Collaborative Research: US GEOTRACES GP-17-OCE and -ANT Sections: External sources, cycling and processes affecting mercury speciation in the South Pacific and Southern Oceans

该项目将评估海洋和大气中各种形式的汞的浓度，以研究控制海洋偏远地区汞浓度和化学成分的因素。拟议的工作将检查汞的来源，主要来自大气，以及汞如何最终从海水中去除。具体来说，本研究的重点是南极洲周围的南太平洋和南大洋，这些地区远离人类活动及其对生物圈的相关汞输入。人类活动大大增加了生物圈中的汞含量和人类食用的海产品中的汞含量，从而增加了它们的潜在暴露量，但对这些偏远地区的影响却知之甚少。这些测量将在两次海洋探险中进行，这是国际GEOTRACES计划的一部分。GEOTRACES旨在研究世界大气、表层和深海中微量元素及其同位素的浓度和分布。汞之所以引起关注，主要是因为它能够在海洋食物链中生物积累，主要以有机形式甲基汞（MeHg）积累。鱼类和其他海洋生物中甲基汞含量的升高是人类和野生动物健康关注的问题，因为它们通过食用海产品接触甲基汞，而控制这种接触的因素尚不清楚。拟议的工作将支持三所参与院校的三名研究生和几名本科生。在这两次考察中，研究小组将收集大气、水柱和沉积物中主要汞形态浓度的高分辨率数据，以研究这些地区的汞来源，以及导致汞转化为毒性更强、具有生物蓄积性的甲基汞的过程。各种汞（气态元素汞、离子汞、甲基汞和二甲基汞）的溶解形式和颗粒形式将在大气和整个水柱中使用高分辨率采样和新技术进行测定。此外，大气和水样中汞稳定同位素的测量将用于确定汞向这些地区的来源（例如，地质或人为输入）和输送机制（例如，干或湿沉积、冰川融化）。这一综合性项目将利用汞物种形成和汞源跟踪能力，评估人类活动和气候变化对改变这些海水中汞和甲基汞含量的重要性，以及由此导致的人类消耗的海洋生物中的汞含量。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project will evaluate the concentrations of mercury (Hg) in its various forms in the ocean and atmosphere to examine the factors that control its concentration and chemistry in remote regions of the ocean. The proposed work will examine mercury sources, primarily from the atmosphere, and how mercury is finally removed from ocean waters. Specifically, this study is focused on the South Pacific and Southern Ocean around Antarctica, regions that are remote from human activity and their associated Hg inputs to the biosphere. Human activity has substantially enhanced the amount of Hg in the biosphere and its levels in seafood consumed by humans, and therefore their potential exposure, but its impact in these remote regions is poorly constrained. The measurements will be made during two ocean expeditions that form part of the international GEOTRACES program. GEOTRACES aims to examine the concentrations and distributions of trace elements and their isotopes in the atmosphere, surface and deep oceans of the world. Mercury is a primarily a concern because of its ability to bioaccumulate in marine food chains, primarily in its organic form, methylmercury (MeHg). Elevated levels of MeHg in fish and other marine organisms is a concern for human and wildlife health due to exposure through seafood consumption, and the factors controlling this exposure are not well understood. The proposed work will support three graduate and several undergraduate students across the three participating institutions.During the two expeditions, the research team will collect high resolution data on the concentrations of the primary Hg forms in the atmosphere, the water column, and the sediments, to examine the sources of Hg to these regions and the processes that lead to the conversion of Hg to its more toxic and bioaccumulative form, MeHg. Dissolved and particulate forms of the various Hg species (gaseous elemental Hg, ionic Hg, MeHg and dimethylmercury) will be determined in the atmosphere and throughout the water column using high resolution sampling and novel techniques. Additionally, measurements of Hg stable isotopes in atmospheric and water samples will be used to identify sources (e.g., geogenic or anthropogenic inputs) and delivery mechanisms (e.g., dry or wet deposition, glacial melt) of Hg to these regions. This comprehensive project will leverage Hg speciation and Hg source tracking capabilities to assess the importance of human activity and climate change in altering the amount of Hg and MeHg in these ocean waters, and the resultant levels in marine organisms consumed by humans.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.