Constraining the air-sea exchange of inorganic and methylated mercury with high resolution spatial and temporal measurements in the Sargasso Sea

汞（Hg）是一种全球性污染物，主要通过人类活动，通过有意使用或作为煤、矿石和其他产品中的微量元素释放到生物圈。气候变化加剧了这些排放。大气中的汞主要是单质汞（Hg0），这是一种停留时间相对较长的气体，可以在全球范围内输送到偏远地区。经大气化学反应转化为离子汞后，通过降水、气溶胶和气态汞沉积沉积到海洋中。在地表水中，离子汞被生物和非生物转化为Hg0，然后通过气体交换返回大气。总体而言，大气沉积是海洋汞的主要来源，而Hg0气体逃逸是海洋汞的主要损失机制，因此海气交换的程度改变了海洋汞的负担并影响了全球汞循环。此外，海洋离子汞可以转化为毒性和生物蓄积性更强的甲基汞（MeHg），甲基汞集中在海产品中，足以成为全球人类健康问题并影响野生动物。了解调节海气汞交换的因素对于评估人类和气候变化对海产品中甲基汞含量和人类健康的影响至关重要。该项目由化学海洋学计划和大气化学计划共同资助，将评估海洋表面和大气中的汞浓度，以研究控制其浓度和化学成分的因素，以及汞源和汇的大小。关于特定地点海洋表层汞形态的季节和时间变化及其海气交换的数据有限，这是本研究的主要重点。测量将在百慕大附近的北大西洋进行，在每月和特定的以hg为重点的巡航期间。在百慕大的大气采样站也将收集大气样本。在巡航期间，将收集大气（气态和气溶胶）和地表水（气态元素汞，溶解和颗粒离子汞，甲基汞和二甲基汞）中的高分辨率汞形态数据，以研究汞的来源及其转化，以及这如何影响甲基汞的形成。此外，大气和水样中汞稳定同位素的测量将用于确定汞的来源（例如，地质或人为输入）和向该地区输送汞的机制。这项拟议的研究将进一步评估自然变异、人类活动和气候变化对改变海洋和人类食用的海洋生物中汞和甲基汞水平的重要性。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。

Mercury (Hg), a global pollutant, is released to the biosphere predominantly by human activity, through intentional use or as a trace element in coal, ores, and other products. These releases are exacerbated by climate change. Atmospheric Hg is predominantly elemental Hg (Hg0) - a gas with a relatively long residence time that can be transported globally to remote regions. After its transformation by atmospheric chemical reactions to ionic Hg, it is deposited to the ocean through precipitation, aerosol, and gaseous Hg deposition. In surface waters, ionic Hg is biologically and abiotically transformed into Hg0, which is then returned to the atmosphere via gas exchange. Overall, atmospheric deposition is the primary source, and Hg0 gas evasion is the primary loss mechanism for ocean Hg. The extent of air-sea exchange therefore alters the ocean Hg burden and impacts the global mercury cycle. Furthermore, the oceanic ionic Hg can be transformed into the more toxic and bioaccumulative methylmercury (MeHg), which concentrates in seafood sufficiently to be a global human health concern and impact wildlife. Understanding the factors that mediate the air-sea exchange of Hg is of vital importance for assessing the impact of humans and climate change on MeHg levels in seafood, and human health.The project, co-funded by the Chemical Oceanography Program and the Atmospheric Chemistry Program, will evaluate the concentrations of Hg in the surface ocean and atmosphere to examine the factors controlling their concentration and chemistry, and the magnitude of the Hg sources and sinks. There is limited data examining the seasonal and temporal variability of Hg speciation in the surface ocean at a specific location, and its air-sea exchange, and this is the study’s primary focus. Measurements will be made in the North Atlantic Ocean near Bermuda, during both monthly and specific Hg-focused cruises. Atmospheric samples will be collected as well at the atmospheric sampling station in Bermuda. During cruises, high resolution Hg speciation data in the atmosphere (gaseous and aerosol) and surface waters (gaseous elemental Hg, dissolved and particulate ionic Hg, MeHg and dimethylmercury) will be gathered to examine the sources of Hg and its transformations, and how this impacts the formation of MeHg. 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 of Hg to this region. This proposed research will further assess the importance of natural variability, human activity, and climate change on altering Hg and MeHg levels in the ocean, and 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.