Spatial and Temporal Variability of Pb, Fe, Zn, and their Stable Isotope Ratios in the Tropical and Subtropical Atlantic and Pacific Oceans

美国麻省理工学院的一名研究人员提议开展铅（Pb）、铁（Fe）、锌（Zn）及其稳定同位素的协同研究，以评估人类活动对海洋化学的影响，并提高我们对微量金属在调节海洋生物地球化学循环中的作用的认识。该项目的具体目标如下：(1)确定微量元素变异、粉尘通量、海洋和生物变化之间的联系；(2)确定北大西洋西部上北大西洋深水Pb最大值的空间演化；(3)评价氧最小铁最大值是通过西北非洲海域还原性沉积物中铁通量的平流混合向西发展，还是通过浮游生物对过量吸收尘铁的原位再矿化作用向西发展；(4)确定Pb同位素比值能否建立Pb向大西洋东部深大西洋输运的时间尺度；(5)评估大西洋首次开放海洋测量的铁同位素比率，确定我们是否可以区分尘埃铁和再矿化的生物铁，并考虑上层海洋Zn同位素比率是否反映了渐进的生物瑞利分馏。为了达到既定目标，科学家将继续在选定的BTM和MOSEAN部署上使用系载水采样器进行百慕大和夏威夷的铅和铁时间序列，在BATS和HOT巡航上使用单单元MITESS/ATE部署，并完成2005年夏季Endeavor 408在热带大西洋西部巡航期间收集的Pb剖面的分析。此外，还将开展海上野外考察，建立热带大西洋铁最大值与浅层氧最小值相关的空间变异性，并在最古老的东大西洋深水中寻找独特的19世纪中期Pb同位素比值。最后，在Fe和Zn同位素工作方面，将进行表层和中深水海水Fe同位素、北太平洋海水Zn同位素剖面和秘鲁上升流区Zn同位素的递进生物分馏研究。至于更广泛的影响，本项目将资助一名研究生。然而，预计本科生也将包括在这项工作中，并与研究生一起接受培训，了解如何使用最先进的仪器获得高质量的微量金属和同位素数据。

OCE-0647446A researcher from Massachusetts Institute of Technology proposes to carry out coordinated studies of lead (Pb), iron (Fe), zinc (Zn), and their stable isotopes to assess the anthropogenic impact on ocean chemistry and improve our understanding of the role of trace metals in regulating ocean biogeochemical cycles. The specific goals of this project are the following: (1) determine links between trace element variability, dust flux, oceanographic and biological changes; (2) ascertain the spatial evolution of the upper North Atlantic Deep Water Pb maximum in the western North Atlantic; (3) evaluate whether the oxygen-minimum Fe-maximum develops westward via advective mixing from Fe fluxes from reducing sediments off NW Africa, or from in-situ re-mineralization of luxury-uptake dust Fe by plankton; (4) determine whether Pb isotope ratios can be used to establish the time scale of Pb transport into the eastern deep Atlantic; and (5) assess the first open-ocean measurements of Fe isotope ratios in the Atlantic and determine whether we can distinguish dust Fe from re-mineralized biological Fe and consider whether upper ocean Zn isotope ratios reflect progressive biological Rayleigh fractionation. To attain the outlined goals, the scientist will continue the Bermuda and Hawaii Pb and Fe time-series using the moored water sampler on selected BTM and MOSEAN deployments, the single-unit MITESS/ATE deployments on BATS and HOT cruises, and complete the analysis of Pb profiles collected during the summer 2005 Endeavor 408 cruise in the western tropical Atlantic. In addition, sea-going fieldwork will be carried out to establish the spatial variability of the tropical Atlantic Fe maximum associated with the shallow oxygen minimum, and to find unique mid-19th century Pb isotope ratios in the oldest east Atlantic deep water. Lastly, for the Fe and Zn isotope work, seawater Fe isotopes from surface and mid-depth waters, a seawater Zn isotope profile from the North Pacific, and a study of the progressive biological fractionation of Zn isotopes in the Peruvian upwelling region will be done.As regards broader impacts, one graduate student will be supported by this project. However, it is anticipated that undergraduate students will also be included in the work and be trained along with the graduate student on how to obtain high quality trace metal and isotopic data using state of the art instrumentation.