Examining Marine Phosphate Sources and Sinks using Advanced Spectromicroscopy and NMR Techniques

全球营养模式中的ABSTRACTOCE-0526161OCE-0526178OCE-0526309Changes需要了解水柱含氧量和沉积物磷释放之间的关系。在过去的三十年里，海洋中的氮负荷急剧增加，而磷的增加则更加有限。河流和大气中的NOx输入已使几个生态系统进入亚缺氧状态。这两个因素的结合表明，沿海海洋环境将日益受到磷的限制。这限制富营养化的程度取决于低氧水平如何改变沉积再矿化。为此，来自德克萨斯大学、佐治亚理工学院和南卡罗来纳大学的研究人员计划使用固态31P核磁共振和P-EDGE X射线吸收和荧光近边缘光谱来评估氧浓度对磷释放和储存的作用。这些方法将使他们能够识别和量化来自Cariaco盆地和Effingham Inlet的沉积物、水柱颗粒、孔隙水和溶解的有机部分中的不同有机和聚合磷相。此外，磷的组成和浓度将在与微生物介导的储存和降解机制相关的尺度上绘制在颗粒物中。结果将被用来(1)确定有无氧对P形态和再矿化是否有显著影响，以及(2)如果在成岩过程中颗粒内磷存储的微尺度结构发生变化，则确定哪些磷形态优先从微区再矿化/释放。至于更广泛的影响，除了显著提高我们对海洋环境中磷循环的理解外，这项研究还将为佐治亚理工学院的一名研究生和南卡罗来纳大学的一名研究生和一名本科生提供支持和培训。预计这项研究的结果将被纳入当地中学的演示和一个由南卡罗来纳大学PI协调的名为Science Quest的项目中。在佐治亚理工学院，研究生将参加旨在改善当地初中和/或高中地球科学教育的学生和教师增强伙伴关系(STEP)。

ABSTRACTOCE-0526161OCE-0526178OCE-0526309Changes in global nutrient patterns require understanding the connections between water column oxygen levels and the release of sedimentary phosphorus. Nitrogen loadings to the oceans have increased dramatically over the past three decades, while P increases have been more limited. Riverborne and atmospheric NOx inputs have driven several ecosystems into suboxic conditions. The combination of these two factors suggests that coastal marine environments will be increasingly P limited. The degree to which this limits eutrophication depends upon how low oxygen levels shift sedimentary remineralization. For this reason, researchers from the University of Texas, the Georgia Institute of Technology, and the University of South Carolina plan to assess the role of oxygen concentrations on the release and storage of phosphorus using solid state 31P Nuclear Magnetic Resonance and P-edge X-ray absorption and fluorescence near edge spectroscopy. The methods will allow them to identify and quantify the different organic and polymeric phosphorus phases in sediments, water column particulates, porewaters and dissolved organic fractions from the Cariaco Basin and Effingham Inlet. In addition, the phosphorus composition and concentrations will be mapped within particulates at scales relevant to microbially-mediated storage and degradation mechanisms. Results will be used to (1) determine whether the presence or absence of oxygen has a marked influence on P speciation and remineralization, and (2) if the microscale structure of phosphorus storage within particulates changes during diagenesis, determine what phosphorus species are preferentially remineralized/released from microsites. As regards broader impacts, besides significantly improving our understanding of phosphorus cycling in the marine environment, this study will provide support and training for one graduate student from Georgia Institute of Technology and one graduate student and one undergraduate student from the University of South Carolina. It is anticipated that results from this research will be incorporated into local middle school demonstrations and a program called ScienceQuest coordinated by the PI from the University of South Carolina. At Georgia Institute of Technology, the graduate student will participate in the Student and Teacher Enhancement Partnership (STEP) that aims to improve earth science education at local middle and/or high schools.