The Riverine Fluxes of Rhenium and Molybdenum to the Ocean

铼和钼沿河流流入海洋的通量

• 批准号: 0519387
• 负责人: Bernhard Peucker-Ehrenbrink
• 金额: $ 14.98万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-15 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0519387&HistoricalAwards=false
• 关键词: Riverine; Fluxes; Rhenium; Molybdenum; Ocean

EAR-0519387PEUCKER-EHRENBRINKIntellectual Merit: Data presented in this proposal challenge the conventional view of conservative behavior of rhenium in estuaries. Rhenium and molybdenum define the radiogenic Re-Os and the stable Mo isotope systems that have important basic and applied science applications. Both elements are thought to exhibit conservative behavior in oxic aquatic environments. They are characterized by long residence times in seawater that result from relatively high dissolved concentrations in seawater (Re: 40 pM; Mo: 105 nM) and low averageriverine concentrations (Re: 2 pM; Mo: 5 nM). Both elements are redox-sensitive and accumulate in reducing sediments. They are easily mobilized from such sediments during oxic weathering and can be used as indicators of oxidation of old sedimentary organic matter.The notion of conservative Re behavior is challenged by our finding of a pronounced nonconservative Re concentration profile in the Hudson River Estuary salinity profile. The projected freshwater concentration of ~60 pM exceeds the accepted world-average river concentration 30-fold. High Re concentrations of ~90 pM in fresh Mississippi River water indicate that the high Re concentrations in the Hudson River are no exception. Though similarly high Re concentrations were detected in the early 1990s in rivers draining into the Black Sea, these concentrations were interpreted as reflecting anthropogenic contamination (coal burning).This proposal has three goals:1) Surveys of Re (and Mo) concentrations will be conducted along the salinity gradient in theHudson River estuary to determine whether the non-conservative Re profile is a steady-state feature. Two cruises will be conducted at very different flow stages to determine whether this feature is caused by a natural process or by anthropogenic contamination.2) In collaboration with Prof. Franco Marcantonio (Tulane Univ.) the behavior of Re (and Mo) will be studied in the Mississippi River estuary. In addition, a year-long, bi-weekly time series of Re and Mo concentrations as well as a tri-monthly time series of Re and Mo concentrations in major Mississippi tributaries will be analyzed to identify source regions of high Re input.3) Estimates of world-average riverine Re and Mo fluxes will be revised. This will be achieved through a collaborative research component that is based on the use of standardized, low-cost and well-tested sampling/filtration kits to be sent to collaborators world-wide, as well as the analyses of archived river water samples stored at WHOI and elsewhere (by collaborators).Broader Implications: Constraining riverine fluxes of Re and Mo is critical for using the radiogenic Re-Os and stable Mo isotope systems as indicators of organic-matter cycling. The potentially wide-spread Re contamination of modern river systems may indicate a leaky industrial Re cycle or another anthropogenic source. The use of standardized sample kits aims at testing whether this method provides an economical way of improving global riverine fluxes for "hard to contaminate" elements, such as oxyanions Re, Mo, and U. If successful, this method will be used in the future as a combined educational and research tool for involving science teachers and their pupils in geochemical research. The project will support the scientific education of Research Assistant Tracy Abbruzzese and MIT/WHOI Joint Program student Christian Miller.

PEUCKER-EHRENBRINK智力优点：本提案中提供的数据挑战了河口中鱼类保守行为的传统观点。铼和钼定义了放射成因的铼-锇和稳定的钼同位素系统，具有重要的基础和应用科学应用。这两种元素被认为在有毒的水生环境中表现出保守的行为。它们的特征在于在海水中的长停留时间，这是由于在海水中相对高的溶解浓度（Re：40 pM; Mo：105 nM）和低的平均肝豆碱浓度（Re：2 pM; Mo：5 nM）。这两种元素都对氧化还原敏感，并在还原性沉积物中积累。他们很容易动员，从这样的沉积物在氧化风化，可作为旧的沉积有机质的氧化指标。保守的Re行为的概念受到挑战，我们发现一个显着的非保守Re浓度分布在哈德逊河口盐度剖面。预计淡水浓度约为60 pM，超过公认的世界平均河流浓度30倍。密西西比河淡水中的高Re浓度约为90 pM，表明哈德逊河中的高Re浓度也不例外。虽然在20世纪90年代早期在排入黑海的河流中检测到类似的高Re浓度，但这些浓度被解释为反映了人为污染（燃煤）。本提案有三个目标：1）将在thehudson河口沿着盐度梯度进行Re（和Mo）浓度调查，以确定非保守Re剖面是否为稳态特征。将在非常不同的水流阶段进行两次巡航，以确定这一特征是由自然过程还是人为污染造成的。Re（和Mo）的行为将在密西西比河口进行研究。此外，为期一年的，双周的时间序列的Re和Mo浓度以及三个月的时间序列的Re和Mo浓度在主要密西西比支流将进行分析，以确定高Re输入的源区。3）估计的世界平均河流Re和Mo通量将进行修订。这将通过一个合作研究部分来实现，该部分的基础是使用标准化、低成本和经过良好测试的采样/过滤工具包，将其发送给世界各地的合作者，以及分析储存在世界卫生组织和其他地方的存档河水样本（由合作者提供）。约束河流通量的Re和Mo是至关重要的使用放射性成因的Re-Os和稳定的Mo同位素系统作为有机质循环的指标。现代河流系统中潜在的广泛分布的Re污染可能表明工业Re循环泄漏或其他人为来源。使用标准化的样品包旨在测试这种方法是否提供了一种经济的方式来改善全球河流通量的“难污染”元素，如含氧阴离子Re，Mo和U。如果成功的话，这种方法将在未来作为一种综合的教育和研究工具，使科学教师和学生参与地球化学研究。该项目将支持研究助理Tracy Abbruzzese和MIT/WHOI联合项目学生Christian米勒的科学教育。