US GEOTRACES Pacific Meridional Transect: Determination of the air-sea exchange of inorganic and methylated mercury in the anthropogenically-impacted and remote Pacific Ocean

人类活动极大地增加了环境中的汞含量，尤其是表层海洋中的汞。大部分汞以气体、颗粒或降水的形式从大气进入海洋。海洋和大气交界处的复杂物理和化学过程控制着汞的滞留量，因此最终可以在海产品中积累。甲基汞(MeHg)是汞的一种化学形态，通常残留在生物体中，影响人类和野生动物的健康和发育。这项研究将评估从阿拉斯加到塔希提岛的海洋大气和表层海洋中汞及其“甲基”形态的浓度。巡航的空间范围将使人们能够比较北太平洋和偏远地区的海-气交换和汞浓度，北太平洋的人类排放量很大，对人类的影响最小。研究人员将使用现有的技术并开发新的方法来研究汞在表层海洋中的命运和运输。这些发现将为GEOTRACES计划贡献关键的汞数据，从而增强其作为广泛海洋微量元素研究的一部分的整体影响。这些发现将有可能为与汞有关的公共政策和全球环境条约提供信息，从而为评估当前和未来气候情景中的人类汞风险提供数据。教育影响将包括支持一名研究生和他们使用实地数据撰写的论文，以及几名将获得高水平实践研究经验的本科生。这项研究将利用最近的分析进展，高分辨率地确定表层、海洋和大气中无机汞的浓度和形态。分析方法还将扩大到包括甲基化汞化合物的测量，包括甲基汞和二甲基汞。这些测量以及在GEOTRACES太平洋子午线横断面巡航期间收集的辅助数据，将使我们能够评估主要形态的无机汞和甲基化汞的大气输入和就地海洋损失。还将根据合作伙伴在巡航期间收集的一套环境变量对交换进行评估。由此产生的数据将有助于评估汞对大气和海洋的人为输入的长期影响，以及影响通过气体逃逸从海洋中损失汞的因素。这些研究将建立在之前作为GEOTRACES计划和其他NSF资助研究的一部分而获得的结果的基础上，增加新的测量方法，并加强对公海汞的来源和汇的理解。

Human activity has greatly increased the amount of mercury (Hg) in the environment, and particularly in the surface ocean. Most of the Hg enters the ocean from the atmosphere as a gas, on particles, or in precipitation. Complex physical and chemical processes at the interface between the ocean and atmosphere control the amount of Hg that is retained and therefore that can ultimately accumulate in seafood. Methylmercury (MeHg) is a chemical form of Hg that is commonly retained in organisms and impacts the health and development of humans and wildlife. This research will assess concentrations of Hg together with its "methyl" forms in the atmosphere and surface ocean at sea from Alaska to Tahiti. The spatial extent of the cruise will allow comparison of the air-sea exchange and concentrations of mercury in both the North Pacific where human emissions are large and in remote regions with minimal human impact. The researchers will use established techniques and develop new methods to examine the fate and transport of mercury within the surface ocean. These findings will contribute key Hg data to the GEOTRACES program and thus enhance its overall impact as part of an extensive marine trace element study. Findings will have potential to inform public policy and global environmental treaties related to Hg, thus providing data to evaluate human risk from Hg in present and future climate scenarios. Educational impact will include support for a graduate student and their dissertation using the field data, as well as several undergraduates that will gain high level, hands-on research experience. The research will take advantage of recent analytical advances that enable high resolution determination of the concentrations and forms of inorganic Hg in the surface ocean and atmosphere. The analytical approach will also be expanded to include measurements of methylated Hg compounds, including MeHg and dimethylmercury. These measurements, and ancillary data collected during the GEOTRACES Pacific Meridional Transect cruise, will allow assessment of both atmospheric input and in situ oceanic loss for the dominant forms of inorganic and methylated Hg. Exchange will also be evaluated in the context of the suite of environmental variables collected by collaborators during the cruise. The resulting data will help assess the long-term impact of anthropogenic inputs of Hg to the atmosphere and ocean, and the factors that influence the loss of Hg from the ocean by gas evasion. The studies will build on previous results obtained as part of the GEOTRACES program and other NSF-funded studies, adding novel measurements and building an enhanced understanding of the sources and sinks of Hg to the open ocean.