The spatiotemporal dynamics of denitrification in groundwater are still not well-understood because of a lack of efficient methods to quantify this biogeochemical reaction pathway. Previous research used the ratio of N2 to argon (Ar) to quantify net production of N2 via denitrification by separating the biologically generated N2 component from the atmospheric-generated components. However, this method does not allow the quantification of the atmospheric components accurately because the differences in gas partitioning between N2 and Ar are being neglected. Moreover, conventional (noble) gas analysis in water is both expensive and labor-intensive. We overcome these limitations by using a portable mass spectrometer system, which enables a fast and efficient in situ analysis of dissolved (noble) gases in groundwater. By analyzing a larger set of (noble) gases (N2, He, Ar, and Kr) combined with a physically meaningful excess air model, we quantified N2 originating from denitrification. Consequently, we were able to study the spatiotemporal dynamics of N2 production due to denitrification in riparian groundwater over a six-month period. Our results show that denitrification is highly variable in space and time, emphasizing the need for spatially and temporally resolved data to accurately account for denitrification dynamics in groundwater.

中文翻译：

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追踪河岸地下水中反硝化作用的新方法。

由于缺乏有效的方法来量化该生物地球化学反应途径，地下水中反硝化的时空动态仍未得到很好的理解。先前的研究使用N2与氩气（Ar）的比率，通过将生物产生的N2成分与大气产生的成分分离，通过反硝化来量化N2的净产量。但是，由于忽略了N 2和Ar之间的气体分配差异，因此该方法不能准确地定量大气成分。此外，水中的常规（稀有）气体分析既昂贵又费力。我们通过使用便携式质谱仪系统克服了这些局限性，该系统能够对地下水中的溶解（稀有）气体进行快速有效的原位分析。通过分析较大的一组（稀有）气体（N2，He，Ar和Kr）并结合物理上有意义的过量空气模型，我们对源自反硝化作用的N2进行了量化。因此，我们能够研究在六个月内由于河岸地下水中的反硝化作用而产生的N2的时空动态。我们的研究结果表明，反硝化作用在空间和时间上变化很大，强调需要在空间和时间上解析的数据来准确说明地下水中的反硝化作用动力学。