Chapter 2

CHEMISTRY AND THE ANTHROSPHERE: ENVIRONMENTAL CHEMISTRY AND GREEN CHEMISTRY

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Environmental Chemistry, 9th Edition

Stanley E. Manahan

Taylor and Francis/CRC Press

2010

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2.1 Environmental Chemistry

Environmental chemistry is the study of the sources, reactions, transport, effects, and fates of chemical species in the hydrosphere, the atmosphere, the geosphere, and the anthrosphere and the effects of human activities thereon

See Figure 2.1 (next slide) for an illustration of this definition as exemplified by pollutant sulfur dioxide

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Major Categories of Environmental Chemistry • Aquatic Chemistry deals with chemical phenomena in the

hydrosphere

• Biochemical processes are particularly important

• Atmospheric chemistry deals with chemical processes in the atmosphere

• Many of these are photochemical

• Geochemistry and soil chemistry

• Toxicological chemistry

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2.2 Matter and Cycles of Matter Biogeochemical cycles, often elemental cycles involving

• Carbon • Oxygen • Nitrogen • Sulfur • Phosphorus

•

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Carbon Cycle 6

Nitrogen Cycle 7

The Oxygen Cycle (Chapter 9, Figure 9.11) 8

The Phosphorus Cycle 9

The Sulfur Cycle 10

2.3 The Anthrosphere and Environmental Chemistry Anthrosphere : That part of the environment made or modified by humans and used for their activities

Impact of humans

• Early impact was low, but not insignificant

• Impact in last 200 years has been enormous

• The anthropocene in which human activities predominate in determining Earth’s environment

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The anthrosphere is categorized by the ways in which humans do things and includes • Dwellings

• Structures used for manufacturing, commerce, education, other

• Utilities such as water, fuel, electricity distribution systems

• Transportation systems such as railroads

• Components used for food production, processing, distribution

• Machines of all kinds

• Communications structures and devices

• Structures and machines used for extractive industries

• Mining • Petroleum production

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Fig. 2.7 Key Components of the Anthrosphere 13

2.7 Effects of the Anthrosphere on Earth (Fig 2.8) 14

Figure 2.9 Evolution of anthrosphere to more environmentally compatible state

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Green Chemistry Green chemistry is the sustainable, safe, and non-polluting practice of chemical science and manufacturing in a manner that consumes minimum amounts of materials and energy while producing little or no waste material

Twelve principles of green chemistry

1. Prevent wastes

2. Use all materials

3. Avoid hazardous substances

4. Minimize toxicity

5. Minimize auxiliary substances

6. Minimize energy consumption

7. Use renewables

8. Minimize protecting groups

9. Maximize reagent selectivity

10. Degradability of products released

11. Monitor and carefully control processes

12. Avoid extremes

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Some Specific Aspects of Green Chemistry 1. Chemical transformations under mild conditions 2. Green catalysts 3. Solventless processes 4. Less dangerous, less polluting solvents 5. Use supercritical fluids (carbon dioxide) 6. Intensify processes, such as with small-volume reactors 7. Use electrons as mass-less reagents for oxidation and

reduction 8. Renewable feedstocks 9. Design for degradability of products released to the

environment 10. Use biodegradable polymers such as those synthesized

biochemically

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Three undesirable characteristics of chemicals 1. Those that are persistent 2. Those that undergo bioaccumulation 3. Those that are toxic Persistence/bioaccumulation/toxicity characteristics of common chemicals (PBT) • U.S. Environmental Protection Agency PBT Profiler on the

following website http://www.epa.gov/oppt/sf/tools/pbtprofiler.htm

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Green Chemistry and Environmental Chemistry Green chemistry’s goal of environmental protection can best be accomplished by the implementation of green chemistry

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