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.
