Summary
Contents
Subject index
This unique addition to reference literature provides an introduction to the major concepts and contemporary issues that are essential for students of environmental science and environmental studies to know. With over 200 entries authored by world-class names like Anthony Brazel, John Day and Edward Keller, this text is divided into six sections: Environmental Science, Environments, Paradigms & Concepts, Processes & Dynamics, Scales & Techniques, and Environmental Issues.
Nitrogen Cycle
Nitrogen Cycle
The nitrogen cycle is one of the most complicated material cycles in nature. This is because nitrogen can exist in many different forms, because it is involved in so many biogeochemical processes, and because it has been so affected by human activities. Nitrogen can exist in a valence state of +2 to −5. It can exist in various gaseous states (N2 and N2O, NH3), several inorganic dissolved states (NO3−, NO2−, NH4+), and as a number of organic compounds (i.e., urea, amino acids, proteins, DNA). Nitrogen is also a component of various rocks and is released with weathering. Nitrogen gas (N2) makes up about 80% of the atmosphere, but it cannot be directly used by living organisms. Nitrogen fixation is the process of ...
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