Collaborative Research: A Novel Tracer Approach to Estimate the Atmospheric Input of Trace Elements into the Global Ocean

大气中向全球海洋输入的许多化学物质等于或超过来自河流的化学物质，因此构成了这些元素的重要预算组成部分。此外，大气输入的微量元素在海洋生物地球化学过程中起着关键作用。然而，对这种输入的评估很困难，因为对海洋沉积率的测量很少，而且容易受到时间和空间变化问题的影响。由于缺乏直接测量，海洋界必须依赖大气输送和沉积模型，而这些模型本身对于降雨量和气溶胶去除参数化的限制很少。因此，经常使用间接方法来估计大气输入，例如使用从大气输送到海洋的天然放射性核素。在该项目开发的一项新颖应用中，迈阿密大学和佛罗里达州立大学的研究人员将使用地表水和低层大气中的 7Be 测量值，结合气溶胶和雨水中的微量元素测量值，来估计相关微量元素进入副热带北大西洋的大气输入量。 7Be 是一种宇宙射线产生的放射性同位素，它与对流层中的粒子结合，随后沉积到海洋表面。由于其半衰期相对较短（53.3 天），因此可以合理地将上层海洋中的 7Be 衰变库存等同于由于湿加干沉积而从大气中流出的 7Be 通量。这提供了化学物质的大气浓度与其向海洋的沉积之间的关键联系。这些物种包括许多 GEOTRACES 计划感兴趣的物种，例如铝、锰、铁、铜、锌和镉。然后，可以通过将 7Be 大气通量（由其海洋库存确定）乘以气溶胶和湿沉降中的 TE/7Be 比率来估算这些重要微量元素 (TE) 的大气通量。更广泛的影响：这项研究将直接解决国际 GEOTRACES 科学计划的关键目标之一：“开发和完善表层海洋中的化学示踪剂，以量化大气沉积”。提供有关海洋相关微量元素的大气输入估计的能力将为化学海洋学和其他领域做出广泛贡献，包括了解人为对海洋的影响以及TEs的大气输入在海洋生态中发挥的作用。 该项目的结果将有利于其他国际倡议，例如 SOLAS 计划，并且这项工作中生成的数据将可用于对气溶胶沉积和大气输入模型进行地面实况验证。研究生的教育和培训是这项研究的重要组成部分。 PI 定期教授本科生和研究生课程，并将他们的实地考察结果纳入讲座材料中，以激励下一代地球科学家。 FSU 化学和/或生物学专业的本科生（男性、女性、少数族裔）将通过每年申请 REU 补充剂的方式参与研究。 随着它们的发展，结果将在国家/国际科学会议上展示，并在同行评审的期刊上发表。数据将按照NSF/OCE的要求及时提交。

The atmospheric input of numerous chemical species into the global ocean equals or exceeds that from river sources and thus constitutes an important budgetary component for these elements. In addition, the atmospheric input of trace elements plays a key role in ocean biogeochemical processes. Assessment of this input is difficult however because measurements of deposition rates to the ocean are rare and susceptible to problems of temporal and spatial variability. Given the dearth of direct measurements, the ocean community must rely on atmospheric transport and deposition models which themselves are poorly constrained as to rainfall amounts and aerosol removal parameterization. Thus indirect methods, such as the use of natural radionuclides delivered to the ocean from the atmosphere are often used to estimate atmospheric inputs. In a novel application developed in this project, researchers at the University of Miami and Florida State University will use measurements of 7Be in the surface waters and in the lower atmosphere, coupled with trace element measurements in aerosols and rain, to provide estimates of the atmospheric input of relevant trace elements into the subtropical North Atlantic. 7Be is a cosmic ray produced radioisotope that becomes associated with particles in the troposphere and subsequently deposited to the surface ocean. Because of its relatively short half-life (53.3 days) it is reasonable to equate the inventory of 7Be decay in the upper ocean to the flux of 7Be from the atmosphere due to wet plus dry deposition. This provides a key linkage between the atmospheric concentration of chemical species and their deposition to the ocean. Such species include many of interest to the GEOTRACES program such as Al, Mn, Fe, Cu, Zn, and Cd. The atmospheric flux of these important trace elements (TEs) can then be estimated from multiplying the 7Be atmospheric flux (determined by its ocean inventory) by the TE/7Be ratios in aerosols and wet deposition. Broader Impacts: This research will directly addresse one of the critical objectives in the International GEOTRACES Science Plan: "Develop and refine chemical tracers in the surface ocean for quantification of atmospheric deposition". The ability to provide estimates of the atmospheric input of relevant trace elements to the ocean will contribute widely to the field of chemical oceanography and elsewhere, including understanding anthropogenic impacts on the oceans and the role atmospheric input of TEs plays in ocean ecology. The results of this project will benefit other international initiatives such as the SOLAS program, and data generated in this work will be available to allow ground-truthing of models of aerosol deposition and atmospheric input. Education and training of graduate students are essential components of this research. The PIs regularly teach undergraduate and graduate classes and incorporate the results of their fieldwork into lecture materials to motivate the next generation of Earth scientists. Undergraduate FSU chemistry and/or biology majors (males, females, minorities) will be involved in the research via annual requests for REU supplements. As they evolve, results will be presented at national/international scientific meetings, and published in peer-reviewed journals. The data will be submitted in a timely manner according to the requirements of NSF/OCE.