Gaseous products of nitrite decomposition in soils

Abstract

Studies of the gaseous products formed by chemical decomposition of nitrite in soils showed that substantial amounts of N 2 and NO 2 and small amounts of N 2O were evolved on treatment of neutral and acidic soils with nitrite, the largest amount of N 2 being formed in an acidic soil having a high organic matter content. The amount of NO 2 produced was inversely related to soil pH, but significant amounts of NO 2 were evolved from soils having pH values above 7. The failure of some investigators to detect NO 2 as a product of nitrite decomposition in acidic soils can be attributed to use of closed experimental systems that promoted sorption of this gas by moist soil and conversion of NO 2 to nitrate. A study of the selfdecomposition reaction of nitrous acid showed that this reaction does not proceed according to the classical equation 3HNO 2 = HNO 3 + 2NO + H 2O and is better represented by the equation 2HNO 2 = NO + NO 2 + H 2O. Evidence was obtained that organic soil constituents are responsible for the reduction of nitrite to N 2 and N 2O and for the fixation of nitrite N observed on treatment of soils with nitrite and that inorganic soil constituents are not involved in these reactions. Several experiments indicated that most of the NO 2 evolved on treatment of soils with nitrite is formed by self-decomposition of nitrous acid and by atmospheric oxidation of NO produced by this reaction.