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微量元素和同位素（TEI）是美国GEOTRACES在未来三年资助的北大西洋阶段的目标的核心。放射性核素210 Po-210 Pb对被美国GEOTRACES北大西洋区域调查部分实施计划指定为优先TEI之一。自GEOSECS以来，这对仪器已经被应用于量化海洋内的颗粒清除和碳通量，但对海洋界面的过程仍然知之甚少。大气源和半衰期的两种同位素（138天和22.3 y）目前的时间框架，特别适合于跟踪界面（空气-水，生物水，沉积物-水）在北大西洋部分的过程。根据该奖项，特拉华州大学、韦恩州立大学和皇后学院的研究人员将参加美国GEOTRACES北大西洋活动，研究这两种放射性同位素与其他微量元素之间的关系。将被调查的同位素示踪剂。 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210铅的主要输入到海洋表面，水平将取决于大陆输入混合物的来源，在西部温带和东部亚热带部分。在生物-水界面，他们假设在上层沃茨遇到的不同生物颗粒类型将影响210 Po和210 Pb的分馏和矿化深度。 在颗粒-水界面处，他们假设中间成岩霞状层（INL）或热液羽流之间的界面将是增强的210 Po和210 Pb从周围沃茨清除的区域。为了验证这些假设，他们将沿着GEOTRACES北大西洋剖面采集并分析数百个溶解和颗粒（大大小小）样本的210 Po和210 Pb。大约三分之二的样本将集中在六个指定的“超级站”，其中一半位于主温跃层上方，另一半位于BNL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。另外三分之一将详细介绍整个INL从沿海沃茨分离的羽流，整个BNL，和热液羽流内。数据将根据界面清除模型按颗粒类型（例如细颗粒/胶体颗粒、岩生颗粒和生物颗粒）进行综合。因此，拟议的工作将与GEOTRACES的大西洋测量科已经资助的其他粒子反应（如Th、Pa）或溶解（如Ra）放射性核素同位素的GEOTRACES项目密切协调。更广泛的影响：更广泛的影响与整个GEOTRACES计划密切相关，以加强（1）研究基础设施，提供广泛的210 Po和210 Pb数据，可用于地球化学清除模型，（2）通过指导研究生和本科生进行教育，通过拟议研究的例子进行教学，（3）代表性不足的学生参与地球科学事业，（4）对海洋放射化学毕业生进行研究培训，以及5）通过出版物、演示文稿和专门的公共UD网站（www.ocean.udel.edu）和GEOTRACES（www.geotraces.org）广泛传播研究成果。

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).