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GEOTRACES北极考察的一部分。与国际GEOTRACES计划中的其他多国计划一样，美国北极考察的目标是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。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22.1年）和钋-210（半衰期138天），以确定颗粒反应性TEI从水柱中的去除速率，并研究负责其清除的过程，横向和纵向迁移和沉积。沿着拟议的北极地理轨迹部分将遇到各种各样的过程，拟议的研究将在解释观测到的TEI分布中发挥关键作用，并解决以下问题：（1）太平洋沃茨和大陆架颗粒为主的地区之间的钋和铅的清除强度的变化是什么？(2)在楚科奇海不同营养物浓度的区域，钋和铅的清除强度是如何变化的？(3)加拿大海盆和马卡罗夫海盆之间的清除强度有何不同？(4)该区域沉积物增加的重点是哪些领域，边界清除和颗粒横向迁移对铅-210在水柱和沉积物中分布的作用有多重要？(5)该区域颗粒有机物的季节尺度垂直通量是多少，有机物和其他TEI的横向与垂直输送的相对重要性是多少？(6)颗粒混合率在整个盆地中如何变化以及影响减少率？(7)陆架区的底层沃茨是否由于沉积物的再活化而富集了钋-210？解决这些问题的能力将允许更好地理解控制其他研究者将测量的其他TEI在该区域的分布的过程。该研究的更广泛影响包括1名博士的参与。学生和至少2名本科生。首席研究员是一位早期职业科学家，该项目将帮助他扩展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，这些活动将为公众和高中生提供关于海洋生态系统及其如何影响其环境福祉的教育机会。此外，这项研究也将成为更广泛的北极GEOTRACES外展计划的一部分，该计划计划通过与PolarTREC和COSEE-Alaska的合作伙伴关系，支持高中科学教师参与巡航。

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.