Collaborative research: Transformations and mercury isotopic fractionation of methylmercury by marine phytoplankton

合作研究：海洋浮游植物对甲基汞的转化和汞同位素分馏

• 批准号: 1634048
• 负责人: Robert Mason
• 金额: $ 25.84万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1634048&HistoricalAwards=false
• 关键词: Collaborative; research; Transformations; mercury; isotopic

The accumulation of mercury (Hg) in seafood is a public health concern. The presence of Hg in seafood depends to a large degree on the air-sea exchange of Hg, with atmospheric deposition leading to accumulation of Hg in the ocean. The pathways to seafood start with the uptake of Hg by phytoplankton from seawater where is has always been assumed to accumulate to be eaten by grazers and passed on to larger organisms. This project challenges this assumption with preliminary data that suggests certain phytoplankton species can transform Hg to volatile forms (mercury vapor & dimethylmercury) that are lost to the atmosphere, a processes that removes Hg from the ocean rather than simply concentrating it into the ecosystem and seafood. This process, which has not been studied before, could dramatically alter our view of the Hg cycle in the ocean. The researchers funded by this project will look for the specific phytoplankton species that are capable of volatilizing Hg and quantify the rates at which they do so. They will also examine the suspected role of associated sulfur and selenium compounds in the process, as well as quantifying the changes in the Hg isotopic values for potential use as chemical tracers of the source of Hg in the ecosystem and food supply. These results should allow oceanographers to better quantify and refine our knowledge of Hg cycling in the ocean. The project will support participation of graduate students, a postdoctoral scientist, and incorporation of new information directly into courses taught by the researchers. Funding will also support continuing activities by the participants in activities that disseminate information on mercury and its effect on public and environmental health. Biogeochemical cycling of mercury (Hg) in the ocean may be more complex than previously assumed. New evidence has challenged the idea that methylmercury (MeHg) merely accumulates in phytoplankton and undergoes little to no transformation before being passed into the food web. This project aims to more fully elucidate the mechanisms behind the intracellular transformation of MeHg to volatile Hg and dimethylmercury (Me2Hg) that can be lost to the atmosphere, as well as to evaluate the range of algal taxa that can perform this transformation using directed culture work. Additionally, the PIs will investigate evidence that thiols, organic selenium (Se) compounds, and sulfides are required to facilitate these reactions within the phytoplankton, and specific pathways will be investigated and quantified through this research. Stable Hg isotopic data has been used to track Hg sources and pathways in marine systems and its fractionation during these MeHg transformations will also be quantified for future field study of marine Hg. The investigators hypothesize that coccolithophorids and other haptophytes capable of these intracellular reactions may account for a significant portion of the production of volatile Hg in the ocean. If this turns out to be the case, understanding and quantifying these volatilization processes may significantly alter our current understanding of the overall biogeochemical cycling of Hg in the ocean.

海鲜中汞（HG）的积累是一个公共卫生问题。 海鲜中汞的存在在很大程度上取决于汞的空气交换，大气沉积导致海洋中汞的积累。海鲜的途径始于海水中的浮游植物的吸收汞，人们一直认为始终被认为会积聚被放牧者食用并传递给更大的生物体。该项目通过初步数据挑战了这一假设，这些数据表明某些浮游植物物种可以将HG转化为挥发性形式（Mercury Vapor＆Dimethylmercury），这些形式损失了大气，这一过程将其从海洋中移出而不是将其集中到生态系统和海鲜中。这个过程以前尚未研究过，可以极大地改变我们对海洋中HG周期的看法。该项目资助的研究人员将寻找能够挥发HG并量化其速率的特定浮游植物物种。 他们还将检查相关硫和硒化合物在此过程中的可疑作用，并量化Hg同位素值的变化，以作为生态系统和食品供应中HG的化学示踪剂的潜在使用。这些结果应使海洋学家能够更好地量化和完善我们对海洋中汞循环的了解。该项目将支持研究生，博士后科学家的参与，并将新信息直接纳入研究人员教授的课程中。资金还将支持参与者的持续活动，以传播有关汞信息及其对公共和环境健康的影响的活动。海洋中汞（HG）的生物地球化学循环可能比以前假设的更为复杂。新的证据挑战了甲基汞（MEHG）仅在浮游植物中积累的观念，并且在进入食物网之前几乎没有转变。该项目的目的是更充分阐明MEHG向挥发性HG和二甲基汞（ME2HG）的细胞内转化背后的机制，这些机制可能会损失到大气中，并评估可以使用定向文化工作进行这种转化的藻类分类群。此外，PI将调查证据表明，需要硫醇，有机硒（SE）化合物和硫化物来促进浮游植物内的这些反应，并通过这项研究研究和量化特定的途径。稳定的HG同位素数据已用于跟踪海洋系统中的HG源和途径，并且在这些MEHG转换过程中的分馏也将被量化以进行海洋HG的未来现场研究。研究人员假设能够使用这些细胞内反应的可甲磷脂和其他乳腺植物可能是海洋中挥发性HG的很大一部分。如果情况如此，理解和量化这些挥发过程可能会显着改变我们对海洋中HG总体生物地球化学循环的当前理解。

项目成果

Historic contamination alters mercury sources and cycling in temperate estuaries relative to uncontaminated sites.

历史污染改变了温带河口相对于未污染地点的汞来源和循环。

• DOI: 10.1016/j.watres.2020.116684
• 发表时间: 2021-02-15
• 期刊: Water research
• 影响因子: 12.8
• 作者: Seelen EA;Chen CY;Balcom PH;Buckman KL;Taylor VF;Mason RP
• 通讯作者: Mason RP

Updated Global and Oceanic Mercury Budgets for the United Nations Global Mercury Assessment 2018

• DOI: 10.1021/acs.est.8b01246
• 发表时间: 2018-10-16
• 期刊: ENVIRONMENTAL SCIENCE & TECHNOLOGY
• 影响因子: 11.4
• 作者: Outridge, P. M.;Mason, R. P.;Heimburger-Boavida, L. E.
• 通讯作者: Heimburger-Boavida, L. E.