Nitrite isotope characteristics and associated soil N transformations.

Nitrite (NO) is a crucial compound in the N soil cycle. As an intermediate of nearly all N transformations, its isotopic signature may provide precious information on the active pathways and processes. NO analyses have already been applied in N tracing studies, increasing their interpretation perspectives. Natural abundance NO isotope studies in soils were so far not applied and this study aims at testing if such analyses are useful in tracing the soil N cycle. We conducted laboratory soil incubations with parallel natural abundance and N treatments, accompanied by isotopic analyses of soil N compounds (NO, NO, NH). The double N tracing method was used as a reference method for estimations of N transformation processes based on natural abundance nitrite dynamics. We obtained a very good agreement between the results from nitrite isotope model proposed here and the N tracing approach. Natural abundance nitrite isotope studies are a promising tool to our understanding of soil N cycling.