere. It can take 10 to 20 years for chlorofluorocarbon molecules to get into the stratosphere. They can then react with the ozone for up to 120 years. UV + O3 O2 + O O2 + O ---> O3 Ozone formation Ozone Depletion (causing ozone hole) global warming Cl + O3 ClO + O2 ClO + O Cl + O2 Ozone Depletion In 1987, several industrialized countries including Canada, the United States, the United Kingdom, Sweden, Norway, Netherlands, the Soviet Union, and West Germany agreed to freeze chlorofluorocarbon and halon (used in fire extinguishers) production and reduce production by 50% by 2000. This document, known as the Montreal Protocol, was ratified by Congress in 1988. As a result, emissions dropped 87% from their peak in 1988. Ozone Depletion Size of ozone hole Global Warming and Climate Change Climatic records indicate over the past 160,000 years a close correlation between greenhouse gas concentration and global temperatures. UN established the Intergovernmental Panel on Climate Change (IPCC) Global Warming and Climate Change The Fourth Assessment Report, Climate Change 2007, concluded: • The average temperature on Earth has increased 0.56 to 0.92°C (1.0-1.7° F) in the past 100 years. 1998 was the hottest year on record; 2005 was the second warmest; 2002 was the third. • Sea level is rising about 1.8 mm/yr or 18 cm in 100 years. • A strong correlation exists between temperature increase and amount of greenhouse gases in the atmosphere. • Human activity greatly increases amounts of greenhouse gases in atmosphere. Global Warming and Climate Change Greenhouse effect: • Greenhouse gases allow sunlight to penetrate the atmosphere. • Sunlight is absorbed by Earth’s surface. • It is reradiated as infrared energy (heat). • The heat is absorbed by gases in the atmosphere. Global Warming and Climate Change Greenhouse effect Global Warming and Climate Change Carbon dioxide is the most abundant of the greenhouse gases. • Deforestation contributes to the amount of carbon dioxide in the atmosphere. Methane comes from biological sources and from some fossil-fuel burning activities. Nitrous oxide enters the atmosphere from fossil fuels and fertilizers. Chlorofluorocarbons from refrigerants, cleaning solvents, and propellants are also a component of the greenhouse effect. Global Warming and Climate Change Although a small increase in the average temperature of the Earth may seem trivial, it could set in motion changes that could significantly alter the climate of major regions of the world. • Computer models suggest a cascade of consequences that affect the hydrologic cycle, sea level, human health, the survival and distribution of organisms, and the use of natural resources by people. Global Warming and Climate Change Potential Consequences of Global Warming • Rising sea level – Beach and coastal wetland erosion – Substantial loss of coastal area – Land area of some island nations and countries like Bangladesh would change dramatically as flooding occurred. Global Warming and Climate Change Potential Consequences of Global Warming Rising Sea Level • Water expands when it is warmed. • Melting glaciers add more water to the oceans. – Beaches and coastal wetlands erode, inundating lowlying areas, and coastal areas become more vulnerable to flooding from storm surges and intense rainfall. – By 2100 sea level is expected to rise 15–90 cm or 6–35 inches. – A 50 cm rise results in substantial land loss in North America. Global Warming and Climate Change Potential Consequences of Global Warming • Health effects – Most direct effect of climate change would be impacts of hotter temperatures. – Hot temperatures force cardiovascular system to work harder to cool the body. – Heat exhaustion and some respiratory problems increase. – Aggravate air quality problems. – Spread of tropical disease such as malaria, dengue fever, yellow fever, and encephalitis to temperate parts of the world. Global Warming and Climate Change Potential Consequences of Global Warming Geographic distribution of organisms could be altered. • Equatorial organisms move toward the poles, and tundra biomes are affected due to the thawing of permafrost. • Coral reefs are affected by increased water temperature and increased acidity of ocean water from dissolved CO2. • Low lying islands and shorelines are impacted by rising sea level. Mangrove forests and marshes will be inundated and subjected to violent weather and storm surges. Global Warming and Climate Change Potential consequences of global warming Climate strongly affects crop yield. In regions with drought and heat stress, yields will fall. Yields will increase in areas with warmer temperatures and more rainfall. Episodes of severe weather will cause crop damage that will affect yields. Global Warming and Climate Change Addressing Climate Change Approaches to dealing with climate change involve technological change coupled with political will and economic realities. • Increase efficiency of energy utilization and reduce carbon dioxide production. – Carbon tax A carbon tax is an environmental tax on emissions of carbon dioxide (CO2). • Increase the amount of carbon dioxide removed from the atmosphere. – Increased vegetation growth – May be a short-term benefit Addressing Climate Change Political and Economic Forces • It will be more difficult to achieve global consensus to reduce CO2 emissions, as CO2 is released as a result of energy consumption which affects all sections of the economy. • Increases in energy efficiency and reductions in greenhouse gas emissions are likely to have important related benefits that could offset the costs. – Improving fuel efficiency and reducing pollution can be offset by lower health care costs and higher worker productivity. Addressing Climate Change – Many candidates for longer-term technological transition have been identified, and some have already begun to penetrate the market. – Wind energy systems competitive with coal-burning power plants – The U.S. DOE has concluded that relying on already proven technology, the U.S. could reduce its carbon emissions by 400 million metric tons in 2010. – This would stabilize emissions in that year at 1990 levels. – Savings from reduced energy costs would be roughly equal to the added cost of investment. Addressing Climate Change – Resources and policies to increase investment in renewable and other long-term technologies will be needed. Indoor Air Pollution Growing evidence indicates air within homes and other buildings can be more seriously polluted than outdoor air in the most industrialized cities. These pollutants are thought to have adverse effects on human health. • • • • • • Asbestos Formaldehyde (in many consumer products) Airborne pesticide residues Chloroform Perchloroethylene Paradichlorobenzene Indoor Air Pollution Smoking is the most important pollutant. Weatherizing to increase efficiency slows air exchange and tends to trap pollutants. Movements to reduce indoor air pollution lag behind regulations governing outdoor air pollution. The EPA is conducting research to identify and rank the human health risks that result from exposure to individual indoor pollutants or mixtures of multiple indoor pollutants. Indoor Air Pollution Secondhand smoke is exposure to environmental tobacco smoke as a result of living and working in places where people smoke. In July 1993, the EPA recommended several actions to prevent people from being exposed to secondhand indoor smoke: • People not smoke in their homes or permit others to do so. • All organizations that deal with children have policies that protect children from secondhand smoke. Indoor Air Pollution • Every company has a policy that protects employees from secondhand smoke. • Today only 16 states do not have some kind of a statewide ban on smoking in public places. • Even if a state does not have legislation, many cities and other jurisdictions within those states do. Indoor Air Pollution Radon is an inert radioactive gas with a half-life of 3.8 days. It is formed as a byproduct of uranium-238 decay. It may undergo radioactive decay in human lungs when inhaled. Increased incidence of lung cancer is the only known health effect associated with radon decay products. Indoor Air Pollution Radon usually diffuses up through rocks and soil and escapes harmlessly into the atmosphere, but it can diffuse into groundwater. It can enter a home through an open space in the foundation, from gaps around pipes, or from wells. The EPA and the U.S. surgeon general recommend that all Americans (with a few exceptions) test their homes for radon. If radon is detected, simple and inexpensive actions may be taken to lower the level in the home. Indoor Air Pollution Generalized geologic radon potential of the United States Indoor Air Pollution Noise is unwanted sound. Research has shown that exposure to noise can cause physical as well as mental harm. The loudness of a sound is measured by decibels. The frequency or pitch of a sound is a factor in determining its degree of harm. Noise pollution is linked to a variety of ailments; research has shown it may also cause blood vessels to constrict, it disturbs unborn children, and sometimes causes seizures in epileptics. Indoor Air Pollution The Noise Control Act of 1972 was the first major attempt in the U.S. to protect the public health and welfare from detrimental noise. Many European countries do more to control noise than the U.S. does. • Several European countries have developed quiet construction equipment in conjunction with strongly enforced noise ordinances. Summary The atmosphere has a tremendous ability to disperse pollutants. Carbon monoxide, hydrocarbons, particulate matter, sulfur dioxide, and oxides of nitrogen are the primary air pollutants. The U.S. EPA establishes standards for six pollutants known as criteria air pollutants: carbon monoxide, nitrogen dioxide, sulfur dioxide, volatile organic compounds, ozone, and lead. Acid rain is caused by emissions of sulfur dioxide and oxides of nitrogen in the upper atmosphere. Summary These compounds form acids that are washed from the air when it rains or snows or settle as particles on surfaces. The control of acid rain requires the use of scrubbers, precipitators, and filters, or the removal of sulfur from fuels. Many are concerned about the damaging effects of greenhouse gases: carbon dioxide, nitrous oxide, methane, and chlorofluorocarbons. Summary These greenhouse gases are likely to be causing an increase in the average temperature of the Earth and are leading to major changes in the climate. Significant impacts on our health, the vitality of forests and other natural areas, the distribution of freshwater supplies, and the productivity of agriculture are among the probable consequences of climate change. Summary Chlorofluorocarbons also lead to the destruction of ozone in the upper atmosphere, which results in increased amounts of ultraviolet light reaching Earth. Many commonly used materials release gases into closed spaces (indoor air pollution) where they cause health problems. The most important of these health problems are associated with tobacco smoking.