ENVIRONMENTAL CHEMISTRY

Environmental Chemistry, 10th Ed. Answer Manual 1

ENVIRONMENTAL CHEMISTRY

Tenth Edition

ANSWER MANUAL

Stanley E. Manahan

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Environmental Chemistry, 10th Ed, Answer Manual 3 3

Chapter 1 Environmental Chemistry and the Five Spheres of the Environment

• Much of what is known about Earth's past history is based upon paleo-environmental studies.

Doing some research on the internet, suggest what is meant by these studies. How can past climatic conditions, temperature, and atmospheric carbon dioxide levels be inferred going back hundreds of thousands of years based on ice cores and even millions of years based on fossils?Answer: Paleontology deals with ancient fossils, the nature of which reflects the climatic conditions under which they existed millions of years ago. Ice cores contain entrained air, the composition of which reflects climatic conditions from when the ice was formed as long as hundreds of thousands of years ago.

• The idea of climate change caused by human activities appears to be relatively recent. However,

it was proposed quite some time ago in a paper entitled “On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground.” When was this paper published and who was the author? What were his credentials and credibility?Answer: The article in question was published in 1896 in the Philosophical Magazine and Journal of Science by Svante Arrhenius, a Swedish Nobel-Prize-winning physicist and chemist with outstanding credentials and credibility.

• The definition of environmental chemistry shown in Figure 1.4 could very well be illustrated

with nitrogen oxides, NO and NO2, emitted to the atmosphere. What would be the sources of these gaseous nitrogen oxides? Which secondary air pollutant would they form interacting with volatile hydrocarbons in the sunlight? Could acid rain result from these oxides and, if so, what would be the formula of the acid?Answer: The nitrogen oxides of most importance would come from pollutant combustion sources. Through photochemical reactions involving hydrocarbons the nitrogen oxides can cause the formation of photochemical smog. Acid rain in the form of HNO3 can also be formed as a secondary air pollutant.

• A number of reputable scientists now believe that the Holocene is ending and a new era has

begun. What is the Holocene? What is the new era that may well be replacing it and how does it relate to material in this chapter? What are some of the environmental implications of this change?Answer: The Holocene is the relatively hospitable epoch under which humans have existed for the last approximately 10,000 years. It is being replaced by the Anthropocene in which human activities predominate in determining conditions on Earth.

• In the late 1800s there was concern that within the nitrogen biogeochemical cycle, not enough

of the atmosphere’s inexhaustible store of nitrogen was being “fixed” to chemical forms that could be utilized by plants and that food shortages would result from a shortage of fixed nitrogen. What happened to change this situation? In what respect did this development save many lives and how did it also make possible the loss of millions of people in warfare after about 1900?Answer: The discovery of a synthetic chemical method to capture atmospheric nitrogen as ammonia, NH3, enabled nitrogen fertilization of soil vastly increasing food productivity.However, explosive organonitrogen compounds synthesized starting with ammonia killed 2 / 4

Environmental Chemistry, 10th Ed, Answer Manual 4 4 millions of people in warfare.

• In what respect is the term “solid earth” a misnomer? What are some specific events in the last

decade that cast some doubt on “solid earth?” How did one of these events specifically impact the anthrosphere and perhaps change the course of future energy developments?Answer: The earth’s outer shell rests on top of a layer of hot, molten rock. Earth is prone to earthquakes and volcanoes. The Fukushima Daiichi nuclear disaster that resulted from a massive earthquake and tsunami on the coast of Japan has essentially shut down Japan’s once- thriving nuclear energy development.

• In what important, fundamental respect does the phosphorus cycle differ from the carbon,

oxygen, and nitrogen cycles?Answer: The phosphorus cycle does not have an atmospheric component as do the other cycles mentioned.

• Most people are aware that atmospheric carbon dioxide contributes to global warming and

climate change. In what respect, however, is the atmosphere’s carbon dioxide part of Earth’s natural capital, that is, where would we be without it? What crucial natural phenomenon causes a slight, but perceptible change in atmospheric carbon dioxide levels over the course of a year?Answer: In addition to keeping Earth’s temperature at a livable level, atmospheric carbon dioxide provides the carbon for the photosynthetic organisms that provide food for essentially all organisms. Especially in the Northern Hemisphere, atmospheric carbon dioxide levels go through an annual cycle as the result of photosynthesis.

• Figure 1.4 illustrates the definition of environmental chemistry in terms of a common pollutant.

What command and control regulations have been implemented in limiting this source of pollution? What “end-of-pipe” measures have been used? Suggest how the practices of green chemistry might serve as alternatives to these measures?Answer: Command and control regulations have been put in place to limit allowable emissions of sulfur dioxide. “End-of-pipe” control measures have concentrated upon removing pollutants from the waste stream after they have been produced, such as by scrubbing sulfur dioxide from a coal-fired powerplant stack. The practice of green chemistry seeks to prevent pollutants from being produced.

• As it applies to environmental processes and pollution, the term “sink” is sometimes used.

With some search on the internet, explain what is meant by a sink as it applies to environmental pollution. In what sense is Earth’s ability to act as a sink part of its natural capital? Explain.Answer: A sink is the final resting place of a pollutant. The geosphere’s ability to absorb and degrade wastes placed in it is an important part of its natural capital.

• In dealing with pollution and the potential for pollution, three approaches are pollution

prevention, end-of-pipe measures, and remediation. What do these terms mean in terms of pollution control? Which is the most desirable, and which is the least? Explain.Answer: In descending order of desirability these means of pollution control are (1) prevention of the production of pollutants, (2) end-of-pipe measures that remove pollutants from waste streams before they can be discharged, and (3) remediation by treating or removing pollutants after they have been discharged, usually to the geosphere.

• With respect to increased production of corn to provide fuel ethanol, it is stated in this chapter

that, “Increased demand for fertilizer in the form of chemically combined nitrogen means that more ammonia is synthesized using atmospheric nitrogen and impacting the nitrogen cycle.” With respect to which resource of Earth’s capital is the synthetic production of nitrogen 3 / 4

Environmental Chemistry, 10th Ed, Answer Manual 5 5 fertilizer as it is now done a problem, and in respect to which resource is it not a problem.Explain.Answer: Currently the hydrogen required to make ammonia is extracted from methane, a depleting resource of natural capital, in a process that discharges carbon dioxide to the atmosphere. Elemental nitrogen is also used, but the atmosphere has an inexhaustible store of that resource.

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