Biogeochemical Cycles
  Spheres of B. Cycles
  Nitrogen Properties
  Simple Nitrogen Cycle
  Human Influences
  Spheres of the N Cycle
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The concept of biogeochemical cycles provides the framework for this project. It is a concept that recognizes the dynamism of multiple, complex processes that move, transform and store chemicals in the geosphere, atmosphere, hydrosphere, and biosphere. The term biogeochemical cycles expresses the interactions among the organic (bio-) and inorganic (geo-) worlds, and focuses on the chemistry (chemical-), and movement (cycles) of chemical elements and compounds. In its simplest form, cycling describes the movement of elements through various media and their return to their original state. Applying the concept of biogeochemical cycles provides a framework to identify and evaluate the sources and fates of chemical elements in a systems approach.

Separate biogeochemical cycles can be identified for each chemical element, such as the nitrogen (N), phosphorous (P), and carbon (C) cycles. However, through chemical transformations, elements combine to form compounds, and the biogeochemical cycle of each element must also be considered in relation to the biogeochemical cycles of other elements.

Elements and compounds also exist in the gaseous, solid, and liquid phases and can be transformed from one phase to another. In studying biogeochemical cycles, it is important to express in a common unit the amount of each element in all its phases and all its chemical compounds. This allows for establishing an "accounting system" for each element and for consideration of the conservation of mass. The principle of conservation of mass assumes that elements are neither created nor destroyed in the system. This assumption allows for conducting mass balance studies. Mass balance studies track all chemical forms and physical phases of an element, accounting for storage, transport, and transformation of the element.

Elements and compounds are stored in major reservoirs - the atmosphere, hydrosphere, geosphere, and biosphere. The reservoirs are also interconnected, such that the output from one reservoir can become the input to another. Movements of elements and compounds within each reservoir and among reservoirs are called fluxes. Thus, interactions among the atmosphere, surface waters, ground waters, soils, plants, trees, and sediments must be considered in biogeochemical cycles. Water (H2O) is an important medium for transporting and transforming chemicals and the hydrologic cycle is an important factor in biogeochemical cycles.

Suggested Reading:

Aldrich, S.R. 1980. Nitrogen in Relation to Food, Environment, and Energy. Special Publication 61, Agricultural Experiment Station, College of Agriculture, University of Illinois, Urbana-Champaign.

Baur, W.H., and F. Wlotzka. 1978. Nitrogen. Handbook of Geochemistry. Vol. II/1. Element H(1) to Al(13), Wedepohl, K.H. (executive ed.) Springer-Verlag, Berlin.

Berner, R.A. and A.C. Lasaga. 1989. Modeling the geochemical carbon cycle. Scientific American 260(3):74-81.

Bolin, B., E.T. Degens, S. Kempe, and P. Ketner (eds.). 1979. The Global Carbon Cycle. SCOPE Series 13. John Wiley & Sons, Inc., New York.

Delwiche, C.C. 1970. The nitrogen-cycle. Scientific American 223(3):136-147, 264.

Dignon, J., and S. Hameed. 1989. Global emissions of nitrogen and sulfur oxides. J. Air. Pollut. Contr. Assoc. 39:180-186.

Furley, P.A., and W.W. Newey. 1983. Geography of the Biosphere. Butterworths, London.

Houghton, R.A. 1987. Terrestrial metabolism and atmospheric CO2 concentrations. BioScience 37:672-678.

Houghton, R.A., and G.M. Woodwell. 1989. Global climatic change. Scientific American 260(4):36-44.

Kramer, J.R. 1965. History of sea water. Constant temperature-pressure equilibrium models compared to liquid inclusion analyses. Geochim. Cosmochim. Acta 29:921-945.

Kump, L.R., and F.T. Mackenzie. 1996. Regulation of atmospheric O2: Feedback in the microbial feedbag. Science 271:459-460.

Parton, W.J., J.W.B. Stewart, and C.V. Cole. 1988. Dynamics of C, N, P and S in grassland soils: A model. Biogeochemistry 5:109-131.

Sawyer, C.N. 1970. The nitrogen cycle. Proc., Twelfth Sanitary Engineering Conf. College of Engineering, University of Illinois, Urbana-Champaign, pp. 6-13.

Spitzy, A.N. 1988. Dissolved organic matter in groundwaters from different climates. SCOPE/UNEP Sonderband Heft 66:377-413.

Sprent, J.I. 1987. The Ecology of the Nitrogen Cycle. Cambridge University Press, New York.

Stevenson, F.J. and M.A, Cole. 1999. Cycles of Soil: Carbon, Nitrogen, Phosphorus, Micronutrients. Second Edition. John Wiley & Sons, Inc., New York.

Svensson, B.H., and R. Soderlund (eds.). 1976. Nitrogen, Phosphorus and Sulphur-Global Cycles. SCOPE Report 7. Ecol. Bull. (Stockholm) No. 22.

Van der Hoek, K., J.W. Erisman, S. Smeulders, J.R. Wisniewski, and J. Wisniewski (eds.). 1998. Nitrogen, the Confer-N-s: First International Nitrogen Conference 1998. 23-27 March 1998, Noordwijkerhout, The Netherlands. Elsevier, Amsterdam.

Viets, F.G., Jr., and R.H. Hageman. 1971. Factors affecting the accumulation of nitrate in soil, water, and plants. Agriculture Handbook 413. U.S. Government Printing Office, Washington, DC.

Welch, L.F. 1979. Nitrogen Use and Behavior in Crop Production. Illinois Agricultural Experiment Station Bull. 761, Urbana.

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