Abstract Natural organic matter (NOM) is an important redox-active component in soils and aquifers that comprises numerous functional moieties spanning a wide range of redox potentials. Tracking reversible electron transfer from and to NOM in biogeochemical redox processes has been a challenge for decades. Reasons include side reactions of reactants used to determine the redox state of NOM and slow reaction kinetics of reactants or traditional non-mediated electrochemical methods. Furthermore, partially irreversible reactions/methods employed hamper the experimental determination of redox properties of NOM. Recent advances in mediated electrochemical analysis, however, have greatly improved our ability to characterize the redox properties of NOM. Thus, mediated electrochemical analysis may become an important tool in expanding our understanding of NOM-fueled biogeochemical N cycling in anoxic environments. Nonetheless, this technique has rarely been applied to investigate microbial pathways of reversible NOM redox cycling such as its coupling to anoxic nitrogen (N) cycling. Here we advocate for employing mediated electrochemical analysis to address such topics in the future and provide recommendations for a successful experimental application of this method in the presence of reactive N-species. To this end, we review recent applications of mediated electrochemical analysis in studying microbial NOM cycling. We exemplify the potential of mediated electrochemical techniques for biogeochemical research by discussing how microbial NOM redox cycling is linked to anaerobic N cycling. We focus on anaerobic ammonium oxidation (anammox) and reduction of N-oxides that are related to N loss and nitrous oxide (N2O) mitigation. Finally, we present strategies to work around problems arising from electroactive intermediates that hamper the application of mediated electrochemical analysis in microbial experiments.

中文翻译：

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介导电化学分析作为揭示天然有机物微生物氧化还原循环与缺氧氮循环之间联系的新兴工具

摘要 天然有机质 (NOM) 是土壤和含水层中一种重要的氧化还原活性成分，它包含众多具有广泛氧化还原电位的功能部分。几十年来，在生物地球化学氧化还原过程中跟踪来自和向 NOM 的可逆电子转移一直是一个挑战。原因包括用于确定 NOM 氧化还原状态的反应物的副反应和反应物的缓慢反应动力学或传统的非介导电化学方法。此外，部分不可逆的反应/方法阻碍了 NOM 氧化还原特性的实验测定。然而，介导电化学分析的最新进展极大地提高了我们表征 NOM 氧化还原特性的能力。因此，介导的电化学分析可能成为扩展我们对缺氧环境中 NOM 燃料生物地球化学 N 循环的理解的重要工具。尽管如此，该技术很少应用于研究可逆 NOM 氧化还原循环的微生物途径，例如其与缺氧氮 (N) 循环的耦合。在这里，我们提倡在未来采用介导电化学分析来解决这些问题，并为在反应性 N 物种存在的情况下成功应用该方法提供建议。为此，我们回顾了介导电化学分析在研究微生物 NOM 循环中的最新应用。我们通过讨论微生物 NOM 氧化还原循环如何与厌氧氮循环联系起来，举例说明介导电化学技术在生物地球化学研究中的潜力。我们专注于厌氧氨氧化 (anammox) 和减少与 N 损失和一氧化二氮 (N2O) 缓解相关的 N 氧化物。最后，我们提出了解决由电活性中间体引起的问题的策略，这些问题阻碍了介导电化学分析在微生物实验中的应用。