Y-90/Sr-90 and Th-234/U-238 Disequilibria: The Utility of Dual fast Process Chronometers as Tracers of Particle Dynamics in Shallow Coastal, Estuarine and Freshwater Systems

Y-90/Sr-90 和 Th-234/U-238 不平衡：双快速过程精密计时器作为浅海、河口和淡水系统中粒子动力学示踪剂的用途

• 批准号: 0351824
• 负责人: James Waples
• 金额: $ 50万
• 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: 2004
• 资助国家: 美国
• 起止时间: 2004-05-01 至 2008-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0351824&HistoricalAwards=false
• 关键词: 90; Sr; Th; 234; 238

ABSTRACTOCE-0351824In marine environments, particle-reactive scavenging rates, sediment trap efficiencies (e.g., Buesseler et al., 1994), surface sediment mixing, and vertical and horizontal particle transport rates have all been calculated in part by measuring the disequilibrium between naturally occurring, particle-reactive 234Th and its generally soluble parent, 238U. While measurements of 234Th/238U disequilibria have proven very useful in understanding particle dynamics in the open ocean, the utility and facility of using this radio chronometer diminishes in nearshore, estuarine and freshwater systems. Interestingly, 90Y is similar to 234Th in that it is particle reactive while its parent is generally non-reactive and a conservative constituent in aquatic systems. However, 90Y has a half-life of only 64 hours while 234Th has a half-life of 24.1 days.In this study, researchers at the University of Wisconsin-Milwaukee intend to explore the utility of simultaneously measuring 90Y /90Sr and 234Th/238U disequilibria in both nearshore and offshore Lake Michigan as a novel means of quantifying short term temporal dynamics of particles in aquatic systems. Under steady state and non-steady state conditions both dissolved ( 0.45 um) and particle bound nuclide activities of 90Y, 90Sr, 234Th and 238U will be measured. Over the four-year project, these nuclides will be measured simultaneously in both shallow (20 m) and deep ( 100 m) water stations with special emphasis on collecting samples during periods of calm, intense bottom sediment resuspension, intense primary production, and a whiting event. During the third and fourth years of this project, daily variations in 90Y /90Sr and 234Th/238U disequilibria in the water column will be measured in conjunction with daily measurements of excess particle-bound inventories of 90Y and 234Th on the lakebed during a series of 5-day cruises over different physical/seasonal regimes. Mathematical expressions used to relate 234Th/238U disequilibria to the physical dynamics of particles and particle-reactive species also apply to the 90Y /90Sr pair so that separate estimates of both particle scavenging and removal rates will be made.

Abstractoce-0351824在海洋环境，颗粒反应性清除率，沉积物陷阱效率（例如Buesseler等人，1994年），表面沉积物混合以及垂直和水平颗粒传输速率均已通过零件来计算出来，粒子反应性234及其通常可溶的父，238U。虽然证明234/238U不平衡的测量对于理解开阔的粒子动态非常有用，但使用此无线电计时仪的效用和设施减少了近海，河口和淡水系统。 有趣的是，90年代与第234位相似，因为它的粒子反应性，而其母体通常无反应性并且在水生系统中是保守的成分。但是，90岁的半衰期仅为64小时，而234th的半衰期为24.1天。在这项研究中，威斯康星大学 - 米尔沃基大学的研究人员打算同时探索90y /90sr和234th /238U的实用性密歇根州近海和海上湖中的不平衡是量化水生系统中颗粒短期时间动力学的一种新颖手段。在稳态和非稳态条件下，将测量溶解（0.45 UM）和90y，90SR，234th和238U的粒子结合的核素活性。 在四年的项目中，这些核心将在浅层（20 m）和深（100 m）的水站中同时测量，并特别强调在平静，强烈的底部沉积物重新悬浮，强烈的原发性生产和A的时期内收集样品白色事件。在该项目的第三年和第四年中，水柱中的90年 /90SR和234 /238U不平衡的变化将与每天测量一系列90岁的颗粒库存和在一系列湖泊中的颗粒结合库存的每日测量。在不同的身体/季节性方案上进行了5天的巡游。用于将234 /238U与颗粒的物理动力学和粒子反应性物种的物理动力学相关的数学表达式也适用于90Y /90SR对，因此将对粒子清除和​​去除率进行单独的估计。