GEOTRACES Arctic section: Application of 210Po and 210Pb distribution at contrasting interface regimes of Western Arctic

GEOTRACES 北极部分：210Po 和 210Pb 分布在北极西部对比界面区的应用

• 批准号: 1434578
• 负责人: Mark Baskaran
• 金额: $ 26.58万
• 依托单位: Wayne State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-10-15 至 2019-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1434578&HistoricalAwards=false
• 关键词: GEOTRACES; Arctic; section; Application; 210Po

In this project, a team of investigators participating in the 2015 U.S. Arctic GEOTRACES expedition will study the distribution of the naturally-occurring radioactive isotopes lead-210 and polonium-210 in the western and central Arctic Ocean. These measurements are expected to be very useful in helping to meet the goals of the U.S. Arctic GEOTRACES expedition: namely, to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes (TEIs) in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions. Some trace elements are essential to life, others are known biological toxins, and still others are important because they can be used as tracers of a variety of physical, chemical, and biological processes in the sea. A primary source of lead-210 to the oceans is from the atmosphere, where it is produced from the decay of radon-222. In the oceans, it decays to polonium-210. The half-lives of polonium-210 (138 days) and lead-210 (22.3 years) provide "natural clocks" with which to investigate processes such as the sorption of elements on to sinking particles, and the transport of elements between the ocean margins and deep basins.The lead investigator proposes to concentrate sampling and investigate processes at three "interfaces:" the air-sea-ice interface at the surface, the interface between biologically produced particles and water, and the interface between non-biological particles and water. The investigator proposes the following three hypotheses: 1) At the air-sea interface, the polonium-210/lead-210 ratios can be used to "age date" the sea ice (and sediments contained within the ice). 2) At the biotic-water interface, different biogenic particle types encountered in the upper waters will affect the fractionation and remineralization depths of polonium-210 and lead-210. 3) At the particle-water interface, layers of resuspended sediments in the water column will be zones of enhanced polonium and lead scavenging from the surrounding waters. These processes are important for understanding the distributions of other key particle-reactive trace elements such as iron, lead, and manganese. To test these hypotheses, the investigator will sample and analyze about four hundred dissolved and particulate (large and small) samples, 10 multi-year ice cores, ice-rafted sediments, and water from melt ponds for polonium-210 and lead-210 along the GEOTRACES Western Arctic section. About half of the samples will be focused at the four designated "super stations", with half of these in the highly dynamic upper water column and the other half near the sea floor where resuspension of bottom sediments can affect element cycling. The depths will be chosen according to regional atmospheric input, ecosystems, and coordinated sampling with groups measuring other trace elements and isotopes. The remainder of the samples will be ice cores, water from melt ponds, ice-rafted sediments in sea ice, and atmospheric aerosol samples. The proposed work will be closely coordinated with other GEOTRACES. The broader impacts are closely linked to the GEOTRACES program as a whole to enhance (1) research infrastructure by providing a broad array of polonium-210 and lead-210 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 Wayne State University websites (www.clas.wayne.edu) and at GEOTRACES (www.geotraces.org).

在这个项目中，参加2015年美国北极GEOTRACES考察的一组调查人员将研究北冰洋西部和中部天然放射性同位素铅-210和钋-210的分布。这些测量预计将有助于实现美国北极GEOTRACES考察的目标：即确定控制海洋中关键微量元素和同位素（TEI）分布的过程和量化通量，并确定这些分布对环境条件变化的敏感性。一些微量元素是生命所必需的，另一些是已知的生物毒素，还有一些是重要的，因为它们可以用作海洋中各种物理，化学和生物过程的示踪剂。铅-210进入海洋的一个主要来源是大气，它是由氡-222衰变产生的。在海洋中，它会衰变为钋-210。钋-210的半衰期（138天）和铅-210（22.3年）提供了“自然钟”，可用来调查各种过程，例如元素吸附在下沉颗粒上，以及元素在海洋边缘和深海盆地之间的迁移。“表面的空气-海冰界面，生物产生的颗粒和水之间的界面，以及非生物颗粒和水之间的界面。研究人员提出了以下三个假设：1）在海-气界面，钋-210/铅-210的比例可以用来“年龄”海冰（和冰内所含的沉积物）。 2)在生物-水界面上，在上层沃茨中遇到的不同生物颗粒类型将影响钋-210和铅-210的分馏和矿化深度。3)在颗粒-水界面处，水柱中的再悬浮沉积物层将成为增强的从周围沃茨清除钋和铅的区域。这些过程对于了解其他关键的颗粒反应性微量元素（如铁、铅和锰）的分布非常重要。为了验证这些假设，研究人员将对大约400个溶解和颗粒（大小）样本、10个多年冰芯、冰筏沉积物以及沿GEOTRACES北极西部沿着融化池中的水进行取样和分析。大约一半的样本将集中在四个指定的“超级站”，其中一半在高度动态的上层水柱，另一半在海底附近，因为海底沉积物的再悬浮会影响元素的循环。深度将根据区域大气输入、生态系统和与测量其他微量元素和同位素的小组协调采样来选择。其余的样品将是冰芯、融化池的水、海冰中的冰筏沉积物和大气气溶胶样品。拟议的工作将与其他GEOTRACES密切协调。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，提供广泛的对地球化学清除模型有用的钋-210和铅-210数据，（2）通过指导研究生和本科生进行教育，通过实例教学
从拟议的研究，（3）代表性不足的学生参与地球科学的职业生涯，（4）海洋放射化学毕业生的研究培训，以及5）通过出版物，演讲，以及专门的公共韦恩州立大学网站（www.clas.wayne.edu）和GEOTRACES（www.geotraces.org）。