Inorganic Nitrogen Transformations Through the Oxidation and Reduction of Iron

In acid solution nitrate can be reduced by ferrous iron to N 2 through such intermediates as nitrogen tetraoxide, nitrous acid, hyponitrous acid and nitrous oxide or through nitrogen tetraoxide, nitrous acid, nitric oxide, and nitrous oxide. These sequences show similarities to those occurring in the denitrification process. In a basic solution the reduction of nitrite to N 2 may go through nitric oxide, N 2 O 2 2‐ , and nitrous oxide, or it may be reduced to ammonia through hydroxylamine, and hydrazine. Hydrazine and hydroxylamine are very unstable in the presence of iron in solution. In acid solution both hydrazine and hydroxylamine are oxidized by ferric iron to N 2 and N 2 O. The amount of N 2 O formed is proportional to the ferric iron concentration.