organisms. Mineralization of biomass by microbial decay returns phosphorus to the salt solution from which it may precipitate as mineral matter The anthrosphere is an important reservoir of phosphorus in the environment Large quantities of phosphates are extracted from phosphate minerals for fertilizer industrial chemicals, and food additives. Phosphorus is a constituent of some extremely toxic compounds, especially organophosphate insecticides and military poIson nerve gase The sulfur Cvcle The sulfur cycle, which is illustrated in Figure 1.8, is relatively complex in that it involves several gaseous species, poorly soluble minerals, and several species in solution. It is tied with the oxygen cycle in that sulfur combines with oxygen to form gaseous sulfur dioxide, SO2, an atmospheric pollutant, and soluble sulfate ion, sO Atmospheric sulfur, SO,, H,S H2SO4, CS,,(CH3hS Interchange of atmospheric sulfur species with other Inorganic SO42- in both soluble and insoluble forms Assimilation Oxidation by organisms Elemental sulfur. S oxidation H2S Biological sulfur, including Decompos- Sulfides as H,S and as metal SH groups fion sulfides, such as Fes Biodegradation Microbially produced organic Xenobiotic sulfur such as that sulfur in small molecules, largely as-SH and R-SR groups groups in insecticides Figure 1. 8. The sulfur cycle C 2000 CRC Press LlC
organisms. Mineralization of biomass by microbial decay returns phosphorus to the salt solution from which it may precipitate as mineral matter. The anthrosphere is an important reservoir of phosphorus in the environment. Large quantities of phosphates are extracted from phosphate minerals for fertilizer, industrial chemicals, and food additives. Phosphorus is a constituent of some extremely toxic compounds, especially organophosphate insecticides and military poison nerve gases. The Sulfur Cycle The sulfur cycle, which is illustrated in Figure 1.8, is relatively complex in that it involves several gaseous species, poorly soluble minerals, and several species in solution. It is tied with the oxygen cycle in that sulfur combines with oxygen to form gaseoussulfur dioxide, SO2, an atmospheric pollutant, and soluble sulfate ion, SO4 2- . Sulfate reduction Sulfide oxidation Sulfides as H2S and as metal sulfides, such as FeS Atmospheric sulfur, SO2, H2S, H2SO4, CS2, (CH3) 2S Xenobiotic sulfur such as that in groups in insecticides P S Elemental sulfur, S H2S oxidation S oxidation Biological sulfur, including -SH groups Decomposition Inorganic SO4 2- in both soluble and insoluble forms Microbially produced organic sulfur in small molecules, largely as -SH and R-S-R groups Microbial metabolism Assimilation by organisms Interchange of atmospheric sulfur species with other environmental spheres Biodegradation Figure 1.8. The sulfur cycle. © 2000 CRC Press LLC
Among the significant species involved in the sulfur cycle are gaseous hydrogen sulfide, H2S; mineral sulfides, such as PbS, sulfuric acid, H,SO4, the main constitu- ent of acid rain; and biologically bound sulfur in sulfur-containing proteins Insofar as pollution is concerned, the most significant part of the sulfur cycle is the presence of pollutant So2 gas and H2sO4 in the atmosphere. The former is a somewhat toxic gaseous air pollutant evolved in the combustion of sulfur-containing fossil fuels. Sulfur dioxide is discussed further as an air pollutant in Chapter 11, and its toxicological chemistry is covered in Chapter 22. The major detrimental effect of sulfur dioxide in the atmosphere is its tendency to oxidize in the atmosphere to produce sulfuric acid. This species is responsible for acidic precipitation, acid rain, discussed as a major atmospheric pollutant in Chapter 14 1.7. HUMAN IMPACT AND POLLUTION The demands of increasing population coupled with the desire of most people for a higher material standard of living are resulting in worldwide pollution on a massive scale. Environmental pollution can be divided among the categories of water,air, and land pollution. All three of these areas are linked. For example, some gases emitted to the atmosphere can be converted to strong acids by atmospheric chemical processes, fall to the earth as acid rain, and pollute water with acidity Improperly discarded hazardous wastes can leach into groundwater that is eventually eleased as polluted water into streams Some definitions Pertaining to pollution In some cases pollution is a clear-cut phenomenon, whereas in others it lies largely in the eyes of the beholder. Toxic organochlorine solvent residues leached into water supplies from a hazardous waste chemical dump are pollutants in any bodys view. However, loud rock music amplified to a high decibel level by sometimes questionable miracle of modern electronics is pleasant to some people and a very definite form of noise pollution to others. Frequently, time and place determine what may be called a pollutant. The phosphate that the sewage treatment plant operator has to remove from wastewater is chemically the same as the phos phate that the farmer a few miles away has to buy at high prices for fertilizer. Most pollutants are, in fact, resources gone to waste; as resources become more scarce and expensive, economic pressure will almost automatically force solutions to many pollution problems A reasonable definition of a pollutant is a substance present in greater than natural concentration as a result of human activity that has a net detrimental effect environment something of value in that environment. Contam- inants, which are not classified as pollutants unless they have some detrimental effect, cause deviations from the normal composition of an environment Every pollutant originates from a source. The source is particularly imp ecause it is generally the logical place to eliminate pollution. After a pollutant is eleased from a source, it may act upon a receptor. The receptor is anything that is affected by the pollutant. Humans whose eyes smart from oxidants in the atmosphere are receptors. Trout fingerlings that may die after exposure to dieldrin in water are C 2000 CRC Press llc
Among the significant species involved in the sulfur cycle are gaseous hydrogen sulfide, H2S; mineral sulfides, such as PbS, sulfuric acid, H2SO4, the main constituent of acid rain; and biologically bound sulfur in sulfur-containing proteins. Insofar as pollution is concerned, the most significant part of the sulfur cycle is the presence of pollutant SO2 gas and H2SO4 in the atmosphere. The former is a somewhat toxic gaseous air pollutant evolved in the combustion of sulfur-containing fossil fuels. Sulfur dioxide is discussed further as an air pollutant in Chapter 11, and its toxicological chemistry is covered in Chapter 22. The major detrimental effect of sulfur dioxide in the atmosphere is its tendency to oxidize in the atmosphere to produce sulfuric acid. This species is responsible for acidic precipitation, “acid rain,” discussed as a major atmospheric pollutant in Chapter 14. 1.7. HUMAN IMPACT AND POLLUTION The demands of increasing population coupled with the desire of most people for a higher material standard of living are resulting in worldwide pollution on a massive scale. Environmental pollution can be divided among the categories of water, air, and land pollution. All three of these areas are linked. For example, some gases emitted to the atmosphere can be converted to strong acids by atmospheric chemical processes, fall to the earth as acid rain, and pollute water with acidity. Improperly discarded hazardous wastes can leach into groundwater that is eventually released as polluted water into streams. Some Definitions Pertaining to Pollution In some cases pollution is a clear-cut phenomenon, whereas in others it lies largely in the eyes of the beholder. Toxic organochlorine solvent residues leached into water supplies from a hazardous waste chemical dump are pollutants in anybody’s view. However, loud rock music amplified to a high decibel level by the sometimes questionable miracle of modern electronics is pleasant to some people, and a very definite form of noise pollution to others. Frequently, time and place determine what may be called a pollutant. The phosphate that the sewage treatment plant operator has to remove from wastewater is chemically the same as the phosphate that the farmer a few miles away has to buy at high prices for fertilizer. Most pollutants are, in fact, resources gone to waste; as resources become more scarce and expensive, economic pressure will almost automatically force solutions to many pollution problems. A reasonable definition of a pollutant is a substance present in greater than natural concentration as a result of human activity that has a net detrimental effect upon its environment or upon something of value in that environment. Contaminants, which are not classified as pollutants unless they have some detrimental effect, cause deviations from the normal composition of an environment. Every pollutant originates from a source. The source is particularly important because it is generally the logical place to eliminate pollution. After a pollutant is released from a source, it may act upon a receptor. The receptor is anything that is affected by the pollutant. Humans whose eyes smart from oxidants in the atmosphere are receptors. Trout fingerlings that may die after exposure to dieldrin in water are © 2000 CRC Press LLC
also receptors. Eventually, if the pollutant is long-lived, it may be deposited in a sink, a long-time repository of the pollutant. Here it will remain for a long time, though not necessarily permanently. Thus, a limestone wall may be a sink fo atmospheric sulfuric acid through the reaction CaCO3+ H SO4 > CasO4 Ho+ CO2 (1.71) which fixes the sulfate as part of the wall composition Pollution of various Spheres of the Environment Pollution of surface water and groundwater are discussed in some detail in Chapter 7, Particulate air pollutants are covered in Chapter 10, gaseous inorganic pollutants in Chapter ll, and organic air pollutants and associated photochemic smog in Chapters 12 and 13. Some air pollutants, particularly those that may result in irreversible global warming or destruction of the protective stratospheric ozone layer, are of such a magnitude that they have the potential to threaten life on earth These are discussed in Chapter 14, "The Endangered Global Atmosphere. The most serious kind of pollutant that is likely to contaminate the geosphere, particularly soil, consists of hazardous wastes. A simple definition of a hazardous waste is that it is a potentially dangerous substance that has been discarded, abandoned, neglected, released, or designated as a waste material, or is one that may interact with other ubstances to pose a threat. Hazardous wastes are addressed specifically in Chapters 1. 8. TECHNOLOGY: THE PROBLEMS IT POSES AND THE SOLUTIONS IT OFFERS Modern technology has provided the means for massive alteration of the nvironment and pollution of the environment. However, technology intelligently applied with a strong environmental awareness also provides the means for dealing with problems of environmental pollution and degradation Some of the major ways in which modern technology has contributed to envi- ronmental alteration and pollution are the following Agricultural practices that have resulted in intensive cultivation of land drainage of wetlands, irrigation of arid lands, and application of herbicides Manufacturing of huge quantities of industrial products that consumes vast amounts of raw materials and produces large quantities of air pollutants water pollutants, and hazardous waste by-products Extraction and production of minerals and other raw materials with accompanying environmental disruption and pollution Energy production and utilization with environmental effects that include disruption of soil by strip mining, pollution of water by release of salt C 2000 CRC Press llc
also receptors. Eventually, if the pollutant is long-lived, it may be deposited in a sink, a long-time repository of the pollutant. Here it will remain for a long time, though not necessarily permanently. Thus, a limestone wall may be a sink for atmospheric sulfuric acid through the reaction, CaCO3 + H2SO4 ® CaSO4 + H2O + CO2 (1.7.1) which fixes the sulfate as part of the wall composition. Pollution of Various Spheres of the Environment Pollution of surface water and groundwater are discussed in some detail in Chapter 7, Particulate air pollutants are covered in Chapter 10, gaseous inorganic air pollutants in Chapter 11, and organic air pollutants and associated photochemical smog in Chapters 12 and 13. Some air pollutants, particularly those that may result in irreversible global warming or destruction of the protective stratospheric ozone layer, are of such a magnitude that they have the potential to threaten life on earth. These are discussed in Chapter 14, “The Endangered Global Atmosphere.” The most serious kind of pollutant that is likely to contaminate the geosphere, particularly soil, consists of hazardous wastes. A simple definition of a hazardous waste is that it is a potentially dangerous substance that has been discarded, abandoned, neglected, released, or designated as a waste material, or is one that may interact with other substances to pose a threat. Hazardous wastes are addressed specifically in Chapters 19 and 20. 1.8. TECHNOLOGY: THE PROBLEMS IT POSES AND THE SOLUTIONS IT OFFERS Modern technology has provided the means for massive alteration of the environment and pollution of the environment. However, technology intelligently applied with a strong environmental awareness also provides the means for dealing with problems of environmental pollution and degradation. Some of the major ways in which modern technology has contributed to environmental alteration and pollution are the following: • Agricultural practices that have resulted in intensive cultivation of land, drainage of wetlands, irrigation of arid lands, and application of herbicides and insecticides • Manufacturing of huge quantities of industrial products that consumes vast amounts of raw materials and produces large quantities of air pollutants, water pollutants, and hazardous waste by-products • Extraction and production of minerals and other raw materials with accompanying environmental disruption and pollution • Energy production and utilization with environmental effects that include disruption of soil by strip mining, pollution of water by release of salt- © 2000 CRC Press LLC
water from petroleum production, and emission of air pollutants such as acid-rain-forming sulfur dioxide Modern transportation practices, particularly reliance on the automobile that cause scarring of land surfaces from road construction, emission of air pollutants, and greatly increased demands for fossil fuel resources Despite all of the problems that it raises, technology based on a firm foundation of environmental science can be very effectively applied to the solution of environ- mental problems. One important example of this is the redesign of basic manufac turing processes to minimize raw material consumption, energy use, and waste production. Consider a generalized manufacturing process shown in Figure 1. 9. With proper design the environmental acceptability of such a process can be greatly enhanced. In some cases raw materials and energy sources can be chosen in ways that minimize environmental impact. If the process involves manufacture of a chemical, it may be possible to completely alter the reactions used so that the entire operation is more environmentally friendly. Raw materials and water may be ecycled to the maximum extent possible. Best available technologies may be employed to minimize air, water, and solid waste emissions Reactants Contaminants (impurities) Reaction media (water, organ solvents) emIssIo Products and ischarges that ma useful byproducts require treatment Reclaimed byproducts Wastewater Solids and re 1.9. A manufacturing process viewed from the standpoint of minimization of environ- er, There are numerous ways in which technology can be applied to minimize ong these are Use of state-of-the-art computerized control to achieve ffi maximum utilization of raw materials, and minimum pre duction of pollutant by-proo C 2000 CRC Press LlC
water from petroleum production, and emission of air pollutants such as acid-rain-forming sulfur dioxide • Modern transportation practices, particularly reliance on the automobile, that cause scarring of land surfaces from road construction, emission of air pollutants, and greatly increased demands for fossil fuel resources Despite all of the problems that it raises, technology based on a firm foundation of environmental science can be very effectively applied to the solution of environmental problems. One important example of this is the redesign of basic manufacturing processes to minimize raw material consumption, energy use, and waste production. Consider a generalized manufacturing process shown in Figure 1.9. With proper design the environmental acceptability of such a process can be greatly enhanced. In some cases raw materials and energy sources can be chosen in ways that minimize environmental impact. If the process involves manufacture of a chemical, it may be possible to completely alter the reactions used so that the entire operation is more environmentally friendly. Raw materials and water may be recycled to the maximum extent possible. Best available technologies may be employed to minimize air, water, and solid waste emissions. Reclaimed byproducts Solids and sludges Wastewater Recycle Discharges that may require treatment Manufacturing process Reactants Contaminants (impurities) Reaction media (water, organic solvents) Catalysts Products and useful byproducts Atmospheric emissions Figure 1.9. A manufacturing process viewed from the standpoint of minimization of environmental impact. There are numerous ways in which technology can be applied to minimize environmental impact. Among these are the following: • Use of state-of-the-art computerized control to achieve maximum energy efficiency, maximum utilization of raw materials, and minimum production of pollutant by-products © 2000 CRC Press LLC
Use of materials that minimize pollution problems, for example heat resistant materials that enable use of high temperatures for efficient thermal processes Application of processes and materials that enable maximum materials recycling and minimum waste product production, for example, advanced membrane processes for wastewater treatment to enable water recycling Application of advanced biotechnologies such as in the biological treat ment of wastes Use of best available catalysts for efficient synthesis Use of lasers for precision machining and processing to minimize waste production The applications of modern technology to environmental improvement are addressed in several chapters of this book. Chapter 8,Water Treatment, discusses technologically-based treatment of water. The technology of air pollution control is discussed in various sections of Chapters 10-13. Hazardous waste treatment is addressed specifically in Chapter 20 LITERATURE CITED 1. Cunningham, William P, and Barbara Woodworth Saigo, environmentai Science a Global Concern. 5th ed. Wm. C. Brown/McGraw-Hill. New York 1998 2. Manahan, Stanley E, Toxicological Chemistry, 2nd ed, Lewis Publishers/CRC Press. Boca Raton. FL. 1992 3. Montgomery, Carla W, Environmental Geology, 5th ed, Wm. C Brown/McGraw-Hill, New York, 1997 4. Smith, Robert Leo, Elements of Ecology, 4th ed, Benjamin Cummings, Menlo Park, CA, 1998 5. Graedel, T. E, and Paul J. Crutzen Atmospheric Change, An Earth System Perspective, W.H. Freeman and Company, New York, 1993 6. Berner. Elizabeth K. and robert A. Berner. Global Environment. Water. Air nd Geochemical Cycles, Prentice Hall, Englewood Cliffs, NJ, 1994 7. Geochemical Cycles, Chapter 23 in Inorganic Geochemistry, Gunter Faure Macmillan Publishing Co, New York, pp 500-525, 1991 SUPPLEMENTARY REFERENCES Alexander. David E. and rhodes Fairbridge, Eds, Encyclopedia of Environmental Science, Kluwer Academic Publishers, Hingham, MA, 1999 Andrews, J. E, An Introduction to Environmental Chemistry, Blackwell Science, Cambridge. MA. 1996 C 2000 CRC Press LlC
• Use of materials that minimize pollution problems, for example heatresistant materials that enable use of high temperatures for efficient thermal processes • Application of processes and materials that enable maximum materials recycling and minimum waste product production, for example, advanced membrane processes for wastewater treatment to enable water recycling • Application of advanced biotechnologies such as in the biological treatment of wastes • Use of best available catalysts for efficient synthesis • Use of lasers for precision machining and processing to minimize waste production The applications of modern technology to environmental improvement are addressed in several chapters of this book. Chapter 8, “Water Treatment,” discusses technologically-based treatment of water. The technology of air pollution control is discussed in various sections of Chapters 10-13. Hazardous waste treatment is addressed specifically in Chapter 20. LITERATURE CITED 1. Cunningham, William P., and Barbara Woodworth Saigo, Environmental Science, a Global Concern, 5th ed., Wm. C. Brown/McGraw-Hill, New York, 1998. 2. Manahan, Stanley E., Toxicological Chemistry, 2nd ed., Lewis Publishers/CRC Press, Boca Raton, FL, 1992. 3. Montgomery, Carla W., Environmental Geology, 5th ed., Wm. C. Brown/McGraw-Hill, New York, 1997. 4. Smith, Robert Leo, Elements of Ecology, 4th ed., Benjamin Cummings, Menlo Park, CA, 1998. 5. Graedel, T. E., and Paul J. Crutzen Atmospheric Change, An Earth System Perspective, W. H. Freeman and Company, New York, 1993. 6. Berner, Elizabeth K. and Robert A. Berner, Global Environment: Water, Air, and Geochemical Cycles, Prentice Hall, Englewood Cliffs, NJ, 1994. 7. “Geochemical Cycles,” Chapter 23 in Inorganic Geochemistry, Gunter Faure, Macmillan Publishing Co., New York, pp. 500-525, 1991. SUPPLEMENTARY REFERENCES Alexander, David E. and Rhodes W. Fairbridge, Eds., Encyclopedia of Environmental Science, Kluwer Academic Publishers, Hingham, MA, 1999. Andrews, J. E., An Introduction to Environmental Chemistry, Blackwell Science, Cambridge, MA, 1996. © 2000 CRC Press LLC