River , denitrification

Baker CJ, Maltby E. 1995. Nitrate removal by river marginal wetlands factors affecting the provision of a suitable denitrification environment. In Hughes JMR, Heath-waite AL, eds. Hydrology and Hydrochemistry of British Wetlands. Chichester Wiley, 291-313. 

Thus, in order to balance the electrons, 1 mM e have to be consumed by denitrification. Hence, the calculated consumption of nitrate is 1 mM e = 0.2 mM NO = 2.8 mg N-L 1, which is more than is present in the river water. Note, however, that reaction (ii) produces 0.15 mM = 2.1 mg N L 1 nitrate. Thus, one would expect a net decrease in nitrate of only 0.7 mg N L 1, which compares well with the observed 0.5 mg N L"1 decrease. The measured concentration changes of the four water constituents are, therefore, reasonable. 

Grischek, T., K. M. Hiscock, T. Metschies, P. F. Dennis, and W. Nestler. 1998. Factors affecting denitrification during infiltration of river water into a sand and gravel aquifer in Saxony, Germany. Water Research 32 450—460. 

The nitrogen supplies on land consist of the assimilable nitrogen in the soil VS2 0.19-104tkm-2, in plants (12 1091), and living organisms (0.2 1091). A diversity of nitrogen fluxes is formed here of the processes of nitrification, denitrification, ammonification, fixation, and river run-off. The intensities of these fluxes depend on climatic conditions, temperature regime, moisture, as well as the chemical and physical properties of soil. Many qualitative and quantitative characteristics of these dependences have been described in the literature (Hellebrandt et al., 2003). Let us consider some of them. 

Estuaries have been shown to be active sites of N2O production. DIN loading to sediments was positively correlated with N2O fluxes, indicating that eutrophication may be linked with increases in global emissions of N2O. In fact, a model of DIN transport by world rivers and estuaries indicates that 90% of the denitrification in rivers and estuaries occurs in the northern hemisphere. 

Figure 16.2 Model-predicted latitudinal distribution in the North Atlantic Basin (a) estuarine denitrification (b) total nitrogen transport by rivers. (Modified from Seitzinger, 2000.)...

Laursen, A.E., and Seitzinger, S.R (2002) Measurement of denitrification in rivers an integrated, whole reach approach. Hydrobiologia 485, 67-81. 

Patrick, O., Slawayk, G., Garcia, N., and Bonin, P. (1996) Evidence of denitrification and nitrate ammonification in the river Rhone plume (northwest Mediterranean Sea). Mar. Ecol. Prog. Ser. 141, 275-281. 

Sebilo, M., Billen, G, Grably, M., and Mariotti, A. (2003) Isotopic composition of nitrate-nitrogen as a marker of riparian and benthic denitrification at the scale of the whole Seine River system. Biogeochemistry 63 35-51. 

Land use changes, such as conversion of tropical forests to cattle pastures, affect biological N fixation, mineralization, nitrification, and denitrification (Davidson et al. 1993, Keller and Reiners 1994, Matson et al. 1987, Montagnini and Buschbacher 1989, Neill et al. 1995). Matson et al. (1987) estimated that N mobilized annually from deforestation was equivalent to more than half of the industrial N fixed globally and greater than the total amount of N delivered to oceans by rivers. 

In anoxic waters, such as the deep basin of the central Baltic Sea or parts of the shallow Po River delta, N2O is consumed by water-column denitrification. 

Bianchi, M., Bonn, P., and Fehatra (1994). Bacterial nitrification and denitrification rates in the Rhone River plume (northwestern Mediterranean Sea). Marine Ecology-Progress Series 103, 197-202. 

Magalhaes, C. M., Joye, S. B., Moreira, R. M., Weibe, W. J., and Bordalo, A. A. (2005). Effect of salinity and inorganic nitrogen concentrations on nitrification and denitrification rates in intertidal sediments and rocky biofifins of the Douro River estuary, Portugal. Water Research 9, 1783—1794. 

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