Trace metal signatures in continental sedimentary systems: Isotope constraints, biogeochemistry, and potential as a paleoclimatic tracer

大陆沉积系统中的痕量金属特征：同位素限制、生物地球化学和作为古气候示踪剂的潜力

• 批准号: 0518322
• 负责人: James McManus
• 金额: $ 23.01万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-15 至 2008-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0518322&HistoricalAwards=false
• 关键词: Trace; metal; signatures; continental; sedimentary

Intellectual merit. The proposed work will address hypotheses regarding thebiogeochemical interactions that lead to the removal of molybdenum, uranium, andvanadium from aquatic systems and the fractionation of Mo isotopes that occurs duringorganic matter decomposition. Our study site, Lake Tanganyika, is an ancient rift lake thathas an oxygenated upper water column and sulfidic deep waters. The existence ofsedimentary deposits underlying both these waters offers an exciting and timely opportunityto quantify changes in metal solubility and to test predictions regarding isotope fractionationassociated with metal precipitation. Our work is guided by two hypotheses that predict aclose link between metal accumulation rate and carbon cycling. These hypotheses predictdifferent behavior for Mo isotopes depending on whether or not the overlying water hassulfide present. (1) In regions where the overlying water column is absent of sulfide, wehypothesize that trace element accumulation in the sediments and Mo isotope compositionsare closely coupled to the cycling of organic carbon. (2) Where sediments are bathed withsulfide-rich water, we hypothesize that trace element enrichments remain sensitive to theorganic carbon cycling but Mo isotope values are invariant. Although we use thesehypotheses as a guide for our research, we do expect that the targeted elements will exhibit arange of sensitivities to organic carbon cycling and water column sulfide concentrations.Broader impacts I: Scientific value. The targeted elements already offer potential asbiogeochemical tracers, and this proposal represents an exciting opportunity to addressimportant issues regarding their environmental chemistry. Molybdenum isotopes alsoretain potential as a tracer for the availability of oxygen and sulfide through geologic time,and this proposal will allow us to examine how the presence of water column sulfideinfluences Mo isotope behavior. Finally, the African Great Lakes harbor rich records ofclimate history extending back to the Miocene. What we offer here is an opportunity tocalibrate a suite of sedimentary tracers that could ultimately provide powerful insights onbiogeochemical process, not only in Tanganyika, but in other sedimentary systems as well.Broader impacts II: Human impacts and opportunities for education. LakeTanganyika is a valuable resource to the East African people. The lake contains asignificant fraction of the Earth's fresh water and supplies the economies of several nationswith a valuable fisheries resource. In a broad sense, this proposal offers tools foraddressing questions related to how the lake's carbon dynamics have responded to pastchanges in climate. As part of this proposal, McManus will be participating in the Nyanzaproject during the summer of 2006. The Nyanza Project is an undergraduate/graduate fieldresearch program that offers opportunities to study paleoclimatology and geology in acontinental rift cradling one of the world's oldest lakes. As a participant in the programMcManus will be engaged in training both U.S. and African students, and we plan onhaving one African student and two U.S. students working on our field research. We willalso support an OSU undergraduate during our second year of funding. Undergraduatestudents have contributed significantly to the PI's research program resulting in abstractsdelivered at major conferences, university-wide student research programs, and coauthorshipon two manuscripts. Our college is beginning to engage students from our university'shonors college in research and we are planning on initiating an REU program in the nearterm. We anticipate having a student from one of these programs participating in theproposed research as well. Finally, this proposal will provide support for a postdoctoralresearch associate (Chris Siebert).

智力优点。拟议的工作将介绍有关Biogeochemical相互作用的假设，这些假设导致钼，铀和Vanadium从水生系统中删除，以及在有机事物期间发生的MO同位素分馏。我们的研究地点Tanganyika湖是一个古老的裂谷湖，它是一个含氧的上水柱和硫化深水。这两种水域的基础矿床的存在提供了令人兴奋的及时机会，可以量化金属溶解度的变化，并测试有关金属沉淀相关的同位素分馏的预测。我们的工作以两个假设指导，这些假设可以预测金属积累速率与碳循环之间的联系。这些假设预测了MO同位素的不同行为，具体取决于是否存在上面的水硫化物。 （1）在上覆的水柱没有硫化物的区域中，Wehypotheshesse the痕迹在沉积物中积累了痕量元素，而Mo同位素组成与有机碳的循环紧密耦合。 （2）如果沉积物用富含硫化物的水沐浴，我们假设痕量元素富集对理论碳循环仍然敏感，但MO同位素值是不变的。尽管我们使用这些型号作为研究的指南，但我们确实希望目标元素将表现出对有机碳循环和水柱硫化物浓度的敏感性。目标元素已经提供了潜在的Asbiogeochemical Tracers，该提案代表了一个令人兴奋的机会，以解决有关其环境化学的问题。钼同位素的Alsoretain潜力作为通过地质时间氧气和硫化物的示踪剂，该建议将使我们能够研究水柱硫化物硫化物MO同位素行为的存在。最后，非洲伟大的湖泊藏有悠久历史记录，延伸到中新世。我们在这里提供的是一个机会，可以实现一套沉积示踪剂，这些示踪剂最终可以提供强有力的见解，不仅在Tanganyika中，而且在其他沉积系统中，也可以在其他沉积系统中提供。 Laketanganyika是东非人民的宝贵资源。该湖中包含地球淡水的不足部分，并为几个国家的经济提供了有价值的渔业资源。从广义上讲，该提案提供了与湖泊动力学在气候下对糊状的反应有关的工具。作为该提案的一部分，McManus将在2006年夏季参加Nyanzaproject。Nyanza项目是一个本科/研究生实地研究计划，提供了研究大陆裂谷中的古气候和地质学的机会。作为计划的参与者，将参与培训美国和非洲学生，我们计划向一名非洲学生和两名从事我们现场研究的美国学生进行。我们在第二年的资助中支持OSU本科生。本科生对PI的研究计划做出了重大贡献，导致在主要会议，大学范围内的学生研究计划和共同统治下进行了摘要。我们的学院开始吸引我们大学工作学院的学生进行研究，我们计划在近期启动REU计划。我们预计也有一个来自其中一项计划的学生也参加了该计划。最后，该建议将为博士后研究员（Chris Siebert）提供支持。