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。来自大陆的尘埃是输送到海洋中的大部分铁的主要来源。然而，这种铁在表层海洋中不溶解，大多数沉入海底，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中铁的重要来源。科学家团队将量化生物地球化学和物理过程，这些过程会影响从沉积物到大陆边缘水柱的铁通量。他们将测量北大西洋西部和地中海西部海底的铁通量。船上对不同形态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存在，而不是以无机(矿物)形式存在。以前的大多数研究都是在海洋东部进行的，那里的深水被输送到海面。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。该项目将为两名来自少数族裔群体的博士生提供培训，他们将获得科学和工程方面的经验。将为本科生开设顶峰课程，为学生创造学习和从事海洋野外工作的机会。研究人员将参与有意义的推广活动，通过动手实验和在线教案激发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。这项研究将利用原位海底通量测量、原位物理测量和由反应迁移模型计算支持的铁形态分析：(1)调查向沉积物输入的有机碳通量对沉积物中铁的释放的作用；(2)确定可能影响海底溶解铁通量的底层水迁移过程；(3)利用拟议研究期间产生的数据，包括法国机遇号邮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提供营养物质方面的作用。拟议的研究还将有助于确定底层水的输送如何影响沉积物-水界面的化学物质交换。这项研究的结果将提供可纳入海洋环流模型的新数据，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区域扩大的影响。该项目包括培训两名来自传统上代表人数较少的少数民族的博士生，几名理工科本科生，以及巡游期间的客座学生。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。为了让环境领域方法课程的大四学生接触到海洋学研究，需要额外的航海时间。PI和他的小组还将继续开展外联活动，通过演讲和动手实验，让访问佐治亚理工学院的K-12学生接触到化学海洋学研究。将通过科学、数学和计算综合教育中心向K-12教师提供一个包含教案和播客的网站。科学团队还将在巡航期间通过卫星通信和社交媒体与学生互动。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.