Nitrogen reservoirs nitrite

The rank order of size of the reservoirs of nitrogen on earth are atmospheric N2, nitrate in sea water, and organic nitrogen of the biosphete and soils (Sverdrup et al., 1942), Nitrite and free ammonium are rare by comparison. Nitrate is also found at low concentrations in soils and fresh water. NO is extremely rare in the environment and when detected in sea water is typically at concentrations of less than 1 nM (Ward and Zafiriou, 1988). 

It was shown in 1989 by Anson et al." that Fe snbstitnted HPT s can function as catalysts for mnltielectron reduction of nitrite anion to ammonia, a process that requires 6 electrons. While in the presence of many other electrocatalysts that reaction occurs via a sales of one-electron steps and the prodncts inclnde hydroxylamine, in the case of electrocatalysis by a heteropoly tnngstate, no hydroxylamine was observed and the major prodnct of the redaction was ammonia. The first step in the electrocatalytic process observed by Anson is the complexation of nitrite by iron from the heteropoly complex. Next the rednced tnngsten cage serves as a reservoir for the storage of electrons that are snbseqnently transferred to nitrogen in a concerted, intramolecular, multiple electron process. The nniqne catalytic reactivity of the iron snbstitnted HPT in this process was... 

Ammonia and nitrate assimilation are the two principle processes by which nitrogen is obtained during primary production. In highly productive lakes exploitation of these reservoirs may be so intense that dissolved NH4+ and NOy concentrations are below detection level. Nitrite (NOy") provides an additional, but subsidiary, dissolved N source. 

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