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N<sub>2</sub>O isotope approaches for source partitioning of N<sub>2</sub>O production and estimation of N<sub>2</sub>O reduction – validation with the <sup>15</sup>N gas-flux method in laboratory and field studies
oleh: D. Lewicka-Szczebak, D. Lewicka-Szczebak, M. P. Lewicki, R. Well
| Format: | Article |
|---|---|
| Diterbitkan: | Copernicus Publications 2020-11-01 |
Deskripsi
<p>The approaches based on natural abundance <span class="inline-formula">N<sub>2</sub>O</span> stable isotopes are often applied for the estimation of mixing proportions between various <span class="inline-formula">N<sub>2</sub>O</span>-producing pathways as well as for estimation of the extent of <span class="inline-formula">N<sub>2</sub>O</span> reduction to <span class="inline-formula">N<sub>2</sub></span>. But such applications are associated with numerous uncertainties; hence, their limited accuracy needs to be considered. Here we present the first systematic validation of these methods for laboratory and field studies by applying the <span class="inline-formula"><sup>15</sup>N</span> gas-flux method as the reference approach.</p> <p>Besides applying dual-isotope plots for interpretation of <span class="inline-formula">N<sub>2</sub>O</span> isotopic data, for the first time we propose a three dimensional <span class="inline-formula">N<sub>2</sub>O</span> isotopocule model based on Bayesian statistics to estimate the <span class="inline-formula">N<sub>2</sub>O</span> mixing proportions and reduction extent based simultaneously on three <span class="inline-formula">N<sub>2</sub>O</span> isotopic signatures (<span class="inline-formula"><i>δ</i><sup>15</sup>N</span>, <span class="inline-formula"><i>δ</i><sup>15</sup>N</span><span class="inline-formula"><sup>SP</sup></span>, and <span class="inline-formula"><i>δ</i><sup>18</sup>O</span>). Determination of the mixing proportions of individual pathways with <span class="inline-formula">N<sub>2</sub>O</span> isotopic approaches often appears imprecise, mainly due to imperfect isotopic separation of the particular pathways. Nevertheless, the estimation of <span class="inline-formula">N<sub>2</sub>O</span> reduction is much more robust, when applying an optimal calculation strategy, typically reaching an accuracy of <span class="inline-formula">N<sub>2</sub>O</span> residual fraction determination of about 0.15.</p>