GEOTRACES Arctic Section: Determining the Pathways, Fate, and Flux of Atmospherically Derived Trace Elements in the ocean/ice system

在这个项目中，参加2015年美国北极地学考察的一组调查人员将研究北冰洋西部和中部铍-7的面积和深度分布。铍-7(化学代码7Be)是一种无害的自然产生的放射性同位素(半衰期=53天)，在全球高层大气中由宇宙射线与某些大气气体相互作用产生。它不断地落到地球表面，特别是在降水期间，在那里它可以作为一种方便的示踪剂，用于各种环境过程。预计这将非常有助于实现美国北极地学考察的目标：即确定控制海洋中关键微量元素和同位素分布的过程和通量，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。7Be研究小组与海洋痕量元素专家组成的多机构小组合作，应使该小组能够确定大气气溶胶沉积作为将微量元素从大陆输送到北冰洋深处的途径的重要性，并研究表层海冰的存在或不存在如何影响水柱中痕量元素的行为。像这次探险的许多其他参与者一样，7Be的研究人员计划培训研究生进行研究，并参与阿拉斯加沿海社区的公共教育推广工作。该项目将解决国际地球科学和北极实施计划中制定的三项优先任务。首先，它将对影响许多感兴趣的微量元素(TEI)分布的基本运输过程提供现实的估计。7Be的水柱测量将被用作物理混合过程的示踪剂，物理混合过程重新分配上层水柱中的生物活性物种。对TEI所在水团的循环、混合和通风的定量知识可以评估这些元素在时间和空间上的就地生物地球化学行为。其次，7Be将被用于追踪北极集水区内大气沉积元素的分配。北极是迄今为止研究过的其他地学盆地中独一无二的。对于许多TEI来说，不仅在水柱中测量，而且在冰、雪和融化池塘的额外储存库中测量也是至关重要的。这些集水区内的7Be清单将用于追踪北冰洋/冰系统内大气沉积元素的分配情况。第三，将利用7Be数据改进TEI大气沉降量的量化方法。将利用地表水和低层大气中7Be的测量来估算相关TEI的大气输入。在北极，气溶胶沉积是输送微量元素物种的重要途径，但迄今为止，对这一输入的评估被证明是困难的。

In this project, a group of investigators participating in the 2015 U.S. Arctic GEOTRACES expedition will study the areal and depth distribution of Beryllium-7 in the western and central Arctic Ocean. Beryllium-7 (chemical symbol 7Be) is a harmless, naturally-occurring radioisotope (half-life = 53 days) generated worldwide in the upper atmosphere by cosmic ray interaction with certain atmospheric gases. It continuously falls to the Earth's surface, especially during precipitation events, where it can be used as a convenient tracer for a wide variety of environmental processes. It is 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 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. Working alongside a multi-institutional team of ocean trace element experts, the work of the 7Be research group should enable the team to determine the importance of atmospheric deposition of aerosols as a pathway for delivering trace elements from the continents to the deep Arctic Ocean and also to study how the presence or absence of surface sea ice influences the behavior of trace elements in the water column. Like many other participants in the expedition, the 7Be researchers plan to train graduate students in their research and to be involved in public educational outreach efforts in coastal communities in Alaska.This project will address three priority tasks formulated within the International GEOTRACES Science and Arctic Implementation Plans. First, it will provide realistic estimates of the underlying transport processes influencing distributions of many trace elements of interest (TEIs). Water column measurements of 7Be will be used as a tracer of physical mixing processes, which redistribute biologically active species in the upper water column. Quantitative knowledge of the circulation, mixing, and ventilation of the water masses within which TEIs reside allows an assessment of the time- and space-integrated in situ biogeochemical behavior of these elements. Secondly, 7Be will be used to trace the partitioning of atmospherically deposited elements within the Arctic catchments. The Arctic is unique to other GEOTRACES basins studied to date. For numerous TEIs, measurement not only in the water column, but also in the additional repositories of ice, snow and melt ponds is critical. The inventory of 7Be within these catchments will be used to trace the partitioning of atmospherically deposited elements within the Arctic ocean/ice system. Thirdly, 7Be data will be used to improve methods for quantifying the atmospheric deposition of TEIs. Measurements of 7Be in the surface waters and in the lower atmosphere will be used to develop estimates of the atmospheric input of relevant TEIs. In the Arctic, aerosol deposition is an important pathway for delivering trace element species, but assessment of this input has heretofore proven to be difficult.