Mercury Species Cycling and Fluxes in the Oceanic Water Column

汞（Hg）在海洋环境中不断移动，通过一个复杂的生物地球化学循环，包括汞在海气界面上的交换，多种汞氧化状态的变化，以及许多生物活性有机金属化合物的形成。人们对汞循环的许多方面知之甚少，特别是单甲基汞和二甲基汞（分别为MMHg和DMHg）的形成。甲基汞在海洋环境中具有重要意义，因为它的毒性和在水生食物网中生物积累的能力。在拟议的研究中，伍兹霍尔海洋研究所的一名科学家将进行物种形成、通量和过程测量，以评估水柱中汞（Hg）和甲基汞（MMHg）的循环。这些数据将用于检验以下假设：(1)甲基化发生在整个水柱顶部100米；(2)整个水柱的MMHg颗粒通量超过外部输入，表明水柱净产量；(3)下沉颗粒和悬浮颗粒是生物甲基化增强的位点；(4)在光区发生显著的光去甲基化；(5)硫酸盐还原不能解释生物甲基化；(6)当综合整个水柱时，海洋汞甲基化可以提供足够多的MMHg来解释鱼类的积累率。就更广泛的影响而言，该科学家将与伍兹霍尔海洋学研究所教育和媒体关系工作人员合作，在区域和国家报纸上发表关于研究结果（即研究图像、数字、说明性文字、教育活动）的图文介绍。作为该项目的一部分，一名研究生将在现场和实验室工作方面得到支持和培训。

Mercury (Hg) in the marine environment is constantly moved through a complex biogeochemical cycle which includes the exchange of mercury across the sea-air interface, multiple mercury oxidation state changes, and the formation of numerous bioactive organometallic compounds. Many aspects of the mercury cycle are poorly understood, particularly the formation of mono- and di-methylmercury (MMHg and DMHg, respectively). Methylmercury is of significance in the marine environment, because of its toxicity and ability to bioaccumulate in aquatic food webs. In the proposed research, a scientist from the Woods Hole Oceanographic Institute would carry out speciation, flux, and process measurements to assess the cycling of mercury (Hg) and methylmercury (MMHg) in the water column. The data would be used to test the following hypotheses: (1) methylation occurs throughout the top 100 m of the water column; (2) particulate fluxes of MMHg throughout the water column exceed external inputs indicating net water column production; (3) sinking and suspended particles are sites of enhanced biological methylation; (4) significant photodemethylation occurs in the euphotic zone; (5) sulfate reduction cannot explain biological methylation; and (6) when integrated over the entire water column, pelagic methylation of Hg can provide more than enough MMHg to explain fish accumulation rates.In terms of the broader impacts, the scientist, in collaboration with the Woods Hole Oceanographic Institution Education and Media Relations staff, would publish a graphic presentation on results from the study (i.e., research images, figures, descriptive text, educational activities) in regional and national newspapers. One graduate student would be supported and trained in field and laboratory work as part of this project.