Nitrite isotope characteristics and associated soil N transformations

Abstract

Nitrite (NO2−) 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. NO2− analyses have already been applied in 15N tracing studies, increasing their interpretation perspectives. Natural abundance NO2− 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 15N treatments, accompanied by isotopic analyses of soil N compounds (NO3−, NO2−, NH4+). The double 15N 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 15N tracing approach. Natural abundance nitrite isotope studies are a promising tool to our understanding of soil N cycling.

Nitrite Cycling in Warming Arctic and Subarctic Waters

“…In fact, the variability of δ 15 $${\mathrm{N}}_{{\text{NO}}_{2}}$$ in Arctic and subarctic waters is similar to that in other marine regions, as well as river ecosystems (Table 1). The δ 15 $${\mathrm{N}}_{{\text{NO}}_{2}}$$ in soil environments is higher than in rivers and oceans due to active denitrification (Lewicka‐Szczebak et al., 2021). In terms of δ 18 $${\mathrm{O}}_{{\text{NO}}_{2}}$$, the δ 18 $${\mathrm{O}}_{{\text{NO}}_{2}}$$ values in the Bering and Chukchi PNMs are slightly lower than those in other marine and soil environments (Table 1).…”

“…The NO 2 − dual isotope technique is a powerful tool in helping us to address the NO 2 − dynamics in various ecosystems, such as in soil (Lewicka‐Szczebak et al., 2021), riverine (Jacob et al., 2016; Liu et al., 2020), and marine environments (Buchwald & Casciotti, 2013; Buchwald et al., 2015; Chen et al., 2021; Liu et al., 2020). However, environmental NO 2 − isotope datasets are still rare and have not been applied to wider ecosystems.…”

FRAME—Monte Carlo model for evaluation of the stable isotope mixing and fractionation

“…Moreover, can be modified by O isotope exchange with ambient soil water [ 32 ]. The NO 2 - isotope model was only recently proposed for differentiating nitrite sources in soil [ 33 ], where the natural abundance isotope model was calculated by applying a simple fitting procedure (by Excel Solver) without giving the probability ranges for the model outputs. Here, we show how the application of the FRAME modelling tool may increase the insight into the determined processes.…”

“…We show the calculations based on the mean NO 2 - isotopic signatures from the laboratory experiment L1 (as published in [ 33 ], the isotopic signatures for the sources and stable isotopic fractionation factors for the sinks are adopted after the literature [ 33 ]. Input values are summarised in Table 8 ).…”

Isotopic Elucidation of Microbial Nitrogen Transformations in Forest Soils

“…But no study yet has targeted the isotopic patterns of the multiple pools of interconnected soil N forms. The development of reliable methods for identifying N transformations based on natural abundance of stable 15 N isotopes can provide an approach allowing studies under undisturbed soil conditions, ensuring original N transformation rates that can be traced without disturbance, and further evaluating labile N dynamics at larger time and space scales (Lewicka‐Szczebak et al., 2021).…”