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Oxygen decline in the ocean: Implications for oceanic N2O production and the atmosphere

海洋中的氧气下降：对海洋 N2O 产生和大气的影响

基本信息

批准号：
283583671
负责人：
Privatdozentin Dr. Christa Marandino, since 7/2016
金额：
--
依托单位：
BIOS - Bermuda Institute of Ocean Sciences
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2022-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/283583671?language=en
关键词：
Oxygen decline ocean Implications oceanic

项目摘要

N2O is an important greenhouse gas in the troposphere and has a per mol global warming potential ~300 times that of CO2. The atmospheric lifetime of N2O is also sufficiently long enough for it to survive transport to the stratosphere where it undergoes ozone depleting photochemical reactions (de Bie et al. 2002). The ocean is a significant source of N2O to the atmosphere, accounting for ~35% of all natural sources. The microbial production of N2O, (via NH4+ oxidation, nitrifier-denitrification, denitrification), is largely regulated by dissolved oxygen (DO) concentrations. Below a certain but poorly defined DO threshold, N2O production will increase substantially. There is increasing evidence that DO concentrations in the ocean are decreasing; given the atmospheric importance of N2O, this raises cause for concern as it will undoubtedly lead to an increase in oceanic N2O production and emissions to the atmosphere. Before this happens it is critical that we 1) identify the current N2O conditions (i.e. N2O distributions, N2O production and the production pathways) in the ocean, and 2) determine how N2O conditions will change under different future DO scenarios. To address the first point, work will be conducted in the north eastern tropical Atlantic where DO concentrations are more characteristic of much of the contemporary ocean. To address the second point, we will conduct work in two extreme oxygen minimum zones (the eastern tropical South Pacific and a low DO eddy in the north eastern tropical Atlantic) where DO concentrations are much lower than in much of the present day ocean. In each of our study regions we will measure 1) N2O concentrations, 2) del15N, del18O and 15N site preference signatures of N2O to determine the relative importance of the different N2O producing pathways to bulk N2O pools, and 3) N2O production rates via each of the different production pathways using 15N tracer techniques. Molecular analyses will also be conducted to characterize and quantify the different N2O producing organisms. Of course, if we are to accurately assess the impact that increasing N2O production in the ocean, as a result of decreasing DO concentrations, will have for the atmosphere, it is critical that we develop a more comprehensive understanding of the factors that influence sea-to-air fluxes of N2O. To address this, we will use the eddy covariance technique to directly measure N2O fluxes from the ocean and compare these to a range of physical, chemical and biological parameters.

N2O是对流层中重要的温室气体，其每摩尔全球变暖潜势是CO2的300倍。N2O在大气中的寿命也足够长，足以使它在运输到平流层时经受消耗臭氧的光化学反应（de Bie et al. 2002）。海洋是大气中N2O的重要来源，占所有自然来源的约35%。微生物生产N2O（通过NH4+氧化、硝化反硝化、反硝化）在很大程度上受溶解氧（DO）浓度的调节。低于一定但定义不明确的DO阈值，N2O产量将大幅增加。越来越多的证据表明，海洋中的DO浓度正在下降；鉴于一氧化二氮在大气中的重要性，这引起了人们的关注，因为它无疑将导致海洋一氧化二氮的产生和向大气排放的增加。在此之前，我们必须1)确定海洋中当前的N2O条件（即N2O分布、N2O产生和产生途径），以及2)确定未来不同DO情景下N2O条件将如何变化。为了解决第一个问题，将在热带大西洋东北部开展工作，那里的DO浓度更具有当代海洋的特点。为了解决第二点，我们将在两个极端氧最低区（热带南太平洋东部和热带大西洋东北部的低DO涡）开展工作，那里的DO浓度远低于当今大部分海洋。在我们的每个研究区域，我们将测量1)N2O浓度，2)N2O的del15N、del18O和15N位点偏好特征，以确定不同的N2O生成途径对大量N2O库的相对重要性，以及3)使用15N示踪技术通过每种不同的N2O生成途径生成N2O的速率。分子分析也将进行表征和量化不同的N2O生产生物。当然，如果我们要准确评估由于DO浓度下降而导致海洋中N2O产量增加对大气的影响，就必须对影响N2O海洋-空气通量的因素有更全面的了解。为了解决这个问题，我们将使用涡动相关技术直接测量来自海洋的N2O通量，并将其与一系列物理、化学和生物参数进行比较。