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，以研究在海洋偏远地区控制其浓度和化学成分的因素。这项拟议的工作将研究汞的来源，主要是来自大气，以及汞最终是如何从海水中去除的。具体地说，这项研究的重点是南太平洋和南极洲周围的南大洋，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汞的含量及其在人类消费的海产品中的水平，因此增加了汞的潜在暴露，但其对这些偏远地区的影响受到的限制很小。这些测量将在两次海洋探险期间进行，这两次探险是国际地球轨道计划的一部分。GeoTRACE旨在研究全球大气、表层和深海中痕量元素及其同位素的浓度和分布。汞主要是一个令人担忧的问题，因为它能够在海洋食物链中生物积累，主要是以其有机形式--甲基汞(MeHg)的形式。鱼类和其他海洋生物中甲基汞水平的升高是通过食用海鲜接触到人类和野生动物健康的一个令人担忧的问题，控制这种接触的因素还不是很清楚。这项拟议的工作将支持三个参与机构的三名研究生和几名本科生。在两次探险期间，研究小组将收集关于大气、水柱和沉积物中初级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、更具生物累积性的汞的过程。将使用高分辨率采样和新技术，在大气和整个水柱中确定各种汞物种(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。此外，大气和水样中汞稳定同位素的测量将被用来确定汞的来源(例如，地质或人为输入)和向这些地区输送汞的机制(例如，干或湿沉积、冰川融化)。这一综合性项目将利用汞形态形成和汞来源追踪能力，评估人类活动和气候变化在改变这些海洋水域中汞和甲基汞的数量以及人类消耗的海洋生物中由此产生的水平方面的重要性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.