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

Th（IV）和Pa（IV，V）同位素是海洋学研究中的重要代用指标，例如，通过使用234 Th/POC比值追踪颗粒动力学和颗粒有机物（POC）通量，以及通过使用231 Pa/230 Th比值研究边界清除、古生产力和海洋环流。尽管几乎是常规的，但这些方法依赖于通常约束不良的、凭经验确定的和可变的同位素比或与POC的比。以前进行的实验室和现场调查表明，Th（IV）的去除可以控制通过结合外聚酸多糖（APS）丰富的生物分子，可能产生的浮游植物和细菌。然而，德克萨斯A& M大学-加尔维斯顿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），并且最有效的结合将发生在浮游植物物种（如硅藻，prymnesiophytes和蓝藻）产生的富含APS的生物分子上。&基金会和阿拉斯加大学费尔班克斯校区将研究海洋中Pa（IV，V）和Th（IV）之间可能的分馏机制。由于Pa/Th比值在海洋学应用中经常被用作替代指标，因此了解这种机制至关重要。拟议的跨学科的实验方法将需要表征研究的仪器方法，结合控制实验室和现场实验。实验室研究包括摄取实验的一些基板，包括纯化APS收获浮游植物和细菌培养物中使用的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，无论是在化学上，在分子组成方面，和物理上，在表面活性方面，新发现的强Th（IV）络合APS的~13 kDa的分子量，发现在颗粒和胶体材料收集从墨西哥湾，大西洋和太平洋和中国南海。本研究的实地项目将包括收集和提取用于实验室研究的各种类型的有机物质，以及确定放射化学和生物化学参数的时空变化。

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.