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北极考察项目的一部分。与国际地质足迹计划中的其他多国倡议一样，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（TEIs）分布的过程和量化通量，并确定这些分布对变化的环境条件的敏感性。有些微量元素是生命所必需的，有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。在这个更广泛的框架内，该项目的目标是测量自然存在的放射性核素镭-226（半衰期1600年）、铅-210（半衰期22.1 y）和钋-210（半衰期138天），以确定水柱中颗粒反应性放射性核素的去除率，并研究其清除、横向和垂直运输以及在底部沉积物中积累的过程。沿着拟议的北极GEOTRACES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)太平洋水域和大陆架颗粒主导区域之间钋和铅清除强度的变异性是什么？(2)楚科奇海不同营养物浓度区域对钋和铅的清除强度有何变化？(3)加拿大盆地和马卡罗夫盆地的扫食强度有何差异？(4)该地区哪些区域的沉积物集中增强？边界清除和颗粒侧向运移对铅-210在水柱和沉积物中的分布有多重要？(5)该地区颗粒有机质垂直通量的季节尺度以及有机质和其他TEIs横向与垂直输送的相对重要性是什么？(6)整个流域的颗粒混合率和影响减少率如何变化？(7)陆架区底部水体是否因沉积物再活化而富集钋-210 ？解决这些问题的能力将有助于更好地理解控制该地区其他tei分布的过程，这些过程将由其他研究人员测量。该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。首席研究员是一位早期的科学家，这个项目将帮助他扩展他在北极地区的专业知识，并进一步发展他的职业生涯。调查员参与了许多当地的外联活动，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，支持一名高中科学教师参加这次巡航。

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.