Collaborative Research: GEOTRACES Peru-Tahiti Nitrogen Isotope Measurements

合作研究：GEOTRACES 秘鲁-塔希提岛氮同位素测量

• 批准号: 1233140
• 负责人: Meredith Hastings
• 金额: $ 15.45万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-03-01 至 2017-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1233140&HistoricalAwards=false
• 关键词: Collaborative; Research; GEOTRACES; Peru; Tahiti

Nitrogen (N) is an essential macronutrient whose availability can limit primary production and the capacity of the biological pump to export carbon from the surface ocean on seasonal, annual, decadal, and millennial timescales. The inventory of fixed (bioavailable) N in the ocean is driven by biological processes such as nitrogen fixation, denitrification, and anaerobic ammonia oxidation (anammox). Water column oxygen deficient zones (ODZs) are important sites for fixed N loss, as well as N2O production, and they are projected to expand and intensify in the coming years as global warming increases ocean stratification and decreases ventilation. It is important to understand the distribution of nitrate, nitrite, and N2O isotopes in relation to current ocean conditions of oxygen and trace element availability order to interpret past and future changes in nitrate ä15N signals. In this project, a team of researchers from Stanford University, University of Massachusetts at Dartmouth, and Brown University will measure the nitrogen- and oxygen-isotopic composition (del15N and del18O) of nitrate, nitrite, and nitrous oxide in seawater samples collected along the GEOTRACES Pacific Peru-Tahiti Section. Values of del15N and del18O will also be measured in nitrate from aerosol and rain samples to inform our interpretation of the N isotope budget and isotopic gradients within the tropical South Pacific. Finally, N2/Ar and N2 del15N will be determined to close the N mass and isotope budgets. Nitrate del15N is a GEOTRACES "core parameter" that will complement other measurements, such as bioactive trace element concentrations and speciation, Si isotope variations, as well as redox and productivity proxies. The GEOTRACES Peru-Tahiti section provides a rare opportunity to track the fate of the isotopic signals of N loss from one of the largest water column ODZs. Furthermore, little is known about the effect of N recycling through hydrothermal vents on nitrate isotopes in the deep ocean, and this section will allow quantitative tracking of this input. Together, these measurements will yield insight into the relative rates of modern N cycle processes and will provide background information for paleoceanographic applications.Broader impacts: This project will provide a high-quality nitrate isotope data set from undersampled parts of the South Pacific for use by the broader oceanographic community via BCO-DMO. Educational impacts include the mentoring of a graduate, undergraduate, and high school students at Stanford, and the inclusion of undergraduates in state-of-the-art collaborative research at Brown and UMass-Dartmouth. The project will also support development and implementation of an oceans component for the annual 6th grade teacher workshop offered by Stanford University's School of Earth. This program includes both instruction for the teachers on cutting-edge research in Earth Science and Oceanography, and support for them to include the material into their classroom activities.

氮（N）是必不可少的大量营养素，其可用性可以限制初级生产和生物泵在季节，年度，年代和千禧年时间表上从地面海洋中出口碳的能力。海洋中固定（生物利用）N的清单是由诸如氮固定，硝化和厌氧氨氧化（Anammox）等生物学过程驱动的。水柱氧不足区域（ODZ）是固定N损失和N2O产生的重要地点，随着未来几年，随着全球变暖增加海洋分层并下降通风，它们预计将在未来几年扩展和增强。重要的是要了解硝酸盐，亚硝酸盐和N2O同位素的分布，与当前的氧气和痕量元素可用性顺序有关，以解释硝酸盐ä15n信号的过去和将来变化。 In this project, a team of researchers from Stanford University, University of Massachusetts at Dartmouth, and Brown University will measure the nitrogen- and oxygen-isotopic composition (del15N and del18O) of nitrate, nitrite, and nitrous oxide in seawater samples collected along the GEOTRACES Pacific Peru-Tahiti Section. DEL15N和DEL18O的值也将在硝酸盐中从气溶胶和雨水样本中进行测量，以告知我们对热带南太平洋中N同位素预算和同位素梯度的解释。最后，N2/AR和N2 DEL15N将决定关闭N质量和同位素预算。硝酸盐DEL15N是一种地理位置“核心参数”，它将补充其他测量值，例如生物活性痕量元素浓度和规格，SI同位素变化以及氧化还原和生产力代理。 Geotraces Peru-Tahiti部分提供了难得的机会，可以跟踪最大的水柱ODZ之一的N损失的同位素信号的命运。此外，对于深海中的硝酸盐同位素的氮回收的影响知之甚少，本节将允许对此输入进行定量跟踪。总之，这些测量结果将深入了解现代N周期过程的相对速率，并将为古（Oakosakanograghing应用程序）提供背景信息。BRODER的影响：该项目将提供来自南太平洋不强化部分的高质量硝酸盐同位素数据集，以通过BCO-DMO通过BCO-DMO提供广泛的海洋学社区使用。教育影响包括斯坦福大学的毕业生，本科生和高中生的心理，以及在布朗和UMass-Dartmouth的最先进的合作研究中纳入本科生。该项目还将支持斯坦福大学地球学校提供的年度六年级教师研讨会的海洋组成部分的开发和实施。该计划包括针对教师关于地球科学和海洋学尖端研究的指示，并支持将材料包括在课堂活动中。