Nitrogen sedimentary cycle

To begin the discussion, we will present briefly a view of the modern carbon cycle, with emphasis on processes, fluxes, reservoirs, and the "CO2 problem". In Chapter 4 we introduced this "problem" here it is developed further. We will then investigate the rock cycle and the sedimentary cycles of those elements most intimately involved with carbon. Weathering processes and source minerals, basalt-seawater reactions, and present-day sinks and oceanic balances of Ca, Mg, and C will be emphasized. The modern cycles of organic carbon, phosphorus, nitrogen, sulfur, and strontium are presented, and in Chapter 10 linked to those of Ca, Mg, and inorganic C. In conclusion in Chapter 10, aspects of the historical geochemistry of the carbon cycle are discussed, and tied to the evolution of Earth s surface environment. 

Table 12-8. Global Fluxes and Atmospheric Residence Times of Nitrogen Associated with Biological Nitrogen Fixation, Inorganic Atmospheric Oxidation, Agricultural Fertilizer Production, Combustion Process, and the Sedimentary Cycle...

Altabet, M.A., and R. Francois. 1994. Sedimentary nitrogen isotopic ratio as a recorder for surface ocean nitrate utilization. Global Biogeochemical Cycles 8(1) 103-116. 

A conceptual model of sedimentary nitrogen cycling. Dashed arrows represent pore water diffusion and advection. Dotted arrows represent sedimentation. Source-. After Burdige, D.J. (2006). Geochemistry of Marine Sediments. Princeton University Press, p. 453. 

Burdige, D.J., and Martens, C.S. (1988) Biogeochemical cycling in an organic-rich marine basin 10. The role of amino acids in sedimentary carbon and nitrogen cycling. Geochim. Cosmochim. Acta 52, 1571-1584. 

Montoya, J.P. (1994) Nitrogen isotope fractionation in the modern ocean implications for the sedimentary record. In Carbon Cycling in the Glacial Ocean Constraints on the Ocean s Role in Global Change (Zahn, R., Pedersen, T.F., Kaminski, M.A., and Labeyrie, L., eds.), pp. 259-280, Springe, Berlin. 

Potential processes that may be called upon to explain the large discrepancy between excess N2 and NOs deficits within the SNM are (1) sedimentary denitrification, (2) anammox, (3) metal (Fe, Mn)-catalyzed denitrification, and (4) non-Redfieldian organic matter mineralization (Codispoti et al., 2001 Devol et al., 2006a,b). The first of these possibilities requires a decoupling between nitrogen and phosphorus cycles (e.g. possible greater burial of phosphorus in continental margin sediments). The less likely additional requirement is that the maximal inputs from the sediments should occur at the same depth as the water column peak of N02. In other words, the exact coincidence of the extrema in NOs , N02, ... 

Zopfi, J., Kjaer, T., Nielsen, L. P., and J0rgensen, B. B. (2001). Ecology of Thiploca spp. Nitrate and sulfur storage in relation to chemical microgradients and influence of Thioploca spp. on the sedimentary nitrogen cycle. Appl. Environ. Microbiol. 67, 5530-5537. 

Figure 21.1 Microbial nitrogen cycling processes in sedimentary environments on a coral reef (A) nitrogen fixation (B) ammonification (C) nitrification (D) dissimilatory nitrate reduction and denitrification (E) assimilatory nitrite/nitrate reduction (F) ammonium immobilization and assimilation. Adapted from D Elia and Wiebe (1990). Anammox (the anaerobic oxidation of NH4" with NO2 yielding N2 ) is not represented, as it has not yet been shown to occur on coral reefs, but may be found to be important in reef sediments.

Altabet, M. A., and Francois, R. (1994). Sedimentary nitrogen isotopic ratio records surface ocean nitrate utilization. Global Biogeochem. Cycles 8, 103—116. 

The most common paleoceanographic proxy used to reconstmct past changes in the oceanic N cycle is the of total combustible, or bulk, sedimentary nitrogen (hereafter d Ntuik). Such measurements provide a record, with a variable degree of accuracy, of the N sinking out of the surface ocean at times past (Altabet and Francois,... 

Heterotrophic respiration fueled by the rain of organic matter from the surface ocean is ubiquitous in marine sediments. Its rate determines one of the important characteristics of the sedimentary environment the depth of redox horizons below the sediment-water interface. Heterotrophic respiration is the process by which carbon and nutrients are returned to the water column it is important in the marine fixed nitrogen and sulfur cycles and the accumulation of metabolic products sets the conditions for the removal of phosphorus from the oceans in authigenic minerals. A great deal of effort has been directed toward quantifying the rates, pathways, and effects of metabolism in sediments. 

Klump J. V. and Martens C. S. (1987) Biogeochemical cycling in an organic-rich coastal marine basin 5. Sedimentary nitrogen and phosphorus budgets based upon kinetic models, mass balances, and the stoichiometry of nutrient regeneration. Geochim. Cosmochim. Acta 51, 1161-1173. 

Naik, H. and Naqvi, S.W.A. (2002) Sedimentary nitrogen cycling over the western continental shelf of India. EOS - Transactions of the American Geophysical Union, 83(4), OSM Suppl., Abs. OS 121-05. 

The stable isotope composition of sedimentary organic matter has widely been used to describe the state of the oceanic nitrogen cycle as it allows conclusions on nitrogen sources and transformation processes (i.e. assimilation or denitrification), which are subject to isotopic fractionation (i.e. Francois et al. 1992 Altabet and Francois 1994 Altabet et al. 1999 Thunell et al. 2004). We will briefly discuss this issue because early diagenesis... 

The ion exchangeable form of nitrogen (lEF-N) is the most active part of nitrogen in sediments, which plays an essential role in the nitrogen cycle. And the NO3-N was the dominant state in lEF-N in Jiaozhou Bay sediments. Factors influencing the distribution and concentrations of lEF-N in sediments include mainly temperature, salinity, pH, OC (organic carbon) and the characteristics of clay minerals, etc. The correlative coefficients of lEF-N and other sedimentary environmental parameters were calculated and tabulated in Table 3.29. 

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