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质。来自大陆的尘埃是大部分铁输送到海洋的主要来源。然而，这种铁不溶于海洋表面，大部分沉淀到底部，而不是被浮游植物利用。该项目调查沉积物是否可以成为海洋铁的重要来源。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地球化学和物理过程。他们将测量沿着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海底通量研究。这项研究将重新检查来自沉积物的铁是否主要以有机形式与无机（矿物）形式存在。以前的大多数研究都是在海洋东部进行的，那里的深层沃茨被输送到表面。此外，从沉积物中扩散出来的溶解铁的确切成分往往还没有确定。该项目将为两名博士提供培训。来自代表性不足的少数群体的学生将获得科学和工程方面的经验。将为本科生提供一个顶点课程，为学生创造学习和从事海洋学实地工作的机会。研究人员将参与有意义的外联活动，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教师分享，供课堂使用。本研究将利用原位底栖通量测量、原位物理测量和反应输运模型计算支持的铁形态分析，以：（1）研究有机碳输入到沉积物的通量对沉积物中铁释放的作用;（2）确定可能影响溶解铁底栖通量的底层水输运过程;以及（3）利用拟议研究期间产生的数据，包括来自法国机会号巡航的数据，以及来自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沃茨提供营养物方面的作用。拟议的研究还将有助于确定底层沃茨的迁移如何影响沉积物-水界面的化学品交换。这项研究的结果将提供新的数据，可以纳入海洋环流模型，以预测气候变化对海洋生产力，大气CO2消耗，沉积物碳转化和氧气最小区的扩展的影响。该项目包括培养两名博士。来自传统上代表性不足的少数民族的学生，来自科学和工程的几名本科生，以及游轮期间的客座学生。的博士学生将通过格鲁吉亚理工学院新的海洋科学与工程项目招募，该项目提供工程和科学方面的培训。要求额外的船舶时间，以暴露高年级本科生从环境领域的方法顶点课程海洋学研究。PI和他的团队还将继续开展外联活动，通过演示和动手实验，让访问格鲁吉亚理工学院的K-12学生了解化学海洋学研究。一个网站与课程计划和播客将提供给K-12教师通过教育中心整合科学，数学和计算。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NSF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.