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

toce - 0351559 / OCE- 0350758Th（IV）和Pa（IV，V）同位素是海洋研究的重要指标，例如通过234 /POC比值追踪粒子动力学和颗粒有机质（POC）通量，以及通过231Pa/230Th比值研究边界清除、古生产力和海洋环流。尽管这些方法几乎是常规的，但它们往往依赖于约束不佳的、经验确定的和可变的同位素比率或与POC的比率。先前进行的实验室和实地调查表明，Th（IV）的去除可以通过与富含外聚酸多糖（APS）的生物分子结合来控制，这些生物分子可能由浮游植物和细菌产生。然而，德克萨斯a&m大学加尔维斯顿分校和阿拉斯加大学费尔班克斯分校的研究人员认为，存在于海水中的Pa(V)必须首先被有机生物分子还原为Pa(IV)，然后才能有效地与固相结合，而最有效的结合将发生在浮游植物物种（如硅藻、水原体和蓝藻）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。了解这种机制是必要的，因为在海洋学应用中经常使用Pa/Th比值作为代理。拟议的跨学科实验方法将需要仪器方法进行特征研究，并结合受控实验室和现场实验。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物中收获的纯化APS，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强Th（IV）络合APS，从分子组成的化学角度，以及从表面活性的物理角度，在墨西哥湾、大西洋、太平洋和南中国海收集的颗粒和胶体材料中发现了~13 kDa分子量的强Th（IV）络合APS。本研究的实地项目将包括收集和提取用于实验室研究的不同类型的有机物质，以及确定放射化学和生化参数的时空变化。

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.