Collaborative Research: TH(IV) and PA(IV, V) Binding to Exopolymeric Acid and Polysaccharides in Marine Environments

合作研究：TH(IV) 和 PA(IV, V) 与海洋环境中的外聚酸和多糖的结合

• 批准号: 0350758
• 负责人: Laodong Guo
• 金额: $ 20万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-04-15 至 2006-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0350758&HistoricalAwards=false
• 关键词: Collaborative; Research; TH; IV; PA

ABSTRACTOCE- 0351559 / OCE- 0350758Th(IV) and Pa(IV,V) isotopes are important proxies in oceanographic investigations, such as, for tracing particle dynamics and particulate organic matter (POC) fluxes out of the euphotic zone through the use of 234Th/POC ratios, and for studying boundary scavenging, paleoproductivity and ocean circulation through the use of 231Pa/230Th ratios. Even though almost routine, these approaches rely on often poorly constrained, empirically determined and variable isotope ratios or ratios to POC. Previously conducted laboratory and field investigations suggest that Th(IV) removal could be controlled through binding by exopolymeric acid polysaccharide (APS) rich biomolecules, potentially produced by both phytoplankton and bacteria. However, researchers at Texas A&M University - Galveston and the University of Alaska Fairbanks Campus believe that Pa(V) present in ocean water must first be reduced to Pa(IV) by organic biomolecules before efficient binding to solid phases can occur, and that the most efficient binding would occur to APS-rich biomolecules produced by phytoplankton species such as diatoms, prymnesiophytes and cyanobacteria.In this study, the team of scientists at Texas A&M Research Foundation and the University of Alaska Fairbanks Campus will investigate the possible fractionation mechanisms between Pa(IV,V) and Th(IV) in the ocean. It is essential to understand such a mechanism, since the Pa/Th ratio is frequently used as a proxy in oceanographic applications. The proposed interdisciplinary experimental approaches will require instrumental approaches for characterization studies, in combination with controlled laboratory and field experimentation. Laboratory studies consist of uptake experiments to a number of substrates, including purified APS harvested from phytoplankton and bacterial cultures to be used in Th(IV) and Pa(IV,V) binding assessments. The most important analytical task will be to better characterize, both chemically, in terms of molecular composition, and physically, in terms of surface activity, the newly discovered strongly Th(IV) complexing APS of ~13 kDa molecular weight, found in particulate and colloidal material collected from the Gulf of Mexico, Atlantic and Pacific Ocean and the South China Sea. The field program in this study will include collection and extraction of diverse types of organic matter for use in laboratory studies, as well as the determination of temporal and spatial variations of radiochemical and biochemical parameters.

摘要-0351559/OCE-0350758Th(IV)和Pa(IV，V)同位素在海洋学研究中具有重要的应用价值，如利用234Pa/230Th比值示踪颗粒动力学和颗粒有机物通量，研究边界清除、古生产力和海洋环流等。尽管几乎是例行公事，但这些方法往往依赖于约束较差的、经验确定的和可变的同位素比率或POC比率。以往的实验室和现场研究表明，Th(IV)的去除可以通过富含胞外多聚酸(APS)的生物分子的结合来控制，这些生物分子可能由浮游植物和细菌产生。然而，德克萨斯农工大学加尔维斯顿分校和阿拉斯加大学费尔班克斯校区的研究人员认为，在与固相发生有效结合之前，海水中存在的PA(V)必须首先被有机生物分子还原为Pa(IV)，并且最有效的结合发生在由浮游植物物种(如硅藻、裸藻和蓝藻)产生的富含APS的生物分子上。在这项研究中，德克萨斯农工大学研究基金会和阿拉斯加大学费尔班克斯校区的科学家团队将研究海洋中PA(IV，V)和Th(IV)之间可能的分馏机制。理解这种机制是非常必要的，因为在海洋学应用中，Pa/Th比经常被用作替代指标。拟议的跨学科实验方法将需要用于表征研究的仪器方法，并结合受控实验室和实地实验。实验室研究包括对许多底物的吸收实验，包括从浮游植物和细菌培养中收获的纯化AP，用于Th(IV)和PA(IV，V)结合评估。最重要的分析任务将是更好地表征新发现的分子组成和表面活性方面的强Th(IV)络合AP，这些AP是从墨西哥湾、大西洋、太平洋和南中国海收集的颗粒和胶体材料中发现的。这项研究的实地方案将包括收集和提取用于实验室研究的不同类型的有机物，以及确定放射化学和生化参数的时间和空间变化。