GEOTRACES Arctic Section: Disequilibria between Radium-226, Lead-210 and Polonium-210 in the Arctic Ocean and their implications for trace metal distribution

该项目将成为2015年美国地理追踪北极探险队的一部分。与国际地质勘测计划中的其他多国倡议一样，美国北极探险的目标是识别控制海洋中关键微量元素和同位素(TEI)分布的过程和通量，并确定这些分布对不断变化的环境条件的敏感性。一些微量元素对生命是必不可少的，另一些是已知的生物毒素，还有一些很重要，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。在这一更广泛的框架内，该项目的目标是测量天然存在的放射性核素镭-226(半衰期1600年)、铅-210(半衰期22.1y)和钚-210(半衰期138天)，以确定颗粒反应性TEI从水柱中的去除率，并研究其在底层沉积物中清除、横向和垂直迁移和积累的过程。拟议的北极地学剖面将遇到广泛的过程，拟议的研究将在解释观测到的TEI分布方面发挥关键作用，并解决以下问题：(1)太平洋水域与大陆架颗粒为主区域之间对钋和铅的清除强度有何不同？(2)在楚科奇海不同营养浓度的地区，钚和铅的清除强度是如何变化的？(3)加拿大盆地和马卡洛夫盆地之间的清除强度是如何变化的？(4)哪些是沉积物集中增强的区域在这一地区，边界清除和颗粒的横向输送对铅-210在水柱和沉积物中的分布有多重要？(5)该地区颗粒有机物的季节尺度垂直通量是什么，以及有机物和其他TEI横向和垂直输送的相对重要性？(6)整个盆地的颗粒混合率和影响减少率是如何变化的？(7)由于沉积物的再动员，陆架区底层水域是否富含钚-210？解决这些问题的能力将有助于更好地理解控制其他TEI在该地区的分布的过程，这些过程将由其他调查人员测量。这项研究的更广泛影响包括1名博士生和至少2名本科生的参与。首席调查员是一名职业生涯早期的科学家，该项目将帮助他扩大在北极地区的专业知识，并进一步发展他的职业生涯。调查员参与了许多地方外联活动，这些活动将为普通公众和高中生提供关于海洋生态系统及其如何影响他们的环境福祉的教育机会。此外，这项研究也将是更广泛的北极GEOTRACES推广计划的一部分，该计划通过与PolarTREC和COSEE-Alaska合作，支持一名高中科学教师参与邮轮。

This project will form part of the 2015 U.S. GEOTRACES Arctic expedition. In common with other multinational initiatives in the International GEOTRACES Program, the goals of the U.S. Arctic expedition are 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. Within this broader framework, the goal of this project is to measure the naturally occurring radionuclides radium-226 (half-life 1600 years), lead-210 (half-life 22.1 y) and polonium-210 (half-life 138 days) to determine removal rates of particle reactive TEIs from the water column and to study the processes responsible for their scavenging, lateral and vertical transport and accumulation in bottom sediments. A wide range of processes will be encountered along the proposed ARCTIC GEOTRACES section and the proposed study will play a key role in the interpretation of observed TEI distributions and address the following questions: (1) What is the variability in scavenging intensity of polonium and lead between the Pacific waters and that of particle dominated areas of the shelf? (2) How does the scavenging intensity of polonium and lead change across areas of varying nutrient concentrations in the Chukchi Sea? (3) How does the scavenging intensity vary between Canadian Basin and the Makarov Basin? (4) Which are the areas of enhanced sediment focusing in this region and how important is the role of boundary scavenging and lateral transport of particles with respect to lead-210 distribution in water column and sediments? (5) What are the seasonal scale vertical fluxes of particulate organic matter in this region and the relative importance of lateral versus vertical transport of organic matter and other TEIs? (6) How do particle mixing rates vary across the basin and impact reduction rates? (7) Are the bottom waters in the shelf region enriched in polonium-210 due to sediment remobilization? The ability to address these questions will allow better understanding of processes controlling the distribution in this region of other TEIs that will be measured by other investigators. The broader impacts of the research include the involvement of 1 Ph.D. student and at least 2 undergraduate students. The lead investigator is an early-career scientist and this project will help him in extending his expertise in the Arctic region and further development of his career. The investigator is involved in numerous local outreach activities that will provide opportunities for education of the general public and high school students about marine ecosystems and how it affects their environmental well-being. Moreover this research will also be a part of the broader Arctic GEOTRACES outreach program which plans to support the participation of a high-school science teacher on the cruise through partnership with PolarTREC and COSEE-Alaska.