Collaborative Research: Ge/Si as a Tracer of Terrestrial Silica Cycling

合作研究：Ge/Si 作为陆地二氧化硅循环的示踪剂

• 批准号: 0208336
• 负责人: Andrew Kurtz
• 金额: $ 7.08万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-03-01 至 2006-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0208336&HistoricalAwards=false
• 关键词: Collaborative; Research; Ge; Si; Tracer

ABSTRACTWeathering of silicate minerals on continents is a major source of silicon (Si) for formation of secondary silicate minerals in soil, opal phytoliths in plants and ultimately for diatoms in the oceans. Even though Si is a significant element in the biogeochemistry of Earth, it does not have a well developed tracer to provide a clear understanding of how organic and inorganic processes affect Si behavior and the pathways that Si follows as it moves from rock to clay or water or organism. Germanium (Ge) and Si behave chemically in a similar fashion and have been treated as a pseudo-isotopic tracer of the behavior of Si in the surficial environment. We have conducted preliminary research that demonstrates clear and logical changes in the Ge/Si ratio in response to soil and plant processes. Here we propose a systematic analysis of Ge fractionation from Si during: 1) incongruent weathering and the formation of secondary alumino-silicate clay minerals, 2) formation of iron oxides in soil, and 3) plant uptake and opal biosynthesis leading to formation of phytoliths.We propose a field-based project where we quantify the Ge/Si ratios of rock minerals, soil minerals, soil water and plant phytoliths in soils forming on extrusive volcanic rock and on intrusive plutonic rocks in a humid tropical weathering environment. Ge/Si ratios will be determined on fresh parent materials and soils from a series of well-studied tropical soil sites in Hawaii (basaltic substrate) and Luquillo, Puerto Rico (granitoid substrate). Pore waters and mineral separates (where applicable) from the same horizons as the soil samples will be analyzed. We will also analyze plant phytoliths from dominant vegetation. We will use the data to test specific hypotheses about processes that control Ge/Si fractionation in the weathering environment. The proposed research will compare and contrast the behavior of the Ge/Si system in aphanitic basaltic environments with plutonic granitoid environments, where we expect that the mechanisms of fractionation will differ because of the differences in chemical composition, mineralogy, and crystallinity. It will also specifically investigate the role of plant uptake of Si and the biogenic silica cycle in soil systems. The results of this study will provide the basic data needed to develop Ge/Si ratios as a quantitative tracer of silica during weathering, plant cycling, and in surface waters.

在大陆上的硅酸盐矿物质的抽象生气是硅（SI）的主要来源，用于在土壤中形成二硅酸盐矿物质，植物中的蛋白石植物岩，最终用于海洋中的硅藻。即使SI是地球生物地球化学中的重要元素，它也没有发达的示踪剂，可以清楚地了解有机和无机过程如何影响Si行为以及SI从岩石到粘土或水或有机体移动时所遵循的途径。锗（GE）和SI以类似的方式进行化学表现，并被视为SI在表面环境中SI行为的伪异位示踪剂。我们进行了初步研究，该研究表明，对土壤和植物过程的响应，GE/SI比率明显变化。 Here we propose a systematic analysis of Ge fractionation from Si during: 1) incongruent weathering and the formation of secondary alumino-silicate clay minerals, 2) formation of iron oxides in soil, and 3) plant uptake and opal biosynthesis leading to formation of phytoliths.We propose a field-based project where we quantify the Ge/Si ratios of rock minerals, soil minerals, soil water and plant在潮湿的热带风化环境中，在挤出火山岩和侵入性的岩石岩石上形成的土壤中的植物岩。 GE/SI比率将在夏威夷（玄武岩底物）和波多黎各（Granitoid Substrate）的一系列良好研究的热带土壤地点的新鲜父材料和土壤上确定。将分析与土壤样品相同的范围内分离的孔隙水和矿物水。我们还将分析主要植被的植物植物石。我们将使用数据来测试有关控制GE/SI分馏在风化环境中的过程的特定假设。拟议的研究将比较和对比GE/SI系统在语法基底环境中的行为与岩体花岗岩环境，我们期望分馏的机制会有所不同，因为化学成分，矿物质学和结晶度的差异。它还将专门研究植物对Si的摄取和土壤系统中生物二氧化硅周期的作用。这项研究的结果将提供在风化，植物循环和地表水中开发GE/SI比作为二氧化硅的定量示踪所需的基本数据。