Nitrogen cycle transformations

One of the things that environmental scientists do IS to keep track of important elements in the biosphere—in what form do these ele ments normally occur to what are they transformed and how are they returned to their normal state Careful studies have given clear although compli cated pictures of the nitrogen cycle the sulfur cy cle and the phosphorus cycle for example The carbon cycle begins and ends with atmospheric carbon dioxide It can be represented in an abbrevi ated form as... 

The atmospheric part of the nitrogen cycle is a good example of the complicated mechanism of transformation of gas substances that are characterized by an intricate set of fluxes at the borders between the basic reservoirs of nitrogen. Nevertheless, the... 

Altabet, M. A. (1988). Variations in nitrogen isotopic composition between sinking and suspended particles Imphcations for nitrogen cycling and particle transformation in the open ocean. Deep Sea Res. 35, 535-554. 

Montoya,. P., and VoB, M. (2006). Nitrogen cycling in anoxic waters Isotope signatures of nitrogen transformations in the Arabian Sea oxygen minimum zone. In Past and Present Water Column Anoxia (Neretin, L., ed.). NATO Science Series, Springer, Dordrecht, pp. 259—281. 

Figure 29.2 Schematic overview of the marine nitrogen cycle. A Important species, their oxidation state (vertical axis), and major biological transformations of nitrogen (arrows). B Typical values of the isotopic enrichment factor (e) are shown for reactions that have been characterized isotopically. Estimates of 6 were drawn from the available literature on N2-fixation and the of diazotrophs (Carpenter et al, 1997 Delwiche and Steyn, 1970 Hoering and Ford, 1960 Macko et al., 1987 Montoya et ah, 2002), denitrification (Barford et ah, 1999 Cline and Kaplan, 1975 Delwiche and Steyn, 1970 Mariotti et ah, 1981,1982 McCready et ah, 1983 Miyake and Wada, 1971 Voss et ah, 2001 Wada, 1980 ), nitrification (Delwiche and Steyn, 1970 Mariotti et ah, 1981 Miyake and Wada, 1971 Ybshida, 1988), N03 uptake (Montoya and McCarthy, 1995 Needoba et ah, 2003 Needoba and Harrison, 2004 Pennock et ah, 1996,1998 Wada and Hattori, 1978 Waser et ah, 1998a, 1998b ), NO2 uptake (Wada and Hattori, 1978 Wada, 1980), NH4 uptake (Cifuentes et ah, 1989 Montoya et ah, 1991 Pennock et ah, 1988 Wada, 1980 Wada and Hattori, 1978), and zooplankton excretion (Checkley and Miller, 1989).

Figure 6 Microbial transformations of the nitrogen cycle. Pathways depicted are 1—N2 fixation 2—DIN assimilation 3—ammonium regeneration 4—nitrification 5—nitrate/nitrite reduction and 6—denitrification.

Depending upon environmental and biological conditions, all of these various organic and inorganic compounds containing nitrogen can be variously transformed. The diverse manners in which the movements and transformations of these chemicals occur is known as the nitrogen cycle. 

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