Processes Controlling the Release of Iron from Continental Margin Sediments

控制大陆边缘沉积物中铁释放的过程

• 批准号: 0851156
• 负责人: Martial Taillefert
• 金额: $ 49.11万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0851156&HistoricalAwards=false
• 关键词: Processes; Controlling; Release; Iron; Continental

Iron is a limiting nutrient, and it is generally accepted that the atmosphere and continental margin sediments are the main source of iron to the oceans. Interestingly, most investigations have focused on the distribution and speciation of iron in the water column. The flux of iron from sediments has only been sparsely measured and only in upwelling zones because of the likelihood that these environments provide a source of iron to surface waters. To establish whether the flux of iron from sediments has important implications for primary productivity, possibly rivalling atmospheric inputs, it is necessary to demonstrate that a flux of iron occurs from a variety of continental margin sediments, including in areas where upwelling is not significant. In this study, researchers at the Georgia Institute of Technology will test three hypotheses to determine whether the flux of iron from continental margin sediments is significant: (1) A significant concentration of iron is produced at the sediment-water interface of continental margins where upwelling is not important. (2) Soluble organic Fe(III) complexes constitute the most important fraction of the iron flux. (3) The flux of iron is indirectly regulated by the organic matter content of the sediment and the intensity of bioturbation which control the extent of iron and sulfate reduction. To test these hypotheses, the flux and speciation of dissolved Fe(III) will be quantified across a gradient in organic content and bioturbation intensity in the sediments of the Carolina depocenter using in situ measurements and state-of-the-art voltammetric techniques. In addition, the biogeochemical processes regulating the flux of iron across the sediment-water interface will be determined using in situ measurements and sediment incubations. This study will assess the importance of the iron flux from continental margin sediments exposed to fully oxygenated waters in zones where upwelling is not significant. Studying these processes in sediments of different organic composition and bioturbation intensity will demonstrate what geochemical conditions induce a flux of iron. Broader Impacts: This study will potentially modify the underlying paradigm that upwelling and low oxygen levels are required to generate an iron flux to the overlying waters and establish whether continental margin sediments should be considered an important source of iron, possibly rivaling atmospheric inputs to fuel primary productivity in the open ocean. This study will also expand our previous work and provide capability for autonomous deep-sea in situ profiling of most terminal electron acceptors and reduced metabolites at a relatively low cost. This instrumentation will be compact and adaptable to any benthic lander, such that deployments in deep-sea sediments on cruises of opportunities could be performed. In situ measurements become a necessary component of oceanographic research, and two Ph.D. students will develop expertise in state-of-the-art voltammetric technology, in situ deployments, and kinetic modeling. Finally, this project will have an important educational component with efforts to integrate undergraduate engineers and scientists in oceanographic research, provide research experience to a teacher every summer and give her the opportunity to bring a new prospective into the classroom, and continue taking up to 20 students to sea each year.

铁是一种限制性营养素，一般认为大气和大陆边沉积物是海洋铁的主要来源。有趣的是，大多数研究都集中在水柱中铁的分布和形态。来自沉积物的铁通量仅被稀疏地测量，并且仅在上升流区，因为这些环境可能为地表沃茨提供铁源。 为了确定沉积物中的铁通量是否对初级生产力有重要影响，可能与大气输入相媲美，必须证明各种大陆边沉积物中，包括在上升流不明显的地区，都有铁通量。在这项研究中，格鲁吉亚理工学院的研究人员将检验三个假设，以确定大陆边缘沉积物中铁的通量是否显著：（1）在上升流不重要的大陆边缘沉积物-水界面处产生显著的铁浓度。(2)可溶性有机Fe（III）络合物构成铁通量的最重要部分。(3)沉积物有机质含量和生物扰动强度间接影响铁的通量，从而控制铁和硫酸盐的还原程度。为了验证这些假设，通量和溶解的Fe（III）的形态将量化跨梯度的有机含量和生物扰动强度的沉积物中的卡罗莱纳使用原位测量和国家的最先进的伏安技术。此外，还将利用现场测量和沉积物培养来确定调节沉积物-水界面铁通量的地球化学过程。这项研究将评估在上升流不显著的区域内暴露于充分充氧沃茨的大陆边缘沉积物的铁通量的重要性。在不同有机组成和生物扰动强度的沉积物中研究这些过程将表明什么样的地球化学条件会引起铁通量。更广泛的影响：这项研究可能会改变基本的模式，即需要上升流和低氧水平才能产生铁通量到上覆的沃茨，并确定是否应将大陆边沉积物视为铁的重要来源，可能与大气输入相媲美，以促进公海的初级生产力。这项研究还将扩大我们以前的工作，并提供以相对较低的成本对大多数末端电子受体和还原代谢物进行自主深海原位剖析的能力。这种仪器将是紧凑的，可适用于任何海底着陆器，这样就可以在机会巡航中部署在深海沉积物中。原位测量成为海洋学研究的必要组成部分，两位博士学生将发展在国家的最先进的伏安技术，在现场部署和动力学建模的专业知识。最后，这个项目将有一个重要的教育组成部分，努力整合本科工程师和科学家在海洋学研究，提供研究经验，以教师每年夏天，让她有机会把一个新的前景进入课堂，并继续采取多达20名学生每年出海。