NITRITE IN SOILS - ACCUMULATION AND ROLE IN THE FORMATION OF GASEOUS N COMPOUNDS

Nitrite is an intermediary compound formed during nitrification as wel l as denitrification. It occasionally accumulates in soils and drainag e water. The nitrite can then undergo transformations to gaseous nitro gen compounds such as NO and NO2. Soil pH controls the abiotic nitrite decomposition to a large extent. Under acidic conditions(pH <5.5), ni trous acid spontaneously decomposes preferentially to NO and NO2. Nitr ite also undergoes reactions with metallic cations (especially ferrous iron) and with organic matter. As a result of these reactions gaseous compounds such as NO, NO2, N2O and CH3ONO can be formed. Through reac tion of nitrite with phenolic compounds nitro- and nitrosocompounds ca n be formed, building up organic N. With normal agricultural practices on slightly acidic soils, the nitrite instability usually does not le ad to economically important N losses from soils. However, the compoun ds formed through its degradation or interaction with other soil const ituents are linked to environmental problems such as tropospheric ozon e formation, acid rain, the greenhouse effect and the destruction of t he stratospheric ozone.