Nitric nitrogen cycle

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. 

Nitrite reductases (NiRs)—enzymes found in several strains of denitrifying bacteria— catalyze the one-electron reduction of nitrite anion to nitric oxide (Equation 1). - In addition to the importance of this process in the global nitrogen cycle (Figure 1), further incentive for the study of the denitrification process is provided by its environmental impact, ranging from the production of NO as a pollutant and NjO as a potent greenhouse gas, to lake eutrophication due to farm runoff that contains high concentrations of nitrates and nitrites. 

There has been a great deal of research on the combustion of small hydrocarbons, including nitrogen-cycle chemistry leading to nitric-oxide formation and abatement [138]. There are a number of methane-air reaction mechanisms that have been developed and validated [274,276,278], the most popular one being GRI-Mech [366]. There is also active research on the kinetics of large hydrocarbon combustion [81,88,171,246,328-330,426]. 

Nitrate, 334-336 Denitrification, 340 Nitric acid, 23 Nitrification, 334 Nitrogen cycle, 326... 

Ammonia is found in the environment as the result of natural and industrial processes. It is released into the environment by the breakdown of organic wastes, and it is a constituent of the soil, the atmosphere, and bodies of water. Ammonia is also a key intermediate in the nitrogen cycle and is a product of amino acid metabolism (WHO 1986). Anhydrous ammonia is used in the production of nitric acid, explosives, synthetic fibers, and fertilizers (Budavari 1989). It is used as a refrigerant as a corrosion inhibitor in the purification of water supplies in steel production as a catalyst for polymers as a preservative for latex and in the production of nitrocellulose, urea formaldehyde, sulfite cooking liquors, and nitroparaffins (ACGIH 1991 Lewis 1993). Ammonium hydroxide (10-35% ammonia) is a major constituent of many cleaning solutions. Ammonia... 

Nitric oxide (NO), nitrous oxide (N2O), dinitrogen (N2), and ammonia (NH3) are constituents of the Earth s atmosphere. They play important roles in the chemistry and climate of the present-day Earth. Moreover, they are intermediates of the oceanic nitrogen cycle. In contrast to most of the other components of the oceanic nitrogen cycle, they exist as dissolved gaseous molecules. Being gases they can be transferred across the seasurface-troposphere interface. 

Capone, D. G. (1991). Aspects of the marine nitrogen cycle with relevance to the dynamics of nitrous and nitric oxide. In Microbial Production and Consumption of Greenhouse Gases Methane, Nitrogen Oxides, and Halomethanes (Rogers, J. E., and Whitman, W. B., eds.). American Society of Microbiology, Washington, DC. pp. 255—275. 

Figure 12 A diagram of the nitrogen cycle with catalyzing enzymes and metal requirements of each step. NIT, nitrogenase AMO, ammonium mono-oxygenase HAO, hydroxylamine oxidoreductase NAR, membrane-bound respiratory nitrate reductase NAP, periplasmic respiratory nitrate reductase NR, assimila-tory nitrate reductase NIR, respiratory nitrite reductase NiR, assimilatory nitrite reductase NOR, nitric oxide reductase N2OR, nitrous oxide reductase.

Capone D. G. (1991) Aspects of the marine nitrogen cycle with relevance to the dynamics of nitrous and nitric oxide. 

NO. Nitric oxide, or nitrogen monoxide, is a colorless gas at room temperature. As we have already seen, it is industrially produced by the oxidation of ammonia. However, in the urban nitrogen cycle, a more significant process is the equilibrium process discussed in Chapter 5. 

Duncan K, Jennings E, Hettenbach S, et al. 1998. Nitrogen cycling and nitric oxide emissions in oil-impacted prairie soils. Biorem J 1(3) 195-208. 

Haber process nitrogen fixation nitrogen-fixing bacteria denitrification nitrogen cycle ammonia hydrazine nitric acid Ostwald process... 

Fig. 2.26 The biogeochemical nitrogen cycle. A ammonia synthesis (man-made N fixation), B oxidation of ammonia (indnstrial prodnction of nitric acid), C fertilizer application, D formation of NO due to high-temperature processes, E Oxidation of N2O within the stratosphere, F oxidation of NO within the troposphere, G ammonia deposition and transformation into ammonium, H biogenic emission, I biogenic N fixation, K denitrification, L nitrification, M assimilation (biogenic formation of amino adds), N mineralization. RNH2 organic bonded N (e. g. amines).

Hollocher, T.C. (1996). The enzymology and occurrence of nitric oxide in the biological nitrogen cycle. In J. Lancaster, Jr. (ed), Nitric oxide Principles and actions. Academic Press, San Diego, p. 289. 

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