Methylated mercury sources and cycling in the high latitude North Atlantic

确定与海洋边界（大气、河流、冰和沉积物）相关的投入和产出对于了解海洋中的汞收支至关重要。沉积物是一个重要的汞储存库，也是离子汞转化为甲基化汞（TMeHg）的场所。汞向深海沃茨的这种潜在来源没有受到严格限制。了解沉积物-水交换的作用在冰岛周围的远北大西洋特别重要，因为这是一个深水形成区，这些沃茨也是北大西洋和北冰洋之间化学品运输的通道。该团队计划利用2021年7月/8月参加GEOTRACES过程巡航（GApr 16）的机会，调查该地区的汞和TMeHg地球化学循环。该项目将支持培养一名博士后学者和一名研究生，以及康州大学的本科生，所有人都将从这项研究中获得研究经验。 H1）底栖沉积物是该区域TMeHg向深水的净源，并将主导TMeHg向北大西洋的供应; H2）虽然沉积物可能由于各种生物化学和物理过程释放无机汞，但沉积物将是TMeHg的净汇;和H3）总体而言，冰岛周围的海洋是总汞的净汇，但也是北大西洋深层TMeHg的来源，这些来源主要来自大陆架和沉积物的TMeHg输入。鉴于将在巡航中进行的其他测量（放射化学通量估计和微量元素分布），GApr 16探险提供了独特的协同作用和机会。该项目将研究总汞和总甲基汞在整个水体以及沉积物和孔隙水中的分布，以研究海洋过程的作用，包括水平流、沉积物再悬浮-再沉积以及沉积物-水界面上的溶解交换对汞循环的影响。利用这一全面的数据集和以前在次极地地区进行的研究中获得的数据，该团队将开发一个区域箱模型，并为北大西洋和北冰洋之间的海洋构建一个全面的汞收支平衡，该奖项反映了NSF的法定使命，并通过利用基金会的知识价值和更广泛的影响审查进行评估，被认为值得支持的搜索.

Determining inputs and outputs associated with ocean boundaries (atmosphere, rivers, ice and sediment) is crucial to understanding mercury (Hg) budgets in the ocean. Sediments are an important mercury reservoir, and a location where ionic mercury is converted to methylated mercury (TMeHg). This potential source of Hg to deep ocean waters is poorly constrained. Understanding the role of sediment-water exchange is especially important in the far North Atlantic, around Iceland, as this is a region of deep water formation and these waters are also a conduit for transport of chemicals between the North Atlantic and Arctic Oceans. The team proposes to use an opportunity to join the GEOTRACES Process Cruise (GApr16) in July/August 2021 to investigate Hg and TMeHg biogeochemical cycling in this region. This project will support training of a postdoctoral scholar and one graduate student, as well as undergraduates at UConn and all will gain research experience from this study. This research is formulated around the hypotheses that: H1) Benthic sediments are a net source of TMeHg to the deep water in this region and will dominate the TMeHg supply into the North Atlantic; H2) While sediment may release inorganic Hg due to various biochemical and physical processes, sediments will be a net sink for THg; and H3) Overall, the seas around Iceland are a net sink for total Hg but a source for TMeHg to the deep North Atlantic Ocean, with the sources being primarily from shelf- and sediment-derived TMeHg inputs. The GApr16 expedition provides a unique synergy and opportunity given the other measurements (radiochemical flux estimates and trace element distributions) that will be made on the cruise. This project will examine the distributions of total Hg (THg) and TMeHg throughout the water column as well as the sediment and porewaters to examine the role of ocean processes including water advection, sediment resuspension-redeposition, and dissolved exchange across the sediment-water interface on Hg cycling. With this holistic dataset and data from prior studies in subpolar regions, the team will develop a regional box model and construct a comprehensive Hg budget for the seas between the North Atlantic and Arctic Oceans, elucidating the role of sediments for the different Hg species.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.