Bismuth-210: A tracer of dynamic scavenging in aquatic systems.

Bismuth-210：水生系统动态清除的示踪剂。

• 批准号: 2023454
• 负责人: James Waples
• 金额: $ 26.97万
• 依托单位: University of Wisconsin-Milwaukee
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2023454&HistoricalAwards=false
• 关键词: Bismuth; 210; tracer; dynamic; scavenging

Chemical cycling in any aquatic system is strongly affected by the transport of particles through that system, and a better understanding of particle dynamics is particularly needed in lakes and shallow marine systems, which play a disproportionately large, yet poorly quantified role in global biogeochemical cycling. Our current understanding of particle flux and attenuation down through the water column has largely relied on the use of sediment traps and naturally occurring particle-reactive radionuclides. However, particle dynamics are chronically understudied in shallow aquatic systems largely because of methodological limitations. The downward transport of particulate matter in shallow waters cannot be reliably quantified with a bottom tethered sediment trap and the choice of radionuclide tracers in high flux and freshwater systems is severely limited. The primary goal of this proposed work is to demonstrate that combined measurements of the natural radionuclide lead-210 (210Pb) and its daughter bismuth-210 (210Bi) can be used to determine particulate flux in a shallow and dynamic aquatic system. A thorough demonstration and testing of the 210Bi/210Pb tracer is imperative before any general application of the tracer is made to study process rates. The project will support two undergraduate students as field and laboratory assistants during summer months and one MS graduate student for the duration of this project. Sample collection and field work will take place in Lake Michigan and will be incorporated into a graduate field course.The goals of this proposed work are to: (i) demonstrate the practicality of a simple technique for measuring the 210Pb-210Bi-210Po radionuclide trio in aquatic systems; (ii) show that 210Bi/210Pb derived particle fluxes are concordant with 234Th/238U derived particle fluxes in a dynamic and “calibrated” nearshore system; and (iii) show that the in situ Kd of 210Bi is greater than that of 210Pb under varying conditions of particle concentration and organic matter content, across a gradient of dissolved oxygen concentrations. Nearshore scavenging processes are chronically understudied due to methodological limitations. Developing a relatively easy to measure and widely occurring particle tracer based on 210Bi/210Pb disequilibria will allow for future process studies of dynamic particle cycling that are critical to understanding system-wide chemistry as well as practical problems associated with the management of trophic status, hypoxia, harmful algal blooms, and contaminant fate and transport.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

任何水生系统中的化学循环都受到通过该系统的颗粒运输的强烈影响，尤其需要更好地了解湖泊和浅海系统中的颗粒动力学，因为它们在全球生物地球化学循环中发挥着不成比例的大而难以量化的作用。我们目前对通过水柱的颗粒通量和衰减的了解在很大程度上依赖于沉积物捕集器和自然产生的颗粒反应性放射性核素的使用。然而，在浅水系统中，颗粒动力学长期研究不足，这在很大程度上是由于方法的限制。浅水中颗粒物的向下输送不能用底部系留沉积物捕捉器可靠地量化，在高通量和淡水系统中放射性核素示踪剂的选择受到严重限制。这项拟议工作的主要目标是证明，对天然放射性核素铅-210(210Pb)及其子体铋-210(210Bi)的联合测量可用于确定浅水和动态水系中的颗粒物通量。在对示踪剂进行任何一般应用以研究工艺速率之前，必须对210Bi/210Pb示踪剂进行彻底的演示和测试。该项目将在夏季支持两名本科生担任现场和实验室助理，并在该项目期间支持一名硕士研究生。样品采集和野外工作将在密歇根湖进行，并将纳入研究生野外课程。这项拟议工作的目标是：(I)证明一种简单的技术在水生系统中测量210Pb-210Bi-210Po放射性核素三元组的实用性；(Ii)证明在动态和“校准”的近岸系统中，210Bi/210Pb派生的粒子通量与234/238U派生的粒子通量是一致的；以及(Iii)表明在不同的颗粒浓度和有机质含量条件下，在不同的颗粒浓度和有机物含量条件下，210Bi的原位Kd值大于210Pb的Kd值。由于方法上的限制，近岸清理过程的研究长期不足。开发一种基于210Bi/210Pb不平衡的相对易于测量和广泛存在的粒子示踪剂，将使未来能够对动态粒子循环的过程进行研究，这些过程对于理解系统范围的化学以及与营养状态、缺氧、有害藻华和污染物的去向和转移的管理相关的实际问题至关重要。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。