Collaborative Research: US GEOTRACES GP17-OCE: Mapping nitrous oxide sources and sinks through isotopic measurements in the Pacific Ocean

一氧化二氮是一种强大的温室气体，是由土壤和海洋中的微生物活动产生的。太平洋是海洋氧化亚氮产生和向大气排放的重要组成部分，因为它在热带太平洋东部的大面积和低氧口袋。在全球海洋中观测到的最大量的一氧化二氮出现在这些低氧的口袋里。这些地区似乎影响了整个太平洋的一氧化二氮分布，但这些地区一氧化二氮的来源可能大不相同。这项工作将使人们更好地了解一氧化二氮在全球海洋中的自然分布，以及对其产生的机制和控制，从而为未来的排放预测提供依据。这将通过收集来自太平洋中部不同水深的氧化亚氮同位素测量来完成，那里的工作相对较少。一氧化二氮同位素组成的测量是一个强大的分析工具，将有助于回答这些关于这种强大的温室气体的重要问题。该项目的斯坦福部分将主要由一名博士生进行，他将接受各种实验室技术、数据分析和计算机建模方面的培训。我们还将利用这个项目的支持，通过斯坦福大学的SURGE（夏季本科生地球科学与工程研究）项目，为未被充分代表的少数民族学生提供首次研究经验，以增加地球科学的多样性。该项目的首席研究员之一Bourbonnais还将在本尼迪克特学院（Benedict College）进行一系列化学海洋学入门讲座，本尼迪克特学院是南卡罗来纳州哥伦比亚市的一所历史悠久的私立黑人文理学院，并支持本尼迪克特学院的两名本科生在南卡罗来纳大学（University of South Carolina）暑期实习。本项目将解决与太平洋N2O循环相关的三个主要问题：(1)太平洋中部N2O分布的哪些特征主要是通过混合和循环还是生物过程驱动的；(2)哪些生物地球化学过程控制了中太平洋生物生成N2O的分布；(3) N2O的产生（数量、机制、产率）与原位氧的可用性有何关系？该合作项目将在GEOTRACES项目下进行，该项目是一项了解全球海洋元素分布的国际努力。随着GEOTRACES GP17和GP15剖面的合成，我们将有机会研究N2O及其同位素（生产机制的指标）相对于氧、微量元素和水质量示踪剂的分布。该项目的数据将通过生物和化学海洋学数据管理处（www.bco-dmo.org）向公众提供。这些数据还将汇编在GEOTRACES数据产品中，这些产品将免费提供。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nitrous oxide is a powerful greenhouse gas that is produced by microbial activity in soils and the ocean. The Pacific Ocean is an important component of oceanic nitrous oxide production and emission to the atmosphere due to its large area and pockets of low oxygen in the eastern tropical Pacific. The largest amounts of nitrous oxide observed in the global ocean occur in these pockets of low oxygen. These regions appear to impact nitrous oxide distributions throughout the Pacific Ocean, but the sources of nitrous oxide in these regions may be quite different. This work will provide a better understanding of both the natural distribution of nitrous oxide in the global ocean, as well as the mechanisms and controls on its production for future emission projections. This will be accomplished by collecting nitrous oxide isotopic measurements at different water depths from the central Pacific, where relatively little work has focused. Measurements of nitrous oxide isotopic composition is a powerful analytical tool that will help to answer these important questions about this powerful greenhouse gas. The Stanford component of this project will be carried out primarily by a PhD student, who will be trained in a variety of laboratory techniques, data analysis, and computer modeling. We will also use support from this project to increase diversity in the Geosciences by providing first-time research experiences to underrepresented minority students through Stanford’s SURGE (Summer Undergraduate Research in Geoscience and Engineering) Program. One of the project’s lead investigators, Bourbonnais, will also give a series of introductory Chemical Oceanography lectures at Benedict College, a private historically black, liberal arts college in Columbia, SC and support two undergraduate students from Benedict College through summer internships at the University of South Carolina. This project will address three main questions related to N2O cycling in the Pacific Ocean: (1) What features of N2O distribution in the central Pacific Ocean are driven primarily through mixing and circulation vs. biological processes; (2) Which biogeochemical processes control the distribution of biologically produced N2O in the central Pacific Ocean; and (3) How does the production (amount, mechanism, yield) of N2O relate to the availability of oxygen in situ? This collaborative project will be carried under the GEOTRACES program, an international effort to understand the distribution of elements in the global ocean. With the synthesis of the GEOTRACES GP17 and GP15 sections, we will have an opportunity to examine the distributions of N2O and its isotopes (an indicator of production mechanisms) relative to oxygen, trace elements, and water mass tracers. Data from this project will be made available to the public through the Biological and Chemical Oceanography-Data Management Office (www.bco-dmo.org). The data will also be compiled in GEOTRACES data products that will be freely available.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.