Collaborative Research: Development of a Submersible, Autonomous Rn-222 Survey System

国际和平研究所要求提供资金，以开发能够在远程操作潜水器(ROV)或自主水下航行器(AUV)上部署时进行现场222Rn分析的潜水系统。这样的系统将允许研究人员通过海底三维网格进行高分辨率的氡测量，然后返回到感兴趣的地点测量222Rn时间序列，以便量化SGD通量。该系统的设计依赖于一种新的技术，当氡淹没在水中时，通过通过封闭的水柱使闭合空气循环鼓泡，从水中喷射氡进行分析。初步证据表明，这是一种可行的方法。海底地下水排放(SGD)作为一种向沿海海洋输送新的和可循环的营养物质的重要机制正迅速得到认可。222Rn和Re同位素等化学示踪剂在探测地下水排泄区和量化近岸(浅)水域的相关通量方面提供了极好的效用，但随着水柱加深、分层加强和物理混合变得更加复杂，采样和测量这些示踪剂的传统方法逐渐变得不那么有用。在大陆架更深的水域(1)露头地质单元可以聚焦SGD，以及(2)在珊瑚礁生态系统等关键生境周围，S测量这些示踪剂的能力仅限于抓取采样尺度的分辨率。这种分辨率通常不足以理解这些排放的路径、驱动力和速率，也不利于量化相关的养分输送通量。因此，在评估SGD的全球意义之前，迫切需要一种能够原位、连续地测量大陆架更深水域SGD的地球化学示踪的工具。广泛影响：由于这项拟议的研究为其他科学家开发了一种新的研究工具，这项研究的成功将对重要深水盆地的SGD研究、量化热液流动的热液研究以及以Rn-222为示踪剂的深水循环和混合研究产生巨大而广泛的影响。调查人员包括了一项外展计划，以赞助一个为期两学期的高级设计诊所团队，该团队由史密斯学院Picker Engineering Program的3-4名本科女性工程专业学生组成。这个本科生团队将获得处理现实世界工程问题的经验，这个项目也将从他们的工程贡献中受益。布雷耶与史密斯学院就NDSF微生物垫采样器项目进行了类似的合作，双方的结果都很出色。作为该项目的一部分，布雷耶和辛格还将指导麻省理工学院/世界卫生组织联合项目的一名博士生，希望史密斯学院的一名工程学学生能够完成这一过渡。彼得森还将担任本科生导师。

The PI's request funding to develop a submersible system capable of in situ 222Rn analysis while deployed from a remotely-operated vehicle (ROV) or autonomous underwater vehicle (AUV). Such a system would allow researchers to conduct high-resolution radon surveying through 3-D grids of bottom water and later return to sites of interest to measure a 222Rn time-series in order to quantify SGD fluxes. The system design relies on a new technique to sparge radon, while submerged, from the water for analysis via bubbling a closed air loop through a contained water column. Preliminary evidence shows this to be a viable approach. Submarine groundwater discharge (SGD) is quickly gaining recognition as an important delivery mechanism of new and recycled nutrients to the coastal ocean. Chemical tracers such as 222Rn and radium isotopes offer excellent utility at detecting groundwater discharge zones and quantifying associated fluxes in nearshore (shallow) waters, but the traditional approaches to sampling and measuring these tracers become progressively less useful as the water column deepens, stratification strengthens, and physical mixing becomes more complex. In deeper waters (1) of the continental shelf where outcropping geological units can focus SGD, and (2) around critical habitats like coral reef ecosystems, one?s ability to measure these tracers is limited to grab sampling-scale resolution. Such resolution is generally not sufficient to understand the pathways, driving forces, and rates of these discharges, nor is it conducive to quantifying associated nutrient delivery fluxes. Prior to assessing the global significance of SGD, then, there exists great need for a tool capable of in situ, continuous measurement of geochemical tracers of SGD in deeper waters of the continental shelf.Broader Impacts: Since this proposed study develops a new research tool available for other scientists, the success of this study will have a large and broad impact on SGD studies in important deep basins, hydrothermal studies quantifying hydrothermal flow, and deep-water circulation and mixing studies using Rn-222 as a tracer. The investigators have included a plan for outreach to sponsor a two-semester, senior Design Clinic team of 3-4 undergraduate female engineering students from Smith College's Picker Engineering Program. This undergraduate team will gain experience working on a real-world engineering problem and this project will likewise benefit from their engineering contribution. Breier has undertaken a similar collaboration with Smith College for the NDSF microbial mat sampler project and the results to both sides have been outstanding. Breier and Singh will also mentor a MIT/WHOI Joint Program Ph.D. student as part of this project, with the hope that one of the Smith College engineering students may make this transition. Peterson will also serve as an undergraduate mentor.