NI: CONFLUENCE - Disentangling the role of rivers as greenhouse gas conduits

NI：汇流 - 阐明河流作为温室气体管道的作用

• 批准号: NE/V009001/2
• 负责人: Joshua Dean
• 金额: $ 7.23万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FV009001%2F2
• 关键词: NI; CONFLUENCE; Disentangling; role; rivers

Rivers emit ~2-3 Pg of carbon as the greenhouse gas carbon dioxide (CO2) to the atmosphere, each year. This is equivalent to 20% of annual anthropogenic CO2 emissions and an important component of the global carbon cycle. Methane (CH4) emissions from river networks are very poorly understood. CH4 is a potent greenhouse gas, 34 times stronger than CO2 over a 100-year timeframe. Rivers are estimated to emit ~27 Tg of CH4 each year, equivalent to 8% of anthropogenic CH4 emissions. However, these CH4 emissions vary greatly both spatially and over time. Rivers, acting as conduits for terrestrial greenhouse gases, can thus influence ongoing climate change. Landscape disturbance, either through human activity or climate change, can enhance river carbon emissions adding substantially to an already overloaded atmospheric carbon pool. This may represent a feedback to the global climate system as river carbon emissions can be enhanced by the impact of climate change on the terrestrial carbon cycle. Characterising the magnitude and source of river carbon emissions across globally representative ecosystems is therefore urgently needed for us to understand and predict current and future climate change.Carbon emissions from rivers are primarily derived from the landscapes they drain. But sources within these landscapes can vary depending on the ecosystem. Carbon sources can include recent atmospheric CO2 fixed into biomass via photosynthesis, carbon that has accumulated in organic soils over millennia such as in Arctic, temperate and tropical peatlands, and even ancient geological carbon derived from erosion and weathering. With such a diverse range of potential carbon sources across ecosystems, it is vital to establish a framework from which to determine whether the source of carbon observed in river networks matches what would be expected from normal landscape function, or if it represents signals of a disturbed carbon cycle. I.e. are older and slower carbon cycles becoming shorter and faster?Isotopes, especially radiocarbon (14C), are a powerful tool for identifying disturbed carbon cycles. Through a network of leading researchers, this project will bring together novel techniques and study sites to serve as a foundation for in-depth investigations into river carbon emissions around the globe. The project will utilise low-cost sensors for measuring the magnitude of river carbon emissions developed by the international Project Partners. These will be combined with in-depth isotopic investigations using novel techniques developed by the UK investigators. A network of existing study site and measurement infrastructure will be established covering a diverse range of ecosystems. The project will therefore provide a springboard from which to constrain the magnitude and source of river carbon emissions through direct observations at globally representative scales.Rivers can drain large landscape areas and as such their water chemistry represents an integrated signal of landscape carbon loss. This project will provide the techniques to tease apart these signals and determine if they represent natural or disturbed carbon cycling. The project will build a database of existing observations of these signals. In addition, we will use the interacting, complimentary techniques brought together in this project to carry out a scoping project to provide preliminary observations of the magnitude and source of carbon emissions from a subset of disturbed landscapes.CONFLUENCE will also include planning for an international meeting of researchers in relevant fields to grow the network of people, techniques and sites beyond the lifetime of this project. CONFLUENCE will be used as a launchpad for consortium funding to use this unprecedented infrastructure to make a step-change in observational capability of freshwater carbon emissions at spatial and temporal scales that individual research groups alone cannot achieve.

河流每年向大气排放约2-3 Pg的碳作为温室气体二氧化碳（CO2）。这相当于每年人为二氧化碳排放量的20%，是全球碳循环的重要组成部分。人们对河流网络的甲烷（CH 4）排放知之甚少。甲烷是一种强有力的温室气体，在100年的时间内比二氧化碳强34倍。据估计，河流每年排放约27 Tg的甲烷，相当于人为甲烷排放量的8%。然而，这些甲烷排放量在空间和时间上都有很大的差异。河流作为陆地温室气体的通道，因此可以影响持续的气候变化。景观干扰，无论是通过人类活动或气候变化，可以增加河流的碳排放量大大增加了已经超载的大气碳库。这可能是对全球气候系统的一种反馈，因为气候变化对陆地碳循环的影响会增加河流的碳排放。因此，我们迫切需要描述全球代表性生态系统中河流碳排放的规模和来源，以了解和预测当前和未来的气候变化。河流的碳排放主要来自其排放的景观。但这些景观中的来源可能因生态系统而异。碳源可以包括最近通过光合作用固定到生物质中的大气CO2，数千年来积累在有机土壤中的碳，例如在北极，温带和热带泥炭地，甚至来自侵蚀和风化的古老地质碳。由于整个生态系统的潜在碳源范围如此广泛，因此必须建立一个框架，以确定在河流网络中观察到的碳源是否与正常景观功能的预期相匹配，或者是否代表碳循环受到干扰的信号。旧的、慢的碳循环会变得更短、更快吗？同位素，特别是放射性碳（14 C），是一个强有力的工具，用于识别干扰碳循环。通过一个由主要研究人员组成的网络，该项目将汇集新技术和研究地点，作为深入调查地球仪河流碳排放的基础。该项目将利用国际项目合作伙伴开发的低成本传感器来测量河流碳排放量。这些将与使用英国研究人员开发的新技术进行的深入同位素调查相结合。将建立一个由现有研究地点和测量基础设施组成的网络，覆盖各种生态系统。因此，该项目将提供一个跳板，通过全球代表性规模的直接观察来限制河流碳排放的规模和来源。河流可以排空大片景观区域，因此其水化学代表了景观碳损失的综合信号。该项目将提供技术来梳理这些信号，并确定它们是否代表自然或受干扰的碳循环。该项目将建立一个关于这些信号的现有观测数据库。此外，我们还将利用本项目中相互作用的互补技术来开展一个范围界定项目，以提供对受干扰景观子集的碳排放量和来源的初步观察。CONFLUENCE还将包括计划召开一次相关领域研究人员的国际会议，以在本项目的生命周期之外发展人员、技术和场地的网络。CONFLUENCE将被用作财团资金的发射台，利用这一前所未有的基础设施，在空间和时间尺度上对淡水碳排放的观测能力进行逐步改变，这是单个研究小组无法实现的。

项目成果

Future directions for river carbon biogeochemistry observations

河流碳生物地球化学观测的未来方向

• DOI: 10.1038/s44221-024-00207-8
• 发表时间: 2024
• 期刊: Nature Water
• 作者: Dean J

Peatland pools are tightly coupled to the contemporary carbon cycle.

• DOI: 10.1111/gcb.16999
• 发表时间: 2023-11
• 期刊: Global Change Biology
• 影响因子: 11.6
• 作者: J. Dean;M. Billett;T. E. Turner;M. Garnett;Roxane Andersen;Rebecca M McKenzie;K. Dinsmore;A. J. Baird;P. Chapman;Joseph Holden