Degradation of nitrate

The concentration of nitrous oxide (N20) in the atmosphere is only about 0.30 ppm but it increases by about 0.2% per year and so is at least partly of anthropogenic origin. Nitrous oxide is a product of the degradation of nitrate fertilizers, but some 7 x 105 tonnes of N2O are released annually to the atmosphere during production of nylon.20 The residence time of N20 in the atmosphere is about 150 years, and it could in the future contribute up to 10% of the anticipated greenhouse warming. 

Chew CF, Zhang TC. Abiotic degradation of nitrates using zero-valent iron and electrokinetic processes. Environ Eng Sci 1999 16 389-401. 

Yang GCC, Hung CH,Tu HC. (2008). Electrokinetically enhanced removal and degradation of nitrate in the subsurface using nanosized Pd/Fe slvaxy. Journal of Environmental Science and Health Part A 43 945-951. 

Corbisier D, Vereist L, Vanlangendonck Y, Van Lierde A (2006) Electro-degradation of nitrate ions and ammonia from power station effluents the ELONITA technique. VGB PowerTech 86 98-101-106... 

Figure 7. The XP spectra of control, carpet rolled and extruded double base rocket propellant in the spectral region of nitrogen and lead. Surface degradation of nitrate ester into oxime-like products and the emergence of lead to surface is observed.

Figure 17.9 (a) Catalytic conversion of nitrate to nitrogen and ammonia via nitrite, (b) Degradation of nitrates using Pd-BC composite catalyst with concomitant evolution of nitrite and ammonium ions with reaction time. 

In a commercial unit, a spray nitrator (39) is operated adiabaticaHy. The Hquid HNO feed is sprayed direcdy into the hot and preheated propane feed. The heat of nitration provides the heat to vaporize the HNO and to preheat it to the desired temperature for nitration. At one time, several spray nitrators were operated in series, with additional HNO being sprayed into each nitrator (32). In such an arrangement, the optimum propane HN02 ratios did not occur, and considerable amounts of nitroparaffins degraded. 

Nitration of pyrroles by the usual methods leads to extensive degradation. However, nitration can be achieved with an equimolar nitric acid—acetic anhydride mixture at low temperatures. In the case of pyrrole, the reaction leads predominandy to substitution at the -position (34), ie, in the following 51% 3-nitropyrrole [5930-94-9] (21) and 13% 2-nitropyrrole [5919-26-6] (22). 

There are a variety of reaction systems that allow the formation of cellulose trinitrate [9046-47-3]. HNO in methylene chloride, CH2CI2, yields a trinitrate with essentially no degradation of the cellulose chain (53). The HNO /acetic acid/acetic anhydride system is also used to obtain the trinitrate product with the fiber stmcture largely intact (51,52). Another polymer analogous reaction utilises a 1 1 mixture of HNO and H PO with 2.5% P2O5 to achieve an almost completely nitrated product (54). 

Acid deposition and the associated particulate nitrates and sulfates are implicated in the deterioration of certain sensitive ecosystems, decreased visibility, negative human health effects, and increased degradation of certain stone building materials and cultural resources, especially those made of limestone and marble. Fine particulate nitrate and sulfate particles... 

The solid-state NMR technique may also be used in cellulose derivatives to follow the degree of substitution and degradation of the chain e.g. as found for cellulose nitrate 16). Investigations on the composition of copolymers may also been done as examplared by celluloseacetate-butyrate given in Fig. 6, 20). Here, owing to relaxation differences the spectra cannot be used for elementary analyses, but for estimating the relative number of the components. 

Arene oxides can be intermediates in the bacterial transformation of aromatic compounds and initiate rearrangements (NIH shifts) (Dalton et al. 1981 Cerniglia et al. 1984 Adriaens 1994). The formation of arene oxides may plausibly provide one mechanism for the formation of nitro-substituted products during degradation of aromatic compounds when nitrate is present in the medium. This is discussed in Chapter 2. 

It is also important to appreciate that an organism that can degrade a given substrate under conditions of nitrate dissimilation may not necessarily display this potential under aerobic conditions. For example, a strain of Pseudomonas sp. could be grown with vanillate under anaerobic conditions in the presence of nitrate but was unable to grow under aerobic conditions with vanillate. 

During degradation in the presence of nitrate this may be reduced, and it has been observed that nitro groups may be introduced into the substrate. Details of this have been discussed in Chapter 2. 

Bregnard TP-A, A Haner, P Hohener, J Zeyer (1997) Anaerobic degradation of pristane in nitrate-reducing microcosms and Qmichme,ntca t jxe. Appl Environ Microbiol 63 2077-2081. 

A rearrangement (NIH shift) occurred during the transformation of 2-chlorobiphenyl to 2-hydroxy-3-chlorobiphenyl by a methanotroph, and is consistent with the formation of an intermediate arene oxide (Adriaens 1994). The occurrence of such intermediates also offers plausible mechanisms for the formation of nitro-containing metabolites that have been observed in the degradation of 4-chlo-robiphenyl in the presence of nitrate (Sylvestre et al. 1982). 

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