Understanding the nitrogen (N) cycle is a great current challenge in environmental science. Humans have more than doubled the circulation of N, leading to degradation of air and water quality and coastal ecosystems in many areas. The development of solutions to N pollution problems has been hindered by large amounts of missing N that dominate N balances at all scales. The uncertainty about N balances is particularly acute in the northeastern U.S., where there are active efforts to address the effects of N pollution on ozone levels, coastal eutrophication and drinking water quality, and to determine critical loads for atmospheric N deposition. Uncertainty has led to increased interest in N gas production as a fate of N. The gases nitric oxide (NO), nitrous oxide (N2O) and dinitrogen (N2) are produced by microbial processes in soils and sediments and can account for a significant percentage of the missing N in balances. However, these fluxes are difficult to quantify because of problematic measurement techniques (especially for N2), high spatial and temporal variability, and a lack of methods for scaling point measurements to larger areas. N gas fluxes have long been assumed to be low in the northeastern U.S., based on several studies of N2O flux, at a limited number of sites. However, recent studies suggest that NO fluxes are more important in this region than previously thought, and new data suggest that N2O, and especially N2 fluxes are significant as well. There have also been recent improvements in the development of tools for scaling gas flux measurements. The time is ripe for a critical reassessment of the importance of N gas fluxes.
The investigators propose that N gas fluxes account for about half of the missing N in this region. They have three objectives: refining new methods for measuring N2 fluxes at small scales, developing new methods for scaling N gas fluxes from small scales to the landscape and regional scales, and improving the ability of existing computer models to depict regional N gas fluxes at larger scales.
The project would produce information relevant to controlling N pollution, train graduate students, involve underrepresented groups, and expand education and outreach efforts in university, management and policy arenas. These efforts will be facilitated by existing infrastructure of the Hubbard Brook and Baltimore long-term ecological research (LTER) projects, including websites, extensive educational programs and existing protocols for communicating research results to managers and policy makers.
