Landscape and Regional Scale Studies of Nitrogen Gas Flux

了解氮(N)循环是当前环境科学的一个巨大挑战。人类活动使氮的循环增加了一倍以上，导致许多地区的空气和水质以及沿海生态系统退化。氮污染问题解决方案的发展受到大量缺失氮的阻碍，这些缺失氮在所有尺度上都主导着氮平衡。在美国东北部，氮平衡的不确定性尤其严重，在那里，人们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，并确定大气氮沉积的临界负荷。不确定性增加了人们对氮气体生产作为N的命运的兴趣。一氧化氮（NO）、氧化亚氮（N2O）和二氮（N2）气体是由土壤和沉积物中的微生物过程产生的，可以占平衡中缺失氮的很大比例。然而，由于测量技术存在问题（特别是N2）、高时空变异性以及缺乏将点测量扩展到更大区域的方法，这些通量难以量化。长期以来，根据在有限的几个地点对N2O通量的几项研究，人们一直认为美国东北部的N气体通量很低。然而，最近的研究表明，NO通量在该地区比以前认为的更重要，新的数据表明，N2O，特别是N2通量也很重要。最近在气体通量测量的标度工具的开发方面也有了改进。重新评估氮气体通量重要性的时机已经成熟。研究人员提出，N气体通量约占该地区缺失N的一半。他们有三个目标：改进在小尺度上测量N2通量的新方法，开发从小尺度到景观和区域尺度的N气体通量的新方法，提高现有计算机模型在更大尺度上描述区域N气体通量的能力。该项目将提供有关控制氮污染的资料，培训研究生，使代表性不足的群体参与，并扩大在大学、管理和政策领域的教育和推广工作。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促进，包括网站、广泛的教育计划和现有的协议，以向管理者和政策制定者传达研究成果。

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.