Environmental Science Demystified - Lagout

ACKNOWLEDGMENTSIllustrations in this book were generated with CorelDRAW and MicrosoftPowerPoint and Microsoft Visio, courtesy of the Corel and Microsoft Corporations, respectively.National Oceanographic and Atmospheric Administration (NOAA), Environmental Protection Agency (EPA), and United States Geological Survey (USGS)statistics and forecasts were used where indicated.A very special thanks to Dr. Karen Duston of Rice University for the technical review of this book.Many thanks to Judy Bass at McGraw-Hill for her unfailing confidence andassistance.Thank you also to Rice University’s staff and faculty for their friendship, support, and flexibility in the completion of this work.To my children, grandchildren, and great-grandchildren who will inherit theEarth that is left to them.xiiiCopyright 2005 by The McGraw-Hill Companies, Inc. Click here for terms of use.

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ENVIRONMENTAL SCIENCEDEMYSTIFIED

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PART ONEAtmosphereCopyright 2005 by The McGraw-Hill Companies, Inc. Click here for terms of use.

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CHAPTER1Our Planet EarthNative peoples, completely dependent on nature for everything in their lives, worshipped Earth as a nurturing mother. The soil sprouted plants and trees that provided food, clothing, and shelter. The rivers and seas gave up fish and shellfish forfood, trade articles, and tools. From the atmosphere came rain, snow, and wind towater crops and adjust the seasons. Earth, never stagnant or dull, provided abundantly for early stewards of her resources. Ancient peoples thought that MotherEarth worked together with Father Sun to provide for those who honored her.In early Greek mythology, the Earth goddess, Gaia, mother of the Titans, washonored as an all-nourishing deity. When Gaia was happy, crops flourished, fishermen and hunters were successful, and everything thrived.Today, astronauts who orbit Earth in space ships and scientific laboratoriesmarvel at her beauty while working toward her care. Other scientists, engineers,and test pilots have communicated their wonder and appreciation for our fragileworld through environmental efforts that address global issues. Any study of theenvironment includes many facets of this planet we call home. Environmentalscience encompasses worldwide environmental factors like air, light, moisture,temperature, wind, soil, and other living organisms.Environmental biology includes all the external factors that affect anorganism or community and that influence its development or existence.3Copyright 2005 by The McGraw-Hill Companies, Inc. Click here for terms of use.

4PART ONEAtmosphereThe Earth’s almost limitless beauty and complexity provide broad areas forscientific study. Researchers from many different fields are focusing their skillson the mechanisms and interactions of hundreds of environmental factors. Thesenatural and industrial factors affect the environment in ways that are known andsuspected, as well as those totally unidentified. Although some changes havebeen taking place for millions of years, some appear to be accelerating. Today,environmental scientists are sorting through tons of data in order to increase theirunderstanding of the impacts of modern processes on all environmental aspects.Table 1-1 lists a sampling of the various environmental fields of scientific study.Size and ShapeThe size and shape of the earth was a mystery for thousands of years. Most people thought the land and seas were flat. They were afraid that if they traveled toofar in one direction, they would fall off the edge. Explorers who sailed to the limits of known navigation were considered crazy and on paths to destruction. Sincemany early ships did not return from long voyages, people thought they hadbeen sunk by storms, eaten by sea monsters, or just went too far and fell off.It wasn’t until the Greek philosopher Aristotle (384–322 BC), who noticed thatEarth’s shadow on the moon was curved, that people began to question the “flatearth” idea. It was another 1500 years, however, before the earth’s round shapewas well understood.Compared to the sun, which is over 332,000 times the mass of the Earth, ourhome planet is tiny—a bit like a human compared to an ant. The sun is 1,391,000kilometers in diameter compared to the Earth, which is approximately 12,756 kmin diameter. That means the diameter of the sun is over 100 times thatof the Earth. To picture the size difference, imagine that the sun is the size of abasketball. By comparison, the earth would be about the size of this “o.”Earth’s FormationIn 1755, Immanuel Kant offered the idea that the solar system was formed froma rotating cloud of gas and thin dust. In the years since, this idea has becomeknown as the nebular hypothesis. The clouds that Kant described could be seen

CHAPTER 1Our Planet EarthTable 1-1EnvironmentalscienceFields of study.Area of interestAgrologyAnalysis and management of usable land for growthof food cropsBioengineeringDesigning or reconstructing sustainable ecosystemsBotanyCharacterization, growth, and distribution of plantsConservationbiologyPreserve, manage, or restore endangered areas or speciesEcologyStudy of relationships between living organisms and theirenvironmentEnvironmentalgeologyConservation of resources and future planningExplorationgeophysicsCrustal composition to find resources (e.g. oil, gold)ForestryCharacterization, growth, distribution, and planting of treesGeochemistryChemical composition of rocks and their changesGeomorphologyNature, origin, development, and surface of land formsGeophysicsEarth’s magnetism, gravity, electrical properties, andradioactivityGlaciologyFormation, movement, and makeup of current glaciersHydrologyComposition and flow of water over the earthMineralogyNatural and synthetic minerals with a crystalline structureOceanographyWater makeup, currents, boundaries, topography, marine lifePedologyOrigin, treatment, character, and utilization of soilPetrologyOrigins, composition, alteration, and decay of rockStructural geologyRock changes and distortions within the earth’s layersVolcanologyFormation, activity, temperature, and explosions of volcanoesWildlife biologyCharacterization and distribution of animal communitiesZoologyCharacterization, growth, and distribution of animals5

6PART ONEMantle(2,900 km)Liquid outer core(5,150 km; iron,nickel, silicon,sulfur, and oxygen)Fig. 1-1AtmosphereSolid inner core(6,440 km; iron)Oceaniccrust(105 km)Continental crust(200 km)The Earth has four main layers.by powerful telescopes. The NASA Hubble space telescope has sent backimages of many of these beautiful formations, called nebulae.It is likely that when the Earth was first forming in our young solar neighborhood, it was a molten mass of rock and metals simmering at about 3,600 Fahrenheit (2,000 Celsius). The main cloud elements included hydrogen,helium, carbon, nitrogen, oxygen, silicon, iron, nickel, phosphorus, sulfur, andothers. As the sphere (Earth) cooled, the heavier metals like iron and nickel sunkdeeper into the molten core, while the lighter elements like silicon rose to thesurface, cooled a bit, and began to form a thin crust. Fig. 1-1 shows the way thatearly elements formed into a multilayer crust. This crust floated on a sea ofmolten rock approximately four billion years ago, sputtering volcanic gases andsteam from the impact of visitors like ice comets. Millions more years passedlike this while an atmosphere gradually formed. Rain condensed and poureddown, cooling the crust into one large chunk and gathering into low spots andcracks, forming oceans, seas, lakes, rivers, and streams.Our Place in the GalaxyEven though the sun seems to be the center of our universe, it is really just oneof many kids on the block. Our solar system is found on one of the spiral arms,Orion, of the galaxy known as the Milky Way.

CHAPTER 17Our Planet EarthThe Milky Way is one of millions of galaxies in the universe. TheAndromeda galaxy is the nearest major galaxy to the Milky Way.Think of the Milky Way galaxy as one “continent” among billions of othercontinents in a world called the universe. Its spiraling arms or “countries” arecalled Centaurus, Sagittarius, Orion, Perseus, and Cygnus. The Milky Waygalaxy is 80,000 to 120,000 light years across (a light year is a measure ofdistance equal to or more than 9 trillion km, or 9.46 1012 km). The centerof the Milky Way is made up of a dense molecular cloud that rotates slowlyclockwise, throwing off solar systems and cosmic debris. It contains roughly200 billion (2 1012) stars.Although Andromeda is the closest full-size galaxy to the Milky Way, theSagittarius Dwarf, discovered in 1994, is the closest galaxy. It is 80,000 lightyears away, or nearly 24 kiloparsecs. A parsec is a unit of measurement equal to3.26 light years.AtmosphereEarth’s atmosphere is the key to the development of life on this planet. Otherplanets in our solar system contain various levels of hydrogen, methane, andammonia atmospheres (Jupiter, Neptune), carbon dioxide and nitrogen (Venus,Mars), or hardly any atmosphere at all (Mercury, Pluto).The atmosphere of the Earth, belched from prehistoric volcanoes, extendsnearly 563 km (350 miles) out from the solid surface of our planet. It is madeup of a mixture of gases that combine to allow life to exist. In the lower atmosphere, nitrogen is found in the greatest amounts, 78%, followed by oxygen at21%. Carbon dioxide, vital to the growth of plants, is present in trace levels ofatmospheric gases, along with argon and a sprinkling of neon and other minorgases. Table 1-2 compares the earth’s atmosphere with the atmosphere of neighboring planets.Oxygen, critical to human life, developed as microscopic plants and algaebegan using carbon dioxide and photosynthesis to make food. From that process,oxygen is the most important byproduct.The mixture of gases that we call air penetrates the ground and most openingsin the earth not already filled with water. The atmosphere is perhaps the mostactive of the different environmental components. To people around the world,it has a constantly changing personality.

8PART ONETable 1-2AtmospherePlanets, atmospheric gases.PlanetsAtmospheric gasesSunHydrogen, nitrogenMercuryNoneVenusNoneEarthOxygen, nitrogen,hydrogenMarsNoneJupiterMethane, hydrogenSaturnHydrogen, methaneUranusNoneNeptuneNonePlutoNoneWe will study these atmospheric factors that favor life on Earth when we takea closer look at the atmosphere in Chapter 3.Gaia HypothesisIn 1974, James Lovelock explained that the Earth existed as a single living organism in his Gaia hypothesis. He described how organic and inorganic componentsinteract through complex reactions to balance an environment where life canexist. Lovelock’s Gaia theory considers the evolution of a tightly integrated system made up of all living things and the physical environment: the atmosphere,oceans, and land. Natural regulation of important factors, like climate and chemical composition, is a result of intricate evolutionary development. Like many living organisms and closed-loop self-regulating systems, Lovelock considered Gaiaas one system in which the whole is greater than the sum of its parts.

CHAPTER 1Our Planet EarthAn active, adaptive control process, able to maintain the Earth in overall balance, is known as the Gaia hypothesis.Today, there is heated debate about which global environmental problem isthe most crucial. Depending on a person’s geographical and economic position,it can be pollution, overpopulation, ozone depletion, deforestation, habitatdestruction, global warming, overfishing, drought, radioactive waste storage—or all or none of these. Some scientists believe that these environmental impactswill be overcome in the long run when Gaia makes the corrections needed tobring the Earth back into equilibrium.The problem with these balancing forces is that they can be sudden and violent (think earthquakes and volcanic eruptions). A powerful, natural environmental adjustment often brings disaster upon all inhabitants unfortunate enoughto be in the vicinity.In 1979, Lovelock further described his theory in GAIA: A New Look at Lifeon Earth. Since then, many scientists and environmentalists have begun to studyglobal changes within the context of the Gaia idea, although not everyone agreeswith the theory.The updated Gaia hypothesis proposes that Earth’s atmosphere, oceans, andland masses are held in equilibrium by the living inhabitants of the planet, whichincludes millions of species besides humans. The Gaia concept suggests that thisliving world keeps itself in worldwide environmental balance.One example of this balancing act takes place in the oceans. Salts are constantly added to the oceans by physical and chemical processes, raising salinity.Eventually, affected seas (like the Dead Sea) reach an uninhabitable salinitylevel. According to the Gaia hypothesis, the sea’s salinity is controlled biologically through the mutual action of ocean organisms. In fact, living sea creatures,primarily algae and protozoa, have processed and removed salt throughout geological time, balancing salinity levels that allow life to thrive.Actually, that is fairly straightforward. Salt is removed from ocean waters whenit piles up on the bottom. This happens following the death of microorganismsthat sink to the ocean floor. As ocean salinity rises, plankton that include saltinto their outer coverings die and sink to the ocean depths, lowering salt levels.In this way, the ocean’s salinity stays in equilibrium.The Gaia theory can also be applied to the balancing of atmospheric gasesin fairly constant proportions needed to support life. Without the ongoing biological creation of oxygen and methane, for example, the balance of criticalatmospheric elements would be severely altered. Organisms all over the9

10PART ONEAtmosphereworld work together to create a breathable atmosphere, not just in one habitator location.Scientists questioning the Gaia concept think that evolutionary changesaccount for the adjustments needed for life to exist. The argument goes that whenocean salinity increases, oxygen levels change or global temperatures increase.Only evolved organisms are able to able to survive new conditions, and theirgenetically stronger offspring are then able to thrive in a changed environment.Lovelock counters this by stressing that environmental conditions can’t operate independently of living world processes. Table 1-3 lists the diverse Earthenergy resources and processes to be considered.In the Gaia concept, humans are seen as one species among millions, withno special rights. Whether humans were here or not makes little differenceto Gaia’s survival, which eventually adjusts for overpopulation, global warming, or habitat destruction. Some might even argue that Gaia would functionTable 1-3Energy resources.Solar energyFossil fuelsAtmospheric absorptionSurface heatingWind energyHeat from the earth’s coreShortwave and longwaveradiationFlowing riversHydrologic cycleand precipitationTidal energyGravitational energyTectonic energyEnergy absorption in theearth’s crust

CHAPTER 111Our Planet Earthmore effectively without us here at all. However, whether humans are responsible for environmental problems or not, global balancing may severely impactour future.To understand the Earth as one living system (whether called Gaia or something else) we need to understand more about all the parts that make it unique.BiosphereAll plants and animals on the earth live in the biosphere, which is measured fromthe ocean floor to the top of the atmosphere. It includes all living things, large(whales) and small (bacteria), grouped into species or separate types. The maincompounds that make up the biosphere contain carbon, hydrogen, and oxygen.These elements also interact with other earth systems.The biosphere includes the hydrosphere, crust, and atmosphere. It islocated above the deeper layers of the earth.Surprisingly, life is found in many hostile environments on this planet. Veryhot temperatures (5,000 C) near volcanic spouts rising from the ocean floor, andpolar, subzero temperatures ( 84 C) are at the extreme ends of the temperaturerange. The earth’s biodiversity is truly amazing. Everything from exotic andfearsome deep-ocean creatures to sightless fish in underground lakes exists aspart of the earth’s diverse inhabitants. There are sulfur-fixing bacteria that thrivein sulfur-rich, boiling geothermal pools and frogs that dry out and remain barelyalive in desert soils until the rare rains bring them back to life. This makes environmental study fascinating to people of all cultures, geographies, and interests.However, the large majority of biosphere organisms that grow, reproduce, anddie are found in a much more narrow range. In fact, most of the Earth’s specieslive in a thin slice of the biosphere. This slice is located at temperatures abovezero (most of the year) and in upper ocean depths where sunlight can penetrate.The vertical range of the biosphere is roughly 20,000 meters, but the sectionmost populated with living species is only a fraction of that. It includes a sectionmeasured from just below the ocean’s surface to about 1,000 meters above it.Most living plants and animals live in this narrow layer of the biosphere. Thebiosphere and the impacts of today’s world will be described in greater detail inChapter 2.

12PART ONEAtmosphereHydrosphereThe global ocean, the Earth’s most noticeable feature from space, makes up thelargest single part of the planet’s total covering. The Pacific Ocean, the largestocean, is so big that the land mass of all the continents could fit into it.The combined water of all of the oceans makes up nearly 97% of the earth’swater. These oceans are much deeper on average than the land is high, and makeup what is known as the hydrosphere.The hydrosphere describes the ever-changing total water cycle that ispart of the closed environment of the earth.The hydrosphere is never still. It encompasses the evaporation of oceans intothe atmosphere, the raining of this water back onto land, the run-off into streamsand rivers, and finally the flow back into the oceans. The hydrosphere also contains the water in underground aquifers, lakes, and streams.The cryosphere is a subset of the hydrosphere. It includes all of the Earth’sfrozen water found in colder latitudes and higher elevations in the form of snowand ice. At

ENVIRONMENTAL SCIENCE DEMYSTIFIED LINDA D. WILLIAMS McGRAW-HILL New York Chicago San Francisco