Nitrate formation in soils equilibrated with nitrite at 0.5° C was directly related to soil level of reactive managanese (Mn) oxides. It was demonstrated that synthetic Mn oxides can oxidize nitrite to nitrate and become reduced in the process. Nitrite oxidation, nitrate formation, and MnO 2 reduction were stoichiometrically related reactions in the presence or absence of atmospheric O 2 . Nitrite reduced Mn(IV) to either Mn(II) or Mn(III), but when MnO 2 /nitrite ratios were high, reduction to Mn(III) appeared to predominate. This mechanism of nonmicrobial conversion of nitrite to nitrate may explain why nitrite seldom accumulates in soils, even when Nitrobacter numbers are low and conditions for their growth are unfavorable.
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Richmond J. Bartlett (1981) studied this question.