Collaborative Research: Examining Redox-Sensitive Phosphorus Speciation and Remineralization using X-ray and NMR Spectroscopic Methods

全球营养模式的变化需要了解水柱氧含量和沉积物磷释放之间的联系。 在过去的三十年里，海洋中的氮负荷急剧增加，而磷的增加则较为有限。 河流和大气中的氮氧化物输入已使几个生态系统处于亚氧状态。这两个因素的结合表明沿海海洋环境将越来越受到磷的限制。 这种限制富营养化的程度取决于低氧水平如何改变沉积物的矿化。 出于这个原因，来自德克萨斯大学、格鲁吉亚理工学院和南卡罗来纳州大学的研究人员计划使用固态31 P核磁共振和P边X射线吸收和荧光近边光谱来评估氧浓度对磷的释放和储存的作用。 这些方法将使他们能够识别和量化不同的有机和聚合磷相沉积物，水柱颗粒，孔隙水和溶解的有机馏分从Cariaco盆地和埃芬汉入口。 此外，磷的组成和浓度将映射在颗粒物在规模相关的微生物介导的存储和降解机制。 结果将被用来（1）确定是否存在或不存在的氧气有显着的影响P的形态和矿化，（2）如果在成岩作用过程中颗粒物中的磷存储的微观结构的变化，确定哪些磷物种是优先矿化/释放的微观网站。 至于更广泛的影响，除了显着提高我们对海洋环境中的磷循环的理解，这项研究将提供支持和培训的一名研究生从格鲁吉亚理工学院和一名研究生和一名本科生从南卡罗来纳州的大学。 预计这项研究的结果将被纳入当地中学的示范和一个名为ScienceQuest的计划，该计划由南卡罗来纳州大学的PI协调。 在格鲁吉亚理工学院，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.