Denitrification nitrous oxide

FIGURE 16.10 Soil redox zone where methane and nitrous oxide denitrification occur. (Modified from data by Yu and Patrick, 2003.)... 

Acetylene-block assay Estimates denitrification by determining release of nitrous oxide (NjO) from acetylene-treated soil. 

Denitrification The reduetion of nitrates to nitrites and finally to nitrous oxide or even to moleeular nitrogen eatalyzed by faeultative aerobie soil baeteria working under anaerobie eonditions. 

Bremner, J. M. and Blackmer, A. M. (1981). Terrestrial nitrification as a source of atmospheric nitrous oxide. In Denitrification, Nitrification, and Atmospheric Nitrous Oxide" (C. C. Delwiche, ed.). Wiley, New York. 

Denitrification involves the sequential formation of nitrite, nitric oxide, and nitrous oxide. Two aspects of nitric oxide have attracted attention (a) chemical oxidation of biogenic nitric oxide to Nq, in the context of increased ozone formation (Stohl et al. 1996) and (b) the physiological role in mammalian systems (Feldman et al. 1993 Stuehr et al. 2004), in parasitic infections (James 1995), and in the inhibition of bacterial respiration (Nagata et al. 1998). Nitric oxide may be produced microbiologically in widely different reactions such as... 

Moir JWB, DJ Richardson, SJ Ferguson (1995) The expression of redox proteins of denitrification in Thiosphaerapantropha grown with oxygen, nitrate, and nitrous oxide. Arch Microbiol 164 43-49. 

Wrage N, Velthof GL, van Beusichem ML, Oenema, O.Role of nitrifier denitrification in the production of nitrous oxide. Soil Biol. Biochem. 2001 33 1723-1732. DOI 10.1016/S0038-0717(01)00096-7... 

Kool DM., Dolfing J, Wrage N, Van Groenigen JW. Nitrifier denitrification as a distinct and significant source of nitrous oxide from soil. Soil Biology Biochemistry. 2011 43 174-178. DOI 10.1016/j.soilbio.2010.09.030... 

Sigman et al. [134] have described a bacterial method for measuring the isotopic composition of seawater nitrate at the natural-abundance level. The method is based on the analysis of nitrous oxide gas (N2O) produced quantitatively from nitrate by denitrifying bacteria. The classical denitrification pathway consists of the stepwise reduction of nitrate (NOp to nitrite (N02), nitric oxide (NO), nitrous oxide (N2O), and dinitrogen (N2) ... 

In denitrification, part of the biological nitrogen cycle, nitrate in the soil is converted via four enzymatic reactions stepwise to nitrite, nitric oxide and nitrous oxide to finally yield gaseous nitrogen. 

Emissions of nitric and nitrous oxides are the result of microbial nitrification and denitrification in soils, controlled principally by soil water and mineral N contents, labile organic carbon, and temperature. Nitric oxide is a direct intermediate of both nitrification... 

It is thought that little net NO is produced in denitrification, it being readily reduced to N2O, and nitrification is therefore the main source of NO (Anderson and Levine, 1986 Skiba et al, 1993). Nitrous oxide is also produced in both nitrification and denitrification. At low O2 concentrations in otherwise aerobic soil, small amounts of N2O are formed as a by-product of nitrification, N2O not itself being reduced to NO,. In denitrification, the proportion of N2O produced relative to N2 increases as the availability of O2 increases and that of carbon decreases (Tiedje, 1988). In general only a small fraction of the N nitrified or denitrified in these pathways is released as NO or N2O. The emission is therefore sensitive to the amount of mineral N in the system, which is driven principally by additions of nitrogen fertilizers and deposition of nitrogen from the atmosphere. 

Skiba U, Smith KA, Fowler D. 1993. Nitrification and denitrification as sources of nitric oxide and nitrous oxide in a sandy loam soil. Soil Biology and Biochemistry 25 1527-1536. 

Nitrite reductases and nitrous oxide reductases are relatively newly found copper-containing proteins involved in bacterial denitrification. N2O reductase may bear a relationship to cytochrome oxidase and, indeed, parallels it somewhat in function, being the terminal electron acceptor in its pathway. 

Nitrous oxide (N2O) reductases carry out the terminal reduction step in the denitrification pathway. One has been isolated from Pseudomonas... 

Nitrous oxide is important not only as a greenhouse gas but, as discussed in Chapter 12, as the major natural source of NC/ in the stratosphere, where it is transported due to its long tropospheric lifetime (Crutzen, 1970). The major sources of N20 are nitrification and denitrification in soils and aquatic systems, with smaller amounts directly from anthropogenic processes such as sewage treatment and fossil fuel combustion (e.g., see Delwiche, 1981 Khalil and Rasmussen, 1992 Williams et al., 1992 Nevison et al., 1995, 1996 Prasad, 1994, 1997 Bouwman and Taylor, 1996 and Prasad et al., 1997). The use of fertilizers increases N20 emissions. For pastures at least, soil water content at the time of fertilization appears to be an important factor in determining emissions of N20 (and NO) (Veldkamp et al., 1998). 

Delwiche, C. E., Ed., Denitrification, Nitrification, and Atmospheric Nitrous Oxide, Wiley, New York, 1981. 

Betlach, M. R., and Tiedje, J. M. (1981). Kinetic explanation for accumulation of nitrite, nitric oxide, and nitrous oxide during bacterial denitrification. Appl. Environ. Microbiol. 

Jiingst, A., Braun, C., and Zumft, W. G. (1991a). Close linkage in Pseudomonas stutzeri of the structural genes for respiratory nitrite reductase and nitrous oxide reductase, and other essential genes for denitrification. Mol. Gen. Genet. 225, 241-248. 

Koike, 1., and Hattori, A. (1975). Energy yield of denitrification An estimate for growth yield in continuous culture of Paracoccus denitrificans under nitrate-, nitrite-, and nitrous oxide-limiting conditions. J. Gen. Microbiol. 88, 11-19. 

Crutzen, P.J. 1981. Atmospheric chemical processes of the oxides of nitrogen, including nitrous oxide. In Delwiche, j. (ed.) Denitrification, Nitrification and Nitrous Oxide. Wiley and Sons, New York. pp. 17-44. 

Seitzinger, S.P., Nixon, S.W. and Pilson, M.E.Q., 1984. Denitrification and nitrous oxide production in a coastal marine ecosystem. Limnol. Oceanogr., 29(1) 73-83. 

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