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PART ONE: The Energy—Atmosphere System Overview—Part One Elemental Geosystems begins with the Sun and solar system to launch the first of four parts. Our planet and our lives are powered by radiant energy from the star closest to Earth—the Sun. Each of us depends on many systems that are set into motion by energy from the Sun. These systems are the subjects of Part One. Part One exemplifies the systems organization of the text: it begins with the origin of the solar system and the Sun. Solar energy passes across space to Earth's atmosphere, varying seasonally in its effects on the atmosphere. Insolation then passes through the atmosphere to Earth's surface. From Earth's surface, atmospheric and surface energy balances generate patterns of world temperature and general and local atmospheric circulations. Each part contains related chapters with content arranged according to the flow of individual systems or in a manner consistent with time and the flow of events. In the part-opening photo, two extratropical cyclones swirl in tandem, demonstrating Earth's global atmospheric circulation. Such is the role of physical geography and spatial analysis of Earth’s systems—all involving physical principles in Part One, The Energy—Atmosphere System.


Solar Energy, Seasons, and the Atmosphere The ultimate spatial inquiry is to discern the location of Earth in the Universe. To properly set the stage for a course in the physical geography of Earth, slides, videography, and posters can be used to establish the location and place of our planetary home. Our immediate home is North America, a major continent on planet Earth, the third planet from a typical yellow star in a solar system. That star, our Sun, is only one of billions in the Milky Way Galaxy, which is one of millions of galaxies in the Universe. This chapter examines the nature of the flow of energy and material from the Sun to the outer reaches of Earth's atmosphere. Earth–Sun orbital relations during the year produce the pulse of seasons and the annual changes in daylength, Sun altitude and declination. The passage of solar energy through Earth’s atmospheric layers is profiled, as is the filtering of harmful radiation.

The chapter examines the deterioration of valuable stratospheric ozone as a result of humanproduced gases. Anthropogenic gases—air pollution— affects life, economies, and nature. Policies such as the Clean Air Act dramatically turned the air pollution problem around. CAA benefits outweigh costs by at least 42 to 1. Outline Headings and Key Terms The first-, second-, and third-order headings that divide Chapter 2 serve as an outline for your notes and studies. The key terms and concepts that appear boldface in the text are listed here under their appropriate heading in bold italics. All these highlighted terms appear in the text glossary. Note the check-off box () so you can mark class progress.

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The outline headings for Chapter 2: Geosystems Now 2: “Humans help define the atmosphere” The Solar System Nebular Hypothesis  Milky Way Galaxy  gravity  planetesimal hypothesis Dimensions, Distances, and Earth’s Orbit  speed of light  perihelion  aphelion Solar Energy: From Sun to Earth Electromagnetic Spectrum and Plants  fusion Solar Activity and Solar Wind  solar wind  sunspots  magnetosphere  auroras Electromagnetic Spectrum of Radiant Energy  electromagnetic spectrum  wavelength Incoming Energy at the Top of the Atmosphere  thermopause  insolation Solar Constant  solar constant Uneven Distribution of Insolation  subsolar point Global Net Radiation The Seasons Earth–Sun Relations, Seasons Seasonality  altitude  declination  daylength Reasons for Seasons Revolution  revolution Rotation  rotation  circle of illumination Tilt of Earth’s Axis  plane of the ecliptic Axial Parallelism  axial parallelism Annual March of the Seasons  Tropic of Cancer  Tropic of Capricorn  winter solstice  December solstice  Arctic Circle  vernal equinox  March equinox

 summer solstice  June solstice  Antarctic Circle  autumnal equinox  September equinox Seasonal Observations Atmospheric Composition, Temperature, and Function Ozone Breakdown, Ozone Hole  exosphere Atmospheric Profile  air pressure Atmospheric Composition Criterion Heterosphere  heterosphere Homosphere  homosphere Carbon dioxide Atmospheric Temperature Criterion Thermosphere  thermosphere  kinetic energy  sensible heat Mesosphere  mesosphere Stratosphere  stratosphere Troposphere  troposphere  normal lapse rate  environmental lapse rate Atmospheric Function Criterion Ionosphere  ionosphere Ozonosphere  ozonosphere  ozone layer  chlorofluorocarbons (CFCs) UV Index Helps Save Your Skin Variable Atmospheric Components Natural Sources Natural Factors that Affect Air Pollution Winds Local and Regional Landscapes Temperature Inversions  temperature inversion Anthropogenic Pollution Photochemical Smog  photochemical smog  peroxyacetyl nitrates (PAN) Industrial Smog and Sulfur Oxides  industrial smog  sulfur dioxide  sulfate aerosols Particulates  particulate matter (PM)

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Full file at  aerosols  anthropogenic atmosphere Benefits of the Clean Air Act Geosystems Connection Key Learning Concepts Review MasteringGeography Focus Study 2.1: Stratospheric Ozone Losses: A Continuing Health Hazard Focus Study 2.2: Acid Deposition: Damaging to Ecosystems Critical Thinking 2.1: “A way to calculate sunrise and sunset” Critical Thinking 2.2: “Astronomical factors vary over long time frames” Critical Thinking 2.3: “Measuring the Sun’s changing altitude” Critical Thinking 2.4: “Where is your tropopause?” Critical Thinking 2.5: “Finding your ozone column” Critical Thinking 2.6: “Evaluating costs and benefits” Geo Report 2.1: “Recent solar cycles” Geo Report 2.2: “Why do we always see the same side of the Moon?” Geo Report 2.3: “Outside the airplane” Geo Report 2.4: “Atmospheric carbon dioxide accelerates” Geo Report 2.5: “NASA's Global Hawk makes first scientific flight” Geo Report 2.6: “Smoke gets in your eyes”

• Distinguish between natural and anthropogenic variable gases and materials in the lower atmosphere and describe the sources and effects of air pollution and acid deposition.

The URLs related to this chapter of Elemental Geosystems can be found at

2. If you have seen the Milky Way at night, briefly describe it. Use specifics from the text in your description. From our Earth-bound perspective in the Milky Way, the galaxy appears to stretch across the night sky like a narrow band of hazy light. On a clear night the naked eye can see only a few thousand of the nearly 400 billion stars.

Key Learning Concepts After reading the chapter and using the study guide, the student should be able to: • Distinguish among galaxies, stars, and planets, and locate Earth. • Describe the Sun’s operation and explain the characteristics of the solar wind and the electromagnetic spectrum of radiant energy. • Define solar altitude, solar declination, and daylength, and describe the annual variability of each—Earth’s seasonality. • Construct a general model of the atmosphere based on composition, temperature, and function and diagram this model in a simple sketch. • Describe conditions within the stratosphere; specifically, review the function and status of the ozonosphere (ozone layer).

Annotated Chapter Review Questions • Distinguish among galaxies, stars, and planets, and locate Earth. 1. Describe the Sun's status among stars in the Milky Way Galaxy. Describe the Sun's location, size, and relationship to its planets. Our Sun is both unique to us and commonplace in our galaxy. It is only average in temperature, size, and color when compared with other stars, yet it is the ultimate energy source for almost all life processes in our biosphere. Planets do not produce their own energy. Our Sun is located on a remote, trailing edge of the Milky Way Galaxy, a flattened, disk-shaped mass estimated to contain up to 400 billion stars. An excellent poster for this discussion comes as a supplement with the June 1983 National Geographic magazine (Vol. 163, No. 6, p. 704A), “Journey into the Universe Through Time and Space.” (Back issues are available from NGS.) The same illustration appears modified in the editions of the Atlas of the World by National Geographic, now in its seventh edition (p. 24, “The Universe, Nature's Grandest Design”).

3. Briefly describe Earth's origin as part of the Solar System. According to prevailing theory, our solar system condensed from a large, slowly rotating, collapsing cloud of dust and gas called a nebula. As the nebular cloud organized and flattened into a disk shape, the early proto-Sun grew in mass at the center, drawing more matter to it. Small accretion (growing) eddies— the protoplanets—swirled at varying distances from the center of the solar nebula. The early protoplanets, or planetesimals, were located at approximately the same distances from the Sun that the planets are today. The beginnings of the Sun and the solar system are estimated to have occurred more than 4.6 billion years

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ago. These processes are now observed as occurring elsewhere in the galaxy. Astronomers so far have observed almost two dozen stars with planets orbiting about them. 4. Compare the locations of the eight planets of the Solar System. Examine Figure 2.1, p. 39. A comparison of Earth with the other planets is interesting. The average distance from the Sun to Earth is referred to as an astronomical unit, or A.U., and is used as a basic measurement unit in the Solar System. The average distance from the Sun in terms of astronomical units are as follows: Mercury = 0.39, Venus = 0.72, Earth = 1.0, Mars = 1.52, Jupiter = 5.20, Saturn = 9.54, Uranus = 19.18, Neptune = 30.70, and the dwarf planet Pluto varies from 30 to 49. Note: Pluto's motion is so skewed from the plane of the ecliptic and eccentric in orbit that Neptune actually was further from the Sun than Pluto from 1979 until 1999. In 2006, Pluto was reclassified by the IAU as a dwarf planet. 5. How far is Earth from the Sun in terms of light speed? In terms of kilometers and miles? Earth's orbit around the Sun is presently elliptical—a closed, oval-shaped path (Figure 2.1d). Earth's average distance from the Sun is approximately 8 minutes, 20 seconds or 150 million km (93 million mi). 6. Briefly describe the relationship among these concepts: Universe, Milky Way Galaxy, Solar System, Sun, Earth, and Moon. The Universe is infinite in size and dimension from our perspective. Tens of billions of galaxies are known to populate the Universe we can observe, each composed of hundreds of billions of stars. Our Sun is a typical yellow-dwarf thermonuclear (fusion) star, somewhat less than a million miles in diameter. Planets orbit about stars such as our Solar System. Our Sun and the orbiting planets are revolving around the Milky Way Galaxy in a vast clockwise spiral. Similar multiple-planet solar systems are now being studied through the Hubble and other telescopes. 7. Diagram in a simple sketch Earth's orbit about the Sun. How much does it vary during the course of a year? See diagram 2.1d. Earth is at perihelion, its closest position to the Sun, on January 3 at 147,255,000 km (91,500,000 mi) and at aphelion, its farthest distance from the Sun, on July 4 at 152,083,000 km (94,500,000 mi). This seasonal difference in distance from the Sun results in a variation of 3.4 percent in the solar output that is intercepted by Earth.

_____________ • Describe the Sun’s operation, and explain the characteristics of the solar wind and the electromagnetic spectrum of radiant energy. 8. How does the Sun produce such tremendous quantities of energy? The solar mass produces tremendous pressure and high temperatures deep in its dense interior region. Under these conditions, pairs of hydrogen nuclei, the lightest of all the natural elements, are forced to fuse together. This process of forcibly joining positively charged nuclei is called fusion. In the fusion reaction hydrogen nuclei form helium, the second lightest element in nature, and liberate enormous quantities of energy in the form of free protons, neutrons, and electrons. During each second of operation, the Sun consumes 657 million tons of hydrogen, converting it into 652.5 million tons of helium. The difference of 4.5 million tons is the quantity that is converted directly to energy—resulting in literally disappearing solar mass. Notes on the Essence of Matter and Fusion. A few basics might be of assistance to support possible questions. An atom is the smallest particle of matter that still has distinct properties and can enter into chemical combination. The central core of an atom is called the nucleus and is composed of tightly packed particles called protons (positive charge) and neutrons (neutral charge). Many other smaller particles reside in the nucleus as well. Electrons are small, almost weightless, negative electrical charges (probabilistic energy potentials in quantum physics) that exist about the nucleus at varying distances (energy levels). The nucleus in the center of the atom is surrounded by vast amounts of empty space. A neutral atom has the same number of electrons and protons, thereby creating a balanced neutral charge. An ion is an ionized atom that has an electric charge with a gained or lost electron. Hydrogen in its most common form (isotope) has one electron and one proton. Oxygen possesses eight protons with eight orbiting electrons, and so on up the periodic table of elements. Two or more atoms bound together form a molecule; molecules together form compounds. Hydrogen has one proton and one electron in its principal form; add a neutron to the nucleus and it becomes a deuterium hydrogen atom. Helium has two protons and two electrons. Under the conditions of temperature and pressure in the Sun's core, pairs of hydrogen nuclei, the lightest of all the natural elements, are forced to fuse together in various isotopic combinations. This process of forcibly joining positively charged nuclei is called fusion. An unstable form of helium, Helium-3, is formed and a neutron is

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Full file at liberated as energy. Helium-3 fuses further with another deuterium to form Helium-4, a stable form of helium, and in this case a proton is liberated as energy. The Sun has converted about 8 percent of its mass to helium overall. The text gives a simple equation of the fusion reaction with hydrogen nuclei forming helium, the second lightest element in nature, and liberating enormous quantities of energy in the form of free protons, neutrons, and electrons that are propelled out from the core of the Sun. The liberated energy takes approximately 10 million years to migrate through the Sun's gaseous densities to its surface! Every second a tremendous conversion of hydrogen to helium and liberated energy takes place. During each second of operation the Sun consumes 657 million tons of hydrogen, converting it into 652.5 million tons of helium. The difference of 4.5 million tons is the quantity that is converted directly to energy– literally disappearing solar mass just as Einstein postulated in his E = m . c2 equation, where the nuclear energy [E] in matter can be calculated for a given mass [m] by multiplying mass times the speed of light [c] squared. Energy and matter are interchangeable. Figure 2.2, p. 40, presents three images produced by the SOHO satellite, a joint effort of the European Space Agency and NASA. Note the correlation between the sunspot grouping and an intense X-ray source on the Sun. See NASA's site at or the ESA's site at for movies and more images. 9. What is the sunspot cycle? What stage in the cycle is expected for 2013? A regular cycle exists for sunspot occurrences, averaging 11 years from maximum peak to maximum peak; however, the cycle may vary from 7 to 17 years. In recent cycles, a solar minimum occurred in 1976, whereas a solar maximum took place in 1979, when over 100 sunspots were visible. Another minimum was reached in 1986, and an extremely active solar maximum occurred in 1990 with over 200 sunspots, 11 years from the previous maximum, in keeping with the average. A sunspot minimum occurred in 1997, an intense maximum in 2001, a minimum in 2008, and a forecasted maximum in 2013 maintains the average. 10. Describe Earth's magnetosphere and its effects on the solar wind and the electromagnetic spectrum. Earth's outer defense against the solar wind is the magnetosphere, which is a magnetic force field surrounding Earth, generated by dynamo-like motions within our planet. As the solar wind approaches Earth, the streams of charged particles are deflected by the magnetosphere and course along the magnetic field lines. The extreme northern and southern polar regions

of the upper atmosphere are the points of entry for the solar wind stream. 11. Summarize the known effects of the solar wind relative to Earth's environment. The interaction of the solar wind and the upper layers of Earth’s atmosphere produces the remarkable auroras that occur toward both poles. These lighting effects are the aurora borealis (northern lights) and aurora australis (southern lights) in the upper atmosphere, 80–500 km (50–300 mi) above Earth’s surface. They appear as folded sheets of green, yellow, blue, and red light that undulate across the skies of high latitudes poleward of 65°, as shown in Figure 2.4. During the 2001 solar maximum, auroras were visible as far south as Jamaica, Texas, and California. (For auroral activity, see; for forecasts, see 12. Describe the various segments of the electromagnetic spectrum, from shortest to longest wavelength. What wavelengths are mainly produced by the Sun? Which are principally radiated by Earth to space? See Figures 2.5 and 2.6. All the radiant energy produced by the Sun is in the form of electromagnetic energy and, when placed in an ordered range, forms part of the electromagnetic spectrum. The Sun emits radiant energy composed of 8 percent ultraviolet, X-ray, and gamma ray wavelengths; 47 percent visible light wavelengths; and 45 percent infrared wavelengths. Wavelengths emitted from the Earth back to the Sun are of lower intensity and composed mostly of infrared wavelengths. 13. What is the solar constant? Why is it important to know? The average value of insolation received at the thermopause (on a plane surface perpendicular to the Sun's rays) when Earth is at its average distance from the Sun. That value of the solar constant is 1372 watts per square meter (W/m2). A watt is equal to one joule (a unit of energy) per second and is the standard unit of power in the SI-metric system. (See Appendix C in Elemental Geosystems for more information on measurement conversions.) In nonmetric calorie heat units, the solar constant is expressed as approximately 2 calories (1.968) per cm2 per minute, or 2 langleys per minute (a langley being 1 cal per cm2). A calorie is the amount of energy required to raise the temperature of one gram of water (at 15 °C) one degree Celsius and is equal to 4.184 joules. Knowing the amount of insolation intercepted by Earth is important to climatologists and other scientists as a basis for atmospheric and surface energy measurements and calculations.

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14. If Earth were flat and oriented perpendicularly to incoming solar radiation (insolation), what would be the latitudinal distribution of solar energy at the top of the atmosphere? The atmosphere is like a giant heat engine driven by differences in insolation from place to place. If Earth were flat there would be an even distribution of energy by latitude with no differences from place to place and therefore little motion produced. • Define solar altitude, solar declination, and daylength, and describe the annual variability of each—Earth’s seasonality. 15. The concept of seasonality refers to what specific phenomena? How do these two aspects of seasonality change during the year at 0° latitude? At 40°? At 90°? Seasonality refers to both the seasonal variation of the Sun's rays above the horizon and changing daylengths during the year. Seasonal variations are a response to the change in the Sun's altitude, or the angular difference between the horizon and the Sun. Seasonality also means a changing duration of exposure, or daylength, which varies during the year depending on latitude. People living at the equator always receive equal hours of day and night, whereas people living along 40° N or S latitude experience about six hours of difference in daylight hours between winter and summer; those at 50° N or S latitude experience almost eight hours of annual daylength variation. At the polar extremes, the range extends from a six-month period of no insolation to a six-month period of continuous 24-hour days. 16. Differentiate between the Sun's altitude and its declination at Earth's surface. The Sun's altitude is the angular difference between the horizon and the Sun. The Sun is directly overhead at zenith only at the subsolar point. The Sun's declination—that is, the angular distance from the equator to the place where direct overhead insolation is received—annually migrates through 47 degrees of latitude between the two tropics at 23.5° N and 23.5° S latitudes. 17. For the latitude at which you live, how does daylength vary during the year? How does the Sun's altitude vary? Does your local newspaper publish a weather calendar containing such information? Check out Figure 2.15 for some guidance.

from sunset on 19 November until sunrise at 1:09 P.M. local time 23 January. Scientists are studying what the effects of this are on an individual's biological rhythms, moods, and behavioral patterns. Add to this that the outside temperature is approximately –57 °C (–70 °F), so that people are indoors more in winter. The effects on people in Fairbanks, where night is about 21 hours in length, are being studied. Effects on those living in higher latitudes are being studied as well. Some actually develop a seasonal disorder related to these long periods without the Sun. Treatment involves “phototherapy,” full-spectrum light exposure. This light simulates the Sun's spectrum at the surface at about the time of the onset of twilight. Whatever the results of such research, it appears that to stay active and busy is important, that women are affected more than men, that Caucasians are affected more than native Eskimos, and that adults are affected more than children—some 35 million people are possibly affected. Refer to the following: Bruce Bower, “Here Comes the Sun,” Science News, 142, July 25, 1992: 62– 3. This reviews scientific efforts to understand winter depression known as “seasonally affective disorder,” or SAD. Another source is Dr. Norman E. Rosenthal, National Institute of Mental Health, Bethesda, M.D. 18. List the five physical factors that operate together to produce seasons. Table 2.1 details these factors: Earth's revolution and rotation, its tilt and fixed-axis orientation, and its sphericity. 19. Describe Earth’s revolution and rotation, and differentiate between them. The structure of Earth's orbit and revolution about the Sun is described in Figures 2.1 and 2.11. Earth's revolution determines the length of the year and the seasons. Earth's rotation, or turning, is a complex motion that averages 24 hours in duration. Rotation determines daylength, produces the apparent deflection of winds and ocean currents, and produces the twice daily action of the tides in relation to the gravitational pull of the Sun and the Moon. Earth's axis is an imaginary line extending through the planet from the North to South geographic poles. 20. Define Earth's present tilt relative to its orbit about the Sun. Think of Earth's elliptical orbit about the Sun as a level plane, with half of the Sun and Earth above the plane and half below. This level surface is termed the plane of the ecliptic. Earth's axis is tilted 23.5° from a perpendicular to this plane.

Seasons and Health Issues. Imagine living in Barrow, Alaska, where the night lasts for 65 days

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Full file at • Construct a general model of the atmosphere based on the criteria composition, temperature, and function, and diagram this model in a simple sketch. 21. What is air? Where did the components in Earth's present atmosphere originate? Earth's atmosphere is a unique reservoir of gases, the product of billions of years of development. The modern atmosphere is probably Earth's fourth general atmosphere. The principal substance of this atmosphere is air, the medium of life as well as a major industrial and chemical raw material. Air is a simple additive mixture of gases that is naturally odorless, colorless, tasteless, and formless, blended so thoroughly that it behaves as if it were a single gas. The primordial, evolutionary, and living atmospheres are discussed in Chapter 2. The outgassing hypothesis is discussed in Chapter 5. This modern atmosphere is, in reality, a gaseous mixture of ancient origins—the sum of all the exhalations and inhalations of life on Earth throughout time. 23. What three distinct criteria are employed in dividing the atmosphere for study? The atmosphere is conveniently classified using three criteria: composition, temperature, and function. Based on chemical composition, the atmosphere is divided into two broad regions: the heterosphere and the homosphere. Based on temperature, the atmosphere is divided into four distinct zones: the thermosphere, mesosphere, stratosphere, and troposphere. Finally, two specific zones are identified on the basis of function relative to their role of removing most of the harmful wavelengths of solar radiation—these are the ionosphere and the ozonosphere, or ozone layer. See the left-hand column in Figure 2.18. 24. Describe the overall temperature profile of the atmosphere and list the four layers defined by temperature. The temperature profile in Figure 2.16 shows that temperatures rise sharply in the thermosphere, up to 1200 °C (2200 °F) and higher at the top of the atmosphere. Individual molecules of nitrogen and oxygen, and atoms of oxygen, are excited to high levels of vibration from the intense radiation present in this portion of the atmosphere. This kinetic energy, the energy of motion, is the vibrational energy stated as temperature, although the density of the molecules is so low that little heat is produced. Heating in the lower atmosphere closer to Earth differs because the active molecules in the denser atmosphere transmit their kinetic energy as sensible heat. The mesosphere is the coldest portion of the atmosphere, averaging –90° C

(–130° F), although that temperature may vary by 25 C° to 30 C° (45 F° to 54 F°). Temperatures increase throughout the stratosphere, from –57°C (–70°F) at 20 km (tropopause), warming to freezing at 50 km (stratopause). The tropopause is defined by an average temperature of –57°C (–70°F), but its exact location varies with the seasons of the year, latitude, and sea level temperatures and pressures. Tropospheric temperatures decrease with increasing altitude at an average of 6.4C° per km (3.5F° per 1000 ft), a rate known as the normal lapse rate. The actual lapse rate at any particular time and place under local weather conditions is called the environmental lapse rate, and may vary greatly from the normal lapse rate. The lab manual and student study guide both have students work with these concepts. 25. Describe the two divisions of the atmosphere based on composition. The heterosphere is arranged in layers based on the atomic weight of atoms and gases, and reactions with the incoming solar beam. 26. What are the two primary functional layers of the atmosphere and what do each do? Ionosphere and stratosphere. See Figure 2.20 and observe the shorter wavelengths that are filtered in the functional layers of the atmosphere. 27. Name the four most prevalent stable gases in the homosphere. Where did each originate? Is the amount of any of these changing at this time? The homosphere comprises an even mixture of gases: Symbol N2 O2 Ar CO2

% by Vol. 78.084 20.946 0.934 0.0394

Parts per million 780,840 209,460 9,340 394

The atmosphere is a vast reservoir of relatively inert nitrogen, principally originating from volcanic sources. In the soil, nitrogen is bound up by nitrogenfixing bacteria and is returned to the atmosphere by denitrifying bacteria that remove it from organic materials. Oxygen, a by-product of photosynthesis, is essential for life processes. Along with other elements, oxygen forms compounds that compose about half of Earth's crust. Argon is a residue from the radioactive decay of a form of potassium (40K). A slow process of accumulation accounts for all that is present in the modern atmosphere. Argon is completely inert and as a noble gas is unusable in life processes. Although it has increased over the past 200 years, carbon dioxide is included in this list of stable gases. It is a natural by-

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product of life processes, and the implications of its current increase are critical to society and the future. The role of carbon dioxide in the gradual warming of Earth is discussed in Chapters 3 and 6. • Describe conditions within the stratosphere; specifically review the function and status of the ozonosphere or ozone layer. 28. Why is stratospheric ozone (O 3) so important? Describe the effects created by increases in ultraviolet light reaching the surface. Ozone absorbs wavelengths of ultraviolet light and subsequently reradiates this energy at longer wavelengths as infrared energy. Through this process, most harmful ultraviolet radiation is converted, effectively "filtering" it and safeguarding life at Earth's surface. See Focus Study 2.1 for greater discussion of the effects caused by ozone depletion. 29. Summarize the ozone predicament and the present trends, and any treaties to protect the ozone layer. See Focus Study 2.1 for a review of current treaties and their status. Environment Canada has launched a scientific observatory to study the ozone layer over Canada. This high-Arctic facility now is operational at a remote weather station near Eureka on Ellesmere Island, N.W.T., about 1000 km from the North Pole. The Arctic ozone depletion affects concentrations at lower latitudes and thus should draw the United States into further cooperation. 30. Evaluate Crutzen, Rowland, and Molina's use of the scientific method in investigating stratospheric ozone depletion. The possible depletion of the ozone layer by human activity was first suggested during the summer of 1974 by University of California, Irvine professors F. Sherwood Rowland and Mario J. Molina. Rowland and Molina hypothesized that the stable, large CFC molecules remained intact in the atmosphere, eventually migrating upward and working their way into the stratosphere. CFCs do not dissolve in water and do not break down biologically. The increased ultraviolet light encountered by the CFC molecule in the stratosphere dissociates, or splits, the CFC molecules, releasing chlorine (Cl) atoms and forming chlorine oxide (ClO) molecules. At present, after much scientific evidence and verification of actual depletion of stratospheric ozone by chlorine atoms (1987–1990), even industry has had to admit that the problem is real. The scientific method is discussed in Focus Study 1.1. Recall in the chapter when Dr. Rowland stated his frustration: “What's the use of having

developed a science well enough to make predictions, if in the end all we are willing to do is stand around and wait for them to come true....Unfortunately, this means that if there is a disaster in the making in the stratosphere, we are probably not going to avoid it.” (Roger B. Barry, “The Annals of Chemistry,” The New Yorker, 9 June 1986, p. 83.) The Nobel Committee awarded these men, and Paul Crutzen, the 1995 Nobel Prize for chemistry for their important discovery and actions (see page 55). In 1994 an international scientific consensus confirmed previous assessments of the anthropogenic (human-caused) disruption of the ozone layer—in other words chlorine atoms and chlorine monoxide molecules in the stratosphere are of human origin. The report, Scientific Assessment of Ozone Depletion, was prepared by NASA, NOAA, United Nations Environment Programme, and World Meteorological Organization. • Distinguish between natural and anthropogenic variable gases and materials in the lower atmosphere and describe the sources and effects of air pollution. 31. Why are anthropogenic gases more significant to human health than those produced from natural sources? Natural sources produce a greater quantity of nitrogen oxides, carbon monoxide, and carbon dioxide than do certain human-made sources. However, any attempt to diminish the impact of human-made air pollution through a comparison with natural sources is irrelevant, for we have co-evolved and adapted to the presence of certain natural ingredients in the air. We have not evolved in relation to the concentrations of anthropogenic (human-caused) contaminants found in our metropolitan areas. 32. In what ways does a temperature inversion worsen an air pollution episode? Why? A temperature inversion occurs when the normal decrease of temperature with increasing altitude reverses at any point from ground level up to several thousand feet. Such an inversion most often results from certain weather conditions, for example when the air near the ground is radiatively cooled on clear nights or when cold air drains into valleys. The warm air inversion in Figure 2.23 prevents the vertical mixing of pollutants with other atmospheric gases. Thus, instead of being carried away, the pollutants are trapped below the inversion layer. During the winter months in eastern and midwestern regions of the United States, high pressure areas created by subsiding cold air masses produce inversion conditions that trap air pollution. In

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Full file at the West, summer subtropical high pressure systems also cause inversions and produce air stagnation. 33. What is the difference between industrial smog and photochemical smog? The air pollution associated with coal-burning industries is known as industrial smog. The term smog was coined by a London physician at the turn of last century to describe the combination of fog and smoke containing sulfur, an impurity found in fossil fuels. The combination of sulfur and moisture droplets forms a sulfuric acid mist that is extremely dangerous in high concentrations. Photochemical smog is another type of pollution that was not generally experienced in the past but developed with the advent of the automobile. Today, it is the major component of anthropogenic air pollution. Photochemical smog results from the interaction of sunlight and the products of automobile exhaust. Although the term smog is a misnomer it is generally used to describe this phenomenon. Smog is responsible for the hazy appearance of the sky and the reduced intensity of sunlight in many of our cities. 34. Describe the relationship between automobiles and the production of ozone and PAN in city air. What are the principal negative impacts of these gases? The nitrogen dioxide derived from automobiles, and power plants to a lesser extent, is highly reactive with ultraviolet light, which liberates atomic oxygen (O) and a nitric oxide (NO) molecule (Figure 2.24). The free oxygen atom combines with an oxygen molecule (O2) to form the oxidant ozone (O3); the same gas that is beneficial in the stratosphere is an air pollution hazard at Earth's surface. In addition to forming O3, the nitric oxide (NO) molecule reacts with hydrocarbons (HC) to produce a whole family of chemicals generally called peroxyacetyl nitrates (PAN). PAN produces no known health effects in humans but is particularly damaging to plants, which provided the clue for discovery of these photochemical reactions.

Certain anthropogenic gases are converted in the atmosphere into acids that are removed by wet and dry deposition processes. Nitrogen and sulfur oxides (NOx, and SOx) released in the combustion of fossil fuels can produce nitric acid (HNO3) and sulfuric acid (H2SO4) in the atmosphere. Precipitation as acidic as pH 2.0 has fallen in the eastern United States, Scandinavia, and Europe. By comparison, vinegar and lemon juice register slightly less than 3.0. Aquatic life perishes when lakes drop below pH 4.8. 36. In summary, what are the results from the first 20 years under Clean Air Act regulations? The Benefits of the Clean Air Act, 1970 to 1990 (Office of Policy, Planning, and Evaluation, U.S. EPA) calculated the following: •

The total direct cost to implement the Clean Air Act for all federal, state, and local rules from 1970 to 1990 was $523 billion (in 1990-value dollars). This cost was borne by businesses, consumers, and government entities. The estimate of direct monetized benefits from the Clean Air Act from 1970 to 1990 falls in a range from $5.6 to $49.4 trillion with a central mean of $22.2 trillion. Therefore, the net financial benefit of the Clean Air Act is $21.7 trillion! “The finding is overwhelming. The benefits far exceed the costs of the CAA in the first 20 years,” said Richard Morgenstern, associate administrator for policy planning and evaluation at the EPA.

The benefits to society, directly and indirectly, have been widespread across the entire population: improved health and environment, less lead to harm children, lowered cancer rates, less acid deposition, an estimated 206,000 fewer deaths related to air pollution in 1990 alone, among many benefits described. These benefits took place during a period in which the U.S. population grew by 22 percent and the economy expanded by 70 percent.

35. How are sulfur impurities in fossil fuels related to the formation of acid in the atmosphere and acid deposition on the land?

33 Instructor Resource Manual for Elemental Geosystems, 7e © 2013 Pearson Education, Inc. By Charles E. Thomsen

34 Instructor Resource Manual for Elemental Geosystems, 7e © 2013 Pearson Education, Inc. By Charles E. Thomsen

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