Collaborative Research: Mechanisms and Controls of Nitrous Oxide Production in the Eastern Tropical North Pacific Ocean

合作研究：热带北太平洋东部一氧化二氮产生的机制和控制

• 批准号: 1657868
• 负责人: Karen Casciotti
• 金额: $ 35.86万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-10-01 至 2020-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1657868&HistoricalAwards=false
• 关键词: Collaborative; Research; Mechanisms; Controls; Nitrous

Nitrous oxide (N2O) is present at very low concentrations in the atmosphere but is an important greenhouse gas and ozone destroying substance. As with other climate-active gases like methane and carbon dioxide, human activities are responsible for most of its production, either directly through fossil fuel burning or agricultural activities. However, about a third of natural N2O emissions come from the ocean, but even these emissions can be indirectly affected by human activities. About half of the ocean source is derived from three specific geographic regions in the Pacific Ocean and Arabian Sea. These three oceanic regions are places where oxygen concentrations are so low in the intermediate depths that metabolic processes requiring the absence of oxygen are able to occur. These regions are called Oxygen Minimum Zones (OMZs) and they have microbiological processes that occur nowhere else in global ocean waters. In the work proposed here, we will investigate how the microbiological pathways of N2O production and consumption are regulated by environmental conditions such as oxygen and nutrient concentration. This work will involve a research expedition to one of the OMZs, the Eastern Tropical Pacific Ocean off the coast of Mexico. On the cruise, we will perform experiments and collect samples for analysis in our home laboratories at Princeton and Stanford Universities. Advising of graduate students and teaching at the graduate and undergraduate levels at both institutions will be linked to this research. This work is particularly timely because global warming has already indirectly affected the size and geographic extent of the OMZs. Greater expanse of low oxygen water could cause N2O production to increase, leading to increased fluxes of N2O to the atmosphere. In the atmosphere, the role of N2O in ozone destruction and as a greenhouse gas could be critical elements of global change. Nitrous oxide (N2O) is an important greenhouse gas and ozone destroying substance. About a third of natural N2O emissions come from the ocean, and about half of the ocean source is derived from waters with oxygen deficient intermediate waters (oxygen minimum zones, OMZs). Nitrification is recognized as the main source of N2O in the ocean, but denitrification also likely contributes to the net source in and around OMZs. Because nitrification and denitrification are performed by microbes with very different metabolisms and environmental controls, their contributions to N2O production are expected to differ in response to changes in oxygenation and nutrient inputs. Thus it is important to understand the regulation of N2O production by both processes. The main goal of this project is to quantify the environmental regulation of N2O production and consumption pathways in and around OMZs in order to obtain predictive understanding of N2O distributions and fluxes in the ocean. To do this, production and consumption of N2O will be measured using stable isotope tracer incubations at stations located within and outside one of the major OMZs in the Eastern Tropical North Pacific ocean. The dependence of the rate processes on substrate, product, and oxygen concentrations will be determined, and the composition of the microbial assemblages will be assessed to determine whether different microbial components are involved under different environmental conditions. Natural abundance stable isotope and isotopomer measurements of N2O will be interpreted in concert with measured rates to deduce the sources and pathways (nitrification, nitrifier-denitrification, denitrification, and ?hybrid? formation) involved in N2O production and consumption. This work will also involve a novel application of isotopomer measurements of N2O from incubations to identify the placement of 15N from NH4+ and NO2- within labeled N2O pools. OMZ regions are the sites of unique nitrogen cycling processes that are critical in determining the fixed nitrogen inventory of the ocean. If OMZs expand as predicted due to anthropogenic changes in the coming decades, changes in these chemical distributions may affect the atmospheric flux of nitrous oxide as well as modify overall ocean productivity via changes in the fixed nitrogen inventory. Understanding the regulation and environmental control of the processes responsible for N2O production and consumption is the foundation of understanding their response to global change.

一氧化二氮（N2O）在大气中的浓度非常低，但却是一种重要的温室气体和臭氧破坏物质。与甲烷和二氧化碳等其他气候活跃气体一样，人类活动负责其大部分生产，无论是直接通过化石燃料燃烧还是农业活动。 然而，大约三分之一的自然氧化亚氮排放来自海洋，但即使这些排放也可能受到人类活动的间接影响。 大约一半的海洋资源来自太平洋和阿拉伯海的三个特定地理区域。 这三个海洋区域的中间深度氧气浓度非常低，以至于需要缺氧的代谢过程才能发生。 这些区域被称为最低氧气区 (OMZ)，它们具有全球海洋水域中其他地方不会发生的微生物过程。 在此提出的工作中，我们将研究 N2O 产生和消耗的微生物途径如何受到环境条件（例如氧气和营养物浓度）的调节。 这项工作将涉及对 OMZ 之一（墨西哥海岸附近的东热带太平洋）进行研究考察。 在航行中，我们将在普林斯顿大学和斯坦福大学的家庭实验室进行实验并收集样本进行分析。两个机构的研究生咨询以及研究生和本科生的教学将与这项研究联系起来。这项工作特别及时，因为全球变暖已经间接影响了 OMZ 的规模和地理范围。 更大范围的低氧水可能会导致 N2O 产量增加，从而导致 N2O 进入大气的通量增加。 在大气中，N2O 在臭氧破坏中的作用以及作为温室气体的作用可能是全球变化的关键因素。一氧化二氮（N2O）是一种重要的温室气体和臭氧破坏物质。 约三分之一的自然 N2O 排放来自海洋，约一半的海洋来源来自缺氧中间水域（最低氧区，OMZ）。 硝化作用被认为是海洋中 N2O 的主要来源，但反硝化作用也可能对 OMZ 及其周围的净来源​​做出贡献。由于硝化和反硝化是由代谢和环境控制截然不同的微生物进行的，因此它们对 N2O 产生的贡献预计会因氧合作用和养分输入的变化而有所不同。 因此，了解这两种过程对 N2O 产生的调节非常重要。 该项目的主要目标是量化 OMZ 内及其周围 N2O 生产和消耗路径的环境监管，以获得对海洋中 N2O 分布和通量的预测性了解。为此，将使用位于东部热带北太平洋主要 OMZ 内外的监测站的稳定同位素示踪剂孵化来测量 N2O 的生产和消耗。将确定速率过程对底物、产物和氧气浓度的依赖性，并且将评估微生物组合的组成，以确定不同的环境条件下是否涉及不同的微生物组分。 N2O 的自然丰度稳定同位素和同位素异构体测量值将与测量的速率一起进行解释，以推断 N2O 产生和消耗所涉及的来源和途径（硝化作用、硝化菌反硝化作用、反硝化作用和“混合”形成）。这项工作还将涉及对孵化过程中 N2O 同位素异构体测量的新颖应用，以确定 NH4+ 和 NO2- 中 15N 在标记 N2O 库中的位置。 OMZ 区域是独特的氮循环过程的场所，对于确定海洋固定氮库存至关重要。如果 OMZ 由于未来几十年的人为变化而按预期扩大，这些化学分布的变化可能会影响一氧化二氮的大气通量，并通过固定氮库存的变化改变总体海洋生产力。了解 N2O 生产和消耗过程的监管和环境控制是了解其对全球变化的响应的基础。

项目成果

Amperometric sensor for nanomolar nitrous oxide analysis

用于纳摩尔一氧化二氮分析的电流传感器

• DOI: 10.1016/j.aca.2019.12.019
• 发表时间: 2020-03
• 期刊: Analytica Chimica Acta
• 影响因子: 6.2
• 作者: Damgaard, Lars Riis;Kelly, Colette;Casciotti, Karen;Ward, Bess B.;Revsbech, Niels Peter
• 通讯作者: Revsbech, Niels Peter