Collaborative Research: Development of an In Situ Porewater Sampler Coupled to an Underwater Mass Spectrometer for High-Resolution Biogenic Gas Measurements in Permeable Sediments

合作研究：开发与水下质谱仪耦合的原位孔隙水采样器，用于可渗透沉积物中的高分辨率生物气体测量

• 批准号: 1435690
• 负责人: Robinson Fulweiler
• 金额: $ 46.28万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1435690&HistoricalAwards=false
• 关键词: Collaborative; Research; Development; Situ; Porewater

Continental shelves are known as rich fishing grounds but they also provide a suite of less constrained, valuable ecosystem services. In particular, these borderlands between the near shore environment and open ocean, are biogeochemical "hot spots" mediating fluxes of carbon (C) and nitrogen (N) to the deep sea. The tight coupling between C and N has important implications for ocean productivity, atmospheric carbon dioxide (CO2) levels, and ultimately global climate. Because continental shelves are broad and shallow, much of the C and N cycling occurs within their sediments - approximately 70% of which are covered with permeable sands. Traditionally, it was thought the sandy sediments were unimportant in C and N cycling but, over the last two decades research has revealed that sandy sediments may be key players in marine biogeochemical cycles. However, the ability to quantify the contributions of sandy shelf environments has been limited by the absence of effective methods for sampling these environments on appropriate time scales. In this research, the investigators will develop a novel field-deployable porewater sampling device coupled to an underwater mass spectrometer. This system will measure a full suite of biogenic gases (e.g., O2, CO2, N2, Ar, CH4, H2S) across a vertical gradient and calculate in situ reaction rates based on simultaneous estimates of gas concentrations and vertical advective porewater exchange. Along with the development of this instrument, the investigators will also create an online instruction manual with videos explaining how to build the porewater sampling system, how to calibrate and test the mass spectrometer, etc., with the goal of propagating this technology to the wider community. Successful completion of this work will produce a flexible porewater sampling and analysis platform that can be reproduced by scientists and engineers using off the shelf components. The research will employ membrane inlet mass spectrometer analysis of the porewater, but this sampling platform could be used with other in situ analytical instrumentation as well. Importantly, this instrumentation will broadly expand our capabilities to measure C and N cycling in permeable marine sediments, and, in doing so, will provide relevant data for biogeochemical and global climate models.The principal investigators (PIs) will design, build, and field test a novel porewater sampling interface for integration with an underwater membrane introduction mass spectrometer. The device will allow highly resolved, real-time measurements, with minimal sampling artifacts, of biogeochemically important gases (e.g., O2, CH4, N2, H2S) as well as total dissolved inorganic carbon (DIC) (as CO2) in porewater of permeable sediments. Included in the system are sensors that allow vertical advection within porewater to be inferred from heat transport, thus permitting both in situ gas concentrations and reaction rates to be calculated in real time. This system will represent a major advance in the ability to measure coupled biogeochemical processes within permeable sediments and will contribute to a better understanding of the biogeochemistry of continental shelves. Continental shelf sediments process much of the carbon and nitrogen exported from land or fixed in overlying waters. Lab-scale experiments indicate that organic matter processing within permeable sediments is rapid and efficient. Additionally, it appears that diagenesis and nutrient recycling are controlled by advection of bottom water through the pore space of these permeable surficial sediments. Advection determines the rate of particle capture (by bed filtration), the rate and pathways of mineralization (by oxidant flux), and the rate of return of remineralized nutrients to the water column. At present there is a disconnect between what is understood about permeable sediment biogeochemistry from small-scale manipulations and how continental shelf biogeochemistry is represented in a modeling framework. The "missing link" is a set of reliable tools to measure dynamic processes in the field, and thus to provide good data and a basis for appropriate parameterization for modeling. The instrumentation to be built by the PIs and their students will overcome several of the present limitations of porewater sampling in permeable sediment environments. The system is designed to operate in situ without enclosure artifacts. It is designed to sample over extended time periods, making it more likely to capture transient events that may dominate sediment-water exchange. Because the sampling interface is coupled to a mass spectrometer, the system can collect accurate and precise data for multiple chemical species simultaneously. The mass spectrometer and porewater sampling interface will represent a major step forward in the ability to measure biogeochemical properties in permeable sediment environments. Data from this instrument system will allow researchers to address fundamental uncertainties about the roles of sandy sediments in global biogeochemistry such as the efficiency of denitrification or the production and consumption of greenhouse gases such as CH4 and N2O within sediments. To assist the transfer of knowledge gained here to the wider community, a website will be developed for this instrument with part lists, and a blog where interested scientists can hold discussions on the instrument and potential broader applications of the technology. Additionally, instructional videos on relevant topics (e.g., construction, calibration, troubleshooting, field deployment) will be hosted via a YouTube channel dedicated to this project. One Ph.D. student will receive interdisciplinary research training at the junctures between engineering, oceanography, and biogeochemistry. Undergraduate students will be trained in field and laboratory methods and a concerted effort to attract women and minorities will be made using resources available at Boston University (e.g., BU Summer Undergraduate Research Fellowship recruits minority students) and at the Skidaway Institute of Oceanography.

大陆货架被称为丰富的捕鱼场，但它们还提供了一套较少约束，有价值的生态系统服务的套件。特别是，这些边境环境与开阔的海洋之间的这些边境是生物地球化学的“热点”，将碳（C）和氮（N）的通量介导了深海。 C和N之间的紧密耦合对海洋生产率，大气二氧化碳（CO2）水平以及最终的全球气候具有重要意义。由于大陆架子宽且浅，因此大部分C和N循环发生在其沉积物内 - 大约70％被渗透的沙子覆盖。传统上，人们认为沙质沉积物在C和N循环中并不重要，但是在过去的二十年中，研究表明，沙质沉积物可能是海洋生物地球化学循环中的主要参与者。但是，量化沙质货架环境的贡献的能力受到缺乏在适当时间尺度上对这些环境采样的有效方法的限制。在这项研究中，研究人员将开发出一种新型的可采用孔隙水的抽样装置，并结合了水下质谱仪。该系统将在垂直梯度上测量一套完整的生物气体（例如O2，CO2，N2，AR，CH4，H2S），并基于同时估计气体浓度和垂直的促储料水交换的原位反应速率。随着该乐器的开发，调查人员还将创建一份在线说明手册，其中包含视频，解释如何构建毛孔抽样系统，如何校准和测试质谱仪等，目的是向更广泛的社区传播这项技术。这项工作的成功完成将产生灵活的孔水抽样和分析平台，该平台可以由科学家和工程师使用架子组件复制。这项研究将采用孔隙水的膜入口质谱仪分析，但该采样平台也可以与其他原位分析仪器一起使用。重要的是，该仪器将广泛扩大我们在可渗透的海洋沉积物中测量C和N循环的能力，并且在此过程中，将为生物地球化学和全球气候模型提供相关数据。首席研究人员（PIS）将设计，构建和现场测试与新颖的孔隙水样采样界面，以与底层量表的整合进行整合。该设备将允许使用最小的采样伪像的高度解决，实时测量，以生物地球化学上重要的气体（例如O2，CH4，N2，H2S）以及可渗透性沉积物中的总溶解无机碳（DIC）（AS CO2）。系统中包含的是传感器，这些传感器允许通过热传输来推断孔隙水中的垂直对流，从而可以实时计算原位气体浓度和反应速率。 该系统将代表测量可渗透沉积物内生物地球化学过程的能力的重大进步，并有助于更好地理解大陆架子的生物地球化学。大陆架沉积物处理从土地出口或固定在上面水域的大部分碳和氮。实验室规模的实验表明，可渗透沉积物内的有机物处理是快速有效的。此外，似乎通过这些渗透表面沉积物的孔隙空间来控制成岩作用和养分回收。对流决定了颗粒捕获的速率（通过床过滤），矿化的速率和途径（通过氧化剂通量）以及回想起的营养素回到水柱的回报率。目前，小型操作中有关渗透性沉积物生物地球化学的理解与大陆架生物地球化学在建模框架中如何表示的之间存在脱节。 “缺失链接”是一组可靠的工具，用于测量现场中的动态过程，从而提供良好的数据和用于建模的适当参数化的基础。 PIS及其学生将要建造的仪器将克服在渗透的沉积物环境中钻水采样的当前局限性。该系统旨在在没有外壳的情况下原位操作。它旨在在延长的时间段内进行采样，从而更有可能捕获可能主导沉积物 - 水交换的瞬态事件。由于采样界面耦合到质谱仪，因此系统可以同时收集多种化学物种的准确和精确数据。质谱仪和孔隙水采样界面将代表在可渗透沉积物环境中测量生物地球化学特性的能力方面迈出的重要一步。 来自该仪器系统的数据将使研究人员能够解决有关沙质沉积物在全球生物地球化学中的作用的根本不确定性，例如反硝化效率或CH4和N2O等温室气体在沉积物中的生产和消耗。 为了协助这里获得的知识转移到更广泛的社区，将为该乐器列表开发一个网站，以及有兴趣的科学家可以在该仪器上进行讨论和该技术的潜在应用程序的讨论。此外，将通过专门针对该项目的YouTube频道托管有关相关主题（例如构造，校准，故障排除，现场部署）的教学视频。一位博士学生将在工程，海洋学和生物地球化学之间的关头接受跨学科研究培训。 本科生将接受野外和实验室方法的培训，并使用波士顿大学（例如BU夏季本科研究奖学金招募少数群体学生）和Skidaway海洋学研究所提供的资源来吸引妇女和少数群体。