Source, Composition, and Stability of Soluble Iron Fluxing from Continental Margin Sediments

铁是世界海洋中的一种限制性营养物质，在调节浮游植物的生长方面起着关键作用。海洋中铁的主要来源是大气，通过风吹来的陆地尘埃，以及海底，通过大陆架沉积物的输入。虽然对大气输入进行了充分的研究，但对来自沉积物的海洋输入的铁进行了很少的测量，因此，对来自沉积物的铁对铁池以及最终对海洋初级生产力的相对重要性了解甚少。在这项研究中，研究人员将检查海洋中沉积物来源的铁的化学性质，以评估其对浮游植物利用铁的贡献。本研究的结果将进一步加深我们对海洋铁输入及其对海洋初级生产力的重要性的认识。该项目将有助于培养研究生，并为工程和物理科学专业的本科生提供海上一天等教育机会。大气和大陆边缘沉积物是向公海提供限制性营养铁的主要来源。然而，沉积物中铁的化学形式尚未得到很好的研究，只能定量为还原铁或通过0.45µm过滤器的溶解铁。铁氧合的动力学表明，它应该在上覆水域迅速沉淀，挑战了沉积物是初级生产铁的重要来源的观点。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，可能与大气输入相抗衡，有必要证明源自沉积物的铁以稳定铁的形式存在，并且可能在水柱中停留很长时间。该项目的总体目标是检验以下假设：大陆边缘沉积物中通过沉积物-水界面的铁通量是以有机-铁（III）配合物的形式溶解的，铁通量的大小受上覆水域的氧化还原条件、配合物的组成和下伏沉积物中的生物地球化学过程的影响。为了验证这些假设，将对卡罗莱纳沉积中心和墨西哥湾沉积物中溶解铁（III）的通量和形态进行量化，并使用现场测量和最先进的伏安法和色谱技术确定调节铁的生产和通量的生物地球化学过程，作为环境氧化还原机制的功能。

Iron is a limiting nutrient in the world's oceans and plays a key role in regulating the growth of phytoplankton. The main sources of iron to the open ocean are the atmosphere, through wind-blown terrestrial dust, and the seafloor, through input from continental shelf sediments. While atmospheric inputs have been well-studied, the oceanic input of iron from sediments has only sparsely been measured and, as a result, the relative importance of the sediment-derived iron to the iron pool and, ultimately, primary productivity in the oceans is poorly understood. In this study, researchers will examine the chemical properties of sediment-derived iron in the oceans to assess its contribution to the iron used by phytoplankton. Results from this study will further our understanding of iron inputs to the ocean and their importance to ocean primary productivity. The project will contribute to the training of graduate students, as well as provide educational opportunities such as a day at sea for undergraduate students in engineering and physical science.The atmosphere and continental margin sediments are the main source of the limiting nutrient iron (Fe) to the open ocean. Yet, the chemical form of iron from sediments has not been well examined and only quantified as reduced iron or the dissolved iron passing through 0.45 µm filters. The kinetics of iron oxygenation suggests it should precipitate rapidly in the overlying waters, challenging the view that sediments are important sources of iron for primary production. To establish whether the flux of iron from sediments has important implications for primary productivity, possibly rivaling atmospheric inputs, it is necessary to demonstrate that ferric iron originating in sediments is under the form of stable iron species with potential for a high residence time in the water column. The overall objective of this project is to test the hypotheses that iron fluxing across the sediment-water interface in continental margin sediments is dissolved under the form of organic-Fe(III) complexes and that the magnitude of the iron flux is influenced by the redox conditions in the overlying waters, the composition of the complexes, and the biogeochemical processes in the underlying sediments. To test these hypotheses, the flux and speciation of dissolved Fe(III) will be quantified in the sediments of the Carolina depocenter and the Gulf of Mexico, and the biogeochemical processes regulating the production and the flux of iron as a function of the redox regime of the environment will be determined using in situ measurements and state-of-the-art voltammetric and chromatographic techniques.