Biogeochemical and Physical Processes Regulating the Benthic Flux and Speciation of Iron from Non-Upwelling Continental Margins

铁是海洋浮游植物的重要营养物。大陆上的尘土是输送到海洋中的大部分铁的主要来源。然而，这些铁不溶于海洋表面，大多数都沉淀到海底，而不是被浮游植物利用。该项目调查沉积物是否可能是海洋铁的重要来源。科学家小组将量化影响铁从沉积物到大陆边缘水柱的通量的生物地球化学和物理过程。他们将测量北大西洋西部和地中海西部海底的铁通量。船上对不同形式铁的分析将补充底栖生物通量的研究。这项研究将重新审视来自沉积物的铁是否主要以有机形式还是无机（矿物）形式存在。以前的大多数研究都是在海洋的东部进行的，那里的深水被输送到海面上。此外，从沉积物中扩散出来的溶解铁的确切成分往往无法确定。该项目将为两名来自少数族裔的博士生提供培训，他们将获得科学和工程方面的经验。将为本科生开设一门顶点课程，为学生提供学习和从事海洋实地工作的机会。研究人员将参与有意义的外展活动，通过动手实验和在线课程计划激发K-12学生对化学海洋学研究的兴趣。这些信息将与K-12教师共享，以供课堂使用。本研究将采用原位底栖生物通量测量、原位物理测量和反应输运模型计算支持的铁形态分析：(1)研究有机碳输入通量对沉积物中铁释放的作用；(2)确定可能影响底栖铁通量的底水输送过程；(3)利用拟议研究期间产生的数据，包括法国机遇号游轮的数据和其他已发表研究的数据，将拟议研究的结果外推到全球海洋。这项研究将描述沉积物在向地表水供应营养物中的作用。拟议的研究还将有助于确定底部水的输送如何影响沉积物-水界面上化学物质的交换。该研究结果将为海洋环流模型提供新的数据，以预测气候变化对海洋生产力、大气二氧化碳消耗、沉积物碳转化和氧气最小带扩张的影响。该项目包括培训两名来自传统上未被充分代表的少数民族的博士生，几名来自科学和工程专业的本科生，以及游轮期间的客座学生。这些博士生将通过佐治亚理工学院新的海洋科学与工程项目招收，该项目提供工程和科学方面的培训。需要额外的船上时间来让环境野外方法顶点课程的高年级本科生接触海洋学研究。PI和他的团队还将继续开展外联活动，让参观佐治亚理工学院的K-12学生通过演讲和动手实验了解化学海洋学研究。一个包含课程计划和播客的网站将通过科学、数学和计算机综合教育中心提供给K-12教师。科学团队还将通过卫星通信和社交媒体与学生进行互动。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Iron is an important nutrient for phytoplankton in the ocean. Dust from the continents is the primary source of most of the iron delivered to the ocean. However, this iron is not soluble in the surface ocean, and most settles to the bottom rather than being used by phytoplankton. This project investigates whether sediments could be an important source of iron to the ocean. The team of scientists will quantify biogeochemical and physical processes that influence the flux of iron from sediments to the water column on continental margins. They will measure fluxes of iron at the seafloor along the western North Atlantic Ocean and in the western Mediterranean Sea. Shipboard analyses of different forms of iron will complement the benthic flux studies. This research will re-examine whether the iron coming from sediments is primarily in organic forms versus inorganic (mineral) forms. Most previous studies have been conducted in the eastern parts of the oceans, where deep waters are transported to the surface. In addition, the exact composition of dissolved iron diffusing out of the sediment has often not been determined. The project will provide training for two Ph.D. students from underrepresented minority groups who will gain experience in science and engineering. A capstone course for undergraduate students will be offered that creates opportunities for students to learn and engage in oceanographic field work. The researchers will participate in meaningful outreach to spark the interest of K-12 students in chemical oceanographic research through hands-on experiments and online lesson plans. This information will be shared with K-12 teachers for use in the classroom. This study will use in situ benthic flux measurements, in situ physical measurements, and iron speciation analyses supported by reactive transport model calculations to: (1) investigate the role of the organic carbon input flux to the sediment on the release of iron from the sediment; (2) identify the bottom water transport processes that may affect the benthic flux of dissolved iron; and (3) extrapolate the findings of the proposed study to the global ocean using data generated during the proposed study, including data from the cruise of opportunity in France, and data from other published studies. This study will characterize the role of sediments in the supply of nutrient to surface waters. The proposed research will also help identifying how the transport of bottom waters affects the exchange of chemicals at the sediment-water interface. Results from this study will provide new data that can be incorporated in ocean circulation models to predict the effect of climate change on ocean productivity, atmospheric CO2 consumption, sediment carbon transformation, and the expansion of oxygen minimum zones. This project includes training for two Ph.D. students from traditionally underrepresented minorities, several undergraduates from Science and Engineering, and guest students during the cruises. The Ph.D. students will be recruited via the new Ocean Science and Engineering program at Georgia Tech that provides training in both engineering and science. Additional ship time is requested to expose senior undergraduates from an Environmental Field Methods capstone course to oceanographic research. The PI and his group will also continue outreach activities by exposing K-12 students who visit Georgia Tech to chemical oceanography research via presentations and hands-on experiments. A web site with lesson plans and podcasts will be provided to K-12 teachers via the Center for Education Integrating Science, Mathematics, and Computing. The science team will also interact with students during the cruises via satellite communication and social media.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.