Landscape and Regional Scale Studies of Nitrogen Gas Flux

理解氮(N)循环是当前环境科学面临的一大挑战。人类使氮的循环增加了一倍以上，导致许多地区的空气和水质量以及沿海生态系统的退化。氮污染问题的解决方案的制定受到了大量缺失氮的阻碍，这些氮在所有尺度上都主导着氮的平衡。氮平衡的不确定性在美国东北部尤为严重，那里正在积极努力解决氮污染对臭氧水平、沿海富营养化和饮用水质量的影响，并确定大气氮沉降的临界负荷。不确定性导致了人们对氮气生产的兴趣增加，因为氮素的命运。氮氧化物(NO)、一氧化二氮(N2O)和氮素(N2)是由土壤和沉积物中的微生物过程产生的，可能占平衡中丢失的氮素的很大比例。然而，这些通量很难量化，因为有问题的测量技术(特别是对氮气)、高度的空间和时间变异性，以及缺乏将点测量扩大到更大区域的方法。根据对有限地点N2O通量的几项研究，长期以来，美国东北部的N气体通量一直被认为是低的。然而，最近的研究表明，在这个地区没有通量比之前认为的更重要，新的数据表明，N2O，特别是N2通量也很重要。最近还改进了用于测量气体流量的工具的开发。对氮气通量的重要性进行关键重新评估的时机已经成熟。研究人员提出，N气体通量约占该地区丢失N的一半。它们有三个目标：改进在小尺度上测量氮气通量的新方法，开发从小尺度到地貌和区域尺度上测量N气体通量的新方法，以及改进现有计算机模型在较大尺度上描述区域N气体通量的能力。该项目将提供与控制氮污染有关的信息，培训研究生，让代表性不足的群体参与进来，并扩大大学、管理和政策领域的教育和外联努力。这些努力将由哈伯德·布鲁克和巴尔的摩长期生态研究(LTER)项目的现有基础设施推动，包括网站、广泛的教育项目以及向管理者和政策制定者传达研究结果的现有协议。

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.