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)有关的输入和输出对于了解海洋中汞(Hg)的收支至关重要。沉积物是重要的汞储存库，也是离子汞转化为甲基汞(TMeHg)的地方。这种汞向深海水域的潜在来源受到的限制很小。在冰岛周围的远北大西洋，了解沉积物-水交换的作用尤其重要，因为这是一个深水形成的区域，这些水域也是北大西洋和北冰洋之间运输化学品的管道。该小组建议利用2021年7月/8月参加GEOTRACES Process Cruise(GApr16)的机会，研究该地区汞和三甲基汞的生物地球化学循环。该项目将支持培养一名博士后学者和一名研究生，以及康涅狄格州大学的本科生，所有人都将从这项研究中获得研究经验。这项研究是围绕以下假设制定的：h1)底栖沉积物是该区域深水中三甲基汞的净来源，并将主导北大西洋的三甲基汞供应；h2)虽然沉积物可能由于各种生化和物理过程而释放无机汞，但沉积物将是三汞的净汇；h3)总的来说，冰岛周围海域是总汞的净汇，但也是北大西洋深海三甲基汞的来源，来源主要来自陆架和沉积物来源的三甲基汞输入。考虑到巡航上将进行的其他测量(放射化学通量估计和痕量元素分布)，GApr16探险提供了独特的协同和机会。本项目将研究总汞(THG)和三甲基汞在整个水柱以及沉积物和孔隙水中的分布，以研究海洋过程(包括水平流、沉积物再悬浮-再沉积和沉积物-水界面的溶解交换)对汞循环的作用。有了这个整体数据集和以前在亚极地地区研究的数据，该团队将开发一个区域盒子模型，并构建北大西洋和北冰洋之间海域的综合汞预算，阐明沉积物对不同汞物种的作用。这一奖项反映了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。

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.