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.

铁是一种有限的养分，普遍认为大气和大陆边缘沉积物是海洋铁的主要来源。有趣的是，大多数调查都集中在水柱中铁的分布和物种上。由于这些环境为地表水提供铁的源头，因此仅在沉积物中的铁通量进行了稀疏的测量，并且仅在上流区域中进行测量。 为了确定铁中铁的通量是否对初级生产力具有重要意义，可能具有与大气的投入相媲美，有必要证明铁的通量来自各种大陆边缘沉积物，包括在上升的地区不重要的地区。在这项研究中，佐治亚理工学院的研究人员将检验三个假设，以确定在大陆边缘沉积物中铁的​​通量是否重要：（1）在上升不重要的大陆边缘的沉积物水界面上产生了大量的铁浓度。 （2）可溶性有机FE（III）复合物构成铁通量最重要的部分。 （3）铁的通量受到沉积物的有机物含量以及控制铁和硫酸盐还原程度的生物扰动强度的间接调节。为了检验这些假设，使用原位测量和最先进的伏安算术技术，将在Carolina DepoCenter沉积物中的有机含量和生物扰动强度中量化溶解的Fe（III）的通量和形态。此外，将使用原位测量和沉积物孵育来确定调节铁通量横跨沉积物水界面的生物地球化学过程。这项研究将评估来自暴露于上升流不大的区域中的大陆边缘沉积物中的铁通量的重要性。在不同的有机成分和生物扰动强度的沉积物中研究这些过程将证明地球化学条件会引起铁的通量。更广泛的影响：这项研究可能会改变基本范式，即需要上升和低氧气水平来产生铁通量，以便在上覆水中产生铁通量，并确定是否应将大陆边缘沉积物视为铁的重要来源，这可能是竞争大气输入的重要来源，以在开放海洋中燃料一级生产力。这项研究还将扩大我们以前的工作，并为大多数终端电子受体的自主深海分析和代谢物的原位分析提供了能力，其成本相对较低。该仪器将紧凑并适应任何底栖地着陆器，因此可以在巡游中的深海沉积物中部署机会。原位测量成为海洋学研究的必要组成部分，两位博士学位。学生将在最先进的伏安技术，原位部署和动力学建模方面发展专业知识。最后，该项目将有一个重要的教育组成部分，并努力将本科工程师和科学家整合到海洋学研究中，每年夏天为老师提供研究经验，并为她提供了将新的前瞻性带入课堂的机会，并每年继续将多达20名学生带到海上。