EAGER: Application of high precision isotope tracer measurements to resolve rates of aquatic denitrification

反硝化是硝酸盐被还原为无害的氮气的自然过程。反硝化作用减少了硝酸盐向生物圈的负荷，从而最大限度地减少了沿海富营养化和缺氧以及温室气体一氧化二氮的排放。流域是天然和人为硝酸盐的最大汇；然而，人们对反硝化速率，特别是生态系统规模的反硝化速度知之甚少。通过添加富含稳定氮同位素15N的硝酸盐和测量15N在氮气中的积累量，可以在生态系统规模上评估溪流的反硝化作用。这项研究将开发新的分析方法，以极大地提高氮稳定同位素比率的准确性和精密度，这将使15N-硝酸盐示踪研究能够在目前不切实际的环境中应用。由于这种方法的开发是探索性的，迫切需要资金是适当的；然而，该项目具有巨大的潜力来改变反硝化过程的方法和知识。过量的硝酸盐负荷及其在富营养化中的作用是大量和不断增长的人口最重要的影响之一。因此，这项研究的更广泛的意义和潜在影响是，所提出的方法将为生态系统管理者提供信息，以了解硝酸盐的自然去除速率，并为管理自然和人造环境以促进反硝化奠定基础。

Denitrification is the natural process by which nitrate is reduced to harmless N2 gas. Denitrification reduces loading of nitrate to the biosphere, thereby minimizing coastal eutrophication and hypoxia and emissions of the greenhouse gas, nitrous oxide. Watersheds represent the greatest sink for natural and anthropogenic nitrate; however, rates of denitrification, particularly at ecosystem scales, are poorly understood. Denitrification in streams can be evaluated at ecosystem scales by addition of nitrate enriched in the stable nitrogen isotope 15N and measurement of the accumulation of 15N in N2. This study will develop novel analytical methodology for vastly improving the accuracy and precision of the N2 stable isotope ratio, which will enable application of 15N-nitrate tracer studies in environments where it is currently impractical to do so. EAGER funding is appropriate as this method development is exploratory; nonetheless the project has great potential to transform the approach for and knowledge of the denitrification process.Excessive nitrate loading and its role in eutrophication is one of the most significant impacts of a large and growing human population. Thus, the broader significance and potential impacts of this research are that the methodology proposed will provide ecosystem managers information to understand natural rates of nitrate removal as well as a foundation to manage natural and man-made environments to foster denitrification.