Collaborative Research: GEOTRACES - Application of 210-Pb and 210-Po distribution at North Atlantic interface regimes

天然铀-钍放射性核素系列中的痕量元素和同位素(TEI)是美国地质调查局在未来三年资助的北大西洋阶段的核心目标。放射性核素210Po-210Pb对被美国北大西洋地带性勘测部实施计划指定为优先TEI之一。自从GEOSECS以来，这两个组合已经在量化海洋中的颗粒清除和碳通量方面得到了应用，但在海洋界面上的过程仍然知之甚少。大气来源和两种同位素(138d和22.3y)的半衰期给出了唯一适合北大西洋部分示踪界面(空气-水、生物水和沉积物-水)过程的时间框架。根据这一奖项，特拉华大学、韦恩州立大学和皇后学院的研究人员将参与美国地质调查局北大西洋行动，以研究这两种放射性同位素与将被调查的其他微量元素和同位素示踪剂之间的关系。他们的工作将围绕一系列假设展开。在海-气界面，他们假设，作为210Pb进入表层海洋的主要输入，在西部温带和东部副热带地区，水平将取决于大陆输入混合的来源。在生物-水界面，他们假设在上游遇到的不同生物成因颗粒类型将影响210Po和210Pb的分馏和再矿化深度。在颗粒-水界面，他们假设中间成岩云状层(INL)或热液羽流之间的界面将是从周围水域清除的增强的210Po和210Pb区域。为了验证这些假设，他们将沿着北大西洋地段对数百个溶解和微粒(大大小小)样品进行采样和分析，以获取210Po和210Pb。大约三分之二的样本将集中在六个指定的“超级空间站”，一半在主温跃层之上，另一半在BNL的下方。深度将根据区域大气输入、生态系统和协调的TEI采样来选择。另外三分之一将通过INL从沿海水域分离的羽流、跨越BNL和在热液羽流中进行详细描述。数据将根据界面清除模型按颗粒类型(例如细小/胶体、致石和生源)合成。因此，拟议的工作将与已获得资助的地球观测系统放射性核素监测系统密切协调，以便在地球观测系统大西洋勘测科监测其他粒子反应性(如Th、Pa)或溶解(如Ra)放射性核素同位素。更广泛的影响：更广泛的影响与GEOTRACES计划作为一个整体密切相关，以加强(1)研究基础设施，提供广泛的可用于生物地球化学清除模型的210Po和210Pb数据，(2)通过指导研究生和本科生进行教育，从拟议的研究中以身作则进行教学，(3)未被充分代表的学生参与地球科学的职业生涯，(4)对毕业生进行海洋放射化学的研究培训，以及5)通过出版物、演讲和专门的公共UD网站(www.Ocean.udel.edu)和GEOTRACES(www.getraces.org)广泛传播结果。

Trace elements and isotopes (TEIs) in the natural U-Th radionuclide series are central to the goals of the U.S. GEOTRACES during its funded North Atlantic phase over the next three years. The radionuclide 210Po-210Pb pair is designated as one of the priority TEIs by the U.S. GEOTRACES Zonal North Atlantic Survey Section Implementation Plan. The pair has seen application since GEOSECS for quantifying particulate scavenging and carbon flux within the ocean, but processes are still poorly understood at oceanic interfaces. The atmospheric source and half lives of the two isotopes (138 d and 22.3 y) present time frames uniquely suited to trace interface (air-water, bio-water, and sediment-water) processes in the North Atlantic sections. Under this award, researchers at the University of Delaware, Wayne State University, and Queens College will participate in the U.S.GEOTRACES North Atlantic campaign to study the relationships between these two radioisotopes and the other trace elements and isotopic tracers that will be surveyed. Their work will center around a set of hypotheses. At the air-sea interface, they hypothesize that as the primary input of 210Pb into the surface ocean, levels will be source dependent on the continental input mixtures, in the western temperate and easterly sub-tropical sections. At the biotic-water interface, they hypothesize that different biogenic particle types encountered in the upper waters will affect the fractionation and remineralization depths of 210Po and 210Pb. At the particle-water interface, they hypothesize that interfaces between intermediate lithogenic nepheloid layers (INL) or hydrothermal plumes will be zones of enhanced 210Po and 210Pb scavenging from the surrounding waters. To test these hypotheses, they will sample and analyze several hundred dissolved and particulate (large and small) samples for 210Po and 210Pb along the GEOTRACES North Atlantic section. About two thirds of the samples will be focused at the six designated "super stations", half above the main thermocline and the other half down across the BNL. The depths will be chosen according to regional atmospheric input, ecosystems, and coordinated TEI sampling. The other third will be detailed across INL detached plumes from coastal waters, across the BNL, and within hydrothermal plumes. The data will be synthesized according to interface scavenging models by particle types (e.g. fine/colloidal, lithogenic and biogenic). As such, the proposed work will be closely coordinated with GEOTRACES PIs already funded to for other particle-reactive (e.g. Th, Pa) or dissolved (e.g. Ra) radionuclide isotopes in the Atlantic Survey Section of GEOTRACES. Broader Impacts: The broader impacts are closely linked to the GEOTRACES Program as a whole to enhance (1) research infrastructure by providing a broad array of 210Po and 210Pb data useful for biogeochemical scavenging models, (2) education by mentoring graduate and undergraduates, teaching by example from proposed research, (3) participation of under-represented students careers in the geosciences, (4) research training of graduates in marine radiochemistry, and 5) broad dissemination of results through publications, presentations, and on dedicated public UD websites (www.ocean.udel.edu) and at GEOTRACES (www.geotraces.org).