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

许多化学物质进入全球海洋的大气输入等于或超过来自河流来源的大气输入，因此构成这些元素的一个重要预算组成部分。此外，大气中痕量元素的输入在海洋生物地球化学过程中起着关键作用。然而，对这一投入的评估是困难的，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异性问题的影响。由于缺乏直接测量，海洋界必须依赖大气传输和沉积模型，而大气传输和沉积模型本身在降雨量和气溶胶去除参数方面的约束很差。因此，经常使用间接方法，例如使用从大气向海洋输送到海洋的天然放射性核素来估计大气输入。在该项目中开发的一种新应用中，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7Be的测量，以及气溶胶和雨水中的微量元素测量，来估计大气中相关微量元素对亚热带北大西洋的输入。7Be是一种宇宙射线产生的放射性同位素，与对流层中的粒子相关联，随后沉积到表层海洋中。由于7Be的半衰期相对较短(53.3天)，因此有理由将上层海洋中7Be衰变的存量等同于7Be因干湿沉积而从大气中释放出来的通量。这提供了大气中化学物质的浓度与其向海洋的沉积之间的关键联系。这些物种包括许多对地质运输系统计划感兴趣的物种，如铝、锰、铁、铜、锌和镉。然后，这些重要痕量元素(TES)的大气通量可以通过将7Be大气通量(由其海洋清单确定)乘以气溶胶和湿沉积中的TE/7Be比率来估计。更广泛的影响：这项研究将直接针对国际地球物理轨道科学计划的关键目标之一：“开发和改进表层海洋中用于量化大气沉积的化学示踪剂”。提供有关微量元素大气输入海洋的估计数的能力将对化学海洋学领域和其他领域作出广泛贡献，包括了解人类活动对海洋的影响以及大气输入TES在海洋生态中的作用。该项目的成果将有利于其他国际倡议，如SOLAS方案，并将提供这项工作中产生的数据，以便能够对气溶胶沉积和大气输入模型进行地面实况调查。研究生的教育和培训是本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，以激励下一代地球科学家。FSU化学和/或生物专业的本科生(男性、女性、少数民族)将通过每年申请REU补充剂的方式参与研究。随着成果的发展，成果将在国家/国际科学会议上公布，并在同行评议的期刊上发表。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.