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，由土壤和海洋中的微生物活动产生。太平洋是海洋一氧化二氮生产和向大气排放的重要组成部分，因为它在东热带太平洋的面积很大，氧气含量很低。在全球海洋中观察到的最大数量的一氧化二氮出现在这些低氧的区域。这些区域似乎影响了一氧化二氮在整个太平洋的分布，但这些区域的一氧化二氮来源可能有很大的不同。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，以及未来排放预测中一氧化二氮产生的机制和控制。这将通过从中太平洋收集不同水深的一氧化二氮同位素测量来实现，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，将有助于回答关于这种强大的温室气体的这些重要问题。该项目的斯坦福部分将主要由一名博士生执行，该博士生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。我们还将利用该项目的支持，通过斯坦福大学的暑期本科生地球科学与工程研究计划，为未被充分代表的少数族裔学生提供首次研究经验，从而增加地球科学的多样性。该项目的首席研究员之一Bourbonnais还将在南卡罗来纳大学本尼迪克特学院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私立黑人文理学院，并通过暑期实习为本尼迪克特学院的两名本科生提供支持。该项目将解决与太平洋N2O循环有关的三个主要问题：(1)中太平洋N2O分布的哪些特征主要是通过混合和循环而不是生物过程驱动的；(2)哪些生物地球化学过程控制着中太平洋生物产生的N2O的分布；以及(3)N2O的产生(数量、机制、产量)与就地氧气的可用性有何关系？这一合作项目将在GEOTRACES计划下进行，该计划是一项了解全球海洋中元素分布的国际努力。随着GEOTRACES GP17和GP15部分的合成，我们将有机会研究N2O及其同位素(生产机制的指示器)相对于氧、微量元素和水团示踪剂的分布。该项目的数据将通过生物和化学海洋学数据管理办公室(www.bco-dmo.org)向公众公布。这些数据还将被汇编成免费提供的GEOTRACES数据产品。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.