ETBC: A new tool for assessing nitrogen saturation status in forests- Mass-independent D17O of nitrate

ETBC：一种评估森林氮饱和状况的新工具？美国匹兹堡大学首席研究员艾米丽·M·埃利奥特摘要随着美国森林的不断老化，森林中的硝酸盐淋溶可能成为地表水质量损害的一个越来越重要的因素。该项目确定使用不依赖于质量的大气硝酸盐氧同位素示踪剂作为量化森林流域输出大气硝酸盐的经验工具，并评估缺乏长期水质数据的流域的氮饱和状况。研究的目标包括：1)开发一种新的经验工具，用于准确地量化从流域输出的大气硝酸盐及其相关的氮饱和状态；2)在流域内评估氮饱和系统中土壤水淋滤液中硝态氮来源的空间异质性；以及3)表征在阶段性酸化暴雨期间，硝态氮来源对河流水的高分辨率时间动态特征。这项研究有望提供无与伦比的能力，以比以前可能的更高的空间分辨率来评估慢性氮沉积的影响，改变我们对大气沉积、生态系统健康和水质之间相互作用的理解。此外，该项目将为森林管理战略如何影响大气氮输出提供新的见解，对管理敏感系统中的水质产生重要影响，并提高我们对大气氮输出时空变化的过程水平的理解，对生态和水文模型界产生重要影响。

ETBC: A new tool for assessing nitrogen saturation status in forests? Mass-independent oxygen isotopes of nitrateEmily M. Elliott, Principal InvestigatorUniversity of PittsburghPROJECT ABSTRACTAs U.S. forests continue to age, nitrate leaching from forests could become an increasingly important contributor to surface water quality impairment. This project establishes the use of a mass-independent oxygen isotope tracer of atmospheric nitrate as an empirical tool for quantifying export of atmospheric nitrate from forested watersheds and for assessing the nitrogen saturation status of watersheds lacking long-term water quality data. The objectives of research include the following: 1) development of a new empirical tool for accurately quantifying atmospheric nitrate export from watersheds and associated N saturation status; 2) an intra-watershed assessment of spatial heterogeneity of nitrate sources in soil water leachate in a N saturated system; and 3) a characterization of high resolution temporal dynamics of nitrate sources to streamwater during episodic acidification stormflows. This research is expected to provide an unparalleled ability to assess the impacts of chronic N deposition at a much higher spatial resolution than previously possible, transforming our understanding of the interactions between atmospheric deposition, ecosystem health and water quality. Additionally, the project will generate new insight into how forest management strategies can influence atmospheric N export with important implications for managing water quality in sensitive systems and improve our process-level understanding of spatial and temporal variations in atmospheric N export with important implications for the ecological and hydrological modeling communities.